3.3 Discards in selected fisheries

The fisheries have been grouped and analysed by gear type and target species. There is very great diversity within a group and considerable caution must be exercised in generalizing discard rates by fishery. For example, in some tropical shrimp trawl fisheries the use of TEDs and BRDs is strictly enforced, while in others fishing is only permitted during daylight hours, and many fisheries that target shrimp also target other finfish or cephalopods. This diversity is shown by presenting both average discard rates and the respective standard deviations for the subsets of discard database records, for which the discard rate is available.^[56] The weighted (pooled) discard rate better reflects the quantitative importance of discards in such types of fisheries at a global level. Thus both average and weighted discard rates are presented for many fisheries.

3.3.1 Shrimp trawl fisheries

The discard database indicates that shrimp trawl fisheries, and tropical shrimp fisheries in particular, are the single greatest source of discards, accounting for 27.3 percent (1.86 million tonnes) of estimated total discards (see Table 8). The aggregate or weighted discard rate for all shrimp trawl fisheries is 62.3 percent.^[57] These fisheries^[58] have consistently high discard rates deriving from a range of factors.

• Shrimp is often less than 20 percent of the demersal biomass on many shrimp fishing grounds.

• The relatively small mesh size required to capture shrimp inevitably results in large quantities of bycatch.

• Vessels are designed for shrimp retention and have limited freezing and hold capacity for bycatch.

• Transhipment at sea is often discouraged by vessel owners or prohibited by authorities because of concerns about theft, or illegal/unrecorded transhipment.

• The shrimp grounds are often at a considerable distance from the markets for bycatch, rendering its retention and transport to market uneconomical.

• Bycatch species are often of small size and their relatively low value makes bycatch retention uneconomical.

• Enforcement of regulations on minimum landings of bycatch and on discard reduction may be deficient.

The global average (1992-2001) annual nominal catch of shrimp is 2.5 million tonnes (excluding Nephrops and other “langoustine”), of which the penaeid shrimp catch is over 1 million tonnes, the vast majority being harvested by trawlers. However, increases in the global nominal catch of shrimp in recent years to approximately 3 million tonnes means that the total quantity of discards may have increased by 10 to15 percent.

TABLE 7
Frequency distribution of discard rates in shrimp trawl fisheries

Note: includes five records of semi-industrial shrimp trawl fisheries. Tropical shrimp refers to penaeid shrimp.

Source: discard database.

TABLE 8
Discard rates and discards in shrimp trawl fisheries

¹ Records used to compile this table exclude China as catches/landings attributable to targeted shrimp trawling could not be clearly identified.

² Landings include landings of bycatch.

³ The weighted discard rate (column 9) is considered to be the most accurate and representative at a global level

⁴ Includes deepwater non-penaeid trawl fisheries in tropical areas, e.g. Aristaeidae, Solenoceridae.

⁵ Almost exclusively penaeid shrimp fisheries.

Source: discard database.

Tropical shallow water shrimp fisheries

These fisheries^[59] account for 70 percent of total estimated discards from shrimp trawl fisheries. Almost all of these fisheries target penaeid shrimps. They have an average discard rate of 55.8 percent, but the standard deviation of 0.27 (see Table 8) indicates a relatively wide range of discard rates. The weighted discard rate of 67.8 percent is substantially higher than the average, reflecting discards of 1.6 million tonnes for landings of 0.78 million tonnes recorded in the discard database.

Three countries, China, India and Thailand, all with low or negligible discard rates, account for over half of the penaeid shrimp catch. Most shrimp trawl fisheries in South and Southeast Asia have insignificant discards with the notable exception of the Arafura Sea shrimp fishery. This fishery, shrimp fisheries in the Gulf of Mexico, Atlantic United States, Ecuador and on the Guianas shelf account for a large proportion of discards from tropical shrimp fisheries (see Annex A.2.1, Table 15). Several smaller shrimp fisheries have discard rates in excess of 80 percent. These include the Kuwait, French Guiana, Panama and Suriname fisheries. This study suggests a much lower level of discards in present-day tropical shrimp fisheries than previously estimated (Teutscher, 1999), which is one of the major contributing factors to a lower global discard estimate.

An extensive mix of species are discarded, including jellyfish, lizard fish, threadfin bream and juveniles of many commercial whitefish species such as croakers, snappers and emperors, which may be the target species of other fisheries.

Artisanal shrimp fisheries

Most records of artisanal penaeid shrimp fisheries indicated a negligible discard rate. However, there are many exceptions, particularly when trawl, pushnets or similar gears are used, e.g. San Miguel Bay baby trawl (25 percent discard rate), the Brazilian north coast and the Trinidad and Tobago artisanal shrimp fisheries. Many small-scale shrimp trawlers are motorized and some freeze the product on board. It is becoming increasingly difficult to distinguish between small-scale and industrial shrimp fishing vessels.

Coldwater shrimp and prawn

The coldwater shrimp trawl fisheries exhibit an even greater variety than the tropical shrimp in terms of fishing gears, fishing depths and substrates. In aggregate these fisheries have a weighted discard rate of 39 percent and contribute approximately 220000 tonnes to the global discard estimate (see Table 8). The highest recorded discards occur in Peru’s fishery (74 000 tonnes with a discard rate of 81 percent).

