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APPENDIX I

Status of individual stocks


Atlantic Ocean and Mediterranean Sea

Albacore (ALB) in the Mediterranean Sea (MED)

FIGURE AI.1
Cumulative catches of ALB, by gear, in the MED


FIGURE AI.2
ALB catches, by gear, in the MED

Historical catches - The catches of ALB in the MED were stable from the beginning of the fishery until 1980 (Figure AI.1). From 1980 to 1985, the catches increased by almost eight-fold, and in 1985, for the first time, they exceeded 4 000 tonnes. From 1985 to 1989 the catches oscillated around that level. After that the catches began to decrease, reaching a very low level (1 350 tonnes) in 1994. Then the catches again increased, and in 2002 a maximum catch of 5 608 tonnes was taken. The longline catches of ALB in the MED are taken mainly by Italy (3 600 tonnes in 2002) and the purse-seine catches almost exclusively by Greece (1 300 tonnes in 2002).

Stock status - Due to the lack of adequate data, an assessment of ALB in the MED has not been carried out.

2002 catch (tonnes) - Total = 5 608 (LL = 3 706; PS = 1 305; TROLL = 117; PL = 29; OTHER1 = 451).

Maximum annual catch (tonnes) - Taken in 2002 (see above).

Catch-related reference point (tonnes) - Unknown.

Stock size - Unknown.

Fishing mortality - Unknown.

Management recommendations/regulations - There are no ICCAT regulations aimed directly at managing ALB in the MED. The SCRS recommended to ICCAT that reliable data be provided in the future, and that effort be made to recover historical data.

Stock status summary - Stock size: unknown. Fishing mortality: unknown.

1 Mainly gillnets and handlines.

Outlook - Unknown.

Albacore (ALB) in the North Atlantic Ocean (NAO)

FIGURE AI.3
Cumulative catches of ALB, by gear, in the NAO


FIGURE AI.4
ALB catches, by gear, in the NAO

Historical catches - The total catches of ALB in the NAO tended to increase, although with major fluctuations, from 1950 to 1964, when the maximum catch of 64 354 tonnes was taken (Figure AI.3). Since then the catches have decreased, with large fluctuations. The 2002 catch of approximately 22 500 tonnes is the lowest on record. This catch represents only about 35 percent of the maximum catch, taken in 1964. The principal fishing countries and entities employed the following methods of fishing in 2002: pole-and-line fishing, Spain (4 700 tonnes) and Portugal (1 900 tonnes); mid-water paired trawling, France (4 300 tonnes) and Ireland (1 100 tonnes); longlining, the Taiwan Province of China (4 300 tonnes); trolling, Spain (3 900 tonnes).

Stock status - The SCRS of ICCAT decided that it would not be appropriate to conduct a virtual population analysis (VPA) based on 2003 catch-at-age data until the catch-at-size to catch-at-age transformation was reviewed and validated. Consequently, information on the present status of the stock is based on an assessment conducted in 2000 and CPUE and catch data provided to the SCRS since then.

2002 catch (tonnes) - Total = 22 496 (PL = 6 639; LL = 6 006; TROLL = 4 007; PS = 118; OTHER1 = 5 726).

Maximum annual catch (tonnes) - Total = 64 354 (TROLL = 28 058; PL = 20 428; LL = 1 5 868) in 1964.

Catch-related reference point (tonnes) - 32 600 (MSY).

Stock size - The present spawning stock biomass (SSB) is probably about 30 percent below that corresponding to MSY (SSBMSY = 42 300 tonnes). However, due to the uncertainty in these estimates, it is possible that the stock is greater than the BMSY

Fishing mortality - The equilibrium yield-per-recruit analysis conducted in 2000 indicates that the stock is not being growth-overfished (F<Fmax). However, estimates of FMSY indicate that the F in 2000 was about 10 percent greater than FMSY.

Management recommendations/regulations - In 2001 ICCAT established a total allowable catch (TAC) of 34 500 tonnes for ALB in the NAO. In 2003 the 34 500-tonne TAC was extended to 2004, 2005 and 2006. The 1998 recommendation to limit fishing capacity to the average capacity of 1993 to 1995 also remains in force.

Stock status summary - Stock size: possibly below its reference point. Fishing mortality: possibly near or above its reference point.

1 Mainly drift gillnets and mid-water trawls.

Outlook - In 2000 the SCRS recommended that, to maintain a stable SSB in the near future, the catch should not be permitted to exceed 34 500 tonnes (as in 1999) in 2001 and 2002. The SCRS further noted that, to increase the SSB toward the level estimated to correspond to MSY, the catches in 2001 and 2002 should not exceed 31 000 tonnes. According to ICCAT catch statistics, the 2001 and 2002 catches were less than 31 000 tonnes, but it is still too soon to assess whether these level of catches have had a positive effect on the SSB. The ALB-NAO catches are currently restricted to a TAC of 34 500 tonnes.

Albacore (ALB) in the South Atlantic Ocean (SAO)

FIGURE AI.5
Cumulative catches of ALB, by gear, in the SAO


FIGURE AI.6
ALB catches, by gear, in the SAO

Historical catches - The total catches of ALB in the SAO increased sharply during the first years of the fishery, reaching 30 000 tonnes in 1965 (Figure AI.5). Since then the ALB catches have fluctuated widely, with a minimum of 14 600 tonnes in 1984 and a maximum of 40 000 tonnes in 1987, without a clear trend. The 2002 catch of 31 406 tonnes, the greatest since 1981, was about 77 percent of the maximum catch, taken in 1987. The principal fishing countries and entities employed the following methods of fishing in 2002: longlining, the Taiwan Province of China (17 700 tonnes); pole-and-line fishing, South Africa (6 199 tonnes) and Namibia (2 900 tonnes).

Stock status - A stock assessment for ALB in the SAO was conducted by the SCRS of ICCAT in 2003. The results were similar to those obtained in 2000.

2002 catch (tonnes) - Total = 31 406 (LL = 21 506; PL = 9 539; PS = 38; OTHER = 323).

Maximum annual catch (tonnes) - Total = 40 630 (LL = 30 964; PL = 8 181; PS = 948; OTHER = 537) in 1987.

Catch-related reference point (tonnes) - 30 915 (MSY).

Stock size - The SSB declined substantially after the mid-1980s, but has leveled off in recent years, and in 2002 it was well above the SSB corresponding to MSY.

Fishing mortality - F was estimated to be about 60 percent of FMSY in both 2001 and 2003.

Management recommendations/regulations - In 1999 ICCAT established a TAC for ALB in the SAO. The TAC for 2004 was set at 29 200 tonnes, slightly less than the catch-related reference point.

Stock status summary - Stock size: above its reference point. Fishing mortality: below its reference point.

Outlook - The SCRS recommended that the catch not exceed 31 000 tonnes (MSY) for the next three to five years. The catches of ALB in the SAO have been above or close to MSY since 1988. Catches of this level would probably reduce the stock toward the BMSY. The ALB-SAO catches are currently restricted by a TAC of 29 200 tonnes.

Atlantic Bluefin (BFT) in the Eastern Atlantic Ocean (EAO)

FIGURE AI.7
Cumulative catches of BFT, by gear, in the EAO


FIGURE AI.8
BFT catches, by gear, in the EAO

Historical catches - The catches of BFT in the EAO (including the Mediterranean Sea) increased from 1950 to 1955, reaching almost 40 000 tonnes in 1955 (Figure AI.7). After that the catches declined to a minimum of approximately 10 000 tonnes in 1970. The catches then increased until 1996, when the maximum catch of approximately 50 000 tonnes was taken. After that the catches decreased to 33 093 tonnes in 2002. The 2002 catch was about 65 percent of the maximum catch, taken in 1996.

The principal fishing countries and entities employed the following methods of fishing in 2002: purse seining, France (5 800 tonnes), Italy (3 200 tonnes), Tunisia (2 500 tonnes), Turkey (2 300 tonnes) and Spain (1 700 tonnes); longlining, Japan (2 900 tonnes); pole-and-line fishing, Spain (2 400 tonnes); trap fishing, Morocco (1 700 tonnes) and Spain (1 500 tonnes).

Stock status - A stock assessment for BFT was conducted in 2002 and reviewed in 2003 by the SCRS of ICCAT. There is considerable concern regarding the quality of the catch, fishing effort and catch-at-size data especially for the Mediterranean Sea, so the assessment was regarded as uncertain.

2002 catch (tonnes) - Total = 33 093 (PS = 18 341; LL = 5 160; PL = 2 569; TROLL = 12; OTHER1 = 7 011).

Maximum annual catch (tonnes) - Total = 50 762 (PS = 26 344; LL = 12 959; PL = 5 362; OTHER = 6 097) in 1996.

Catch-related reference point (tonnes) - Unknown.

Stock size - The SSB in 2000 was about 86 percent of its level in 1970 (the first year for which an estimate is available). The recruitment has fluctuated, without showing a clear trend, in recent years.

Fishing mortality - An increase in F, especially for older fish after 1993, has been observed. In 2000 F was almost 2.5 times greater than that corresponding to the maximum yield per recruit.

Management recommendations/regulations - In spite of serious concerns regarding the status of the stock, no definite fisheries management recommendations were made by the SCRS in 2003, due to the poor quality of the catch, fishing effort and catch-at-size data and, consequently, the uncertainty of the stock assessment. Beginning in 1998, the BFT catches in the EAO have been restricted by TACs; these were fixed at 32 000 tonnes for 2003 through 2006. Closed areas and/or seasons limiting the use of specific gears have been adopted by ICCAT to protect juveniles and to restrict the catches during the spawning season. The minimum catch size is 6.4 kg (with 15-percent tolerance in number of fish) and 3.2 kg (with no tolerance).

Stock status summary - Stock size: below its reference point. Fishing mortality: above its reference point.

1 Mainly mid-water trawls, traps, handlines, gillnets and recreational gear.

Outlook - The present catch level is not sustainable. If the total fishing mortality is reduced substantially, especially for immature fish, the catches would decrease and the stock biomass would increase. After the recovery of the biomass to a higher level (e.g. to the level of the early 1970s), catches greater than the present ones (possibly more than 50 000 tonnes per year, depending on the selectivity pattern) could be sustained. The catches are currently restricted by TACs of 32 000 tonnes.

Atlantic Bluefin (BFT) in the Western Atlantic Ocean (WAO)

FIGURE AI.9
Cumulative catches of BFT, by gear, in the WAO


FIGURE AI.10
BFT catches, by gear, in the WAO

Historical catches - The catches of BFT in the WAO increased almost by 20-fold from 1960 to 1964, when the maximum catch of 18 679 tonnes was taken (Figure AI.9). The catches subsequently decreased sharply, and oscillated between 3 200 and 6 700 tonnes between 1968 and 1981. The catch decreased to 1 400 tonnes in 1982 as a result of a catch limit imposed by ICCAT. The 2002 catch (3 220 tonnes), the greatest since 1981, was about 17 percent of the maximum catch, taken in 1964. The greatest catches of BFT in the WAO were taken by the United States (1 900 tonnes), Canada (640 tonnes) and Japan (575 tonnes).

