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A great deal of concern has been expressed by fishery managers and conservation/environmental groups that bycatch and discards may be contributing to biological overfishing and altering the structure of marine ecosystems. Such claims are frequently based on observations of large numbers of discards and high discard ratios or rates as provided in the previous chapter, but infrequently on detailed population assessments of impacted stocks. This is perhaps because comprehensive and historical datasets involving discards have been unavailable to demonstrate such claims. Regardless, a growing body of literature does support the conclusion that for some species and regions of the world, biological and ecological impacts are discernible.

General Observations

Shrimp trawlers in the Australian northern prawn fishery (NPF) discard some 1.5 tons and 70,000 individuals per vessel per night of the fishery (Northern Territory of Australia Dept. of Primary Industry and Fisheries 1992). More than 240 species, including 75 families of fish, 11 of shark, and several of crustaceans and mollusks have been identified in the discard of some 30,000 mt of annual discards for this region. Fifty species and 28 families have been identified in the landed fraction of the Malaysian shrimp bycatch. A total of 59 families and 46 species were collected during bycatch research in the Philippines (Ordonez 1985). In Singapore, 51 families were catalogued in the landed bycatch. Juveniles of commercially important species accounted for 32% of the Singapore bycatch, while 48% of the bycatch represented low-valued species which could be used for direct consumption or processed into fish paste and other products (Abdullah et al. 1983). In the same study, roughly 20% of the bycatch consisted of species considered unacceptable for human consumption (Sinoda et al. 1978). Off Brazil, 147 species have been reported in the bycatch and total discards constitute billions of fish. Claims have been made that “the inshore trawling with small meshes is placing at risk the whole ecosystem of the region” (Conolly 1992). In the Gulf of Mexico shrimp fisheries, an estimated five billion croaker (Micropogonias undulatus), 19 million red snapper (Lutjanus spp.), and three million Spanish mackerel (Scomberomonrus cavalla) were reported discarded in 1989 (Murray et al. 1992).

Data for the 1992 Bering Sea pollock trawl fishery show discards of nearly 130 species, including over 100 million pollock, 8.5 million rock sole, 3.2 million Pacific cod, and 2.3 million flounders (NOAA/NMFS 1992). Another 200 million pollock were reported to be discarded in other Bering Sea groundfish fisheries. The aggregate discards in the Bering Sea and Gulf of Alaska bottom fisheries approach 1 billion animals annually, exclusive of discards occurring in the inshore salmon and herring fisheries and offshore crab fisheries. In the North Sea, the Northeast U.S., some areas of West Africa, and off Brazil, discards of some species are reported in many years to equal or exceed the landed catches.

Although the aforementioned numbers are enormous, that alone is insufficient basis for de facto inferences about their biological or ecological impact. The 300+ million pollock discards observed in the Bering Sea in 1992, for example, represent 1.6% of the exploitable numbers of pollock in the Bering Sea, and for most years pollock discards constituted about 0.5% of the exploitable pollock biomass. Squid driftnet fisheries were frequently called “walls of death” (Nobbe 1990) and an “enormously wasteful fishery that vacuums life from the sea leaving a biological desert in its wake” (Campbell 1991) prior to the international driftnet ban which went into effect in 1992. Yet the present study of global discards demonstrates the rates of squid driftnet discards per number of retained individuals in the South Korean and Taiwanese fisheries are some of the lowest observed for any gear type in any fishery in the world. Of the 60+ species discarded in the squid driftnet fisheries, two populations appeared to be unable to support bycatch harvest levels like those observed in the Japanese squid driftnet fishery (Sidney Review 1991). For one of the two species, leatherback turtles, the severity of the effects “may vary from insignificant to very significant, depending on the stock composition of turtles taken by the squid driftnet fishery” (Sidney Review 1991).

Obviously, large quantities or numbers of discards do not necessarily equate with significant biological or ecological impacts. Conversely, to presume effects are minimal or absent because discard quantities or rates are low may also be misleading. Impact studies which bridge the gap between discard quantities and the consequences of these losses at the population and community levels are a necessary prerequisite to improvements in our understanding of the effect of fishery discards on biological populations and marine environments.

The impact of discards on non-target populations may differ significantly from the effects felt by target species and may depend on life history features of the impacted species. Species having life history strategies similar to the target species may not suffer to the same degree as those species with significantly different life history features. For example, species having low reproductive rates, elevated parental care, and low rates of natural mortality, “k” strategist species, may suffer greater impacts than “r” strategist species, especially if target species fishing strategies and quotas are “r” strategy based. Thus, the impacts of high discard numbers on cod, pollock, and flounders may be less than relatively low discard numbers on marine mammals, turtles, sharks, skates, and other similar species.

However, discards of small fish may generate very high levels of discard mortality that can impact even “r” selected species. Thus, discarding may contribute in a major way to problems of growth and recruitment overfishing in the directed fisheries and result in significant reductions in population levels of nontargeted species. Various studies have demonstrated bycatch and discards can alter the character of species assemblies (Wassenberg and Hill 1987; Hudson and Furness 1988; Blaber and Wassenberg 1989). Such shifts have the potential to alter predator/prey relationships, increase food for scavengers, modify the structure and function of benthic communities (as the result of oxygen depletion), and increase competition between fishers, marine mammals, and other sea life for the available resources. Although these impacts are more often inferred than demonstrated by careful research, the body of evidence supporting such claims has markedly increased over the past decade.

Population Level Impacts

A number of recent studies tends to confirm bycatch and discards are negatively impacting the levels of target species and non-target species. High discard rates of undersized target species in the Gulf of Marine groundfish fisheries have been identified as a contributing factor in population declines observed in the region (Saville 1980). In the Irish Sea, Brander (1981) notes the decline and scarcity of the once abundant common skate (Raja batis). Evidence strongly supports bycatch in the major groundfish fisheries as the reason for the demise of this species. Further, in the North Atlantic, minimum landing sizes for cod, haddock, and whiting in the mixed fishery lead to harvests of undersized cod and haddock which are, in turn, discarded. Chapter 7 discusses age-specific fishing mortality rates induced by discards for haddock and whiting. Discard mortality10 is responsible for 20%, 81%, 54%, and 16% of ages 1–4 fishing mortality, respectively, for haddock and more than 15% of fishing mortality for all whiting age classes under age 5. At these mortality levels, discards clearly exert a strong pressure on sub-adult population numbers. A lower overall exploitation rate which would tend to push harvest pressure away from the minimum legal sizes and, thus, lower discard mortality on immature individuals is suggested.

Many large-scale tropical and subtropical shrimp fisheries suffer from growth overfishing as a result of premature capture of juvenile shrimp on estuarine nursery grounds. Nevertheless, this overfishing problem is not the result of bycatch discarding, and significant changes in shrimping effort do not appear to cause sizable swings in yield, suggesting recruitment overfishing is not a big factor regarding shrimp population dynamics. However, shrimp fisheries are known to harvest large quantities of fish and other sea life and can impose heavy mortalities on non-target species (Blaber et al. 1990).

10Discard mortalities are based on instantaneous mortality values (F).

Studies on the impacts of shrimp fishery discards on finfish species and turtles in the Gulf of Mexico demonstrate reductions in population levels of non-target species. At least one non-target species, the Atlantic croaker, is reported to have declined to 40% of its abundance reported in the 1970s (Tillman 1992). Croaker in the Gulf of Mexico are described by Chittendon and McEachran (1975) as being a good example of the effects of overfishing on an incidentally captured species. It is noted the catch of croakers now consists almost entirely of a single year class of small fish in contrast to several year classes of much larger individual fish sizes in the 1950s. Between 1972 and 1989, 7.9 billion croaker a year were taken in the shrimp fishery (NOAA/NMFS 1992). Further, the Gulf of Mexico Fishery Management Council recently reported, as the result of a comprehensive stock assessment program in 1990, that the principle cause of fishing mortality on red snappers was from discarding in shrimp trawlers (Tillman 1992). Stocks of many other non-target species are known to have declined in abundance. Stock assessment modeling of Atlantic weakfish taken in the shrimp fishery demonstrates discard mortality may have a substantial effect on the long-term population level of this species.