Many of the deepwater shrimp fisheries are located on the slopes of the continental shelves (100-600 m depth) in both tropical and temperate regions. In the Mediterranean and North Atlantic many of these trawlers also target Nephrops. Most of the discard database records are from the Mediterranean and North Atlantic and indicate a high level of discards (20-94 percent). The deepwater shrimp fisheries contribute over 70 000 tonnes to the global discard estimate. The main discards^[60] include small sharks (dogfish), rays, hake and blue whiting.

The fisheries for Pandalidae (Pandalus, Heterocarpus sp.) concentrated in the North Atlantic (Canada, Norway, Iceland) account for approximately 13 000 tonnes of discards. The mandatory use of Nordmore grids and other BRDs in most of these fisheries results in a relatively low discard rate (weighted discard rate of 5.4 percent). There are no records in the discard database for the North Pacific fisheries.

The weighted discard rate for discard database records of Nephrops trawl fisheries^[61] is 43 percent for a total discard estimate of approximately 11 000 tonnes. In the North Atlantic (North Sea and Irish Sea), discards from Nephrops fisheries comprise whiting, haddock, starry ray and broken/undersized Nephrops and flatfish. The high discards of juvenile whiting and haddock have been of particular concern to fishery managers. Obligatory use of square mesh panels for these fisheries in the waters of EU member states has resulted in substantial decreases in discards. Continued progress with gear selectivity and improved compliance with regulations are likely to reduce discards further.

The Belgian Crangon beam trawl fishery has a discard rate of 83 percent. There are no records in the discard database that refer to fisheries for the important sergestid shrimps (21 percent of the global nominal catch), which have both a tropical and coldwater distribution.

Turtle excluder devices (TEDs)

The use of TEDs appears to have little impact on the level of discards. Penaeid shrimp fisheries in which use of TEDs is mandatory account for over 700 000 tonnes of discards with a weighted discard rate of 75 percent (range 0-79 percent).

Bycatch reduction devices (BRDs)

BRDs are used in a wide range of shrimp fisheries with apparent discard reductions in Pandalus fisheries (0.2-29 percent discards), less impact in other coldwater fisheries for Nephrops and other species (44-50 percent discards) and even less impact in tropical fisheries (67-89 percent discards). The low impact in some tropical fisheries may be a result of poor enforcement of BRD regulations, since experimental results clearly indicate significant reductions in unwanted bycatch. Shrimp fisheries in which BRDs are mandatory accounted for almost 0.4 million tonnes of discards (weighted discard rate of 62.8 percent). Although the discard database contains few details of catch and discards in Pandalus fisheries, the extensive and compulsory use^[62] of Nordmore grids and similar BRDs has reduced bycatch to less than 5 percent in many Pandalus fisheries. Additional work is necessary to interpret and include additional information, particularly from the ICES and NAFO areas, from Australia and from the Gulf of Mexico.

There is clear evidence of bycatch reduction through the use of BRDs, in particular in Australian and United States penaeid trawl fisheries. However, the use of BRDs is not widespread in developing countries.^[63] Reduction in discards is more likely to arise from increased utilization of bycatch, rather than reduction of bycatch. Many shrimp trawl fisheries in developing countries are marginally profitable and any reduction in shrimp catch through the use of BRDs may result in significant economic losses.

Trends

There are major differences between the reasons for discard reductions in the tropical and temperate water shrimp fisheries. The tropical fisheries are located in the waters of developing countries with a high demand for lower value bycatch fish, either for human consumption or animal feed. In social and economic terms the total commercial biomass extracted may be more important than shrimp biomass, i.e. the unstated fishery management objective is to maximize the catch, irrespective of the species composition.

TABLE 9
Discard rates and discards in non-shrimp trawl fisheries

¹ The fisheries are sorted on the basis of the primary target species. Additional details are provided in Annex A.

² The weighted discard rate is considered to be the most accurate and representative at a global level.

³ Demersal finfish are fisheries primarily targeting roundfish for human consumption.

⁴ Flatfish fisheries include beam trawl fisheries.

⁵ Midwater trawl fisheries include some fisheries that harvest for both fishmeal and human consumption and include a large proportion of the Alaska pollock fishery.

⁶ Demersal multispecies means that both finfish and shellfish are targeted. The reason for the low discard rate is because of the inclusion of Chinese and Southeast Asian trawl fisheries in this group.

⁷ Deepwater fisheries include those targeting orange roughy, Coryphaenoides and Molva species.

⁸ Fishmeal fisheries are those specifically targeting small pelagics for fishmeal.

⁹ The hake, factory trawler and beam trawl values are presented separately. The reported landings and discards from these fisheries are already weighted in the total in the preceding line.

Source: discard database.