Stock status - A stock assessment for BFT was conducted in 2002 by the SCRS of ICCAT and reviewed in 2003. There are two hypotheses regarding the relationship between SSB and recruitment. One states that the recruitment has been poor because of low SSB levels, while the other assumes that environmental conditions are now less favorable for recruitment. The SCRS conducted projections for two scenarios, the so-called low-and high-recruitment scenarios, which reflect the two hypotheses. The high-recruitment scenario reflects the first hypothesis, i.e. that the recruitment will increase with increased SSB, while the low-recruitment scenario reflects the second hypothesis.

2002 catch (tonnes) - Total = 3 220 (LL = 802; PS = 208; OTHER = 2 210).

Maximum annual catch (tonnes) - Total = 18 679 (LL = 12 410; PS = 5 158; OTHER1 = 1 111) in 1964.

Catch-related reference point (tonnes) - 3 500 (MSY for the low-recruitment scenario); 7 200 (MSY for the high-recruitment scenario).

Stock size - The SSB declined steadily from 1970 through the late 1980s, before leveling off at about 20 percent of its level in 1975 (the reference year used in previous assessments). After 1997 the SSB steadily declined again, and in 2001 it was at 13 percent of its 1975 level (the lowest level since 1970). The recruitment has been low since 1976, except for 1995 and 1998.

Fishing mortality - F for adults was at its highest level since 1970 in 2001.

Management recommendations/regulations - Regulatory measures for BFT in the WAO have been in place since 1981. In 2002 ICCAT set the annual TAC at 2 700 tonnes (effective in 2003). ICCAT adopted a programme in 1998 to rebuild the BFT stock to SSBMSY in the WAO by 2018. A minimum size limit was set at 6.4 kg (with 15-percent tolerance, in number of fish).

Stock status summary - Stock size: below its reference point. Fishing mortality: above its reference point.

1 Mainly rod-and-reel.

Outlook - As it was mentioned earlier, projections of the SSB for two scenarios were conducted by the SCRS. The low-recruitment scenario included the assumption that the future average recruitment will be approximately equal to the average estimated recruitment since 1976, when the recruitment was low. The high-recruitment scenario allowed the average recruitment to increase with spawning stock size up to a maximum level no greater than the average estimated recruitment for 1970-1974, when recruitment was high. These scenarios implied that the SSBMSY is 42 percent and 183 percent of the SSB1975, respectively.

It is unlikely that SSBMSY for the high-recruitment scenario will be reached by 2018 if the recent level of catch (and the TAC) is maintained. For the low-recruitment scenario, assuming that the relatively large recruitment estimates for some recent year-classes are realistic, the SSBMSY could be reached even with an increase of the present catch (and the TAC).

In addition, the projections for the low-recruitment scenario suggest that a catch of 2 500 tonnes per year has a 97-percent probability of allowing the SSB to rebuild to SSBMSY by 2018. A catch of 3 000 tonnes per year has an 83-percent probability of this. The projections for the high-recruitment scenario indicate that a catch of 2 500 tonnes per year has a 20-percent probability of allowing rebuild the SSB to rebuild to SSBMSY by 2018.

It is unclear which of the two hypotheses is more probable.

The BFT-WAO catches are currently restricted by a TAC of 2 700 tonnes.

Bigeye (BET) in the Atlantic Ocean (AO)

FIGURE AI.11
Cumulative catches of BET, by gear, in the AO


FIGURE AI.12
BET catches, by gear, in the AO

Historical catches - The catches of BET in the AO increased, with some fluctuations, from 1950 to 1994, when the maximum catch of 129 506 tonnes was taken (Figure AI.11). During the 1994-1999 period the catches fluctuated between 100 000 and 120 000 tonnes. Since then the catches of BET have sharply decreased. The 2002 catch, 73 110 tonnes, was approximately 56 percent of the maximum catch. The principal fishing countries and entities employed the following methods of fishing in 2002: longlining, the Taiwan Province of China (16 500 tonnes) and Japan (14 700 tonnes); pole-and-line fishing, Ghana (4 300 tonnes), Spain (2 700 tonnes) and Portugal (2 400 tonnes); purse seining, Spain (7 000 tonnes).

Stock status - A full stock assessment for BET was conducted by the SCRS of ICCAT in 2002. The lack of reasonable estimates of some biological parameters considerably hindered it and led to some unrealistic results.

2002 catch (tonnes) - Total = 73 110 (LL = 43 774; PL = 11 640; PS = 16 193; OTHER1 = 1 503).

Maximum annual catch (tonnes) - Total = 129 506 (LL = 78 296; PL = 20 285; PS = 29 952; TROLL = 34; OTHER = 939) in 1994.

Catch-related reference point (tonnes) - MSY between 79 000 and 105 000 (range of estimates based on various production models).

Stock size - The biomass declined considerably between 1993 and 1999 due to the catches greater than the MSY, followed by a leveling off as a consequence of the subsequent decreased catches. The present biomass is about 10 to 20 percent below the level corresponding to the MSY.

Fishing mortality - Production modeling indicates that the present F is about 15 percent greater than that corresponding to the MSY. A yield-per-recruit analysis also supports this conclusion.

Management recommendations/regulations - ICCAT in 2003 recommended limiting the 2004 catch to the average catch of BET taken in 1991 and 1992 (approximately 96 000 tonnes). A moratorium on FAD fishing in the Gulf of Guinea has been implemented by ICCAT since 1999, and the SCRS considers that full compliance with this regulation is crucial for the sustainability of BET. The minimum size limit is 3.2 kg.

Stock status summary - Stock size: below its reference point. Fishing mortality: above its reference point.

1 Mainly trawls and handlines.

Outlook - Stock projections based on the results of a production model were conducted, assuming a catch of 100 000 tonnes in 2002 (very close to the reported catch for 2001) and various levels of constant catch thereafter. They suggested that the biomass of BET will not decline further with constant annual catches of 100 000 tonnes. It is expected that the biomass will increase with catches of 95 000 tonnes or less, and that further declines in the biomass would result with catches of 105 000 tonnes or more. According to a yield-per-recruit analysis, a reduction of fishing effort by the fisheries catching small fish could result in an increase in the yield per recruit by as much as 20 percent.

Skipjack (SKJ) in the Eastern Atlantic Ocean (EAO)

FIGURE AI.13
Cumulative catches of SKJ, by gear, in the EAO


FIGURE AI.14
SKJ catches, by gear, in the EAO

Historical catches - The catches of SKJ in the EAO (including the Mediterranean Sea) increased until 1974 when, for the first time, they exceeded 100 000 tonnes (Figure AI.13). From 1974 to 1990 the catches fluctuated widely, without any clear trend. In 1991, with the introduction of fish-aggregating devices (FADs), the catches increased sharply, attaining a maximum of 169 771 tonnes in 1991. Since then the catches have declined, and the recent catches are comparable to those taken prior to the introduction of FADs. The 2002 catch, 92 945 tonnes, was about 55 percent of the maximum catch. The principal fishing countries and entities employed the following methods of fishing in 2002: purse seining, Spain (21 600 tonnes) and Ghana (20 600 tonnes); pole-and-line fishing, Ghana (11 300 tonnes).

Stock status - The most recent assessment of SKJ in the AO was conducted in 1999 by the SCRS of ICCAT. According to the SCRS, "characteristics such as continuous recruitment but heterogeneous in time and area, variable growth between areas, exploitation by diverse fishing fleets having different and changing catchabilities, make it very difficult to conduct a standard assessment".

2002 catch (tonnes) - Total = 92 945 (PS = 68 634; PL = 24 074; LL = 26; OTHER = 211).

Maximum annual catch (tonnes) - Total = 169 771 (PS = 126 264; PL = 41 612; TROLL = 19; LL = 5; OTHER = 1 871) in 1991.

Catch-related reference point (tonnes) - Unknown.

Stock size - Unknown.

Fishing mortality - Unknown.

Management recommendations/regulations - The owners of French and Spanish vessels voluntarily introduced moratoria on fishing from November 1997 through January 1998, and November 1998 through January 1999. The moratoria, which were implemented to protect juvenile BET, have influenced the catches of SKJ around FADs. Similar moratoria have been recommended by ICCAT since 1999, and these are still in effect.

Stock status summary - Stock size: unknown. Fishing mortality: unknown.

Outlook - Unknown.

Skipjack (SKJ) in the Western Atlantic Ocean (WAO)

FIGURE AI.15
Cumulative catches of SKJ, by gear, in the WAO


FIGURE AI.16
SKJ catches, by gear, in the WAO

Historical catches - The catches of SKJ in the WAO were at low levels until 1979 (Figure AI.15). From 1979 to 1985, the year in which the maximum catch of 40 272 tonnes was taken, the catches increased by six-fold. Then they decreased sharply, and since 1988 the catches have fluctuated between 24 000 and 33 000 tonnes. The 2002 catch, 21 428 tonnes, the lowest catch since 1981, was about 53 percent of the maximum catch. The principal fishing countries employed the following methods of fishing in 2002: pole-and-line fishing, Brazil (18 185 tonnes); purse-seine fishing, Venezuela (2 000 tonnes).

Stock status - The last assessment on SKJ in the AO was conducted in 1999 by the SCRS of ICCAT. That assessment has been considered inconclusive, however. As was already mentioned in the previous section, there are some characteristics of SKJ that make it very difficult to conduct a standard assessment.

2002 catch (tonnes) - Total = 21 428 (PL = 18 737; PS = 2 116; LL = 61; TROLL = 58; OTHER = 456).

Maximum annual catch (tonnes) - Total = 40 272 (PL = 28 490; PS = 11 191; LL = 24; OTHER = 567) in 1985.

Catch-related reference point (tonnes) - Unknown.

Stock size - Standardized abundance indices up to 1998 were available from the Brazilian pole-and-line fishery and the Venezuelan purse-seine fishery, and both indices were stable.

Fishing mortality - Unknown.

Management recommendations/regulations - The owners of French and Spanish vessels voluntarily introduced moratoria for November 1997 through January 1998, and November 1998 through January 1999. The moratoria, which were implemented to protect juvenile BET, have influenced the SKJ catches around FADs. Similar moratoria have been recommended by ICCAT since 1999, and these are still in effect.

Stock status summary - Stock size: unknown. Fishing mortality: unknown.

Outlook - Unknown.