Of course, species of little commercial or social value, such as the large amounts of discard in the tropical shrimp fisheries, may also experience discard mortalities. These species can serve as forage for or predators of commercially valuable species and make contributions to the trophic web. In addition, species of currently low economic value may become important target species in the future. Sturgeon (Acipenser spp.), for example, were considered a nuisance in the Columbia River salmon fisheries of the 19th century (Bricklemyer et al. 1989/1990). Consequently, thousands of sturgeon were caught and discarded, resulting in a population that is now a fraction of its original size.

Sharks are taken incidental to the harvests of many target species. Fisheries directed at sharks, particularly those for fins only, also occur. Some experts now believe total removals of the low fecundity and long-lived sharks are high enough to harm certain species. The U.S. has announced regulations limiting commercial and sport harvests and ban the practice of “finning”11 (Satchell 1992).

Contrary to the preceding paragraphs, sizable amounts of discards do not always result in significant impacts at the population level. In the Northwest Atlantic, from 20 mt to 2,000 mt (up to 108 million individuals) of redfish (Sebastes spp.) are reported discarded each year, although these removals account for less than 2% of redfish stock biomass and 3.4% of the standing population size in numbers (Atkinson 1984). However, the stocks of redfish off the Northeast United States are currently at very low levels and the yield is stated to be only 51% of its long-term potential. Thus, any added fishing mortality will serve to slow the pace of fishery recovery. In the Bering Sea, discards of pollock, cod, and sablefish (Anoplopoma fimbria) constitute less than 10% of the observed fishing mortality for these species (Table 20). Because such losses are counted against the TAC, discarding is an economic concern rather than a problem of unobserved or unaccounted for mortality. Discard mortalities imposed on rock sole (Lepidopsetta bilineata) and unidentified flounders (Pleuronectidae) exceed the mortalities caused by the landed catch. However, the combined discard and reported fishing mortalities for rock sole and flounders are sufficiently low to prevent overfishing, and hence in this instance discarding involves a wasteful fishing practice. For rockfish (Sebastes), a group historically suffering from excessive fishing, discards account for about one-half of the total fishing mortality.

11“Finning” is the practice of cutting off a shark's fin and then returning the animal to the ocean.

Table 20. Annual discard mortalities by species and the percent of total fishing mortality attributed to discards for fisheries in the Northeast Pacific (Bering Sea). Source: NRC and the NMFS.
Pacific cod0.0136.8%
Atka mackerel0.00815.1%
Yellowfin sole0.01226.1%
Rock sole0.01555.6%
Pacific Ocean perch0.00514.3%

Preliminary results like those presented above demonstrate the importance of documenting discard mortality. Such information is needed to get a firmer fix on the fishing mortalities impacting marine populations. Furthermore, the collection and analysis of discard impacts and the levels of imposed mortalities provide insights into potential community-level impacts not detectable from landing statistics alone.

12Mortalities imposed on halibut having their origins in the Bering Sea increase to about 8% because of bycatch taken in the Gulf of Alaska.

Changes in Species Assemblages

As a result of the different quantities and mortality rates imposed on target and non-target species, species assemblages of a region may be altered. Prior to the introduction of shrimp trawling, the families Leiognathidae, Ariidae, Carangidae, Nemipteridae, and Pomadasyidae dominated the marine community along the Terrengganu Coast of Malaysia (Chan and Liew 1986). The abundance of Leiognathidae, a family commonly taken and discarded in tropical shrimp fisheries, dropped sharply after trawling commenced. A similar pattern was noted in the Gulf of Thailand where Leiognathidae and Dasayatidae numbers fell significantly over a period of ten years of shrimp fishery exploitation (Pauly and Neal 1985). Harris and Poiner (1990) have noted certain demersal species discarded in the Gulf of Carpentaria declined in abundance over a twenty-year period, while some pelagic components of the catch increased in abundance.

Fishing mortality effects, including discard mortality, on species assemblages can also cross trophic levels and affect predator/prey relationships. Gulf of Alaska resource assessment surveys conducted in 1960 were dominated by several species of flatfish, king and Tanner crab, Pacific cod, Pacific Ocean perch, and sculpins. A decade later, walleye pollock abundance far surpassed that of any other species in the survey, with Pacific Ocean perch abundance dropping from 36.8 kg to 3.9 kg per trawl hour. Crab abundance also dropped, while the weight per unit of effort for flatfish remained generally stable to increasing (Ronholt et al. 1978). These changes are reported to have resulted from large increases in fishing effort, particularly by the Soviets and Japanese, in the Gulf of Alaska (Alverson 1992b).

Discard mortalities are known to have contributed to species structure changes observed in the Gulf of Alaska. For example, Pacific Ocean perch (POP) harvests reached 350,000 mt in 1965. Although discard rate data were not available from the 1960s, the application of recently collected Gulf of Alaska POP trawl discard rates to the 1965 POP fishery suggests the real fishing discard mortality imposed on this stock may have been 20% higher and led to an actual catch of about 420,000 mt. Not surprisingly, POP catch per unit effort fell from 50-100 kg/hour in the early 1960s to less than 10 kg/hour by the mid-1970s (Shippen 1984). Pacific Ocean perch populations have yet to recover to levels observed in the 1960s.13

Other work has shown the removal of juvenile predators may actually increase prey mortality (Browder 1981). Energy-flow models of the Gulf of Mexico shrimp fishery demonstrate the shrimp fishery there is capable of influencing groundfish predator populations. However, because this mortality reduces the abundance of prey similar in size to shrimp, predation pressure on the shrimp could increase. It is speculated that predators, having fewer options to select from, focus their attention on what remains, in this case the shrimp.

13 Although discards probably contributed to the collapse of the Sebastes population in the Gulf of Alaska, miscalculation of the age also led to unrealistic estimates of yield potentials.

Environmental Impacts

Bycatch and discards also have led to changes in benthic community structure. It has been observed trawl ground gears can penetrate up to 6 cm into bottom sediments and otter boards have been found to dig into the bottom to a depth of 0.3 meters (Caddy and Iles 1972; Arntz and Weber 1970; Krost et al. 1990). Obvious mortalities are generated when benthic species are brought to the surface and then discarded. Not the least of these are mortalities due to increased predation following the redistribution of benthic species into surface waters and on the seabed.

Nevertheless, habitat modifications resulting from discarding may, at times, be confused with habitat modification resulting from the gear itself, or with “unobserved fishing mortalities.” Because habitat and individuals can be damaged, but not brought to the surface, the extent of discard versus gear-induced mortalities may be difficult to quantify. A scallop stock inhabiting the Bass Strait in Australia was essentially eliminated within nine months of the start of a commercial fishery for scallops in the region. Much of the problem was related to an infection caused by decomposing scallops which had been crushed or damaged incidental to the scallop trawl operations. Researchers suspected that four to five times as many scallops were crushed or damaged as were landed (McLoughlin et al. 1991). In New Zealand, several deepwater fishing grounds have been exploited for the first time in recent years. Changes in bottom structure due to discards and trawl damage on these grounds were inferred from reductions in the number of invertebrate fauna brought to the surface over time (Jones 1992).

Grounds poisoning or spoiling is another indirect effect of discards on the benthic community. Poisoning refers to oxygen depletion occurring when non-target catch and processing waste is discarded at sea. If sufficient quantities settle to the bottom, decomposition processes consume enough oxygen to introduce anaerobic conditions. In general, if the discards are low in volume and returned over a broad area as the vessel is moving, it is assumed the discards are consumed by scavengers in the water column or on the bottom. In such instances the chances for depletion are minimal. However, local effects are possible and can be severe if heavy levels of discards occur.

