CHAPTER 2 BIOLOGICAL AND ECOLOGICAL IMPACTS
Introduction
A great deal of concern has been expressed by fishery managers andconservation/environmental groups that bycatch and discards may be contributing tobiological overfishing and altering the structure of marine ecosystems. Such claimsare frequently based on observations of large numbers of discards and high discardratios or rates as provided in the previous chapter, but infrequently on detailedpopulation assessments of impacted stocks. This is perhaps because comprehensiveand historical datasets involving discards have been unavailable to demonstrate suchclaims. Regardless, a growing body of literature does support the conclusion thatfor some species and regions of the world, biological and ecological impacts arediscernible.
General Observations
Shrimp trawlers in the Australian northern prawn fishery (NPF) discardsome 1.5 tons and 70,000 individuals per vessel per night of the fishery (NorthernTerritory of Australia Dept. of Primary Industry and Fisheries 1992). More than240 species, including 75 families of fish, 11 of shark, and several of crustaceansand mollusks have been identified in the discard of some 30,000 mt of annualdiscards for this region. Fifty species and 28 families have been identified in thelanded fraction of the Malaysian shrimp bycatch. A total of 59 families and 46species were collected during bycatch research in the Philippines (Ordonez 1985).In Singapore, 51 families were catalogued in the landed bycatch. Juveniles ofcommercially important species accounted for 32% of the Singapore bycatch, while48% of the bycatch represented low-valued species which could be used for directconsumption or processed into fish paste and other products (Abdullah et al. 1983).In the same study, roughly 20% of the bycatch consisted of species consideredunacceptable for human consumption (Sinoda et al. 1978). Off Brazil, 147 specieshave 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 atrisk the whole ecosystem of the region” (Conolly 1992). In the Gulf of Mexicoshrimp fisheries, an estimated five billion croaker (Micropogonias undulatus), 19million 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 nearly130 species, including over 100 million pollock, 8.5 million rock sole, 3.2 millionPacific cod, and 2.3 million flounders (NOAA/NMFS 1992). Another 200 millionpollock were reported to be discarded in other Bering Sea groundfish fisheries. Theaggregate discards in the Bering Sea and Gulf of Alaska bottom fisheries approach1 billion animals annually, exclusive of discards occurring in the inshore salmonand herring fisheries and offshore crab fisheries. In the North Sea, the NortheastU.S., some areas of West Africa, and off Brazil, discards of some species arereported in many years to equal or exceed the landed catches.
Although the aforementioned numbers are enormous, that alone isinsufficient basis for de facto inferences about their biological or ecological impact.The 300+ million pollock discards observed in the Bering Sea in 1992, forexample, 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 exploitablepollock biomass. Squid driftnet fisheries were frequently called “walls of death”(Nobbe 1990) and an “enormously wasteful fishery that vacuums life from the sealeaving a biological desert in its wake” (Campbell 1991) prior to the internationaldriftnet ban which went into effect in 1992. Yet the present study of globaldiscards demonstrates the rates of squid driftnet discards per number of retainedindividuals in the South Korean and Taiwanese fisheries are some of the lowestobserved for any gear type in any fishery in the world. Of the 60+ speciesdiscarded in the squid driftnet fisheries, two populations appeared to be unable tosupport bycatch harvest levels like those observed in the Japanese squid driftnetfishery (Sidney Review 1991). For one of the two species, leatherback turtles, theseverity of the effects “may vary from insignificant to very significant, dependingon the stock composition of turtles taken by the squid driftnet fishery” (SidneyReview 1991).
Obviously, large quantities or numbers of discards do not necessarily equatewith significant biological or ecological impacts. Conversely, to presume effectsare minimal or absent because discard quantities or rates are low may also bemisleading. Impact studies which bridge the gap between discard quantities and theconsequences of these losses at the population and community levels are a necessaryprerequisite to improvements in our understanding of the effect of fishery discardson biological populations and marine environments.