Yellowfin (YFT) in the Atlantic Ocean (AO)

FIGURE AI.17
Cumulative catches of YFT, by gear, in the AO


FIGURE AI.18
YFT catches, by gear, in the AO

Historical catches - The catches of YFT in the AO increased steadily from 1950 to 1984 (Figure AI.17). After that the catches fluctuated, without a clear trend, until 1990, when the maximum catch of 192 456 tonnes was taken. The catches have decreased since 1990. The 2002 catch was approximately 140 000 tonnes, about 71 percent of the maximum catch. The principal fishing countries or entities employed the following methods of fishing in 2002: purse seining, France (31 300 tonnes), and Spain (30 300 tonnes); longlining, the Taiwan Province of China (4 500 tonnes), Brazil (3 300 tonnes), the United States (2 500 tonnes) and Japan (1 800 tonnes); pole-and-line fishing, Ghana (10 200 tonnes).

Stock status - A stock assessment for YFT was conducted by the SCRS of ICCAT in 2003. Various age-structured and production models were applied.

2002 catch (tonnes) - Total = 137 440 (PS = 95 436; PL = 20 172; LL = 17 202; TROLL = 13; OTHER1 = 4 617).

Maximum annual catch (tonnes) - Total = 192 456 (PS = 134 473; LL = 29 104; PL = 24 278; TROLL = 330; OTHER = 4 271) in 1990.

Catch-related reference point (tonnes) - The MSY is estimated to be between 137 500 and 161 300 tonnes (based on results of age-structured and non-equilibrium production models).

Stock size - The SSB has been steadily decreasing since 1970. Estimates of the current biomass differ, depending on the models used. One model suggests that the current biomass is greater than that corresponding to the MSY, while another suggests that it is less than that biomass (B2001/BMSY = 0.73-1.10).

Fishing mortality - The declining trend in F since the early 1990s seems to have been reversed, and in 2001 F approached the highest level ever. Depending on the methods used, the current value of F was estimated to be either below or above the level corresponding to the MSY (F2001/FMSY = 0.87-1.46).

Management recommendations/regulations - In 2003 the SCRS reaffirmed its support for the ICCAT's 1993 recommendation "that there be no increase in the level of effective fishing effort exerted on Atlantic YFT, over the level observed in 1992". It also recommended that effective measures be found to reduce fishing mortality of small YFT. Moratoria on FAD fishing in the Gulf of Guinea have been implemented by ICCAT since 1999. The minimum size limit for YFT is 3.2 kg.

Stock status summary - Stock size: near its reference point. Fishing mortality: near its reference point.

1 Mainly trawls and handlines.

Outlook - Projections indicate that an increase in the fishing effort is likely to decrease the yield per recruit, while reductions in the fishing mortality on fish less than 3.2 kg could result in substantial gains in the yield per recruit and modest gains in the spawning biomass per recruit. They also suggest that the biomass is likely to decrease if the fishing mortality increases to the 1992 level, which is currently being approached or exceeded.

Indian Ocean

Albacore (ALB) in the Indian Ocean (IO)

FIGURE AI.19
Cumulative catches of ALB, by gear, in the IO


FIGURE AI.20
ALB catches, by gear, in the IO

Historical catches - The catches of ALB in the IO increased during the 1950s, reaching 19 000 tonnes in 1962 (Figure AI.19). Between 1962 and 1997 they fluctuated between 11 000 and 31 000 tonnes, without showing a clear trend. Since 1997 the catches of ALB have increased, and in 2002 the maximum catch of 42 749 tonnes was taken. From 1985 to 1992 large quantities of ALB were taken by drift gillnets[9]. Drift gillnetting ceased on the high seas in 1992, following United Nations General Assembly Resolution 46/215 (Large-scale pelagic drift-net fishing and its impact on the living marine resources of the world's oceans and seas). ALB are caught almost entirely by longlining in the IO. The principal fishing countries or entities in 2002 were the Taiwan Province of China (27 300 tonnes), Japan (3 200 tonnes), Indonesia (2 900 tonnes) and Belize (2 600 tonnes).

Stock status - No assessment has been conducted for ALB by the IOTC. Due to increasing catches of ALB in recent years, during the 7th Session of the IOTC in 2002 its secretariat was asked to prepare a document on the status of ALB. The IOTC convened a Working Party on Temperate Tunas in 2004.

2002 catch (tonnes) - Total = 42 749 (LL = 41 948; PS = 735; TROLL = 4; OTHER = 62).

Maximum annual catch (tonnes) - Taken in 2002 (see above).

Catch-related reference point (tonnes) - Unknown.

Stock size - Unknown.

Fishing mortality - Unknown.

Management recommendations/regulations - No management recommendations or regulations have been adopted.

Stock status summary - Stock size: unknown. Fishing mortality: unknown.

Outlook - Unknown.

Bigeye (BET) in the Indian Ocean (IO)

FIGURE AI.21
Cumulative catches of BET, by gear, in the IO


FIGURE AI.22
BET catches, by gear, in the IO

Historical catches - The catches of BET in the IO have increased steadily, except during the 1969-1973 period, when they declined by almost 50 percent from the 1968 level of 37 000 tonnes (Figure AI.21). In 1992 the catch (72 000 tonnes) was almost double that of the previous year, and after that, until 1999, the catches increased more rapidly, mainly as a consequence of the introduction of FADs. After 1999, when the maximum catch of 150 000 tonnes was taken, the catches decreased precipitously. The 2002 catch, 122 842 tonnes, was about 81 percent of the maximum catch.

The principal fishing countries or entities employed the following methods of fishing in 2002: longlining, the Taiwan Province of China (42 300 tonnes), Indonesia (21 300 tonnes) and Japan (14 000 tonnes); purse seining, the European Union (France and Spain) (19 000 tonnes). Most BET catches by purse seiners are made around FADs and are composed of juveniles.

Stock status - In 2001 the third session of the WPTT of the IOTC conducted a stock assessment, using age-structured production models. In 2002 and 2003 the stock indicators were updated in accordance with new information that had been obtained after 2001. Various uncertainties in the assessments conducted were identified.

2002 catch (tonnes) - Total = 122 842 (LL = 94 283; PS = 27 542; PL = 958; TROLL = 12; OTHER = 47).

Maximum annual catch (tonnes) - Total = 150 122 (LL = 111 015; PS = 38 319; PL = 604; TROLL = 39; OTHER = 145) in 1999.

Catch-related reference point (tonnes) - 102 000 (MSY).

Stock size - The stock size is estimated to be significantly greater than that corresponding to the MSY. This estimation is substantially uncertain, however. The recruitment has increased in recent years, but there is also significant uncertainty in its estimation.

Fishing mortality - F is currently below FMSY, but the catches in recent years have exceeded MSY because the stock size is greater than BMSY, and is not in equilibrium with present F. However, there are large uncertainties associated with the estimates of FMSY and the current F.

Management recommendations/regulations - Despite WPTT's fifth session recommendation that the catches of BET by all gears, particularly those that take juvenile BET around floating objects, be reduced, no management resolutions to reduce the catches of BET have been adopted.

Stock status summary - Stock size: possibly above its reference point. Fishing mortality: possibly below its reference point.

Outlook - The latest assessments suggest that reductions in purse-seine fishing mortality on juveniles could lead to increases in long-term yield and SSB, while decreases in longline fishing mortality could lead to an increase in SSB. The present catches are regarded as not sustainable in the long-term. It is foreseen that when the stock size reaches equilibrium (in 4 to 5 years) with a lower level of abundance, the catches will decrease below MSY, because the current F is below FMSY.

Skipjack (SKJ) in the Indian Ocean (IO)

FIGURE AI.23
Cumulative catches of SKJ, by gear, in the IO


FIGURE Al.24
SKJ catches, by gear, in the IO

Historical catches - The catches of SKJ in the IO increased steadily until 1968 (Figure AI.23). Between 1968 and the early 1980s they remained at about 50 000 tonnes per year. After that they increased sharply, mainly because of the rapid expansion of purse-seine fishing and the introduction of FADs. About 80 percent of purse-seine catches are currently taken in association with FADs. The maximum catch, 482 245 tonnes, was taken in 2002. The principal fishing countries or entities employed the following methods of fishing in 2002: purse seining, the European Union (France and Spain) (149 200 tonnes); pole-and-line fishing, the Maldives (113 650 tonnes); gillnetting, Sri Lanka (42 900 tonnes) and Iran (23 100 tonnes); other gear, Indonesia (43 500 tonnes) and the Seychelles (29 900 tonnes).

Stock status - In 2003, as in earlier years, the fifth session of the WPTT of the IOTC was unable to conduct a full stock assessment for SKJ in the IO due to the lack of sufficient data.

2002 catch (tonnes) - Total = 482 245 (PS = 235 609; PL = 113 658; TROLL = 4 208; LL = 75; OTHER1 = 128 695).

Maximum annual catch (tonnes) - Taken in 2002 (see above).

Catch-related reference point (tonnes) - Unknown.

Stock size - Unknown.

Fishing mortality - Unknown.

Management recommendations/regulations - The WPTT has not made any specific management recommendations for SKJ. The information presented suggests that there is no need for concern about the status of SKJ.

Stock status summary - Stock size: unknown. Fishing mortality: unknown.

1 Mainly gillnets and unclassified gears.

Outlook - SKJ is generally considered to be very resistant to overfishing. In spite of the rate of increase in catches (Figure AI.23), there is no evidence of overexploitation. It is possible that even greater catches are sustainable. However, because SKJ are caught with juvenile BET and YFT, the effects on these two species should be considered when contemplating increasing the fishing effort in order to catch more SKJ.

Yellowfin (YFT) in the Indian Ocean (IO)

FIGURE AI.25
Cumulative catches of YFT, by gear, in the IO


FIGURE AI.26
YFT catches, by gear, in the IO

Historical catches - The catches of YFT in the IO averaged about 45 000 tonnes per year from 1955 to 1983, with a peak of 90 000 tonnes in 1968 (Figure AI.25).

The catch increased sharply from 1983 to 1993, when the maximum catch of more than 350 000 tonnes was taken, which was due mainly to exceptionally high catches in the northern Arabian Sea by longliners of the Taiwan Province of China. The upward trend of 1983-1993 was the consequence of the introduction of purse seiners, mainly of the European Union, to the IO. About half of the YFT caught by purse seiners in the IO is taken around FADs.

The catches decreased after 1993, with some fluctuations, and the catch of 2002 was about 80 percent of the maximum catch.

The principal fishing countries or entities employed the following methods of fishing in 2002: purse seining, the European Union (France and Spain) (91 900 tonnes); longlining, Taiwan Province of China (28 900 tonnes), Indonesia (28 700 tonnes) and Japan (15 200 tonnes); gillnetting, Iran (19 000 tonnes), Sri Lanka (17 400 tonnes) and Oman (11 000 tonnes); pole-and- line fishing, the Maldives (16 300 tonnes).