Although unconfirmed, the dumping in 60 days of some 47,800 mt of discards in the New Zealand west coast hoki (Macruronus novazealandiae) fishery was projected to reduce oxygen saturation to 45%–55%. In the Northeast Atlantic Nephrops fishery, individuals often are “headed” at-sea and the “heads” discarded overboard. The presence of these heads on the bottom has been found to inhibit Nephrops bottom movements (Chapman 1981), thus “spoiling” the ground. The benthic community structure also may change if a greater proportion of the community is comprised of scavenger or decomposer species attracted to the area (Bricklemyer et al. 1989/1990).

Impacts Enhancing Population Levels

Not all of the biological or ecological impacts of discards are considered negative. Hill and Wassenberg (1990), for example, note that “discarding from trawls has the effect of transferring large quantities of biological material from the bottom to the surface. This makes available to surface scavengers food that would otherwise be inaccessible.” In all likelihood, discarding provides ready forage for surface, midwater, and benthic scavengers. Birds, sharks, dolphins, and other marine mammals commonly scavenge for food discarded in fishing operations.

Population increases for some sea birds inhabiting the North Sea have followed changes in prey availability brought about by altered fishing patterns. Primarily as a result of the at-sea discard of non-target species and processing wastes, the number of scavenging sea bird pairs in the North Sea region has risen from 37,000 in 1900 to 614,000 recently (Furness 1993; Hudson and Furness 1988). Birds, seals, and fish were found to be capable of consuming discards in fisheries located in the Wadden Sea (Berghahn 1990). Three species of sea birds are dependent on shrimp fishery discards in Moreton Bay, Australia (Blaber and Wassenberg 1989). Studies conducted in the Australian northern prawn fishery have shown benthic scavengers consume a considerable portion of the discards reaching the bottom (International Conference on Shrimp Bycatch 1992). Steller sea lions have been observed opportunistically following factory trawlers and consuming discards and processing wastes released by these vessels (Perez and Loughlin 1991).

Population enhancement of selected species due to discards may be offset by negative, but unobserved, impacts elsewhere. For example, species scavenging in and around fishing gear also increase their own susceptibility to incidental capture (INPFC 1990). However, population enhancements resulting from discards should not be neglected when considering how to deal with discards in the future. In the case of the changes in sea bird populations noted in the North Sea, a strict ban on discarding may lead to substantial population shifts away from conditions that have been almost a century in the making.

Impacts on Marine Mammals, Turtles and Birds

Marine Mammals

Bycatch and discards have also been shown to influence the population characteristics of marine mammals, sea birds, and sea turtles significantly. Vaquita (Phocoena sinus), a species of harbor porpoise inhabiting the Gulf of California, is taken as a bycatch in the gillnet fisheries of the Gulf. Although the target fishery for totoaba, where many of the incidental takes occur, has been banned, illegal fishing and the stock assessment fishery continue to remove some vaquita (IWC 1991). The vaquita is considered the most endangered marine cetacean in the world, and further incidental takes carry obvious implications.

Fishing practices, including the bottom snagline, are among several factors contributing to mortalities of the baiji (Lipotes vexillifer), or Chinese river dolphin. Additional fisheries enforcement measures have been introduced to protect the species, but only 300 individuals are believed to survive. Harbor porpoise kills in the Gulf of Maine sink gillnet fishery for groundfish are thought to be at least equal to and may be greater than the population growth rate of the stock of harbor porpoise (Murawski 1994). Additional harbor porpoise mortalities are added by the salmon gillnet fisheries off western Greenland, Newfoundland, and Labrador, and some are taken in cod traps. In a report to the International Whaling Commission, Bjorge et al. (1991) have stated these takes are “cause for concern.” However, mortalities of 2.5% of female Hooker sea lions (Phocarctos hookeri) in the trawl squid fisheries off New Zealand are not thought to be contributing to population changes there. Steller sea lion population changes in the North Pacific in recent decades are thought to be a result of several factors, not the least of which is a shift in the forage community structure caused by overharvest or environmental fluctuations impacting species abundance (Alverson 1992b).

Impacts of cetacean mortalities in passive gears were addressed at a 1991 IWC Workshop where scientists noted seven of 54 species population regions (SPR) had mortality rates for passive gears determined “to be not sustainable” (IWC 1991). Populations noted to be suffering from excessive mortalities included the baiji, the vaquita, the Indo-Pacific hump-backed dolphin (Sousa chinensis), two populations of bottlenose dolphins off the coast of South Africa, harbor porpoise in the Northwest Atlantic, and striped dolphin in the Mediterranean.

Considerable concern over declines in several populations and species of dolphins has been raised by scientists who have studied the impacts of bycatch in the ETP tuna seine fisheries. Fortunately, the populations in question have been stable for more than a decade and declines appear to have halted in the late 1970s. A recent study by the National Research Council concludes at present “the Eastern spinner dolphin (Stenella longirostris) is the subject of concern and is currently being proposed for depleted status under the U.S. Marine Mammal Protection Act.” However, the Council's report notes “estimates of numbers as a fraction of prefishery numbers vary widely because baseline estimates of pre-fishery numbers are low and because estimates of mortality rates--themselves very imprecise for the years before the mid-1970s--are used in calculating numbers.” Further, spotted dolphins (Stenella attenuata), subject to the greatest mortality in the ETP tuna seine fishery, “seem not to have been depleted as much as spinners.” Regardless, the evidence is clear that in the early years of the fishery, bycatch mortalities were significantly reducing population sizes of “the most commonly taken dolphins.” However, by the early 1970s, kill rates began to decline, and population sizes of impacted species have since stabilized. Reduction in mortalities were reported to result from (a) training of skippers to perform backdown procedures, (b) helping quiescent dolphins from the net, and (c) making gear modifications.14


Numerous seabirds are taken in gillnet and other fisheries. The importance of sea bird takes increases when such takes come from small local populations. From 2.1% to 9.3% of various populations of gannets (Sula bassana) are reported discarded annually in gillnet fisheries near Newfoundland (Piatt and Nettleship 1987). In the early 1980s, roughly 12% of Newfoundland's breeding population of razorbills (Alca torda) were killed each year in gillnets. As much as 16.3% of some adult common guillemot (Uria aalge) populations were killed by gillnets in and around Newfoundland in 1982 (Piatt and Nettleship 1987). Further, although the numbers are much smaller, the 200 annual mortalities of marbled murrelets (Brachyramphus marmoratus) in Barkley Sound, British Columbia, represent a considerable take from the population residing in the area (Coleman and Wehle 1983). Concerns that incidental takes in the salmon net fisheries may be damaging the marbled murrelet population have led to the introduction of a comprehensive on-board observer program in the purse seine and gillnet fisheries of northern Puget Sound, Washington.

Sea Turtles

Incidental takes of sea turtles in shrimp trawls have drawn a great deal of attention in recent years. Shrimp trawl bycatch of sea turtles has been identified by the National Research Council (1992) as the most significant source of sea turtle mortality in the United States. Since all five species of sea turtles found in the United States are listed as either threatened or endangered, effective controls on all sources of additional mortalities, including bycatch, have been encouraged. After years of development and testing, regulations requiring the use of Turtle Excluder Devices (TEDs) were issued in 1987 (Renaud et al. 1991). Because of concerns over crew safety and reduced shrimp harvesting efficiency, TED use was and still is contested by many shrimp fishermen. Nevertheless, the use of TEDs and Bycatch Reduction Devices (BRDs), which allow non-target fish and turtles to escape, is increasing.

14For a more comprehensive review of both direct and incidental catches of small cetaceans, the reader is referred to the Bjørge et al. (1991) report on “Significant Direct and Incidental Catches of Small Cetaceans” and the report on the “Incidental Capture of Marine Mammals” recently published by the Center for Marine Conservation (Young et al. 1993).