The impact of discards on non-target populations may differ significantlyfrom the effects felt by target species and may depend on life history features of theimpacted species. Species having life history strategies similar to the target speciesmay not suffer to the same degree as those species with significantly different lifehistory features. For example, species having low reproductive rates, elevatedparental care, and low rates of natural mortality, “k” strategist species, may suffergreater impacts than “r” strategist species, especially if target species fishingstrategies and quotas are “r” strategy based. Thus, the impacts of high discardnumbers on cod, pollock, and flounders may be less than relatively low discardnumbers on marine mammals, turtles, sharks, skates, and other similar species.
However, discards of small fish may generate very high levels of discardmortality that can impact even “r” selected species. Thus, discarding maycontribute in a major way to problems of growth and recruitment overfishing in thedirected fisheries and result in significant reductions in population levels of nontargetedspecies. Various studies have demonstrated bycatch and discards can alterthe character of species assemblies (Wassenberg and Hill 1987; Hudson andFurness 1988; Blaber and Wassenberg 1989). Such shifts have the potential to alterpredator/prey relationships, increase food for scavengers, modify the structure andfunction of benthic communities (as the result of oxygen depletion), and increasecompetition between fishers, marine mammals, and other sea life for the availableresources. Although these impacts are more often inferred than demonstrated bycareful research, the body of evidence supporting such claims has markedlyincreased over the past decade.
Population Level Impacts
A number of recent studies tends to confirm bycatch and discards arenegatively impacting the levels of target species and non-target species. Highdiscard rates of undersized target species in the Gulf of Marine groundfish fisherieshave been identified as a contributing factor in population declines observed in theregion (Saville 1980). In the Irish Sea, Brander (1981) notes the decline andscarcity of the once abundant common skate (Raja batis). Evidence stronglysupports bycatch in the major groundfish fisheries as the reason for the demise ofthis species. Further, in the North Atlantic, minimum landing sizes for cod,haddock, and whiting in the mixed fishery lead to harvests of undersized cod andhaddock which are, in turn, discarded. Chapter 7 discusses age-specific fishingmortality rates induced by discards for haddock and whiting. Discard mortality10 isresponsible for 20%, 81%, 54%, and 16% of ages 1–4 fishing mortality,respectively, for haddock and more than 15% of fishing mortality for all whitingage classes under age 5. At these mortality levels, discards clearly exert a strongpressure on sub-adult population numbers. A lower overall exploitation rate whichwould 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 fromgrowth overfishing as a result of premature capture of juvenile shrimp on estuarinenursery grounds. Nevertheless, this overfishing problem is not the result of bycatchdiscarding, and significant changes in shrimping effort do not appear to causesizable swings in yield, suggesting recruitment overfishing is not a big factorregarding shrimp population dynamics. However, shrimp fisheries are known toharvest large quantities of fish and other sea life and can impose heavy mortalitieson 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 andturtles in the Gulf of Mexico demonstrate reductions in population levels of non-targetspecies. At least one non-target species, the Atlantic croaker, is reported tohave 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 capturedspecies. It is noted the catch of croakers now consists almost entirely of a singleyear class of small fish in contrast to several year classes of much larger individualfish sizes in the 1950s. Between 1972 and 1989, 7.9 billion croaker a year weretaken in the shrimp fishery (NOAA/NMFS 1992). Further, the Gulf of MexicoFishery Management Council recently reported, as the result of a comprehensivestock assessment program in 1990, that the principle cause of fishing mortality onred snappers was from discarding in shrimp trawlers (Tillman 1992). Stocks ofmany other non-target species are known to have declined in abundance. Stockassessment modeling of Atlantic weakfish taken in the shrimp fishery demonstratesdiscard mortality may have a substantial effect on the long-term population level ofthis species.
Of course, species of little commercial or social value, such as the largeamounts of discard in the tropical shrimp fisheries, may also experience discardmortalities. These species can serve as forage for or predators of commerciallyvaluable species and make contributions to the trophic web. In addition, species ofcurrently low economic value may become important target species in the future.Sturgeon (Acipenser spp.), for example, were considered a nuisance in theColumbia 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. Fisheriesdirected at sharks, particularly those for fins only, also occur. Some experts nowbelieve total removals of the low fecundity and long-lived sharks are high enough toharm certain species. The U.S. has announced regulations limiting commercial andsport harvests and ban the practice of “finning”11 (Satchell 1992).
