Atilio L. Coan, Jr.
La Jolla Laboratory
Southwest Fisheries Science Center
National Marine Fisheries Service, NOAA
La Jolla, California 92038
Total landings, catch per days fished and sizes of fish caught are reviewed for two types of USA yellowfin tuna fisheries operating in areas of the central and western Pacific through 1990. The largest of these USA fisheries is the distant-water purse-seine fishery which landed highs of 66,400 mt of yellowfin tuna in 1987, and 57,000 mt in 1990, averaged 9 mt per day fished in 1990, and caught yellowfin tuna between 25 and 186 cm.
A USA distant-water purse seine fishery, a multispecies fishery catching predominantly skipjack with lesser quantities of yellowfin and bigeye tunas, is conducted in the central and western Pacific. The carrying capacities of the majority of the purse seine vessels participating in the fishery are 1,000 metric tons (mt) or more (Doulman 1987). The purse seiners are based in either American Samoa or Guam.
Within the USA Exclusive Economic Zone (EEZ), or 200 miles of the coasts of Hawaii, American Samoa, Northern Marianas and Guam, the U.S. has artisanal fisheries for yellowfin tuna and other large pelagics (e.g., marlins, wahoo, etc.). These fisheries are mixtures of commercial, subsistence and recreational fisheries that use a variety of gears. The major gears used to catch yellowfin tuna are longline, handline and troll (Hudgins and Pooley 1987).
The purpose of this paper is to review available data on landings, fishing effort, catch per effort, sizes of fish caught and methods of data collection from these fisheries. Distant-water fisheries are reviewed from their start in 1976 to 1990 and artisanal fisheries from 1954 to 1990.
2. DISTANT-WATER FISHERIES
2.1 Total Landings
Total landings (metric tons) for the USA distant-water central and western Pacific purse seine fishery for tropical tunas are available since 1976 (Table 1). Landings for 1976 to 1978 are estimates from exploratory fishing of vessels chartered by the Pacific Tuna Development Foundation (Anon., 1977; Anon., 1979; Souter and Broadhead, 1978). Landings for 1979 to 1990 are from cannery receipts of landings or transshipments to USA canneries in American Samoa, Puerto Rico and California (Schug and Galea'i, 1987). Some vessels transship their catch directly to foreign ports such as Thailand, Japan, Indonesia, Philippines, Italy and Australia and data are gathered from canneries in those countries whenever possible. Since 1989, landings data for the distant-water fishery are more complete, due to reporting requirements of the South Pacific Regional Tuna Treaty (SPRTT) between the USA and 16 island nations that started in June, 1988 (Coan et al., 1988). There has been 100% coverage of landings since June 15, 1988.
Table 1. U.S. distant-water purse seine landings (metric tons) of tropical tunas in the central and western Pacific. Yellowfin tuna landings include some landings of bigeye tuna. Since trips that start late in one year may land their catch in the next, landings in each calendar year may contain some catches from the previous year.
- indicates that landings are not available but may be greater than zero.
* indicates values less than 10 metric tons.
Landings before 1979 are from Pacific Tuna Development Foundation exploratory fishing charters.
Landings from other U.S. vessels fishing in 1976 to 1978 are unknown.
Values in this table for 1980 to 1985 are different than those in Doulman 1987 due to inclusion here of U.S. vessels operating out of Guam and direct exports.
The USA distant-water purse seine landings of yellowfin tuna since 1979 have increased from approximately 600 mt to a high of 66,400 mt in 1987 (Figure 1, Table 1). Skipjack landings increased from 8,000 mt in 1979, to a high of 124,300 mt in 1984. Reported bigeye landings reached a high of 200 mt in 1981, but can be much higher as landings of this species are reported with yellowfin tuna landings. Estimated yellowfin tuna landings from exploratory fishing records in 1976 to 1978 are approximately 200 mt per year and may represent only a portion of the actual landings.
Data in Table 1 have not been corrected for species composition of yellowfin and bigeye tunas or for overlapping of landings between years (trips catching fish late in the year and landing their catches in the next year). Data collected for 1988 to 1990 show that approximately 4% of the 1989 yellowfin tuna landings were actually catches in 1988, and 10% of the 1990 yellowfin landings were actually catches in 1989. Current estimates from species composition samples taken under the SPRTT indicate that yellowfin landings can be between 6% and 9% bigeye tuna.
Figure 1. Landings (metric tons) of yellowfin and skipjack tunas from the U.S. distant-water central and western Pacific purse seine fishery. Bigeye tuna landings are included in yellowfin landings.