Crouse et al. (1987) found mortality of juvenile loggerheads (Caretta caretta) in shrimp trawls was preventing recovery of this threatened species. In a letter (to the authors), Crouse noted:

A National Academy of Science (Magnuson et al. 1990) study panel, assessing the causes of declines of sea turtle populations in the U.S., pointed to incidental capture and drowning in the shrimp trawl fishery in the southeastern U.S. and Gulf of Mexico as the “major cause of mortality associated with human activities, [killing] more sea turtles than all other human activities combined.” The panel estimated that as many as 50,000 loggerheads and 5,000 Kemp's ridley sea turtles (Lepidochelys kempii) drowned annually in this fishery in the 1980s. This is a particular concern for the Kemp's ridley, since the world's adult female nesting population is estimated to be fewer than 1000 individuals (USFWS and NMFS 1991). Regulations expanding requirements for turtle excluder devices (TEDs), which exclude 97% of the non-leatherback turtles captured, in all U.S. shrimp trawls by December, 1994 were published in December, 1992 (57 FR 57348– 57359). Since sea turtles are very slow to mature (green turtles (Chelonia mydas) may not become reproductively mature until 30–50 years of age), it may take decades to see the effects of management actions such as TEDs. Likewise, this unusually long juvenile period, combined with high mortality of eggs and the early life stages, leaves sea turtles populations highly vulnerable to losses of reproductive and soon-to-be-reproductive individuals (Crouse et al. 1987; Magnuson et al., 1990).
Beyond the shrimp trawl fishery, a number of other fisheries are implicated in sea turtle incidental capture and mortality, however, quantitative data are very hard to come by. Also, as mortality in the shrimp trawl fishery is reduced through the use of TEDs, the frequency of capture in other fisheries appears to be increasing, probably because there are more turtles available to be captured in these other fisheries. In general, otter trawls, gill nets (both anchored and drift) and long lines appear to take significant numbers whenever they co-occur with sea turtles. Other fishing gear types, such as pound nets and purse seines, also capture sea turtles, but they are usually released alive, unless intentionally injured (or eaten) by the fishermen.

Leatherback, loggerhead, and green sea turtles, of which leatherback and green are listed as endangered by the IUCN, were taken in the North Pacific high seas squid driftnet fisheries (FAO Sidney Review 1992). Loggerhead and green sea turtle discard mortalities in the same fishery were low and judged as having an insignificant effect on population characteristics. The severity of leatherback impacts was uncertain because scientists were not sure whether the turtles emanated from the Mexican or Malaysian breeding stocks. The Mexican stock is reportedly quite healthy and could support some incidental takes without consequence. Unfortunately, the Malaysian stock is depressed and additional mortalities induced by incidental takes in the driftnet fishery could worsen its condition.

Chapter Summary

Although a number of ideas have been put forth regarding the consequences of discarding in marine fisheries, supporting evidence of impacts at population levels, as well as ecological impacts, have been sparse until recent years. Nevertheless, there is a growing body of evidence clearly demonstrating the serious character of discarding of various marine population, including some fishes, marine mammals, and turtles. Discarding can be shown to be a significant component of the fishing mortality for species in the North Atlantic, Gulf of Mexico, and Bering Sea. For all world fisheries suffering from growth overfishing, discards are a component of the fishing mortality. Long-term alterations to species assemblages are detectable in many regions, although it is not readily discernible what roles are played by removals of target and non-target species, unobserved fishing mortality, and habitat modifications caused by fishing gears.


Discards introduce a variety of biological, ecological, and social costs. This chapter will focus on those purely economic in nature. Recent assessments of the economic impact of discards on commercial fisheries describe a set of costs far from trivial. Murawski's (1994) analysis of the Northwest Atlantic groundfish fishery found that $50 million of income was forgone to the local trawl fisheries as a result of the premature harvest and discard of the 1987 year class of yellowtail flounder. The value of the Gulf of Maine fisheries could double if discarding could be eliminated (Chapter 6). NRC (1991a) estimated the value of the prohibited species (crab and halibut) losses in the Bering Sea groundfish fisheries as $160 million15 at the first wholsale level. Losses due to discards in the Bering Sea crab fisheries contributed an additional $50 million loss. Earlier evaluation (NRC 1990) placed the value of non-target removals of crab, halibut, and salmon in Gulf of Alaska fisheries lost because of regional discards at between $20 million and $30 million per year. The aggregate Bering Sea and Gulf of Alaska losses of commercially harvested species resulting from discards has thus been in excess of $250 million annually.

These studies provide informative insights into the economic costs of discards. Unfortunately, few such studies exist, and consequently we are left with little more than a skeletal picture of the global scope of economic costs imposed by fishery discard. For example, we note:

  1. In the North Sea bottomfish fishery, the discard of marketable species equals the reported landings for the fishery.

  2. Off the Brazilian coast, discards in the trawl and shrimp fisheries are comparable to the size of the total landed catch.

  3. Off the U.S. East Coast in the Gulf of Maine discards of demersal species range from 35% to 79% of landed catch volume (Chapter 6).

  4. In many of the world's crab fisheries, numbers of discards significantly exceed landed numbers, and the weight of discards may also exceed the weight of landings.

If these discard costs are even remotely accurate, the aggregate economic losses due to discards in many fisheries and regions of the world may easily approach the value of landed catches. Unfortunately, a definitive test of this hypothesis is not possible, based on the current database.

15 Due to lost harvesting opportunities of the trawl fleet.

Because the origins of discard costs are diverse, various authors have suggested such costs be aggregated, based on specific criteria. The classification used by Smith and Lloyd (1989) is particularly informative because it relates economic impact to the group bearing the burden of the identified costs. The authors indicate discard impact costs are felt by those harvesting, processing, marketing, or consuming any species discarded by the target fishery. Control costs are the costs of measures taken by a fishery to minimize its discards. A final category, management costs, is tied to measures attempting to regulate discards. While we agree the cost categories Smith and Lloyd specify correctly describe the types of costs associated with discards, measurement realities make it difficult to assess each of these costs groups separately. Overlap unavoidably ensues. Consequently, in this chapter we have chosen to use a slightly different analytical paradigm, one aggregating the trilogy of coasts delineated by Smith and Lloyd into two broad groups. These two categories, the costs associated with the act of discarding and the costs tied to objectives of monitoring or preventing discards, provide a useful basis upon which to analyze the economic consequences of discards.

Impacts Associated with Discard Mortalities

Discards of Species of Commercial Value to Other Fisheries

In terms of estimates of economic losses imposed by discards, most published studies investigate discard mortalities induced by a fishery on species of commercial value to other fisheries. For obvious reasons, these sorts of mortalities often spawn bitter conflict between fisheries and lead to inter-gear battles and political infighting over resource allocation and bycatch removal quotas. Finding a solution minimizing losses to all gear types, or which satisfies society as a whole, is not an easy task. Complex sets of impacts and counter-impacts occur in all multigear fisheries.16

Linear programming analysis of various bycatch management strategies for the Bering Sea multi-species groundfish fishery was used by NRC (1991a) to search for an optimal solution to the catch and discard problems of the region. Using the extant fleet size, target species catch quotas, and bycatch rates collected by onboard observer programs, the NRC study searched for mixes of fishery start dates, quotas for Alaska pollock, and discard species allocations that would reduce the current estimated $150 million annual cost to halibut, crab, and salmon fisheries while maintaining positive net margins in the groundfish fleet.

16Catching juveniles of a target species may represent an economic loss in terms of foregone economic yield-per-recruit for the misbehaving fishery whether or not they are discarded. The losses are higher if they are discarded, since there are no short-term benefits. However, in most cases, there would be a cost in non-catching the juveniles associated with losses of the target age groups when trying to avoid non-target individuals or expenses due to costs for different gear. If, as in sequential fisheries, the losses are provoked by one fleet (which catches juveniles) but are incurred by another fleet (which targets older age groups), this type of allocation must be taken into account in any corrective measure.