Contrary to the preceding paragraphs, sizable amounts of discards do notalways result in significant impacts at the population level. In the NorthwestAtlantic, from 20 mt to 2,000 mt (up to 108 million individuals) of redfish(Sebastes spp.) are reported discarded each year, although these removals accountfor less than 2% of redfish stock biomass and 3.4% of the standing population sizein numbers (Atkinson 1984). However, the stocks of redfish off the NortheastUnited 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 thepace of fishery recovery. In the Bering Sea, discards of pollock, cod, and sablefish(Anoplopoma fimbria) constitute less than 10% of the observed fishing mortality forthese species (Table 20). Because such losses are counted against the TAC,discarding is an economic concern rather than a problem of unobserved orunaccounted for mortality. Discard mortalities imposed on rock sole (Lepidopsettabilineata) and unidentified flounders (Pleuronectidae) exceed the mortalities causedby the landed catch. However, the combined discard and reported fishingmortalities for rock sole and flounders are sufficiently low to prevent overfishing,and hence in this instance discarding involves a wasteful fishing practice. Forrockfish (Sebastes), a group historically suffering from excessive fishing, discardsaccount 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.
| SPECIES | ESTIMATED DISCARD MORTALITY (1992) | PERCENT OF TOTAL FISHING MORTALITY |
|---|---|---|
| Pollock | 0.016 | 9.4% |
| Pacific cod | 0.013 | 6.8% |
| Atka mackerel | 0.008 | 15.1% |
| Rockfish | 0.004 | 50.0% |
| Yellowfin sole | 0.012 | 26.1% |
| Sablefish | 0.001 | 1.9% |
| Rock sole | 0.015 | 55.6% |
| Flounder | 0.02 | 83.3% |
| Pacific Ocean perch | 0.005 | 14.3% |
| Halibut | 0.0812 | 24.0% |
Preliminary results like those presented above demonstrate the importance ofdocumenting discard mortality. Such information is needed to get a firmer fix onthe fishing mortalities impacting marine populations. Furthermore, the collectionand analysis of discard impacts and the levels of imposed mortalities provideinsights into potential community-level impacts not detectable from landingstatistics alone.
Changes in Species Assemblages
As a result of the different quantities and mortality rates imposed on targetand non-target species, species assemblages of a region may be altered. Prior to theintroduction of shrimp trawling, the families Leiognathidae, Ariidae, Carangidae,Nemipteridae, and Pomadasyidae dominated the marine community along theTerrengganu Coast of Malaysia (Chan and Liew 1986). The abundance ofLeiognathidae, a family commonly taken and discarded in tropical shrimp fisheries,dropped sharply after trawling commenced. A similar pattern was noted in the Gulfof Thailand where Leiognathidae and Dasayatidae numbers fell significantly over aperiod of ten years of shrimp fishery exploitation (Pauly and Neal 1985). Harrisand Poiner (1990) have noted certain demersal species discarded in the Gulf ofCarpentaria declined in abundance over a twenty-year period, while some pelagiccomponents of the catch increased in abundance.
Fishing mortality effects, including discard mortality, on speciesassemblages can also cross trophic levels and affect predator/prey relationships.Gulf of Alaska resource assessment surveys conducted in 1960 were dominated byseveral species of flatfish, king and Tanner crab, Pacific cod, Pacific Ocean perch,and sculpins. A decade later, walleye pollock abundance far surpassed that of anyother species in the survey, with Pacific Ocean perch abundance dropping from36.8 kg to 3.9 kg per trawl hour. Crab abundance also dropped, while the weightper 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 fishingeffort, particularly by the Soviets and Japanese, in the Gulf of Alaska (Alverson1992b).
Discard mortalities are known to have contributed to species structurechanges observed in the Gulf of Alaska. For example, Pacific Ocean perch (POP)harvests reached 350,000 mt in 1965. Although discard rate data were notavailable from the 1960s, the application of recently collected Gulf of Alaska POPtrawl discard rates to the 1965 POP fishery suggests the real fishing discardmortality imposed on this stock may have been 20% higher and led to an actualcatch of about 420,000 mt. Not surprisingly, POP catch per unit effort fell from50-100 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 levelsobserved in the 1960s.13
Other work has shown the removal of juvenile predators may actuallyincrease prey mortality (Browder 1981). Energy-flow models of the Gulf ofMexico shrimp fishery demonstrate the shrimp fishery there is capable ofinfluencing groundfish predator populations. However, because this mortalityreduces the abundance of prey similar in size to shrimp, predation pressure on the shrimp could increase. It is speculated that predators, having fewer options toselect from, focus their attention on what remains, in this case the shrimp.