In contrast, the total biomass harvested in the temperate water shrimp fisheries is likely to be reducing as a result of the introduction of square mesh panels, BRDs and other measures. Overfishing of whitefish and the higher price of shrimp encourages fishers increasingly to target shrimp, while the intricate predator-prey relationships between crustacea and finfish further complicate management of many interrelated fisheries (e.g. NAFO area, Barents Sea and North Sea).

3.3.2 Non-shrimp trawl fisheries

The analysis distinguishes between a number of non-shrimp trawl fisheries, each of which is discussed in more detail below and summarized in Table 9. These fisheries, operating in 49 countries, include:

• demersal finfish trawl, primarily targeting roundfish;

• flatfish (e.g. plaice, sole, flounder) trawl fisheries, including several beam trawl fisheries;

• hake trawl (both ice and freezer vessels combined);

• beam trawl, including those targeting flatfish;

• deepwater trawl fisheries, including those for orange roughy and grenadier;

• cephalopod fisheries targeting squid, octopus and cuttlefish;

• fishmeal fisheries;

• midwater trawl fisheries, some of which may harvest for fishmeal;

• factory trawlers, including the “catcher processors” in GOA/BSAI; and

• an important group of trawl fisheries termed “demersal multispecies” which target several phyla including finfish, cephalopods and crustacea, i.e. these fisheries cannot be readily included in any of the preceding groups.

Details of the discards in these fisheries are provided below and in the supplementary tables in Annex A, Tables 16-19. The fisheries are considered both in relation to the gear used and the target species.

Trawl fisheries with the highest discards include the North Sea beam trawl fisheries; Japan’s small trawl fishery; the Washington/Oregon/California groundfish fishery;^[64] and industrial trawl fisheries in Morocco and Argentina. Substantial discards also occur in South Africa and Angola. The midwater trawl fisheries for small pelagics have the lowest discard rates and are also discussed in Section 3.3.4.

Bottom otter trawl

Bottom otter trawl for finfish is one of the most common fishing gears. Fish landed for direct human consumption has been estimated to be between 13.9 and 17.9 million tonnes (Chopin, in press), or in the order of 20 percent of global marine fishery production (excluding plants). Nineteen trawl fisheries involving 13 countries generate 80 percent of the estimated global bottom trawl landings.

The landings of an equivalent discard database set of fisheries total 15.9 million tonnes with discards of 1.3 million tonnes or 19 percent of the estimated total discards reported in the discard database. The weighted discard rate of these otter trawl fisheries is 7.6 percent.

Among the main finfish fisheries contributing to these discards are the hake fisheries in Argentina, the cephalopod and finfish trawl fisheries in Morocco, the French trawl fisheries in the Bay of Biscay and Celtic Sea, and Japanese fisheries for Alaska pollock. Fisheries with high discard rates include the offshore finfish trawl in Bangladesh, the Algarve finfish trawl (Portugal), several Spanish and Greek Mediterranean fisheries, and several United States fisheries (GOA Alaska pollock bottom trawl, silver hake).

Important demersal multispecies (i.e. targeting other phyla in addition to finfish) otter trawl fisheries include the Japanese “small trawl” fishery, India’s east coast trawl and the Chinese, Myanmar and Thai trawl fisheries which in aggregate contribute over 350 000 tonnes of discards.

Beam and pair trawl

Beam trawl finfish fisheries in the EU show discard rates ranging from 14 to 69 percent. The finfish beam trawl fisheries account for 330 000 tonnes of discards and have a weighted discard rate of 68.7 percent. These discards are primarily from the plaice and sole fisheries in the North Sea. Shrimp beam trawl discard rates range from 8 percent (Pandalus, Canada) to 83 percent (Belgium). Pair trawl fisheries (from Spain, Viet Nam, China and Brazil) for which discard records are available are considered too diverse to be grouped. Discard rates range from 1 to 45 percent.

Flatfish trawl

Flatfish trawl fisheries have a significantly higher discard rate (weighted rate 51.3 percent) than all other non-shrimp trawl fisheries, contributing 0.4 million tonnes to the global total. Discards in EU fisheries include cod, haddock, whiting, plaice, saithe, dab, dogfish, shrimp and Nephrops. Substantial quantities of invertebrates (Echinocardium, starfish and crabs) are also discarded. Arrowtooth flounder is a major component of the discards in the GOA/BSAI fisheries for yellowfin sole, flathead sole and other flatfish. The reasons for the high discard rates in these fisheries are not clear, although the flat muddy and sandy inshore habitats of many flatfish species may serve as important nursery grounds with concentrations of juvenile fish of non-commercial sizes.

Factory trawlers

Factory trawlers are considered to be those with a fishmeal plant on board and/or those producing surimi. Lack of information on the technical characteristics of vessels active in a given fishery precludes clear identification of factory trawlers and, by extension, of factory trawl fisheries. Consequently, discard information on this category of fishery remains tentative. Recorded discards are 90 000 tonnes for a weighted discard rate of 9.6 percent based largely on records of “catcher processor” vessels in the GOA/BSAI groundfish fisheries. Argentine surimi vessels, targeting southern blue whiting and grenadier, are understood to have low or negligible discards. It is likely that substantial quantities of fish that were hitherto discarded are now processed by such vessels and that there are increased discharges of offal, either in liquid or solid form.