Stock status - In 2002 a comprehensive assessment of YFT was conducted by the fourth session of the WPTT of the IOTC. The results obtained with the various methods differed, but the overall conclusions were consistent. In 2003 the stock indicators were updated in accordance with new information that had been obtained after 2002.

2002 catch (tonnes) - Total = 308 477 (PS = 142 271; OTHER1 = 59 019; LL = 82 119; PL = 20 544; TROLL = 4 524).

Maximum annual catch (tonnes) - Total = 386 056 (LL = 203 104; PS = 128 634; OTHER = 41 145; PL = 9 275; TROLL = 3 898) in 1993.

Catch-related reference point (tonnes) - MSY between 280 000 and 350 000.

Stock size - The YFT biomass has been substantially declining since at least the mid-1980s.

Fishing mortality - Since the early 1980s, there has been a continuous increase in F, but no reliable estimate of FMSY has been obtained.

Management recommendations/regulations - New information presented during the fifth session of the WPTT in 2003 confirmed the previous finding that YFT are heavily exploited. The WPTT recommended that the level fishing effort directed at juvenile YFT associated with floating objects be reduced and that the effort directed at YFT not associated with floating objects not be further increased.

Stock status summary - Stock size: unknown. Fishing mortality: unknown.

1 Mainly handlines and gillnets.

Outlook - The current catches of YFT in the IO are sustainable, provided that the fishing effort, especially that directed toward juvenile fish associated with FADs, is not further increased.

Pacific Ocean

Albacore (ALB) in the North Pacific Ocean (NPO)

FIGURE AI.27
Cumulative catches of ALB, by gear, in the NPO


FIGURE AI.28
ALB catches, by gear, in the NPO

Historical catches - Catches of ALB in the NPO peaked in 1976 at 125 000 tonnes, and then declined to 38 000 tonnes in 1991 (Figure AI.27). The catches increased later in the 1990s, and reached 120 000 tonnes in 1999. Since then catches have oscillated between about 80 000 and 90 000 tonnes. The 2002 catch was about 65 percent of the maximum catch. Catches by drift gillnets were very high during the late 1980s and early 1990s. In 1992 the General Assembly of the United Nations imposed a global moratorium on fishing with drift gillnets on the high seas, and since then the catches by this gear have been almost negligible. The principal fishing countries or entities employed the following methods of fishing in 2002: longlining, Japan (29 500 tonnes) and Taiwan Province of China (7 200 tonnes); pole-and-line fishing, Japan (29 600 tonnes); troll fishing, United States (7 400 tonnes) and Canada (3 200 tonnes).

Stock status - A virtual population analysis for ALB in the NPO was conducted in 2002 by the 18th North Pacific Albacore Workshop. Growing concern about the uncertainties in the stock assessment was expressed during the workshop.

2002 catch (tonnes) - Total = 82 236 (LL = 37 476; PL = 29 987; TROLL = 10 663; PS = 856; OTHER1 = 3 254).

Maximum annual catch (tonnes) - Total = 125 622 (PL = 88 041; LL = 17 958; TROLL = 16 183; PS = 1 381; OTHER = 2 059) in 1976.

Catch-related reference point (tonnes) - Unknown.

Stock size - The present biomass (510 000 tonnes) is almost 40 percent greater than that estimated for 1975, the first year for which such estimates are available. However, it is uncertain whether this biomass is above or below that corresponding to the MSY.

Fishing mortality - The estimates of the current F exceed some commonly used indicators of overfishing, e.g. F30% and F40%2.

Management recommendations/regulations - No recommendations have been made.

Stock status summary - Stock size: unknown. Fishing mortality: possibly above its reference point.

1 Mainly gillnets (driftnets) and sport fishing gears.
2 The fishing mortality that will reduce the equilibrium spawning potential per recruit to X% of what it would be without any fishing. F35% has been recommended as a proxy for FMSY.

Outlook - It has been suggested that the biological productivity of ALB in the NPO has increased. Biomass projections were conducted, assuming constant annual fishing mortalities equal to those estimated for 2000. The biomass projections were computed under two scenarios involving: (1) high recruitment (sampled randomly from the recruitments estimated for 1990 to 1997) and (2) low recruitment (sampled from the recruitment series estimated for 1975 to 1989). Under the high-recruitment scenario, the biomass is expected to remain essentially at its 2001 level. Under the low-recruitment scenario, the biomass is expected to decline. In either case, the uncertainty is high; the biomass may deviate considerably from the predicted trend.

Albacore (ALB) in the South Pacific Ocean (SPO)

FIGURE AI.29
Cumulative catches of ALB, by gear, in the SPO


FIGURE AI.30
ALB catches, by gear, in the SPO

Historical catches - After an increase during the 1950s, the catches of ALB in the SPO have been relatively constant since early 1960s (Figure AI.29). The maximum catch, 53 000 tonnes, was taken in 1989, mainly due to a sharp increase in catches by drift gillnets. In 1992 the General Assembly of the United Nations imposed a global moratorium on fishing with drift gillnets on the high seas, and since then the catches by this gear have been almost negligible. The catches of ALB have been increasing since 1996. The 2002 catch, 51 000 tonnes, was 97 percent of 1989 maximum catch. The principal fishing countries or entities employed the following methods of fishing in 2002: longlining, Fiji and the Taiwan Province of China (8 000 tonnes each), American Samoa (6 000 tonnes), Japan (4 800 tonnes), French Polynesia (4 600 tonnes) and Samoa (4 400 tonnes); trolling, New Zealand (3 000 tonnes) and the United States (1 000 tonnes).

Stock status - A stock assessment for ALB in the SPO was conducted in 2003 and presented to the 16th meeting of the SCTB of the SPC. The results were similar to those of 2002.

2002 catch (tonnes) - Total = 50 858 (LL = 45 969; TROLL = 4 477; PL = 262; OTHER = 150).

Maximum annual catch (tonnes) - Total = 52 576 (LL = 22 238; TROLL = 8 370; OTHER1 = 21 968) in 1989.

Catch-related reference point (tonnes) - Unknown.

Stock size - The biomass has been declining since the late 1970s, reaching historic low levels during recent years. This is largely the result of declining recruitment since the mid-1970s. Its negative correlation with El Niño events may explain the low recruitment rates during the 1980s and 1990s. The current biomass is about 60 percent of that during the early 1950s.

Fishing mortality - As longlining is the predominant method of fishing, F is greater for adult than for juvenile ALB. F has increased strongly, especially during recent years, but it is still probably low to moderate.

Management resolutions - In spite of the fact that ALB in the SPO is only moderately exploited, there is some evidence of localized depletion around some small island states. The SCG of the WCPFC has drawn attention to this issue, which could be an important one for the small island states dependent on these resources. No management resolutions have been adopted for ALB in the SPO.

Stock status summary - Stock size: above its reference point. Fishing mortality: below its reference point.

1 Mainly gillnets (driftnets).

Outlook - The current catch levels appear to be sustainable. The exploitation rates, particularly for juvenile fish, appear to be low, but data for the fishery provide little information on the MSY. The catches are likely to continue to increase with further increases in fishing effort, although the extent to which the effort and catches could be increased is unknown. The recruitment and vulnerability to longlining appear to be strongly affected by environmental conditions. It is possible that the stock is now entering a more productive (La Niña-dominated) phase with respect to recruitment.

Bigeye (BET) in the Eastern Pacific Ocean (EPO)

FIGURE AI.31
Cumulative catches of BET, by gear, in the EPO


FIGURE AI.32
BET catches, by gear, in the EPO

Historical catches - The catches of BET in the EPO increased from 1954 to 1978, showing quite wide fluctuations (Figure AI.31). After a period of decreasing catches from 1978 to 1984, the catches almost doubled during the next two years, exceeding 100 000 tonnes for the first time in 1986. Since then the catches have fluctuated widely, without a clear trend. The 2002 catch, 73 000 tonnes, was about 67 percent of the maximum catch of 110 000 tonnes in 2000. The principal fishing countries employed the following methods of fishing in 2002: longlining, Japan (29 800 tonnes); purse-seining, Ecuador (18 500 tonnes), Spain (4 700 tonnes), Vanuatu (1 900 tonnes), the United States (1 700 tonnes) and Panama (1 300 tonnes).

Stock status - The most recent stock assessment for BET in the EPO was conducted by the IATTC in 2003. At the time of the assessment, data for recent longline catches for important parts of the fleet were not available, so the results of the assessment should be interpreted with caution.

2002 catch (tonnes) - Total = 73 416 (LL = 37 786; PS = 35 630).

Maximum annual catch (tonnes) - Total = 109 596 (PS = 70 153; LL = 39 443) in 2000.

Catch-related reference point (tonnes) - Total AMSY = 77 000 (PS = 48 000; LL = 29 000). This is based on the recent fishing mortality patterns and mix of gears.

Stock size - In January 2003 the SSB of BET was greater than that corresponding to the AMSY, but it was forecast that it would be below that level by the end of 2003. The biomass of 1+-year-old BET has been reduced by fishing, and it was predicted that it would reach its lowest observed level (185 000 tonnes) by the end of 2003. This decrease in biomass has been most rapid since 2000, due to a series of weak year classes. The SSB has followed a similar trend, but with a lag of 2 to 3 years, and it is predicted that it will continue to decline over the next few years to below the level corresponding to the AMSY. The abundance of BET recruits does not seem to be related to the SSB. The recruitment is variable, and the mechanisms that explain this variation have not been identified.

Fishing mortality - On average, F for BET less than about 5 years old has increased substantially since 1993, due to the expansion of the purse-seine fisheries that catch BET in association with floating objects. F for fish more than about 6 years old has remained relatively constant.

Management recommendations/regulations - Considering that the studies of YFT and BET show that the current fishing effort exceeds that corresponding to the AMSY for both species, if recruitment is moderately dependent on the amount of spawning, it was decided at the 71st meeting of the IATTC (October 2003) to:

i) close the purse-seine fishery in a part of the EPO1 from 1 December 2003 to 31 December 2003, and in the entire EPO from 1 August 2004 to 11 September 2004 and

ii) ensure that the longline catch of BET in the EPO in 2004 would not exceed that of 2001.

Stock status summary - Stock size: above its reference point. Fishing mortality: above its reference point.

1 From the intersection of longitude 95°W with the west coast of the Americas south to latitude 10°N, then west to longitude 120°W, then south to latitude 5°S, then east to longitude 100°W, then north to latitude 5°N, then east to longitude 85°W, and finally north to the intersection with the west coast of the Americas.