2.2 Total Effort
Total effort in number of vessels participating in the USA distant-water central and western Pacific purse seine fishery ranges from 8 to 62 during the period 1979 to 1990 (Table 2). The number of purse seiners participating in the fishery during the period 1976 to 1978 reflects only vessels fishing under an exploratory fishing charter with the PTDF and may not represent the actual number of vessels fishing in those years.
The data for 1979 to 1990 are tabulated from information on landing receipts or from licenses issued under the SPRTT. Since 1979, the number of purse seiners participating in the fishery increased from 8 to 62 in 1983, decreased to the low 30's in 1986 to 1989, and increased to 41 in 1990. Coverage of total effort data has been 100% since June 15, 1988.
2.3 Catch and Effort
The USA distant-water central and western Pacific purse seine fleet fishing logbook data have been collected by the USA tuna industry for 1976 to 1988. Data for 1979 to 1988 exist, but are currently unavailable to the public. Data are available for 1976 to 1978, but are for PTDF charters only and are not included here due to the small sample size. Data for 1987 to 1990, for operations of this fleet within the EEZs of Pacific island countries, have been published in the South Pacific Commission's Regional Tuna bulletin (SPC, 1989; SPC, 1990; SPC, 1991). Since June 15, 1988, the fleet submits logbooks as a requirement of the SPRTT (Coan et al., 1988). The data are collected, computerized and submitted to the Forum Fisheries Agency, the managing agency for the treaty. Coverage since June 15, 1988, has been 100%.
Table 2. Total number of U.S. distant-water purse seiners fishing for tropical tunas in the central and western Pacific. The number of vessels for 1976 to 1978 are Pacific Tuna Development Foundation exploratory fishing charters and do not include an unknown number of other vessels that may have fished in these years.
|YEAR||NUMBER OF VESSELS|
Monthly catch (mt), effort (days fishing) and catch-per-effort (mt/days fishing) are shown in Table 3. The fishery is usually centered north of Papua New Guinea, with occasional fishing off New Zealand (Figure 2). The fishery is primarily for skipjack (67%), with lesser quantities of yellowfin and bigeye tunas (33%). Yellowfin catches are generally highest in June to November, also the months of higher yellowfin catch rates. The average catch rate for yellowfin tuna in 1990 is 9.0 mt per day fished compared to 7.1 in 1989, 3.1 in 1988, and 12.8 in 1987. Catch rates in 1987 and 1988 may be biased due to poor sampling coverage.
2.4 Length Composition
The USA distant-water central and western Pacific purse seine catches are measured for fork length (FL) from landings in American Samoa (Coan et al., 1988; Honda et al., 1988). For data collected before the SPRTT (1981; 1982; and 1984 to 1987) fifty to 100 fish samples were drawn from each well and no species composition samples were taken. For data collected under the SPRTT (1988 to 1990) fifty to 100 fish were randomly selected from each well and unloaded size category. If yellowfin tuna were mixed with skipjack or bigeye tuna in the landings, then 100 fish were drawn, measured and used for species composition sampling (Coan and Yamasaki, 1990).
Yellowfin tuna in landings of USA purse seiners fishing in the central and western Pacific in 1981, 1982 and 1984 to 1990 range from 25 to 186 centimeters (cm) FL (Figure 3). Fish measured are generally in two modes, 40 to 70 cm and 80 to 120 cm or age 1, 2 and 3 year-old fish.
3. ARTISANAL FISHERIES
3.1 Total Landings
Landings data for artisanal fisheries of Hawaii, American Samoa, Northern Marianas and Guam are gathered by local island fisheries agencies. Various techniques are used to gather and process the data (Hamm, 1985; Hamm and Kassman, 1986; Hamm et al., 1986, Hamm and Quach, 1988; Hamm and Quach, 1989; Hamm et al., 1990; Hamm et al., 1991). The data are placed on the Western Pacific Fishery Information Network (WPACFIN).