The model revealed effecitive vessel-specific incentive or quota systems have great potential to reduce bycatch, new and uncomplicated fishery regulations can lower bycatch significantly, and benefits to the fishers and the nation can rise significantly in conjunction with the additional harvests these changes permit. It also revealed that crab fishermen in the region were their own worst enemy in terms of the bycatch losses they generate and that bycatch can vary tremendously from one vessel type to another. Furthermore, it became clear the current size and structure of the groundfish fleet would prevent it from attaining all of the potential benefits bycatch reduction could provide. Finally, sensitivity analyses altering discard survival rates demonstrated a reduction in the number of fish or crab that die after being taken as bycatch will, in and of itself, make a huge contribution to improving overall benefits.

Aside from the analysis of incentive-based management approaches, some specific regulatory options were investigated in the modeling effort. These uncomplicated scenarios were suggested by fishermen who felt changes, such as a shift in the start date of the Bering Sea groundfish fishery would take advantage of the different distribution of target and bycatch species at certain times of the year. A shift of the start date from the current January opening to November reduced the value of bycatch losses by 30% and permitted the harvest of more groundfish per dollar of bycatch loss than any other comparable model.

Another straightforward scenario required the harvest of the entire pollock resource with midwater trawl gear. This alternative lowered bycatch discard to the lowest levels of any model runs but, unfortunately, also reduced harvest and fishery revenues dramatically. In terms of bycatch discard reduction, performance of this option was exemplary. In terms of accrued economic and food production benefits to the nation, however, the strategy performed rather poorly.

One of the more interesting work products of the study was the finding that if effective bycatch management programs are put in place groundfish harvests almost reach Acceptable Biological Catch (ABC) limits before reaching bycatch quotas. This ABC-level fishery actually costs less in terms of bycatch losses than does the present fishery restricted to the lower Total Allowable Catch (TAC) levels.

Overall, the study demonstrated if fishers were permitted to use their individual capabilities to seek out the optimum mix of catch and bycatch, substantial reductions in aggregate bycatch are possible. The most striking results of the modeling effort were those showing a significant improvement in the bycatch picture (a 70% to 80% reduction in bycatch) with neutral side effects for the groundfisher would be possible if the profit-seeking fisher were given the incentive individually to improve the discard picture. Of course, the model selected those fishers making the best choices, and one could quite correctly argue existing management systems do not operate in such a fashion. Instead, under current management regimes, the rational, profit-seeking fisher, recognizing bycatch quotas on the horizon, races to catch as much fish as soon as possible in order to minimize his loss when those quotas are reached.

Successful incentive programs might emerge if decisions were transferred to the level of the individual fisher through carefully thought out incentive or ITQ programs. The capacity of incentive programs to reduce discard levels is based on the ability of the fishers to use their collective experience to avoid areas where high levels of unwanted species or sizes of species are taken. Furthermore, fishers also have a clear understanding of the implications of success or failure of their efforts, with rewards for success and disincentives/punishment for failure. In most current management systems, such rewards (catch) and punishments (closures) are felt only at the fishery level. With the system of individual incentives/disincentives, individual fishermen have the capacity to control their status. Incentive programs, however, require some sort of accountability process which to date has largely been dependent on relatively costly observer programs.

Discards of Non-Legal Individuals

A second set of -induced mortalities carrying obvious economic implications is what is suffered when a fishery discards immature individuals or non-legal sexes of the same species group it is targeting. Several examples can be found of the benefits of minimizing such losses. Poffenberger (1982) determined shrimp harvest value increased $9.4 million following fishery closures off Texas, permitting juvenile shrimp to grow to more marketable sizes. NRC (1990) estimated annual losses of discarded sublegal or non-legal crabs in the Bering Sea crab fisheries might be as high as $40 million to $50 million in some years. Chapters 5, 6, and 7 in this study provide evidence of significant economic losses resulting from discarding of under-aged demersal fishes.

Disincentives for the capture of immature fish are now emerging in some fisheries. For example, in the Bering Sea groundfish fisheries discards and retained weights are deducted from TAC quotas. The cost to Bering Sea fishermen for the capture of immature pollock by their vessels and by pollock taken by fisheries targeting other species in 1992 is established at about $35 million.17 That is, if the immatures were not taken, the increase in the catch of marketable pollock which would have occurred would have raised the value of the harvest by this amount. As already mentioned, however, such accountability is more the exception than the norm in today's fisheries management. Moreover, with the exception of systems like New Zealand's Individual Transferable Quota, accounting occurs at the fishery rather than at the individual fisher level, and such aggregated programs may serve less well as economic disincentives than do vessel- or fisher-based systems.

17 This loss reflects the increased dollar yield, assuming no change in quota would have occurred if immatures had not been taken. The estimate also assumes constant prices. It does not consider costs that might be incurred to avoid bycatch or the technology that might allow a zero bycatch level.

Much more attention needs to be directed at the cost of this form of discard mortality. With the exception of the large reduction fisheries, most commercial and recreational fisheries are directed at specific size/age classes optimizing economic performance, either on the factory line or for personal pleasure in the sport fishery. Until recently, the discard of non-legal or other-than-optimum sizes/sexes taken in conjunction with the target sizes/sexes has often been ignored in calculating real fishing mortality. Consequently, target quotas are met and fisheries closed only when the tonnage of legal/optimum-sized individuals is reached, despite the possibility that owing to discards, actual mortalities of the species induced by the fishery may be much higher.

Discards of Non-target Species of Little Commercial Value

A third and often overlooked stream of economic costs is associated with discards of non-target species having no economic value to a fishery. While at first glance one might question whether any economic cost can be associated with such removals, failing to account for such losses would neglect the often interdependent nature of species with and without commercial value.

Catching an unwanted species represents an economic loss because of (a) the cost of catching it, sorting it from the target catch, and throwing it back overboard, and (b) the foregone economic value of the discard if it were better exploited.

Costs can be tied to the longer on-deck sorting times necessary to separate and return prohibited or unwanted species to the water. For at-sea processors, lower factory throughput efficiencies and higher processing crew costs due to the additional time required to separate discards from the retained catch are the direct result of the presence of discards in the catch.

In our review of the discard literature, few studies of the actual costs such inefficiencies impose on a fishery have been identified. An index of such losses could be derived by an estimate of “wasted” effort units in a fishery. The value of each unit of wasted effort would reflect harvesting and processing costs and would be some function of the value of “effective” effort units.

While such an index would require scaling to a per-vessel level, ballpark figures offer insights into the scope of this form of economic costs. In 1992, pollock discards accounted for 6.2% of retained pollock harvests in the Bering Sea. For the sake of simplicity, if aggregate catch-per-unit-effort (CPUE) is related linearly to CPUE for retained individuals, then discard effort is a linear function of discard rate and total effort. Thus, for example, one can suggest 6.2% of the effort expended to harvest pollock in the Bering Sea in 1992 was wasted, since it was expended on pollock later discarded. Since data are available on the variable costs of factory trawl operations in the Bering Sea, it can be assumed the entire Bering Sea pollock harvest was taken by such vessels. (Actually, 1992 factory trawl catches accounted for 68% of pollock harvests.) Under these assumptions, “wasted” effort in the 1992 fishery represented an economic operating cost of $1.03 million. While not a definitive response to interest in the inefficiency costs of discards, such an index does demonstrate such inefficiencies should not be overlooked in a rational assessment of total economic costs associated with discards.

If a discard species can be exploited by other sectors, such as turtle watching or another fishery, the value of discard losses depends on how much alternative users are willing to pay. There are also benefits when species take advantage of discards to proliferate. Discarded fish may bring profits to the cephalopod or shrimp industry by increasing food availability and abundance of the target resources.