Hake trawl

Hake is a major target of the demersal finfish trawl fisheries. Trawl fisheries in more than 25 countries harvest the vast majority of the global hake landings of 1.9 million tonnes (Merlucciidae). Argentina dominates the landings (over 0.5 million tonnes) followed by Chile/Peru (0.36 million tonnes), the Namibia/South Africa fishery and a range of United States fisheries.

In the discard database, hake fisheries account for almost 150 000 tonnes of discards for landings of approximately 1 million tonnes and a weighted discard rate of 12.5 percent. The combined Argentine ice and freezer trawl hake fisheries have discards of 30 000 tonnes and a weighted discard rate of 13.9 percent (range: 9.9 percent for freezer trawlers to 19.8 percent for offshore ice trawlers) followed by Chile with over 26 000 tonnes of discards. Discards include small hake and horse mackerel (all fisheries), kingklip and rattails (Africa), arrowtooth flounder, dogfish and ratfish (North Pacific). Minimum size regulations, quotas and bycatch quotas (Chile) are among the reasons for discarding. Namibia pursues a “no-discard” policy’ although “non-commercial species” may be discarded.

Fishmeal demersal trawl fisheries

The discard database records are exclusively from the North Sea/Kattegat/Skaggerak fisheries for sand eel and Norway pout. Landings of over 1 million tonnes have discards under 10 000 tonnes with a weighted discard rate of less than 1 percent.

Deepsea (deepwater) finfish fisheries

Several different types of gear, including trawls, longlines and gillnets are used in these fisheries and growing concern has been expressed over the status of these deepsea or deepwater fisheries (FAO, 2003b). Many of the fishing grounds are located on continental slopes and high seas plateaus or on seamounts outside coastal state jurisdiction. With the exception of small-scale dropline fisheries, discards are considered high in many deep sea fisheries.

The discard database records are from fisheries in the Northeast Atlantic (Gordon, 1999) and Chile and give a weighted discard rate of 39.6 percent (range 31-90 percent) and total discards of 37 000 tonnes. These fisheries target grenadier (Coryphaenoides), ling, seki shark and orange roughy. Discards have been particularly high in the French fishery for roundnose grenadier. Discarded teleosts include grenadiers, whiptails, rabbitfish and oreos. The discards also include a range of chondrichthyans (sharks such as birdbeak dogfish [Deania], batoids and chimaeroids), some of which also constitute part of the retained or target catch (e.g. seki shark in the Hatton Bank/Rockall Trough fisheries). There is evidence that survival of discards from these fisheries is low (Conference Steering Committee, 2003).

The discard database does not contain records of other important deepsea fisheries, e.g. off Namibia and New Zealand and exploratory fisheries such as those for deepwater crab (Hawaii area) and lobster (off Brazil). The Patagonian toothfish fishery is discussed in Section 3.2.10.

Midwater (pelagic) trawl for demersal species

With catches of over 1.2 million tonnes, the Alaska pollock fishery entirely dominates this category. The discard rate here is less than 1 percent and discards are comprised almost entirely of undersized or damaged pollock (see Annex A.6.1 for details). In contrast, other midwater^[65] trawl fisheries have discard rates ranging from 1 percent for Atlantic redfish in Canada to 54 percent for hake in France. Discards in these fisheries include horse mackerel, mackerel, pilchard and black bream.

Midwater (pelagic) trawl for small pelagics

The recorded landings of over 2 million tonnes have discards of under 100 000 tonnes and a weighted discard rate of 4.2 percent. The major fisheries in Iceland (blue whiting, capelin), Norway (blue whiting, capelin) and Namibia (horse mackerel) all have discard rates of less than 2 percent, as do the fisheries for southern blue whiting (Argentina and the Falkland Islands [Malvinas]). Fisheries in the more southerly waters of Area 27 appear to have a greater species mix and higher discards. An estimated 35 000 tonnes is discarded in the combined Netherlands and Irish mackerel and horse mackerel fisheries (Area 27) with discard rates in the order of 11 percent. A substantial proportion of the Netherlands and Irish catch is taken off West Africa where discard rates are in the 2-6 percent range. Russian (and former Soviet bloc) midwater trawlers operating in the North Atlantic generally have negligible discards as potential discards are converted to fishmeal on board. The highest discard rates of up to 38 percent are recorded from the French pelagic trawl fisheries in the Bay of Biscay.

Discarded species include horse mackerel (EU countries), sardine, pilchard, mackerel and sprat. Dolphins (1.4 dolphins/100 tow-hours in French and Irish tuna fisheries) and sunfish are caught incidentally. Small-sized fish of the target species may be discarded as a result of highgrading in the quota-managed European fisheries or because processing equipment cannot handle smaller sizes.

Cephalopod trawl

Discard rates in the cephalopod trawl fisheries range from 3 percent in the fisheries for pelagic species (Loligo, Ilex) in the Falkland Islands (Malvinas) to 45 percent in the fisheries for octopus (Morocco, Mauritania, Japan). Guinea’s cuttlefish-directed trawl fishery has a discard rate of 24 percent. These fisheries produce approximately 35 000 tonnes of discards and have a weighted discard rate of 22.8 percent.