Yellowfin tuna landings in Hawaii are collected through a commercial fishing license system that requires all commercial fishermen to report their individual landings. Data are available for 1945 to 1953 (Boggs and Pooley, 1987), and for 1954 to 1990 (Table 4). Currently, approximately 2,500 fishermen have licenses. The principal methods of fishing for yellowfin tuna in Hawaii are with handline, longline or troll gears. The number of longline vessels operating in the fishery decreased from 76 in 1950 to a low of 14 in 1979, then increased to 138 by 1990 (TNL, 1990; Ito, 1991). Handline vessels increased from 30 to 40 in 1976 to over 230 in 1980. Approximately 160 troll vessels operated in 1976 (Boggs and Pooley, 1987). Hawaiian commercial landings of yellowfin tuna have increased from less than 200 mt in 1956 to over 1,800 mt in 1988. Yellowfin tuna are also caught by Hawaiian subsistence and recreational fishermen. Catches from these fisheries could be as high as 2,000 mt of skipjack and yellowfin annually, but few data are available (Hudgins and Pooley, 1987).
Yellowfin tuna landings in American Samoa, Northern Marianas and Guam are estimated by a random survey of fishermen or from landing receipts of fish buyers. Yellowfin landings have increased from a low of 10 mt in 1979 to a high of 80 mt in 1985 (Table 4), then decreased to approximately 50 mt in 1990 (Hamm et al., 1992). Fisheries are typically small boat (12 to 48 feet), 1 to 2 day commercial, recreational and subsistence operations using primarily troll fishing gear.
3.2 Length Composition
Yellowfin tuna caught by the Hawaiian artisanal longline fishery have been measured for fork length (FL) or weight at the local fish auction. Data are available for 1948 to 1952 (Otsu, 1954), and for 1960 to 1970 (Figure 4). Fish sampled range between 50 and 190 cm FL and the majority of the fish measured were between 116 and 166 cm FL.
Sizes of yellowfin tuna caught by the Hawaiian artisanal handline fishery are available for 1973–75 (Yuen, 1979), and for 1978 (Figure 5). Fish measured in 1973 to 1975 range between 50 and 180 cm FL, and the majority of the fish were less than 132 cm FL. Fish measured in 1978 tended to be smaller, ranging between 47 and 57 cm FL.
Table 3. Sample catch (metric tons, MT), fishing effort (days fished) and catch per effort (CPE, metric tons per day fished) for the U.S. distant-water central and western Pacific purse seine fishery. Sampling coverage from January, 1987 to June, 1988 is unknown (data from South Pacific Commission). Coverage from July, 1988 to December, 1990 is 100% (data from South Pacific Regional Tuna Treaty sampling).
Figure 2. General area fished by the U.S. central and western Pacific distant-water purse seine fishery, 1988–1990.
The major USA fishery for yellowfin tuna in the central and western Pacific is the distant-water purse seine fishery. The fishery operates year round, catching mainly skipjack, primarily off Papua New Guinea and has landed as much as 66,400 mt of yellowfin tuna in 1987. Yellowfin tuna catches and catch rates from the fishery are highest from June to November. The average yellowfin tuna catch rate was 9.0 mt per days fishing in 1990. Collection of data from this fishery has improved since the implementation of the SPRTT. Coverage rates for the fleet are currently 100% for logbook and landings data.
The USA artisanal fisheries for yellowfin tuna operate within 200 miles of the coasts of Hawaii, Guam, American Samoa and Northern Marianas. Yellowfin tuna landings from these fisheries are less than 1,800 mt a year. The majority of the landings are from waters around Hawaii and are made with longline, handline or troll fishing gears. Sizes of yellowfin tuna caught by the Hawaiian artisanal longline and handline fisheries ranged from 50 to 190 cm FL. The larger fish (116 to 190 cm FL) are generally caught by longline gears.
Figure 3. Annual length composition of yellowfin tuna caught by the U.S. central and western Pacific distant-water purse seine fishery, 1981, 1982 and 1984–1990.
Table 4. Yellowfin tuna landings (metric tons) from U.S. artisanal fisheries in the central and western Pacific.
|YEAR||HAWAII||AMERICAN SAMOA||NORTHERN MARIANAS||GUAM|
- indicates that landings are not available but may be greater than zero.
* indicates values less than 10 metric tons.
Hawaiian baitboat and longline fisheries operated before 1954 and as early as the late 1930's, but data are sparse (June 1950, June 1951, Boggs and Pooley 1987)
Figure 4. Annual length composition of yellowfin tuna caught by the Hawaiian artisanal longline fishery.
Figure 5. Length composition of yellowfin tuna caught by the Hawaiian artisanal handline fishery, 1978.
I would like to thank Pat Donley of the Southwest Regional Office and Sally Kuba, David Hamm and Jerry Wetherall of the Honolulu Laboratory, Southwest Fisheries Science Center for their help in providing fishery statistics needed for this report, and Karen Handschuh for typing assistance.
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