Outlook - If the fishing mortality is proportional to the fishing effort, and the current patterns of age-specific selectivity are maintained, the level of fishing effort corresponding to the AMSY is estimated to be about 80 percent of the 2000-2001 effort. Such a reduction in the effort would increase the long-term average yield slightly, but it would significantly increase the spawning potential[10] of the stock.

A simulation study was conducted to estimate how various fishing scenarios would affect the stock of BET in the EPO. Several scenarios were defined by changing the present average fishing effort exerted by the purse seiners and assuming that the longline fishing effort would be constant. The increase of the purse-seine effort to 125 percent of the present one would decrease the spawning biomass ratios[11] (SBR) by about 28 percent by 2006, while the purse-seine catches would decrease by about 3 percent. Decreasing the purse-seine effort to 75 percent of the current level would increase the SBR by about 57 percent, while the purse-seine catches would decrease by about 7 percent. With the current effort level, provided that discards are avoided, it is predicted that by 2006 the catches would increase by about 5 percent.

The results from the simulation study suggest that future changes in the effort exerted by purse seiners would affect the catches by longliners. The longline catch would increase by about 18 percent by 2006 if the purse-seine effort were reduced to 75 percent of the current level. Similarly, the longline catch in 2006 would decrease by about 27 percent if the purse-seine fishing effort were increased to 125 percent of its current level.

It is predicted that changes in the fishing effort would have moderate effects on the average weight of individual BET caught in EPO. The critical weight[12] of BET is about 55 kg, while the current average weight of purse-seine caught BET is about 12 kg.

Bigeye (BET) in the Western and Central Pacific Ocean (WCPO)

FIGURE AI.33
Cumulative catches of BET, by gear, in the WCPO


FIGURE AI.34
BET catches, by gear, in the WCPO

Historical catches - The catches of BET in the WCPO averaged 35 000 tonnes until 1974, after which they increased considerably, reaching a maximum of more than 124 000 tonnes in 2002 (Figure AI.33). The principal fishing countries or entities employed the following methods of fishing in 2002: longlining, Japan (25 400 tonnes), the Republic of Korea (25 000 tonnes) and the Taiwan Province of China (18 500 tonnes); purse seining, Japan (5 800 tonnes), the United States (3 500 tonnes), Papua New Guinea (3 300 tonnes), the Philippines (3 100 tonnes) and the Taiwan Province of China (2 600 tonnes); handlines, ring nets and unclassified gears, Indonesia (11 400 tonnes) and the Philippines (6 500 tonnes).

Stock status - A stock assessment for BET in the WCPO was conducted in 2003 and presented at the 16th meeting of the SCTB of the SPC. The results of the 2003 assessment were very different from those of 2002, due to the incorporation of new data and different standardization of longline effort.

2002 catch (tonnes) - Total = 124 107 (LL = 81 701; PS = 21 072; PL = 2 927; TROLL = 277; OTHER1 = 18 130).

Maximum annual catch (tonnes) - Taken in 2002 (see above).

Catch-related reference point (tonnes) - MSY2 is estimated to be between 40 000 and 80 000, depending on recruitment regime, at the current age-specific selectivity.

Stock size - The present biomass level is above BMSY. The ratio of exploited to unexploited total biomass has been decreasing since 1950, and has approached 0.3 in recent years. The equilibrium biomass at MSY is estimated to be approximately 35 percent of the equilibrium unexploited biomass. The estimated recruitment has been increasing, with some fluctuations, since the early 1980s, reaching the greatest level in 19993.

Fishing mortality - F for both juveniles and adults has increased since the beginning of the fishery. F was formerly greater for adults than for juveniles, but during recent years they have been at about the same level. F appears to be greater than FMSY, although the assessment is uncertain.

Management recommendations/regulations - The SCG of the WCPFC has recommended that there be no further increase in F, at least until the uncertainty in the stock assessment is reduced to acceptable levels.

Stock status summary - Stock size: possibly near its reference point. Fishing mortality: possibly above its reference point.

1 Mainly handline, ring nets and unclassified gears.

2 The estimates of MSY are based on equilibrium recruitment obtained from a Beverton and Holt stock-recruitment relationship. Recent recruitment has been much greater than the equilibrium levels, and MSY would be greater if based on the greater recent recruitment.

3 This pattern may be an artefact related to the surface fishery development and/or the lack of length-frequency data for the early years.

Outlook - The present fishing mortality rates for both juveniles and adults may not be sustainable in the long-term, particularly if the recent increase in the recruitment is not permanent. Yield and biomass projections were conducted for a range of scenarios of fishing effort. The equilibrium biomass was most sensitive to modifications of the fishing mortality by the purse-seine fishery. If the purse-seine fishing mortality were doubled the equilibrium total biomass and equilibrium adult biomass would decrease to 63 and 56 percent, respectively, of their current levels, while the catches would be reduced by 22 percent. Conversely, if the purse-seine fishing mortality were halved, the equilibrium total biomass and equilibrium adult biomass would increase by 5 percent and 32 percent, respectively, while the catches would increase by 12 percent. Modifications of the longline fishing mortality would have smaller, but significant, impacts on the equilibrium biomass levels.

Pacific Bluefin (PBF) in the Pacific Ocean (PO)

FIGURE AI.35
Cumulative catches of PBF, by gear, in the PO


FIGURE AI.36
PBF catches, by gear, in the PO

Historical catches - Catches of PBF in the PO have fluctuated, without a clear trend, since the early 1950s (Figure AI.35). Catches of more than 30 000 tonnes were taken during the early and mid 1960s, and during the late 1970s and early 1980s. After a period of low catches during the late 1980s and early 1990s, attaining the minimum catch of around 8 000 tonnes in 1990, the catches have recovered to a certain extent, but in 2001 and 2002, the catches have decreased again. The 2002 catch was about 48 percent of the 1981 maximum catch. The principal fishing countries or entities employed the following methods of fishing in 2002: purse seining, Japan (8 000 tonnes); longlining, Taiwan Province of China (1 500 tonnes) and Japan (600 tonnes); trolling, Japan (1 000 tonnes).

Stock status - A stock assessment was conducted during the third meeting of the Pacific Bluefin Tuna Working Group (2004) of the ISC. The results were uncertain, and it was possible to discuss only general trends and broad conclusions with a reasonable degree of certainty.

2002 catch (tonnes) - Total = 1 5 618 (PS = 10 446; LL = 2 138; TROLL = 982; PL = 518; OTHER1 = 1 534).

Maximum annual catch (tonnes) - Total = 32 769 (PS = 24 304; TROLL = 2 456; PL = 754; LL = 977; OTHER = 4 278) in 1981.

Catch-related reference point (tonnes) - Unknown.

Stock size - The biomass and SSB of PBF have fluctuated widely over the 51 years for which the stock assessment was carried out (1952-2002). These fluctuations are mainly the result of fluctuations in recruitment during that period. The biomass appears to have recovered from a record low level during the late 1980s to an intermediate level during recent years, largely as a result of better-than-average recruitment during the 1990s (particularly the strong 1994 year class).

Fishing mortality - The recent F is greater than Fmax. In particular, the high F for young fish (ages 0-2) and older fish (ages 6+) may be of concern with respect to maintaining a sustainable fishery in the future.

Management recommendations/regulations - The ISC recommended no further increases in F for any of the fisheries taking PBF.

Stock status summary - Stock size: possibly near its reference point. Fishing mortality: above its reference point.

1 Mainly gillnets and traps.

Outlook - The SSB has been declining since 1995 and if the estimated recent fishing mortality rates continue, the SSB is likely to continue to decline, at least from 2003 to 2005. The results of yield-per-recruit and cohort analyses indicate that greater catches could be obtained if age-0 and age-1 fish were not caught, or their catches significantly reduced. Age-0 fish occur only in the WCPO, and these are caught there by trolling gear. Age-1 fish are caught in both the WCPO and the EPO. The extent to which each fishery should reduce its fishing effort to maximize the catches, while achieving a sustainable exploitation of the stock, is not known.

Skipjack (SKJ) in the Eastern Pacific Ocean (EPO)

FIGURE AI.37
Cumulative catches of SKJ, by gear, in the EPO


FIGURE AI.38
SKJ catches, by gear, in the EPO

Historical catches - SKJ catches had been fluctuating without a clear trend until 1994, when they increased with some fluctuations (Figure AI.37). Since 1999, catches of SKJ have decreased, and the 2002 catch is about 60 percent of its maximum of 265 598 tonnes, taken in 1999. SKJ are caught almost entirely by purse seining in the EPO. In 2002 the principal fishing countries were Ecuador (77 600 tonnes) and Spain (22 000 tonnes).

Stock status - A stock assessment for SKJ in the EPO was conducted by the IATTC in 2002, but not in 2003. The assessment is still considered preliminary because (1) it is not known whether the catch per day is proportional to the abundance of the population accessible to the purse-seine fisheries, (2) it is possible that there is a population of large SKJ that is invulnerable to the fisheries, (3) the stock structure is uncertain and (4) the estimates of the biomass from the 2002 assessment are very different from those of the 2001 assessment.

2002 catch (tonnes) - Total = 158 911 (PS = 1 58 280; PL = 592; LL = 39).

Maximum annual catch (tonnes) - Total = 265 598 (PS = 262 040; PL = 2 109; LL = 96; OTHER = 1353) in 1999.

Catch-related reference point (tonnes) - AMSY and yield-per-recruit calculations suggest that maximum yields would be achievable with infinite fishing mortality, given the current selectivity patterns of the fleet.

Stock size - The biomass of SKJ has been highly variable between 1975 and 2001. A rapid increase was observed late in 1998 and in 1999, but since then it has declined to much lower levels. The SSB was considerably reduced at the beginning of 2002. The variation in the biomass is attributable mostly to changes in recruitment. The absolute biomass and the spawning biomass ratio (SBR1) of SKJ are unknown.

Fishing mortality - The current levels of F are unknown. According to a yield-per-recruit analysis, FMSY would be infinite.

Management recommendations/regulations - At the 71st meeting of the IATTC (October 2003) it was decided to close the purse-seine fishery in a part of the EPO2 from 1 December 2003 to 31 December 2003, and in the entire EPO from 1 August 2004 to 11 September 2004 (see the section on BET in the EPO). This resolution was adopted to avoid increases in fishing effort for YFT and BET, but these species are taken together with SKJ.

Stock status summary - Stock size: unknown. Fishing mortality: unknown.

1 The ratio of spawning biomass during a period of harvest to that which might accumulate in the absence of fishing.

2 From the intersection of longitude 95°W with the west coast of the Americas south to latitude 10°N, then west to longitude 120°W, then south to latitude 5°S, then east to longitude 100°W, then north to latitude 5°N, then east to longitude 85°W, and finally north to the intersection with the west coast of the Americas.