3.3.3 Tuna and HMS fisheries

Discards in the tuna and HMS fisheries were assessed by ocean since information on catches and fishing activities is collected by five regional fisheries management organizations (RFMOs) and regional fisheries bodies (RFBs)^[66] by fishing gear and country. The catch databases maintained by the RFMOs generally include catch information by country and gear, but do not necessarily discriminate catches by fishery. While in some cases the catch for a discrete fishery can be inferred (e.g. Maldives pole and line), in many cases it is not clear whether the reported tuna catch originates from a targeted tuna fishery or is a bycatch of another fishery (e.g. gillnets in the Indian Ocean). Every attempt has been made to avoid double accounting^[67] for tuna catches also recorded as part of national fisheries statistics.

Two relatively comprehensive studies have been made of discards in the SPC area. In the case of the Atlantic HMS fisheries little quantitative information on discards was located. Table 10 summarizes discards and discard rates. Tuna catches in troll and gillnet fisheries cannot readily be separated from catches of other large pelagics.

Longline

There are significant differences between distant water longline fleets that target different species, even for those fleets with the same flag. Smaller longliners will tend to have shorter trips and retain more sharks and other non-target species. The long-range (mostly Asian) vessels are likely to discard greater quantities of bycatch (Nishida and Shiba, 2002). Discard rates for the long-range vessels range from 30 to 40 percent. The SPC discard rate of 40 percent is applied in the absence of other information and a rate of 15 percent is applied to the smaller, locally based longline vessels. Principal discards include Prionace glauca (blue shark), which is probably the most commonly discarded species, Carcharinus sp. and other sharks, damaged fish, albatross, petrels and other seabirds. Landings of sharks, frigate tuna, Kawakawa, Indo-Pacific king mackerel, and narrow-barred Spanish mackerel are not recorded in the IOTC database and it is assumed that industrial longliners discard the catch of most of these species. Discard rates in swordfish longline fisheries vary between 10 percent (Canada and Seychelles) to 19 percent in the Atlantic United States. Hook drop-off is not considered to be a discard.

TABLE 10
Discards and discard rates in fisheries for tuna and HMS

Source: discard database.

Purse seine

Discard rates vary from 1.5 percent in small (<400 GRT) Mexican seiners to 6.9 percent in the IATTC area. Other discard rates are Atlantic, 4.1 percent; Indian Ocean, 5 percent; and SPC area, 5.9 percent. Total recorded discards are approximately 145 000 tonnes. Discards include undersized target species, non-commercial tunas, shark, rainbow runner, dolphinfish, triggerfish, billfish and mantas. Large quantities of jellyfish are discarded in the bluefish and bonito fisheries in Turkish waters. Incidental catches of dolphins are discussed in Section 4.2.3.

Pole and line fisheries

These fisheries are essentially two fisheries - one for bait (usually anchovy) and the main fishery usually directed at skipjack and yellowfin tuna. The major pole and line fisheries are in the Western Pacific, Maldives, Japan, West Africa and Brazil. Discards of approximately 3 000 tonnes give a weighted discard rate of 0.4 percent for catches of over 0.8 million tonnes. Discards in baitfish fisheries have not been assessed.

Traps

Large anchored tuna traps are used on the coasts of Atlantic Morocco and Canada and in Mediterranean countries including Italy, Libyan Arab Jamahiriya and Tunisia. Tuna traps are quite selective and have a low or negligible discard rate, partly because of the large mesh size used in the traps. Canadian fishers are obliged to release bluefin tuna alive from traps licensed to catch herring and mackerel. Cetaceans may sometimes become entangled in trap mooring lines.

Other tuna fisheries

Trolling, handlines and coastal gillnets targeting tuna are also considered to have a low or negligible discard rate. Tuna gillnets are extensively deployed on the Indian subcontinent where discards are generally negligible (e.g. the Sri Lanka offshore gillnet fishery). Available records for harpoon fisheries (Nova Scotia swordfish) indicate zero discards.

Sharks

A study of elasmobranch fisheries cautioned against extrapolating the catch rates from one fishery to another because of the wide variation in the distribution of elasmobranchs (Bonfil, 1994). It is likely that weights of discarded sharks and other species can be derived from available^[68] longline observer data and a more accurate estimation of discards can be made at the level of the RFBs. In the absence of recent comprehensive data on shark catch as a percentage of total longline catch, older^[69] estimates have been used to determine a longline discard rate in the Indian Ocean of 21.7 percent of the total catch. It is assumed that fish subject to predation are discarded (Nishida and Shiba, 2002).

TABLE 11
Discards and discard rates in industrial fisheries for small pelagics

Note: industrial and semi-industrial only. By industrial is meant industrial scale. Industrial does not mean fishing for fishmeal.

Source: discard database.