In many cases, species of commercial value prey upon each other and on those with no commercial value. Removals of a prey species as a discard mortality may have measurable effects on the growth, survival, and reproductive conditions of the exploited species. If negative, these impacts can introduce costly economic effects into the fishery. Conversely, economic benefits may ensue if discard mortalities “fine-tune” the ecosystem, improve prey species populations characteristics, or remove predators which constrict survival of the commercially valuable species. Given our understanding, or lack thereof, of real between-species dependencies in the marine system, these potential economic costs have been largely unknown to date. As this knowledge grows, we should attempt to conduct ever more critical analyses of the extent of such costs.

A special case of the set of costs associated with the discarding of species with and without commercial value bears some mention. This unique situation is of growing concern, is often accompanied by changes to traditional bycatch use patterns, and involves the redistribution of income and landings from artisanal to larger, more mechanized vessels. Pauly and Neal (1985) in their discussion of Southeast Asia shrimp fisheries, notes one of the definitive characteristics of the modernization of the shrimp fleet in Southeast Asia is the trend toward longer trips. For economic reasons related to on-board storage space and the market value of shrimp compared to other species in the catch, a significant portion of the catch of finfishes is discarded. An unfortunate artifact of this trend is the reduction in landings of low-valued species which have historically served as a cheap source of protein for coastal populations and supported animal husbandry. Perhaps as the scarcity of such discarded fish worsens, their value will increase until a new equilibrium is established between landings, demand, and per-unit cost. However, the new unit cost of the bycatch fraction will undoubtedly be higher than it was prior to the modernization of the fleet. Such higher costs may well result in one of two possible scenarios for low-income or impoverished populations of Southeast Asia and other developing regions of the world--an increase in family expenditures to meet protein needs or a reduction in protein consumption.

Costs Associated with Monitoring and Preventing or Reducing Discard Levels

The second category of economic costs associated with discards is tied to the objective of preventing or monitoring discards. Included within this category are management and enforcement costs and costs involving required modifications to gear and changes in fishing patterns in order to reduce bycatch.

The 1992 budget for marine fisheries management in the U.S. of approximately $200 million represented $0.045 of management expenditures per pound of landed harvest weight. It is difficult to determine just how much of this management budget was spent directly or indirectly on bycatch management, monitoring, or prevention. Let us assume, however, that 10% of U.S. costs were spent on discard concerns and that discard budgets in other nations are themselves just 50% of the U.S. allotment for discards. Doing so generates a global tab for discard-related costs of $4.5 billion. Even under conservative assumptions of expenditure allocations, costs associated with the management, monitoring, or prevention of discards are staggering.

Lost fishing opportunity constitutes another area of economic costs associated with discarding. For gear types discontinued because of discard impacts, losses to the involved fishery will be complete. Further, if alternate harvesting systems cannot be introduced for such fisheries, the economic loss to society is also complete, even though ethical and biological/ecological concerns may have been addressed. In fisheries where discard quotas exist, large quantities of target species harvests will be lost when these discard quotas are reached. Attainment of the discard quotas triggers selective species closure or generic, area-wide, across-species bans on fishing. Although such closures can limit the operation of all gear types, equity considerations typically result in restrictions on the offending gear type.

Potential economic costs associated with the closure of fisheries prior to the attainment of the target species quotas are neither trivial nor infrequent. In the Bering Sea in 1991, discard quotas contributed to the closures of the bottom trawl fishery for rock sole, pollock, cod, and flatfish, as well as crab pot fisheries for bairdi Tanner crab. Similarly, in 1990, discard quotas closed eight major fisheries in the region. In the Gulf of Alaska, the halibut bycatch quota has served as a barrier to the development of a large and economically valuable resource. The potential yield of flounders in this region is set at 442,000 mt, but less than 10% of the take is normally harvested. Access to these economically important flounder stocks are currently dependent on the evolution of more selective gear types or the relaxation of current prohibited species quotas. In addition to curtailing access to these species, in an open-access fishery such closures can complicate discard management in the region. As closure in one fishery push effort into other areas, the race for fish intensifies, and as closures approach, selective fishing practices minimizing discards may be ignored. Fishers frequently believe fish they don't catch today may not be available for the taking tomorrow. Clearly, biological, if not economic, wastage is encouraged.

Of course, different management institutions use quotas in different ways. In the multi-species Northeast Atlantic groundfishery, for example, quota attainment for a species requires that species to be discarded overboard. Since many of these discarded individuals die, the management significance of such quotas is drawn into question. Perhaps a more biologically and economically sound approach is reflected in New Zealand's ITQ system. Here, quotas for discard species are subdivided among participating vessels and can be traded. Economic costs of quota attainment for a specific vessel are embodied in the costs associated with the purchase of additional discard quota. Presumably, as the supply of such unused discard quota dwindles, the per unit cost of the discard quota rises. When all such quota is exhausted, vessels without remaining quota are forced out of the fishery. Their costs become the value of their remaining inaccessible target quota less variable and discard quota costs that would have been expended had they harvested the quota. Such a system perhaps better reflects the true cost of discarding.

Observer costs are another item for which total expenditures should be prorated across discards and other fisheries management costs. However, given the presence of operational observer programs in the Northeast Pacific and elsewhere, per-unit observer costs are much more tangible than other management costs. After nearly four years of operation, observer costs associated with full-time coverage of vessels participating in the U.S. Bering Sea and Gulf of Alaska groundfish and crab fisheries range from $3,500 to over $5,000 per month. These costs are paid to observer contractors who hire qualified individuals and place them on contracted vessels.18 Observe costs can clearly be substantial, and this in large part explains why observer programs have not been implemented more comprehensively. Faced with such costs, marginal vessels or even low-marging operations could be forced out of the fishery.

Enforcement costs associated with wild harvest commercial and recreational fisheries are substantial. In the North Pacific alone, U.S. fisheries enforcement costs total $80 million annually. Unfortunately, given the number of stocks currently overfished in global fisheries, ongoing problems with illegal fishing on the high seas and emerging concerns over high-grading and other means of economic poaching, current enforcement capabilities are not real deterrents to such actions. While some of the problems concerned with documenting discard levels can be dealt with through the use of observers, in many fisheries they may be impractical.

Another area of costs imposed when seeking to prevent discards is tied to gear or fishing pattern modifications mandated by bycatch regulations. Griffin and Hendrickson (1992) estimated the present value of the use of bycatch reduction devices in the U.S. Gulf of Mexico shrimp fleet would represent a cost to the fishery of $16.4 million to $27 million over a ten-year period. Fishery closures mandating changes in fishing patterns would be still more costly--$35.2 million to $54.6 million. NRC (1991a) demonstrated the current pattern of fishing by bottom fishermen in the Bering Sea costs the industry and the nation from $30 million to $120 million per year.19

18We understand observer program costs in U.S. East Coast fisheries have reached monthly costs of up to $10,000.

In many fisheries, current fishing practices and gear riggings produce discards carrying with them an assortment of economic costs. Gear modifications or alternative fishing approaches have the potential of reducing the catch of unwanted fish or shellfish, but at what expense to target catch and processing or handling rates? Break-even results may not be good enough to induce fishers to shift fishing practices; that is, unless real financial benefits can be associated with the new gear type/method, fishers will not voluntarily modify their behavior. Although regulations mandating the use of new gear have been imposed in certain fisheries, their effectiveness may be negated if there is strong user-group resistance to employing the new gear. The alternative then becomes the development of gear types, fishing strategies, or fishery management options that encourage fishers to adapt low discard rate practices.