Environmental Impacts
Bycatch and discards also have led to changes in benthic communitystructure. It has been observed trawl ground gears can penetrate up to 6 cm intobottom sediments and otter boards have been found to dig into the bottom to adepth 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 thesurface and then discarded. Not the least of these are mortalities due to increasedpredation following the redistribution of benthic species into surface waters and onthe 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 mortalitiesmay be difficult to quantify. A scallop stock inhabiting the Bass Strait in Australiawas essentially eliminated within nine months of the start of a commercial fisheryfor scallops in the region. Much of the problem was related to an infection causedby decomposing scallops which had been crushed or damaged incidental to thescallop trawl operations. Researchers suspected that four to five times as manyscallops were crushed or damaged as were landed (McLoughlin et al. 1991). InNew Zealand, several deepwater fishing grounds have been exploited for the firsttime in recent years. Changes in bottom structure due to discards and trawl damageon these grounds were inferred from reductions in the number of invertebrate faunabrought to the surface over time (Jones 1992).
Grounds poisoning or spoiling is another indirect effect of discards on thebenthic community. Poisoning refers to oxygen depletion occurring when non-targetcatch and processing waste is discarded at sea. If sufficient quantities settleto the bottom, decomposition processes consume enough oxygen to introduceanaerobic conditions. In general, if the discards are low in volume and returnedover a broad area as the vessel is moving, it is assumed the discards are consumedby scavengers in the water column or on the bottom. In such instances the chancesfor depletion are minimal. However, local effects are possible and can be severe ifheavy levels of discards occur.
Although unconfirmed, the dumping in 60 days of some 47,800 mt ofdiscards in the New Zealand west coast hoki (Macruronus novazealandiae) fisherywas projected to reduce oxygen saturation to 45%–55%. In the Northeast AtlanticNephrops fishery, individuals often are “headed” at-sea and the “heads” discardedoverboard. The presence of these heads on the bottom has been found to inhibitNephrops bottom movements (Chapman 1981), thus “spoiling” the ground. Thebenthic community structure also may change if a greater proportion of thecommunity 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 considerednegative. Hill and Wassenberg (1990), for example, note that “discarding fromtrawls has the effect of transferring large quantities of biological material from thebottom to the surface. This makes available to surface scavengers food that wouldotherwise be inaccessible.” In all likelihood, discarding provides ready forage forsurface, midwater, and benthic scavengers. Birds, sharks, dolphins, and othermarine mammals commonly scavenge for food discarded in fishing operations.
Population increases for some sea birds inhabiting the North Sea havefollowed changes in prey availability brought about by altered fishing patterns.Primarily as a result of the at-sea discard of non-target species and processingwastes, the number of scavenging sea bird pairs in the North Sea region has risenfrom 37,000 in 1900 to 614,000 recently (Furness 1993; Hudson and Furness1988). Birds, seals, and fish were found to be capable of consuming discards infisheries located in the Wadden Sea (Berghahn 1990). Three species of sea birdsare dependent on shrimp fishery discards in Moreton Bay, Australia (Blaber andWassenberg 1989). Studies conducted in the Australian northern prawn fisheryhave shown benthic scavengers consume a considerable portion of the discardsreaching the bottom (International Conference on Shrimp Bycatch 1992). Stellersea lions have been observed opportunistically following factory trawlers andconsuming discards and processing wastes released by these vessels (Perez andLoughlin 1991).
Population enhancement of selected species due to discards may be offset bynegative, but unobserved, impacts elsewhere. For example, species scavenging inand around fishing gear also increase their own susceptibility to incidental capture(INPFC 1990). However, population enhancements resulting from discards shouldnot be neglected when considering how to deal with discards in the future. In thecase of the changes in sea bird populations noted in the North Sea, a strict ban ondiscarding may lead to substantial population shifts away from conditions that havebeen 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 populationcharacteristics of marine mammals, sea birds, and sea turtles significantly. Vaquita(Phocoena sinus), a species of harbor porpoise inhabiting the Gulf of California, istaken as a bycatch in the gillnet fisheries of the Gulf. Although the target fisheryfor totoaba, where many of the incidental takes occur, has been banned, illegalfishing and the stock assessment fishery continue to remove some vaquita (IWC1991). The vaquita is considered the most endangered marine cetacean in theworld, and further incidental takes carry obvious implications.