Outlook - Regardless of the reduction of SSB in 2002, there is no evidence of overexploitation of SKJ. The critical weight[13] is less than the average weight at recruitment to the main fisheries. Further increases in the catches of SKJ in the EPO could be sustainable, provided that further increases in the catches of BET and YFT are avoided. The historical biomass of SKJ was driven by fluctuations in the recruitment, and, because of this, no projections of future biomass have been provided by the IATTC.

Skipjack (SKJ) in the Western and Central Pacific Ocean (WCPO)

FIGURE AI.39
Cumulative catches of SKJ, by gear, in the WCPO


FIGURE AI.40
SKJ catches, by gear, in the WCPO

Historical catches - Catches of SKJ in the WCPO increased greatly from 1950 to 2002 (Figure AI.39). The upward trend became much more pronounced during the early 1980s, when the expansion of the purse-seine fleet began. Average annual catch during the last decade has been more than 1 000 000 tonnes. Maximum catch to date was taken in 2002. The principal fishing countries or entities employed the following methods of fishing in 2002: purse seining, Taiwan Province of China (229 400 tonnes), Japan (184 900 tonnes) and the Republic of Korea (162 000 tonnes); pole-and-line fishing, Indonesia (167 000 tonnes) and Japan (103 000 tonnes); handline, ring nets and unclassified gears, Indonesia and the Philippines (45 000 tonnes each).

Stock status - A stock assessment for SKJ in WCPO was conducted in 2003 and presented to the 16th meeting of the SCTB of the SPC. Some concern has been expressed about the model's ability to produce accurate estimates for some population parameters, particularly their absolute values. Due this concern, the Skipjack Research Group (SRG) of the SCTB has relied largely on trends and ratios, rather than absolute estimates from the model, in making conclusions about the stock status.

2002 catch (tonnes) - Total = 1 320 692 (PS = 931 105; PL = 280 377; LL = 4 200; TROLL = 217; OTHER1 = 104 793).

Maximum annual catch (tonnes) - Taken in 2002 (see above).

Catch-related reference point (tonnes) - 1 600 000 (MSY2).

Stock size - The level of the biomass of SKJ is closely related to the recruitment. The biomass has increased since 1972, with maximum levels in the mid-1980s and the late 1990s, as a result of increases in recruitment. The present biomass is well above BMSY. The difference between fished and unfished biomass has generally been in the range of 20 to 25 percent in recent years. The current recruitment is high, probably due to recent El Niño events.

Fishing mortality - F is less for juveniles than for adults. F for both juveniles and adults increased from 1972 to 1997, after which they both decreased, which is attributed to an increase in biomass. F is currently about 0.20 to 0.25 per year.

Management recommendations/regulations - In 2003 the SCG of the WCPFC has expressed a concern that further increases in SKJ purse-seine catches may result in increased catches of juvenile BET and YFT, which should be avoided (see the sections on BET and YFT in the WCPO). No management resolutions have been adopted for SKJ.

Stock status summary - Stock size: above its reference point. Fishing mortality: below its reference point.

1 Mainly handlines, ring nets and unclassified gears.

2 MSY estimates are based on equilibrium recruitment obtained from a Beverton and Holt stock-recruitment relationship. Recent recruitment has been much higher than the equilibrium levels, and MSY would be higher if based on the higher recent recruitment.

Outlook - Analyses of the stock suggest that SKJ in the WCPO is in a healthy state. Increases in fishing mortality would likely result in increases in the catches. Due to the extremely high productivity of this stock and its high resilience to fishing, the catches may be much more dependent on economic factors than on biological constraints. However, because SKJ is being fished together with YFT and BET, fisheries management measures for these species may have an impact on the future catches of SKJ.

Yellowfin (YFT) in the Eastern Pacific Ocean (EPO)

FIGURE AI.41
YFT cumulative catches, by gear, in EPO


FIGURE AI.42
YFT catches, by gear, in the EPO

Historical catches - The catches of YFT in the EPO increased from the early 1960s to 1976 (Figure AI.41). The catch rates were low during 1978-1983, due to concentration of fishing effort on small fish, and a major El Niño episode, from mid-1982 to the late 1983, which made the fish less vulnerable to capture. The catches increased from 1983 to 1988, decreased from 1988 to 1994, and then increased again to a maximum of 420 000 tonnes in 2002. The catches are made mostly by purse seining. The principal purse-seine fishing countries catching YFT in the EPO in 2002 were Mexico (149 900 tonnes), Venezuela (120 300 tonnes), Ecuador (39 400 tonnes), Colombia (30 000 tonnes) and Panama (20 400 tonnes).

Stock status - A stock assessment for YFT was carried out by IATTC in 2003. Its results are similar to those of previous assessments.

2002 catch (t) - Total = 429 299 (PS = 418 280; LL = 10 091; PL = 928).

Maximum annual catch (t) - Taken in 2002 (see above).

Catch-related reference point (t) - 250 000. This AMSY is based on average recruitment, the recent fishing mortality patterns and mix of gears.

Stock size - The YFT stock has experienced two different productivity regimes (greater recruitment during 1984-2001 than during 1975-1983). Particularly strong cohorts entered the fishery in 1998, 1999 and 2000, which increased the biomass in 1999 and 2000. However, these cohorts have now moved through the fishery, so the biomass decreased in 2001 and 2002. Currently the spawning biomass ratio1 (SBR) appears to be slightly less than the SBR corresponding to the AMSY, but this conclusion should be taken with caution, due to uncertainties in the estimation of the actual SBRs and SBRAMSY.

Fishing mortality - F has been stable in recent years (slightly below FAMSY), and is greatest for age-3 and age-4 fish.

Management recommendations/regulations - At the 71 st meeting of the IATTC (October 2003) it was decided to close the purse-seine fishery in a part of the EPO2 from 1 December 2003 to 31 December 2003, and in the entire EPO from 1 August 2004 to 11 September 2004 (see the section on BET in the EPO).

Stock status summary - Stock size: near its reference point. Fishing mortality: near its reference point.

1 The ratio of spawning biomass during a period of harvest to that which might accumulate in the absence of fishing.

2 From the intersection of longitude 95°W with the west coast of the Americas south to latitude 10°N, then west to longitude 120°W, then south to latitude 5°S, then east to longitude 100°W, then north to latitude 5°N, then east to longitude 85°W, and finally north to the intersection with the west coast of the Americas.

Outlook - The average weight of the YFT in the catch is much less than the critical weight (36 kg).

The present fishing effort is estimated to be less than that corresponding to AMSY, but increasing the effort would probably not produce noticeable increases in the catches. Due to the large recruitment of 1998-2000, the current catches are greater than the AMSY.

The SBR is at about the level corresponding to the AMSY. Projections with the current fishing effort and average recruitment indicate that the stock will increase to a SBR level above that corresponding to the AMSY. However, because the biomass is declining from the relatively high level associated with the strong recruitments during the late 1990s, and because there is some uncertainty about recent and future recruitment and biomass levels, the present fishing mortality should not increase.

A simulation study was conducted to gain further understanding of how several scenarios would affect the stock of YFT in the EPO. These scenarios were defined by changing the average recent effort exerted by the purse-seine fleet and assuming that the longline effort would be constant. An increase of the surface effort by 25 percent would decrease the SBR by about 16 percent by the end of 2007, while the catches would increase by only 3 percent. A decrease in the purse-seine effort by 25 percent would increase the SBR by about 21 percent, while the catches would decrease by 7 percent. With the present effort, it is predicted that at the end of 2007, the SBR would remain, on average, greater than SBRAMSY. Changes in the amount of effort exerted by the surface fleet would substantially affect the longline catches. The longline catch in 2007 would increase by about 31 percent, if the surface effort were reduced by 25 percent. Similarly, the catch during 2007 would decrease by about 22 percent, if the surface effort were increased by 25 percent. Not catching unmarketable YFT around floating objects (or ensuring that the discarded fish would survive) would not significantly increase the spawning stock. Changes in the fishing effort would have moderate effects on the average weight of the fish caught.

Yellowfin (YFT) in the Western and Central Pacific Ocean (WCPO)

FIGURE AI.43
Cumulative catches of YFT, by gear, in the WCPO


FIGURE AI.44
YFT catches, by gear, in the WCPO

Historical catches - The catches of YFT in the WCPO clearly increased from 1950 to 2002 (Figure AI.43). Due to the expansion of the purse-seine fleet, this upward trend accelerated during the late 1970s, with the exception of 1996, when the catches dropped to a relatively low level (325 000 tonnes). The 2002 catch, 446 000 tonnes, is about 89 percent of the maximum catch, 501 000 tonnes, taken in 1998. The principal fishing countries or entities employed the following methods of fishing in 2002: purse seining, the Philippines (29 000 tonnes), the United States (28 600 tonnes), Papua New Guinea (26 200 tonnes), the Taiwan Province of China (26 100 tonnes), Japan (21 300 tonnes) and the Republic of Korea (17 500 tonnes); longlining, the Taiwan Province of China (24 000 tonnes), Japan (17 000 tonnes), the Republic of Korea (13 800 tonnes) and Indonesia (11 200 tonnes); pole-and-line fishing, Indonesia (14 000 tonnes); handlining, the Philippines (67 000 tonnes); unclassified gears, mostly Indonesia (105 000 tonnes).

Stock status - A stock assessment for YFT in WCPO was conducted in 2003 and presented at the 16th meeting of the SCTB of the SPC. Its results are consistent with those obtained in 2002. However, the SCTB and the SCG of the WCPFC identified important gaps in the data from Indonesia and the Philippines. This lack of data has contributed substantially to the uncertainty of the assessments of YFT in the WCPO.

2002 catch (tonnes) - Total = 446 122 (PS = 170 492; LL = 80 039; PL = 17 815; TROLL = 595; OTHER1 = 177 181).

Maximum annual catch (tonnes) - Total = 501 438 (PS = 266 148; LL = 65 967; PL = 17 256; TROLL = 1 173; OTHER = 150 894) in 1998.

Catch-related reference point (tonnes) - MSY between 381 000 and 554 000.

Stock size - The biomass has been declining over time, but remains above BMSY. The present biomass is 20 to 35 percent less than that in the absence of fishing. However, the depletion is greater in equatorial regions (nearly 50 percent). The recruitment has been fluctuating since the 1960s. The trends in recruitment are sensitive to the type of standardization procedure used to standardize the longline effort for the stock assessment analysis.

Fishing mortality - The average F for both juveniles and adults increased strongly over the period of exploitation. However, F/FMSY is still below 1, indicating that the YFT stock in the WCPO is not overfished.

Management resolutions - The SCG recommended in 2003 that further increases in fishing mortality be avoided to reduce the risk of the YFT stock becoming overfished. No management resolutions have been adopted.