Chapter Summary

Economic impacts flowing from discarding include (1) foregone catch as a result of mortalities imposed on recruits to the target fishery, (2) foregone catch resulting from mortalities imposed on target fisheries by fisheries targeting other species, (3) loss of fishing operations resulting from bycatch quotas forcing fishery closures when attained, (4) costs of purchasing new technology, (5) loss of catch when a gear type is outlawed, and (6) loss of catch due to capture of immatures subtracted from the TAC. Other economic losses result from required observed programs and sorting costs. In total, the loss of potential catch resulting from discarding or discard regulations amounts to billions of U.S. dollars, and in many fisheries the losses due to discard mortalities are noted to equal or exceed landed catches.

Much more work is needed to assess adequately the true economic cost of discards on fishers and the benefits and costs of potential solutions to society as a whole. We should not forget, however, that discarding is not all bad. Mortalities associated with discards may decrease key predator or competitor populations. Discards may increase prey availability and enhance system productivity. Furthermore, in many cases, discarding practices permit fisheries to remain cost effective. Currently, society views the benefits of such continued viability as outweighing the potential costs imposed on marine ecosystems. Only in the last few years have environmental groups begun to use political pressure to promote commercial embargoes or trade barriers to overcome this problem. Much more work is needed to assess adequately the true economic costs and benefits of discards on fishers and the societies of which they are a part. Revised cost/benefit accounting procedures and better natural resource economics may offer the basis for more rational alternatives.

19 Current approaches use fishery-wide quotas to control harvest. Such quotas result in a race for fish that produces a waste of fish. NRC found by moving the incentive to fish cleanly to the individual fisher level, discard losses would decline by $30 million to $120 million.


The nature of most economic, biological, and ecological variables is such that if an effect is suspected, measurement and evaluation of the underlying data can usually confirm or reject its presence. If confirmed, the effect can be further parameterized by its dollar value, weight, number, diversity level, or other indices. Thus, the value of the TAC no longer available to halibut longliners because of its removal as discards in the groundfishery is one measure of the economic effect of discards on the halibut fisher. Likewise, a reduction in population abundance due to the growth overfishing of a given species is an index of a biological impact and the elimination of a predator due to excessive discard mortality a reflection of ecological change.

Although disagreements over the presence or absence of an economic, biological, or ecological discard effect may occur due to debates over proper analytical methods or measurement errors, the described impact can usually be recognized by the participants in the fisheries of concern. However, the perception of the consequence of a discard impact or its importance may vary sharply between countries as the result of socio-cultural differences or their dependence on marine resources as a source of protein for their population, religious beliefs, and historical customs. Thus, the success of a proposed international fishery management strategy designed to reduce discard mortality will benefit from an understanding of the distinct attitudes of separate societies towards the biological, economic, esthetic, and ethical aspects of discards. To date, efforts to understand socio-cultural distinctions or different national dependencies upon marine resources as protein staples appear to have played little or no role in regional or international discard policy evolution. Instead, the issue of discards and the “correct” attitude towards them is clouded because each society clings tightly to the vision they believe appropriate. This is particularly true for the emerging bycatch policies that have impacted or will impact bycatch discarding in the ETP purse seine tuna fishery and the high seas driftnet fishery as well as the use of TEDs in world tropical shrimp fisheries.

Discard Conflicts Based in Socio-Cultural Differences

As a consequence of competing socio-cultural visions, the intensity of conflicts over the discard issue should not be surprising. From the perspective of many conservation/environmental groups in the U.S. and elsewhere, it seems appropriate and necessary to demand an embargo on shrimp from Indonesia due to turtle discards in these fisheries (Seattle Post-Intelligencer 1992). On the other hand, to the Indonesian shrimp fisherman whose principal source of income comes from the shrimp he harvests, such an embargo appears unfair and totalitarian. Oregon sport fishermen eager to implement a gillnet ban in state waters are likely to disregard the interests of commercial netters who have operated in the fishery for generations (Fiorillo 1991). Dolphin-safe tuna marketing programs are lauded by many environmental/conservation groups on ethical grounds they protect marine mammals (Kronman 1992). Persuading these groups to take into account the differing concerns of impacted participants or to change their attitudes and management tactics based on technological advances may be difficult, if not unlikely. For example, a significant reduction in dolphin mortality has occurred in tuna fisheries setting on porpoise schools, making such gear theoretically more acceptable. Although the bycatch of juvenile yellowfin (Thunnus albacares), skipjack (Katsuwonus pelamis), and other pelagic fishes has been shown to be very high in some alternative seine fishing modes, efforts to outlaw the use of purse seines or ban sets on porpoise schools in tuna fisheries continue. Dr. Martin Hall of the IATTC (seminar, University of Washington 1994) noted:

Many attempts have been made to solve the tuna-dolphin problem ranging from embargoes to consumer actions…. With dolphin mortality reduced 97% since 1986 and a projected mortality of 3,500 individuals for 1993, this is no longer a conservation issue. This question is now how to harmonize the different priorities and concerns, economic interests, cultural views, etc., of the countries involved in the fishery, in a solution that takes into account both the ecological and social angles of the issue.

Hall (1994) notes the need and difficulties of achieving truly multinational, science-based ecosystem management schemes.

In a similar twist of perception and reality, driftnets have been labeled “walls of death” at the same time Italian and Chinese fishermen have been encouraged to use them because of their reported conservation properties. Data demonstrates some driftnets have relatively low discard ratios. Furthermore, although the thrust of much of this volume is the documentation of bycatch discard quantities and the excessive nature of these losses, at the same time it is noted that some fishers encourage the development of shrimp trawls that take more fish because of potential sales into shoreside protein markets (Pauly and Neal 1985).

With each of these issues, who is right and who is wrong is largely a function of vantage point. After reviewing much of the literature describing the socio-cultural impasses resulting from discards, it appears such national and international standoffs are frequently driven by ethics, esthetics, or societal attitudes toward the consumption of various marine products.

Attitudes Toward Non-Consumptive Uses and Their Impact on Policy Formulation

Hartmann (1992), in his review of the World Fisheries Congress, states that “there is a bias in management towards the needs of the developed countries; the dynamics and ecological social importance of artisanal fisheries are ignored.” Such bias towards first-world interests goes much deeper than just management issues. Conservation and environmental protection attitudes are frequently seen as driven by U.S. and European societies. The 1992 Roper survey on U.S. National Resource Conservation attitudes in the 1990s (National Research Council 1992) offers some insights into the nature of these attitudes. About 80% of Americans consider themselves active environmentalists or sympathetic to environmental concerns. Two-thirds of the populace state they think environmental regulations have not gone far enough. Sixty to seventy percent of Americans also rank environmental concerns before economic ones when compromises between the two cannot be reached.

Environmental and economic concerns of the U.S. public lessen, however, as we move down the economic ladder in the United States. Thirty-eight percent of the least wealthy Americans, as opposed to only 21% of the most well off, believe economic issues outweigh environmental onces. Given the continuum of economic status across socio-economic groups in the U.S., we would not be surprised to witness the steadily increasing concern for economic considerations in many developing countries.

Environmental/conservation concerns date back to the first recitations of the concept of “Public Trust” in English Common Law (Everitt et al. 1980). Public trust precepts simply assert all fish (and wildlife, for that matter) are held in common by all people. In such a context, consumptive and non-consumptive uses of these resources are equally legitimate. As the number and diversity of non-consumptive uses of fish have increased in recent decades, the relevance of these interests to environmental decision-making has also grown. Due largely to their economic well-being, the developed states have witnessed the fastest growth in non-consumptive uses. Given the international influence of these states, their role in promoting national and international bycatch and discard policy is not surprising.

A classic example of the emerging importance of some developed states' attitudes toward the environment and living resources pertains to marine mammals. Although the Roper survey did not investigate U.S. opinions toward marine mammals, Kellert's (1979) review is enlightening. In 1979, issues including DDT and bird survival, leg-hold traps, the Endangered Species Act, the killing of livestock by coyotes, and the Tellico snail darter controversy were major environmental topics. Nevertheless, the issue most widely recognized and opposed by the U.S. public at that time was the commercial and subsistence hunting of harp seals for fur.