Fishing practices, including the bottom snagline, are among several factorscontributing to mortalities of the baiji (Lipotes vexillifer), or Chinese river dolphin.Additional fisheries enforcement measures have been introduced to protect thespecies, but only 300 individuals are believed to survive. Harbor porpoise kills inthe Gulf of Maine sink gillnet fishery for groundfish are thought to be at least equalto and may be greater than the population growth rate of the stock of harborporpoise (Murawski 1994). Additional harbor porpoise mortalities are added by thesalmon gillnet fisheries off western Greenland, Newfoundland, and Labrador, andsome 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 trawlsquid fisheries off New Zealand are not thought to be contributing to populationchanges there. Steller sea lion population changes in the North Pacific in recentdecades are thought to be a result of several factors, not the least of which is a shiftin the forage community structure caused by overharvest or environmentalfluctuations impacting species abundance (Alverson 1992b).
Impacts of cetacean mortalities in passive gears were addressed at a 1991IWC Workshop where scientists noted seven of 54 species population regions (SPR)had mortality rates for passive gears determined “to be not sustainable” (IWC1991). Populations noted to be suffering from excessive mortalities included thebaiji, the vaquita, the Indo-Pacific hump-backed dolphin (Sousa chinensis), twopopulations of bottlenose dolphins off the coast of South Africa, harbor porpoise inthe Northwest Atlantic, and striped dolphin in the Mediterranean.
Considerable concern over declines in several populations and species ofdolphins has been raised by scientists who have studied the impacts of bycatch inthe ETP tuna seine fisheries. Fortunately, the populations in question have beenstable 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 Easternspinner dolphin (Stenella longirostris) is the subject of concern and is currentlybeing 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 prefisherynumbers vary widely because baseline estimates of pre-fishery numbers are low and because estimates of mortality rates--themselves very imprecise for theyears before the mid-1970s--are used in calculating numbers.” Further, spotteddolphins (Stenella attenuata), subject to the greatest mortality in the ETP tuna seinefishery, “seem not to have been depleted as much as spinners.” Regardless, theevidence is clear that in the early years of the fishery, bycatch mortalitieswere significantly reducing population sizes of “the most commonly takendolphins.” However, by the early 1970s, kill rates began to decline, and populationsizes of impacted species have since stabilized. Reduction in mortalities werereported to result from (a) training of skippers to perform backdown procedures,(b) helping quiescent dolphins from the net, and (c) making gear modifications.14
Seabirds
Numerous seabirds are taken in gillnet and other fisheries. The importanceof 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 reporteddiscarded annually in gillnet fisheries near Newfoundland (Piatt and Nettleship1987). In the early 1980s, roughly 12% of Newfoundland's breeding population ofrazorbills (Alca torda) were killed each year in gillnets. As much as 16.3% ofsome adult common guillemot (Uria aalge) populations were killed by gillnets inand around Newfoundland in 1982 (Piatt and Nettleship 1987). Further, althoughthe numbers are much smaller, the 200 annual mortalities of marbled murrelets(Brachyramphus marmoratus) in Barkley Sound, British Columbia, represent aconsiderable take from the population residing in the area (Coleman and Wehle1983). Concerns that incidental takes in the salmon net fisheries may be damagingthe marbled murrelet population have led to the introduction of a comprehensiveon-board observer program in the purse seine and gillnet fisheries of northern PugetSound, Washington.