TABLE 12
Other industrial fisheries for small pelagics

At the global level, assuming that carcasses of all finned^[70] sharks are discarded, over 200 000 tonnes of shark are discarded annually as a result of finning (discard rate of 96 percent). Discards of sharks in high seas fisheries alone are estimated to be 204 000 tonnes annually (Bonfil, 1994).

3.3.4 Small pelagics fisheries

The fisheries for small pelagics generally have low discard rates because the schools tend to be monospecific and the fish tend to be of a similar size. Tables 11 and 12 give details by gear type, based on the information in the discard database.

Purse seine

Purse seines and other seines catch the vast majority of global small pelagics. These seine fisheries contribute over 350 000 tonnes to the global discard estimate and have a weighted discard rate of 1.6 percent. Purse-seine fisheries in Peru, Norway, Chile and Iceland are the main contributors of discards. Because of the volume of catches, even with a low discard rate of 2.5 percent the Peruvian anchoveta fishery discards approximately 250 000 tonnes. Many small pelagic purse-seine fisheries are considered to have a zero discard rate, including United States menhaden, Black Sea anchovy and Malaysian and Vietnamese anchovy. Among the fisheries with the highest discard rates are those in Portugal, Spain and France targeting sardine, mackerel and anchovy. Discards in these fisheries are primarily of other non-target small pelagics including horse mackerel, Scomber japonicus, Boops, Belone sp., jellyfish, juveniles of other species^[71] and small quantities of sharks.

Midwater trawl

These fisheries have already been discussed in Section 3.3.2. With the exception of the South African midwater trawl fishery for small pelagics (43.9 percent discard rate), all other high discard rates are from EU fisheries (seven records ranging from 10 to 47 percent). The quota regulations are a major cause of high discards in all these fisheries.

Slipping of unwanted fish is common in industrial fisheries for small pelagics. The quantity of such discards is particularly difficult to assess.^[72] Norway has made use of crewless video-equipped submersibles to monitor slipping and discards in some of these fisheries.

Among the “other” industrial small pelagics fisheries, those with the highest discard rates are the Norwegian herring seine fishery (7 percent), the eastern Black Sea coastal encircling gillnet (7.4 percent), and Ireland's herring trawl (4.7 percent).

Artisanal

Lift nets, pushnets, beach seines, surround nets, gillnets trolling and a wide variety of other gears deployed in the artisanal fisheries for small pelagics are all considered to have low or negligible discard rates. Senegal produces over 250 000 tonnes of small pelagics with a fleet of outboard powered purse seiners. Numerous other artisanal purse seine fisheries exist producing a large, but unknown quantity of small pelagics (e.g. Bali Straits sardine fishery, Thai coastal fisheries). Mesh size regulations in these fisheries may contribute to discards since smaller fish can become gilled in the nets. Discard rate for such groups of fisheries are not available.

3.3.5 Gillnet fisheries

Surface and bottom gillnet fisheries (including trammel nets) account for under 30 000 tonnes of discards from reported landings of over 3 million tonnes (a weighted discard rate of 0.5 percent). The high level of catch is largely attributable to the Chinese small drift gillnet fishery (2.3 million tonnes). Source references do not always distinguish between surface and bottom gillnets and available gillnet catch statistics may combine both. The gillnet fisheries are highly diverse and would benefit from further disaggregation. They range from deepwater gillnets for hake and monkfish (Area 27, western waters) to surface nets for large pelagics, trammel nets for shrimp and crab and tangle nets for lobster. Some gillnet fisheries may target roe fish such as lumpfish and herring. Dropout from gillnets is not considered a discard. Among the highest discard rates are California’s drift swordfish gillnet fishery and the sink gillnet fisheries in the northeastern United States, Canada’s Greenland halibut fishery (1994 data) and Norway’s lumpfish fishery.

Discards include dogfish, skate, sculpin (Canada), cod, haddock, plaice, saithe and dab (Europe). Coastal gillnet fisheries in France have low discard rates for marketable finfish, while offshore gillnet fisheries with soak times of up to six days may discard 100 percent of gadoid species because of the poor phytosanitary condition of otherwise marketable finfish (Morizur, Pouvreau and Guénolé, 1996). A number of countries prohibit monofilament gillnets but enforcement of such regulations is highly variable.

3.3.6 Non-tuna line and jig fisheries

In aggregate the non-tuna line fisheries have a weighted discard rate of 7.5 percent and discards of 47 000 tonnes. The bottom longline fisheries have a similar weighted discard rate of 7.5 percent, while the handline fisheries show a discard rate of 2 percent.

The BSAI catcher processors targeting Pacific cod contribute over 24 000 tonnes of discards, while the GOA shoreside fleet targeting rockfish shows the highest discard rate (57.4 percent). In addition to the generally high discard rates in the GOA/BSAI line fisheries, toothfish longline (discard rates above 20 percent), artisanal shark fisheries (Peru and elsewhere) and longline fisheries in Norway and Spain (hake) have discard rates in excess of 10 percent.

Discarded species include arrowtooth flounder (GOA/BSAI fisheries), starry ray, dab and redfish (Iceland, the Faeroe Islands), hake, shark and kingklip (South Africa), and macrourids and rajids in the CCAMLR area. In many of these fisheries in Europe and the United States some discarding is attributable to highgrading and species-specific per vessel quotas.