Stock status summary - Stock size: above its reference point. Fishing mortality: near its reference point.

1 Mainly handline and unclassified gears.

Outlook - The present fishing pattern is sustainable. The biomass should remain above that corresponding to the MSY. This situation is due mainly to the low levels of exploitation in the sub-equatorial regions of the WCPO.

Yield projections indicate that increases in the fishing mortality would not result in long-term increases in the catches, and might result in overexploitation. These projections show that the equilibrium biomass is most sensitive to changes in the fishing mortality of the Indonesian fishery. The doubling of the Indonesian fishing mortality would decrease the equilibrium total biomass and adult biomass by 22 percent and 26 percent, respectively, from the current levels. Reducing the Indonesian fishing mortality by half would increase the equilibrium total and adult biomass by 13 percent and 16 percent, respectively, from the current levels. The third most important impact on the equilibrium biomass levels would be in response to changes to the purse-seine fishery. Changes to the longline fishery would have the least impact on the equilibrium biomass levels. Doubling the present longline effort would reduce the total and adult equilibrium biomass levels by only 2 percent and 4 percent, respectively.

The use of FADs increased during the late 1990s, and the mortality rates of juvenile YFT increased accordingly. In addition, deployment of FADs increases the difficulties of assessing the trends in CPUE (causing abrupt changes in catchability), adding uncertainty to the stock assessment. The extent to which this problem could affect the sustainability of the stock in the long-term should be studied further.

All Oceans

Southern bluefin (SBF)

FIGURE AI.45
Cumulative catches of SBT, by gear


FIGURE AI.46
SBF catches, by gear

Historical catches - After a rapid increase in the catches during the 1950s, a maximum catch of 81 605 tonnes was taken in 1961 (Figure AI.45). After that the SBF catches declined significantly, with some fluctuations, until 1990. From 1990 to 2001 the catches fluctuated between 13 500 and 19 500 tonnes. The decline was mainly due to the introduction of a total allowable catch (TAC) in 1989 by the three original members of the CCSBT, Australia, Japan and New Zealand, that reduced the fishing mortality. The growth in this latter period was due to increasing fishing effort by non-members, two of which, the Republic of Korea and the Taiwan Province of China, have since joined CCSBT and stabilized their catches at reduced levels. The 2002 catch (15 193 tonnes) was approximately 20 percent of the 1961 maximum catch. In 2002 the principal fishing countries or entities fishing SBF with longlines were Japan (6 192 tonnes), Indonesia (1 691 tonnes), the Taiwan Province of China (1 137 tonnes), the Republic of Korea (746 tonnes) and New Zealand (450 tonnes). Of these, only Indonesia is not a member of the CCSBT. Australia accounted for most of purse-seine catch, 4 683 tonnes, in 2002.

Stock status - The last full stock assessment of SBT was conducted in 2001. After that a range of stock status indicators were reviewed each year, and the results indicated that there had been no significant changes in the state of the stock since 2001. A new full stock assessment was to be undertaken in 2004.

2002 catch (tonnes) - Total = 15 193 (SURF1 = 4 683; LL = 10 510).

Maximum annual catch (tonnes) - Total = 81 605 (SURF = 3 678; LL =77 927) in 1961.

Catch-related reference point (tonnes) - Unknown.

Stock size - The SSB in 1999 was estimated to be between 5 and 12 percent of the 1960 level. National scientists are not certain of the significance of this level, which appears to have stabilized, with a possible upturn in recent years. The recruitment appears to have declined during the 1990s, especially during 1999 and 2000. Acoustic surveys (2001 and 2002), CPUE data for the Australian surface fishery (2002 and 2003) and aerial surveys (2003) suggest that this decline may have continued during 2001, 2002 and 2003. However, there are some doubts about the validity of these surveys as indices of the global recruitment.

Fishing mortality - F has been reduced since 1988, largely due to decisions by the CCSBT on TACs and national allocations. Recent Fs have not been unduly high, given that the catches since 1990 appear to have stabilized the SSB. It appears that the current removals are close to surplus production. However, the recent Fs may not be low enough to allow the spawning stock to increase.

Management recommendations/regulations - The members of the CCSBT agreed to a TAC of 14 030 tonnes for members, and an additional global allocation for cooperating non-members, of 900 tonnes for the 2003-2004 fishing season. In addition, Australia has introduced individual transferable quotas (ITQs) for SBF, and New Zealand plans to do so as well, beginning in October 2004. Other members of the CCSBT manage their fisheries through a mixture of vessel limits, limits on days fished and area closures.

Stock status summary - Stock size: below its reference point. Fishing mortality: near to above its reference point.

1 Surface gear refers mainly to PS and PL, with a progressive increase in PS catching from 1992 to almost exclusively PS from 1999.

Outlook - According to projections conducted in 2001, with the global catch of about 15 500 tonnes, there is an equal probability that the stock could decline or increase. It was also estimated that there is little chance that the spawning stock can be rebuilt to the 1980 level by 2020 without substantial quota reductions.

Sources of Information

Atlantic Ocean

Albacore

ICCAT. 2003. Report of the Standing Committee on Research and Statistics (SCRS), pp. 40-49. Madrid, Spain. http://www.iccat.es/Documents/ALB.pdf

ICCAT. 2003. Report of the 2003 Albacore stock assessment session. Madrid, Spain. http://www.iccat.es/Documents/DET_alb.pdf

Atlantic Bluefin

ICCAT. 2003. Report of the Standing Committee on Research and Statistics (SCRS), pp. 50-64. Madrid, Spain. http://www.iccat.es/Documents/BFT.pdf

ICCAT. 2003. Report of the 2002 Atlantic bluefin tuna stock assessment session. Col. Vol. Sci. Pap. ICCAT, 55(3): 710-937. Madrid, Spain. http://www.iccat.es/Documents/DET_bft.pdf

Bigeye

ICCAT. 2003. Report of the Standing Committee on Research and Statistics (SCRS), pp. 24-31. Madrid, Spain. http://www.iccat.es/Documents/BET.pdf

ICCAT. 2003. Report of the 2002 ICCAT Bigeye tuna stock assessment session. Col. Vol. Sci. Pap. ICCAT, 55(3): 710-937. Madrid, Spain. http://www.iccat.es/Documents/DET_bet.pdf

Skipjack

ICCAT. 1999. Report of the ICCAT SCRS Skipjack stock assessment session. Madrid, Spain. http://www.iccat.es/Documents/DET_skj.pdf

ICCAT. 2003. Report of the Standing Committee on Research and Statistics (SCRS), pp. 32-39. Madrid, Spain. http://www.iccat.es/Documents/SKJ.pdf

Yellowfin

ICCAT. 2003. Report of the Standing Committee on Research and Statistics (SCRS), pp. 16-23. Madrid, Spain. http://www.iccat.es/Documents/YFT.pdf

ICCAT. 2003. Report of the 2003 Atlantic yellowfin tuna stock assessment session. Madrid, Spain. http://www.iccat.es/Documents/DET_yft.pdf

Indian Ocean

Albacore

IOTC. 2002. Report of the 5th Session of the Scientific Committee. Victoria, Seychelles. http://www.iotc.org/English/documents/miscellaneous/all_reports.php

Bigeye

IOTC. 2002. Report of the 5th Session of the Scientific Committee, pp. 39-46. Victoria, Seychelles. http://www.iotc.org/English/documents/miscellaneous/all_reports.php

IOTC. 2003. Report of the 5th Session of the IOTC Working Party on Tropical Tunas. Victoria, Seychelles. http://www.iotc.org/English/meetings/sc/sccurrentdocs.php

Skipjack

IOTC. 2000. Research plan to study stock structure of skipjack (Katsuwonus pelamis) in the Indian Ocean by genetic analyses. IOTC Proceedings, 3: 414-416. Victoria, Seychelles. http://www.iotc.org/English/documents/proceedings3/wptt.php

IOTC. 2002. Report of the 5th Session of the Scientific Committee, pp. 47-52. Victoria, Seychelles. http://www.iotc.org/English/documents/miscellaneous/all_reports.php

IOTC. 2003. Report of the 5th Session of the IOTC Working Party on Tropical Tunas, pp. 18-25. Victoria, Seychelles. http://www.iotc.org/English/meetings/sc/sccurrentdocs.php

Yellowfin

IOTC. 2002. Report of the 5th Session of the Scientific Committee, pp. 29-38. Victoria, Seychelles. http://www.iotc.org/English/documents/miscellaneous/all_reports.php

IOTC. 2003. Report of the 5th Session of the IOTC Working Party on Tropical Tunas, pp. 18-25. Victoria, Seychelles. http://www.iotc.org/English/meetings/sc/sccurrentdocs.php

Pacific Ocean

Albacore

NPAW. 2003. Report of the 18th North Pacific Albacore Workshop. Interim Scientific Committee for Tuna and Tuna-like Species in the North Pacific Ocean (ISC). La Jolla, (USA), 4-11 December 2002.

SPC. 2003. Stock assessment of albacore tuna in the south Pacific Ocean, by Labelle, M. & Hampton, J. SCTB16 Working Paper. Noumea, New Caledonia. http://www.spc.org.nc/OceanFish/Html/SCTB/SCTB16/alb1.pdf

SPC. 2003. Executive summary of the 16th Meeting of the Standing Committee on Tuna and Billfish (SCTB). Noumea, New Caledonia. http://www.spc.org.nc/OceanFish/Html/SCTB/SCTB16/Execsum.pdf

WCPFC. 2003. Report of the Scientific Coordinating Group (SCG). Noumea, New Caledonia. http://www.spc.org.nc/OceanFish/Html/SCTB/SCTB16/scg2.pdf

Bigeye

IATTC. 2003. Fourth Meeting of the Scientific Working Group. Chairman's Report. Review of Stock Assessments. La Jolla, USA. http://www.iattc.org/PDFFiles/SWG%204%20Chairs%20Report.pdf

IATTC. 2003. Status of bigeye tuna in the eastern Pacific Ocean in 2002 and outlook for 2003 by Harley, S.J. & Maunder, M. N. La Jolla, USA. http://www.iattc.org/StockAssessmentReport4ENG.htm

SPC. 2003. Stock assessment of bigeye tuna in the western and central Pacific Ocean, by Hampton, J., Kleiber, P., Takeuchi, Y., Kurota, H. & Maunder, M. SCTB16 Working Paper. Noumea, New Caledonia. http://www.spc.org.nc/OceanFish/Html/SCTB/SCTB16/bet1.pdf

SPC. 2003. Executive summary of the 16th Meeting of the Standing Committee on Tuna and Billfish (SCTB). Noumea, New Caledonia. http://www.spc.org.nc/OceanFish/Html/SCTB/SCTB16/Execsum.pdf