Media attention to tuna-dolphin concerns, high seas driftnets, manatees, whale stranding, and sea lion declines has greatly fostered the recognition of marine mammal issues since 1979. Lynge (1992) argues whales (and presumably other marine mammals) have been ascribed a “uniquely special” status by Western cultures that segregate biological life into three bundles: humans, whales and all other biological life. Marine mammal intelligence, social organization, communication, and presumed “innocence” has broad appeal in many Western societies, but at the same time, such views have formed a fertile ground for the growth of international socio-cultural conflicts. Lynge (1992) raises the relevant question: Are these attitudes toward marine mammals as universal as perceptions suggest? Does Western thought and attitude supersede that of cultures where respect for an animal and the killing of it go hand in hand?

Contrary to perhaps common belief, marine mammals are not viewed equally by every nation. They are hunted for meat in Peru, Chile, Sri Lanka, Greenland, the U.S. (aboriginal harvest), and many other nations (Northridge 1991b). Regardless, most countries would appear to agree to agree it is better not to kill a marine mammal or sea turtle through incidental contact with a net, trawl, or other piece of fishing gear if such contact and mortality can be avoided. Also, it appears to be agreed it is better to avoid discards whenever possible and have national policies which seek to minimize such waste. However, achieving these goals may require some scientifically documented evidence that a real conservation, ecological, or economic problem exists. When significant ideological differences involving the use of resources occur, efforts to recognize and work within the boundaries of such socio-cultural distinctions must be made.

Discard Conflicts Spawned by Socio-Cultural Differences between Developed and Developing Countries

Recognition of cultural differences between developed and developing countries is particularly critical when addressing resource use issues. Much of the developing world encounters conditions differing starkly from those in developed nations. In the U.S., less than 3% of total protein is derived from fish. In contrast, 60% of the remaining world population receives over 40% of its animal protein from fish, and nearly one billion people in Asia depend on fish for their entire supply of protein. Reduction of fish available for consumption in many developing countries would push the average level of protein consumption in these countries into the “deficiency” category. To replace fish with, say, beef protein would require 200 million more beef cattle per year, a quantity in itself associated with obvious environmental consequences (Strand et al. 1992).

Fish also represent a significant source of export earnings for many developing nations. In 1985, fish accounted for at least 20% of export earnings in 21 countries (Strand et al. 1992). Such earnings permitted developing countries to purchase grain, foodstuffs, and other goods and services otherwise unavailable to them.

On a smaller scale, fish are important in many developing nations. In a study of six villages around the Bay of Bengal, 34% of the households in the villages were completely dependent on fishing for their income, while another 25% depended jointly on fishing and fish marketing (Bay of Bengal News 1992). Fishing formed at least part of the household income in 28% of the remaining 41% of the households. Loss of the fisheries on which these villages depend would have dire consequences.

Socio-Cultural Attitudes Toward Discards Based on Different Dependencies on Marine Resources

Although many ideological confrontations associated with bycatch exist between developed and developing countries, a great many consequential disputes related to discards have occurred between developed nations, such as the whaling and driftnet issues. As a result, a more useful paradigm for the analysis of discard concerns inspired by socio-cultural disputes emerges if one considers these disputes in the light of national dependencies on marine resources as a protein staple. Within such a context, discard attitudes of developed nations with a high dependence on marine protein sources are more closely aligned with those of many developing nations than they are with other developed countries for which marine protein sources are less critical components of the national diet.

The cultural ideologies of a nation more heavily dependent upon marine resources as a source of protein for its own population may have positive effects on bycatch management. For one thing, its domestic fisheries may be far less wasteful. The management policies of that nation may clearly reflect an ideology seeking to maximize the long-term protein yield from the entire resource complex. For example, because utilization of the entire complex of harvested species is more balanced, regulations can be adjusted to reduce effort on one component of that complex that is overexploited without sacrificing efficiency in utilization of the entire complex. Short-term attitudes leading to widespread overexploitation and a deterioration of the viability of the protein resource cannot co-exist with such philosophies.

Under such systems, be they in developed or developing countries, bycatch is not wasted. Bycatch is utilized because the nation itself is dependent upon a larger component of the resource complex for its protein needs. Although different fishermen fish different gear types and, of course, have distinctive bycatch discard concerns, conflicts which could emerge from these differences are subjugated for the greater good. Because the community to which the various groups of fishermen belong is directly dependent upon the resource for food, fishermen give way to a cultural ideology that places wise, yet maximum, use benefiting the community as a whole ahead of inter-gear allocation squabbles.

The many island communities of the world are examples of the cultural ideologies heavily dependent upon marine resources for their own domestic consumption. The geography of island communities in many instances has dictated a food culture distinct from what has developed on Asian, European, and American continents. Compared with the early continental inhabitants who relied upon agriculture and land animals for their food, island communities have turned to animal and plant life from highly productive coastal waters for their main source of protein and vitamins.

The link between the sea and the consumer is much more remote in nations such as the U.S. where fisheries constitute a small component of the food intake. Consequently, social interest in fisheries, if not associated with marine mammals, seabirds, and turtles, has been very slow to develop. Nations with high dependencies on marine resources may look askance at the attitudes of such countries toward marine resource use and management, considering such attitudes wasteful and greedy (Ludwig et al. 1993).

Within-Culture, Social Differences that Drive Discard Conflicts

Clearly, discard problems also offer competing fishers a lever to improve their financial/allocative position in the name of what is right in terms of conservation and the environment. An unfortunate truth of the Olympic fishing system20 is that all too often the arguments on all sides are at least partially correct and worthy of attention. Intensive trawling operations conducted under the constraint of short seasons induce discard mortalities that might otherwise be avoided if more rational systems were in place. But the same can be said of every other gear type. Thus, addressing the discards in Olympic style fisheries will require close attention to the spectrum of fisheries involved, taking into account fishery-specific discard problems.

How prevalent are similar inter-gear disagreements in the developing world? It appears considerable attention has been given to the development of opportunities for marketing discards, but the role discards play in the allocation of target species is still relatively insignificant. As these fisheries continue to develop and shortages of available resources become more acute, we would expect to see an expansion of this problem. Whether the problem reaches the extent now observed in many developed states may be largely a function of whether or not the developing world moves away from the open-access, free-for-all characteristics of Olympic fisheries prevailing in many of today's developed nations' fisheries.

Development of Discard Policies Recognizing Socio-Cultural Differences

Because of the critical importance of fisheries to many developed and developing nations, the evolution of global bycatch and discard strategies should be designed to minimize social conflicts and, to the degree possible, be independent of ideological differences and be based on sound conservation principles. Many of the environmental/conservation programs designed to reduce the catch and discard of marine mammals, turtles, and seabirds have their origins in developed countries. This subset of the world community should be careful to not foist ideological use-based ethics summarily on other nations, be they developed or developing. Instead, if they are sensitive to the socio-cultural and socio-economic circumstances of the developing world in the application of emerging environmental and conservation standards, global acceptance of world bycatch and discard policies will be much more feasible.

20 A fishery having a quota, but open to all interested participants thus stimulating a race for available fish.

The recently signed UNCED agreements and Agenda 21 are excellent examples of instruments of change in our treatment of living ocean resources and the environment. Rather than unilateral pronouncements, these agreements represent months of multi-lateral negotiations attempting to deal with the many rights, beliefs, and obligations of the diverse cultures on this planet. It is hoped this will be more the rule than the exception in our approach to ocean management in the future.

Chapter Summary

Discarding creates a number of problems broadly recognized by the international community. However, stands on ethical issues are not equally appreciated in all countries. Further, solutions to resolve some conservation problems are not fully understood or accepted by various sectors of the world community. Recognition of socio-cultural differences and efforts to bridge current conflict arenas are seen as important to an international effort to promote the reduction in fisheries discarding.

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