Jig fisheries

Jig fisheries tend to be highly selective with a weighted discard rate of 0.1 percent for the squid fisheries and 3.5 percent for finfish fisheries (cod, Pacific cod and mackerel).

Additional details on these fisheries are provided in Annex A.2.2, Table 20.

3.3.7 Multigear and multispecies fisheries

Over 100 fisheries in the discard database were classified either as multigear, as multispecies or as both multigear and multispecies. In many cases this unhelpful designation reflects an aggregation of several fisheries and can be largely attributed to the manner in which statistical information is compiled at national level. Further work could disaggregate each of such “multi” fisheries into a set of differentiated fisheries. Nevertheless, in many fisheries, individual vessels deploy different gears during the same fishing trip and in some cases, e.g. many Asian trawl fisheries, “there is no target species because all species are the target”.^[73]

Most of the fisheries in this group are small-scale fisheries. The artisanal fisheries of the Pacific Islands and Caribbean comprise 43 of the records in this group of fisheries and have an assumed discard rate of 0 percent. The highest discard rate is reported from the multigear shrimp fishery in northern Brazil (50 percent) and the Uruguayan artisanal multigear fishery (15 percent). The weighted discard rate is 1.4 percent, representing discards of 85 000 tonnes from landings of over 6 million tonnes.

3.3.8 Fisheries using other gears

Dredge

Discard rates in dredge fisheries, which are mainly directed at scallops, clams and whelks range from 9 to 60 percent with a weighted average of 28.3 percent and a contribution of over 65 000 tonnes (ten records) to the total discard estimate.

Pushnet

Pushnets exhibit a wide range of discard rates from 90 percent for those collecting penaeid post larvae (Bangladesh) to 0-1 percent for those operating in the Gulf of Thailand and South China Sea, many of which are operated from larger motorized vessels.

Bagnets

Bagnets (five records from Asia and Africa) have a discard rate of less than 1 percent and make a negligible contribution to the total discard estimate.

Other fixed nets

Chinese landings of over 2.6 million tonnes from “stationary” nets dominate the category and have an assumed discard rate of 0.5 percent. Total fixed net discards are estimated to be approximately 24 000 tonnes. With the exception of the Guyana Chinese “seine” (a type of staked fyke net) with a discard rate of 25 percent, all these fisheries (six records) have discard rates below 1 percent.

Traps

Three main types of trap fisheries are distinguished: fixed traps (12 records), small-scale pots and industrial pots. The tuna trap fisheries (Mediterranean and Canada) and the small-scale fixed and arrowhead traps of Asia incur negligible discards. Octopus pots (West Africa, Japan) also have negligible discards. Lobster and crab pots often have high regulatory discards, as fishers are obliged to discard females and undersized specimens in many jurisdictions. In contrast to the negative connotation of many discarding practices, discards with a high survival rate are highly desirable for stock conservation. High discards in several major crustacean pot fisheries, e.g. BSAI crab fishery (over 40 percent) and Canadian lobster fisheries (23 percent) account for high discard rates of 12.4 percent (average 12 records) and 27.7 percent (weighted discard rate). Finfish pot fisheries (14 records) indicate a maximum discard rate of 5.2 percent with the exception of an experimental fishery for toothfish in the CCAMLR area, which has high discards of crabs and other species (61 percent). Finfish pot fisheries account for under 1 500 tonnes of the total discard estimate.

Other gears

Harpoons, used for swordfish in Canada and the United States, are highly selective and unlikely to incur discards. The saury stick-held dip net (Japan), dip nets in Viet Nam and scoop nets in peninsular Malaysia have low to negligible discards.

3.3.9 Artisanal and small-scale fisheries

The terms “artisanal” and “small-scale” fisheries are considered equivalent for the purposes of this study and embrace other categories (e.g. subsistence, traditional, indigenous) used in the national fisheries statistics or fishery terminology of different countries.

While most of these fisheries have been assumed to have a low or negligible discard rate, it is clear that some discarding takes place. Puffer fish, “ciguatera” fish and other poisonous species are discarded. Fish gilled in seine nets may be discarded. Hooked fish damaged by shark attack may also be discarded, although fish heads are often retained. Small quantities of living marine resources are often discarded in beachseining operations. Many artisanal fisheries are highly selective,^[74] e.g. trammel nets targeting shrimp may discard quantities of crabs that become entangled and broken. Artisanal trawlers in Southeast Asia discard benthos such as sponges and tunicates and “baby trawls” in the Philippines have relatively high discard rates. Estuarine stake nets tend to have significant discards. “Jellyfish” of several phyla are frequently discarded.

Nevertheless, little information exists in the available literature quantifying these discards, since discarding is generally not considered to be a priority concern in small-scale and artisanal fisheries. More frequently post-harvest losses are the primary concern. Numerous national experts consider that discards in their national artisanal fisheries are negligible (see Annex C.5, Table 35). Efforts have been made to identify the artisanal^[75] or small-scale component of national landings and, in the absence of information to the contrary, these fisheries have been assumed to have a low or negligible discard rate.