WCPFC. 2003. Report of the Scientific Coordinating Group (SCG). Noumea, New Caledonia. http://www.spc.org.nc/OceanFish/Html/SCTB/SCTB16/scg2.pdf

Pacific Bluefin

IATTC. 2002. Third Meeting of the Scientific Working Group. Background paper A5. La Jolla, USA. http://www.iattc.org/IATTC3rdMeetingoftheScientificWorkingGroupENG.htm

IATTC. 2002. Status of bluefin tuna in the Pacific Ocean by Bayliff, W. H. La Jolla, USA. http://www.iattc.org/StockAssessmentReport2ENG.htm

ISC. 2004. Report of the 3rd ISC Pacific Bluefin Tuna Working Group. Interim Scientific Committee for Tuna and Tuna-Like Species in the North Pacific Ocean (ISC). Honolulu, USA. http://isc.ac.affrc.go.jp/rep/ISC4Plenary06PBT.pdf

Skipjack

IATTC. 2003. Fourth Meeting of the Scientific Working Group. Chairman's Report. Review of Stock Assessments. La Jolla, USA. http://www.iattc.org/PDFFiles/SWG%204%20Chairs%20Report.pdf

IATTC. 2003. Status of skipjack tuna in the eastern Pacific Ocean in 2001 and outlook for 2002 by Maunder, M. N. La Jolla, USA. http://www.iattc.org/StockAssessmentReport4ENG.htm

SPC. 2003. Stock assessment of skipjack tuna in the western and central Pacific Ocean, by Langley, A., Ogura, M. & Hampton, J. SCTB16 Working Paper. Noumea, New Caledonia. http://www.spc.org.nc/OceanFish/Html/SCTB/SCTB16/skj1.pdf

SPC. 2003. Executive summary of the 16th Meeting of the Standing Committee on Tuna and Billfish (SCTB). Noumea, New Caledonia. http://www.spc.org.nc/OceanFish/Html/SCTB/SCTB16/Execsum.pdf

WCPFC. 2003. Report of the Scientific Coordinating Group (SCG). Noumea, New Caledonia. http://www.spc.org.nc/OceanFish/html/SCTB/SCTB16/scg2.pdf

Yellowfin

IATTC. 2003. Fourth Meeting of the Scientific Working Group. Chairman's Report. Review of Stock Assessments. La Jolla, USA. http://www.iattc.org/PDFFiles/SWG%204%20Chairs%20Report.pdf

IATTC. 2003. Status of yellowfin tuna in the eastern Pacific Ocean in 2002 and outlook for 2003, by Maunder, M. N. & Harley, S. J. La Jolla, USA. http://www.iattc.org/StockAssessmentReport4ENG.htm

SPC. 2003. Stock assessment of yellowfin tuna in the western and central Pacific Ocean, by Hampton, J. & Kleiber, P. SCTB16 Working Paper. Noumea, New Caledonia. http://www.spc.org.nc/OceanFish/Html/SCTB/SCTB16/yft1.pdf

SPC. 2003. Executive summary of the 16th Meeting of the Standing Committee on Tuna and Billfish (SCTB). Noumea, New Caledonia. http://www.spc.org.nc/OceanFish/Html/SCTB/SCTB16/Execsum.pdf

WCPFC. 2003. Report of the Scientific Coordinating Group (SCG). Noumea, New Caledonia. http://www.spc.org.nc/OceanFish/Html/SCTB/SCTB16/scg2.pdf

All Oceans

Southern Bluefin

CCSBT. 2001. Report of the Sixth Meeting of the Scientific Committee. Australia. http://www.ccsbt.org/docs/pdf/meeting_reports/ccsbt_8/report_of_sc6.pdf

CCSBT. 2003. Report of the Fourth Meeting of the Stock Assessment Group. Australia. http://www.ccsbt.org/docs/pdf/meeting_reports/ccsbt_10/report_of_sag4.pdf

CCSBT. 2003. Report of the Eighth Meeting of the Scientific Committee. Australia. http://www.ccsbt.org/docs/pdf/meeting_reports/ccsbt_10/report_of_sc8.pdf

CCSBT. 2003. Report of the Tenth Annual Meeting of the Commission. Australia. http://www.ccsbt.org/docs/pdf/meeting_reports/ccsbt_10/report_of_ccsbt10.pdf

APPENDIX II

Stock structure

The maps of distributions of the catches by the principal fishing gears presented in this appendix were produced from the Global Database of Catches of Tunas and Billfishes (described by Carocci et al. in this collection). It contains the data that FAO regularly receives from international organizations and national institutions and published, after standardization and integration, as they are. Therefore, it does not contain data for which FAO has not received proper geo-referencing or data reported in number of fishes instead of tonnes caught.

Albacore (ALB)

Atlantic Ocean - ALB is a temperate species widely distributed in the AO and MED. For the stock assessment purposes, the existence of three stocks is assumed: North and South Atlantic stocks, separated at 5°N, and a Mediterranean stock.

Indian Ocean - A single stock of ALB is assumed to occur in the IO. It is distributed in waters between 20°N and 40°S.

Pacific Ocean - There are two ALB stocks in the PO, one in the northern hemisphere and the other in the southern hemisphere. The SPO stock appears to be homogeneous, but there seem to be two subgroups of the NPO stock.

FIGURE AII.1
Albacore stocks, and distributions of the catches by the principal fishing gears in 1991 to 2001

FAO, 2003

Bigeye (BET)

Atlantic Ocean - BET are distributed over almost the entire AO between 50°N and 45°S. It is assumed that there is a single stock in the AO, but the possibility of other scenarios, such as northern and southern stocks, should not be disregarded.

Indian Ocean - A single stock of BET is assumed to occur in the IO. The distribution of the catches suggests that the range of the stock includes tropical waters, where reproductively active individuals are found, and temperate waters, usually considered to be feeding grounds.

Pacific Ocean - BET are distributed continuously from the Americas to Asia between 40°N and 40°S. In the absence of adequate information on the stock structure of BET in the PO, it has been assumed that there are two stocks, one in the EPO and the other in the WCPO. However, scientists of the IATTC and the SPC have also performed assessments based on the assumption that there is a single stock of BET in the PO.

FIGURE AII.2
Bigeye stocks, and distributions of the catches by the principal fishing gears in 1991 to 2001

FAO, 2003

Skipjack (SKJ)

Atlantic Ocean - Two stocks of SKJ, one east of 30°W and the other west of 30°W, are recognized in the AO. The boundary at 30°W was established when the SKJ fisheries were mostly coastal, but in recent years the fishery of the EAO has extended to the west of 30°W, which might imply that there is some mixing between the presently defined stocks. However, taking into account the large distances, various oceanographic features restricting such mixing, the existence of spawning areas in both the EAO and the WAO and the lack of tagging data indicating trans-Atlantic migrations, the two-stock hypothesis has been retained.

Indian Ocean - A single stock of SKJ is assumed to occur in the IO. Tagging studies indicate that there is little exchange of SKJ between the Maldives and the rest of the IO, but these results are not conclusive. Due to the need for a better understanding of the stock structure of SKJ in the IO, a genetic study is being carried out.

Pacific Ocean - There are two hypotheses for the stock structure of SKJ in the PO, a single stock with isolated subgroups or two or more separate stocks. For stock assessment purposes, it is assumed that there are two stocks of SKJ in the PO, a WCPO stock occurring west of 150°W and an EPO stock occurring east of 150°W. The WCPO has been divided into six sub-areas, thus allowing for the possibility of sub-stocks in this region.

FIGURE AII.3
Skipjack stocks, and distributions of the catches by the principal fishing gears in 1991 to 2001.

FAO, 2003

Yellowfin (YFT)

Atlantic Ocean - It is assumed that there is a single stock of YFT in the AO. This assumption is supported by trans-Atlantic movements evident from tagging data, a 40-year time series of longline catch data that indicates that YFT are distributed continuously throughout the tropical AO and time-area size-frequency data.

Indian Ocean - The stock structure of YFT in the IO is uncertain, but it is assumed for stock assessment purposes that there is a single stock. Longline catch data indicate that YFT are distributed continuously throughout the tropical IO, but there are indications, from more detailed analyses of fisheries data, that the stock structure is more complex. A study of stock structure, using DNA analyses, produced inconclusive results.

Pacific Ocean - The exchange of YFT between the EPO and the WCPO has been studied by examination of data from tagging, morphometric characteristics of the fish, catch-per-unit-of-effort (CPUE) data, sizes of fish caught, etc. The mixing of fish between the EPO and WCPO is not extensive, so, for purposes of stock assessment, it has been assumed that there are two stocks, separated at 150° W longitude. The WCPO has been divided into five-areas, thus allowing for the possibility of sub-stocks in this region.

Atlantic bluefin (BFT)

Atlantic Ocean - ICCAT established two management units for BFT in 1982. This decision was based on discontinuities in the distributions of the catches at that time and on the assumption that mixing of western and eastern BFT was limited. The two management units are separated at 45° W north of 10° N and at 25° W south of the equator, with an eastward shift in the boundary between those parallels. Later, however, it appeared that the distribution of catches across the NAO is nearly continuous. Also, evidence has accumulated that there is more mixing between the two units than previously thought, so research on the stock structure (including modeling) has continued.

FIGURE AII.4
Yellowfin stocks, and distributions of the catches by the principal fishing gears in 1991 to 2001

FAO, 2003

Pacific bluefin (PBF)

Pacific Ocean - It has been assumed that there is a single stock of PBF in the PO. Tagging studies have shown that there is considerable exchange of fish between the EPO and the WCPO. It appears that spawning occurs only in the WCPO, since larval, post-larval, and early juvenile PBF have been caught only in the WPO.

FIGURE AII.5
Atlantic and Pacific bluefin stocks, and distributions of the catches by the principal fishing gears in 1991 to 2001

FAO, 2003

Southern bluefin (SBF)

All Oceans - SBF are found throughout the southern hemisphere, mainly in waters between 30° and 50°S, but only rarely in the AO and the EPO. As SBF spawn in only one area (south of Java, Indonesia), they are managed as a single stock.

FIGURE AII.6
Southern bluefin stocks, and distributions of the catches by the principal fishing gears in 1991 to 2001

FAO, 2003


[9] Driftnets are classified in Figs. AI.19 and AI.20 as "other".
[10] The spawning potential is based on the biomass of mature fish. The age at 50-percent maturity is approximately five years.
[11] The ratio of spawning biomass during a period of harvest to that that might accumulate in the absence of fishing.
[12] The weight of individual fish corresponding to the age at which the gains due to growth exactly balance the losses due to natural mortality.
[13] The weight of individual fish corresponding to the age at which the gains due to growth exactly balance the losses due to natural mortality.

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