Partly as a result of problems arising from the definition of fisheries at the national level, it is difficult to separate clearly artisanal (small-scale) fisheries from industrial fisheries. Consequently, a comparison between the discard rates of these sectors is difficult. However, is quite clear that the vast majority of discards originate in the industrial sector.

Discard database records indicate that catches of at least 8.5 million tonnes can clearly be attributed^[76] to small-scale fisheries. In aggregate these fisheries show a discard rate of 3.7 percent.

Beach seine

The average discard rate (32 percent) is high because beach seines in developed countries (e.g. Australia, Portugal) have high discards. However, the highest landings from beach seines take place in developing countries where the activity has a high social importance and discards are often negligible since even low value fish is used for autoconsumption and crew compensation. The weighted discard rate is 4.4 percent, whereas Table 5 lists beach-seine fisheries in developing countries among the fisheries with a negligible discard rate.

Diver

Diver fisheries (12 records) for abalone, clam, topshell and mother of pearl, lobster, octopus and rare shells all have a zero or negligible discard rate (<1 percent). Damage or mortalities caused by divers to corals or other species has not been estimated although it is reported to be substantial in some areas (e.g. cyanide fishing for live reef fish, “excavating” giant clams or harvesting ornamental corals). Discards of sea urchins may be substantial if gonad condition is poor.

Hand collection

Hand collection, also referred to as hand gathering or gleaning, is a common artisanal and commercial fishing activity. Many collection activities, e.g. for cockles and clams, take place during low-water spring tides. Substantial damage may occur to reefs from walking on corals or overturning rocks. Damage and mortalities may also occur from raking or dragging baskets and sacks and from collection vehicle movement (e.g. tractors). Such damage is not considered a discard. Substantial collection fisheries exist in Chile, Japan and Thailand. Discards in all cases (16 records) are negligible (<0.5 percent) and these fisheries contribute no more than 1 000 tonnes to the total discard estimate.

3.3.10 Discarded species

It is difficult to determine the most important discards by species or species group since the composition of the discards is often inadequately recorded. Most studies focus on the discards of commercial species and it is often unclear whether non-commercial species are recorded, e.g. there are few references to discards of jellyfish. A particular study may provide a list of discarded species without specifying the quantities discarded, or generic designations such as “juveniles of commercial species”, “noncommercial species” or “invertebrates” may be used in the literature. The quantity of discarded invertebrates may be significantly under-reported. Significant discards of sponges, coelenterates^[77] including corals, Ctenophora, echinoderms, tunicates and crabs occur, particularly in trawl and dredge fisheries. Often only the weight of the discarded commercial species is reported. Percentages by weight of the different species are rarely provided or, if provided, it may not be possible to relate the percentages to the total or retained catch. Consequently, little quantitative information on discards by species is contained in the discard database. A synthesis of selected information is provided in Annex A.5, Table 25.

For the purposed of discard estimation a division of the catch into three groups may be useful: species always retained; species always discarded; and species partially/ sometimes discarded. If estimates of the overall catch composition are available, observers may then concentrate on the partially discarded species. Further analysis of the composition and quantity of discarded species may suggest a more effective targeting of market and product research to facilitate greater utilization of these species, and assist in studies on biodiversity and on the impact of fishing on marine ecosystems.

3.3.11 Regulatory measures and discard rates

Analysis of the discard database records by type of regulatory measure, summarized in Table 13, is not particularly useful because of the variety in the fisheries, the influence of other regulatory measures and the weak enforcement of some measures. The “nodiscards” regime will be examined in more detail in Section 4.3.1.

Minimum landing size (MLS)

Many fisheries apply several regulations that directly influence discard rates. MLS regulations, which clearly promote discarding, are often associated with other regulations (e.g. closed areas, closed seasons or quotas) and the impact of a particular regulation is difficult to assess. In some cases the MLS is set below the marketable size. For example, reducing the MLS for whiting in the North Sea would have little effect on discard practices because there is no market for the small whiting. However, a reduced MLS for hake may have an effect in Spain where there is a ready market for small hake. Although there are MLS regulations in many Southeast Asian countries, the generally low discard rates reflect the weak application of these regulations. Sales of unsorted fish, such as “African mix” in West Africa, bycatch purchased at sea by collection vessels, often circumvent the MLS regulations.

Turtle excluder devices (TEDs) and Bycatch reduction devices (BRDs)

Shrimp fisheries using TEDs do not appear to have an appreciably lower discard level (aggregate discard level 62.3 percent) than those that do not use them. Discard rates in fisheries using BRDs range from <6 percent in the NAFO area (as low as 0.2 percent) to 88.7 percent in Australia and Indonesia (Arafura Sea). Time series showing discard rates before and after the introduction of TEDs and/or BRDs are necessary to provide a more accurate assessment^[78] of the impact of these devices. The broad range of discard rates is also partly attributable to varying levels of enforcement of the TED/BRD regulations.

TABLE 13
Weighted average discard rates for fisheries using different discard-related management measures