Sea Turtles
Incidental takes of sea turtles in shrimp trawls have drawn a great deal ofattention in recent years. Shrimp trawl bycatch of sea turtles has been identified bythe National Research Council (1992) as the most significant source of sea turtlemortality in the United States. Since all five species of sea turtles found in theUnited States are listed as either threatened or endangered, effective controls on allsources of additional mortalities, including bycatch, have been encouraged. Afteryears of development and testing, regulations requiring the use of Turtle ExcluderDevices (TEDs) were issued in 1987 (Renaud et al. 1991). Because of concernsover crew safety and reduced shrimp harvesting efficiency, TED use was and still iscontested by many shrimp fishermen. Nevertheless, the use of TEDs and BycatchReduction Devices (BRDs), which allow non-target fish and turtles to escape, isincreasing.
Crouse et al. (1987) found mortality of juvenile loggerheads (Caretta caretta) inshrimp trawls was preventing recovery of this threatened species. In a letter (to theauthors), 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 fisheryin the southeastern U.S. and Gulf of Mexico as the “major cause ofmortality associated with human activities, [killing] more sea turtlesthan all other human activities combined.” The panel estimated thatas 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'sadult female nesting population is estimated to be fewer than 1000individuals (USFWS and NMFS 1991). Regulations expandingrequirements for turtle excluder devices (TEDs), which exclude 97%of the non-leatherback turtles captured, in all U.S. shrimp trawls byDecember, 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 30–50years of age), it may take decades to see the effects of managementactions such as TEDs. Likewise, this unusually long juvenile period,combined with high mortality of eggs and the early life stages, leavessea turtles populations highly vulnerable to losses of reproductive andsoon-to-be-reproductive individuals (Crouse et al. 1987; Magnuson etal., 1990).
Beyond the shrimp trawl fishery, a number of other fisheries areimplicated in sea turtle incidental capture and mortality, however,quantitative data are very hard to come by. Also, as mortality in theshrimp trawl fishery is reduced through the use of TEDs, thefrequency of capture in other fisheries appears to be increasing,probably because there are more turtles available to be captured inthese other fisheries. In general, otter trawls, gill nets (both anchoredand drift) and long lines appear to take significant numbers wheneverthey co-occur with sea turtles. Other fishing gear types, such aspound nets and purse seines, also capture sea turtles, but they areusually released alive, unless intentionally injured (or eaten) by thefishermen.
Leatherback, loggerhead, and green sea turtles, of which leatherback andgreen are listed as endangered by the IUCN, were taken in the North Pacific highseas squid driftnet fisheries (FAO Sidney Review 1992). Loggerhead and green seaturtle discard mortalities in the same fishery were low and judged as having aninsignificant effect on population characteristics. The severity of leatherbackimpacts was uncertain because scientists were not sure whether the turtles emanatedfrom the Mexican or Malaysian breeding stocks. The Mexican stock is reportedlyquite healthy and could support some incidental takes without consequence.Unfortunately, the Malaysian stock is depressed and additional mortalities inducedby incidental takes in the driftnet fishery could worsen its condition.
Chapter Summary
Although a number of ideas have been put forth regarding the consequencesof discarding in marine fisheries, supporting evidence of impacts at populationlevels, as well as ecological impacts, have been sparse until recent years.Nevertheless, there is a growing body of evidence clearly demonstrating the seriouscharacter of discarding of various marine population, including some fishes,marine mammals, and turtles. Discarding can be shown to be a significantcomponent of the fishing mortality for species in the North Atlantic, Gulf ofMexico, and Bering Sea. For all world fisheries suffering from growthoverfishing, discards are a component of the fishing mortality. Long-termalterations to species assemblages are detectable in many regions, although it is notreadily discernible what roles are played by removals of target and non-targetspecies, unobserved fishing mortality, and habitat modifications caused by fishinggears.
CHAPTER 3 ECONOMIC IMPACTS
Discards introduce a variety of biological, ecological, and social costs. Thischapter will focus on those purely economic in nature. Recent assessments of theeconomic impact of discards on commercial fisheries describe a set of costs farfrom trivial. Murawski's (1994) analysis of the Northwest Atlantic groundfishfishery found that $50 million of income was forgone to the local trawl fisheries asa result of the premature harvest and discard of the 1987 year class of yellowtailflounder. The value of the Gulf of Maine fisheries could double if discarding couldbe eliminated (Chapter 6). NRC (1991a) estimated the value of the prohibitedspecies (crab and halibut) losses in the Bering Sea groundfish fisheries as $160million15 at the first wholsale level. Losses due to discards in the Bering Sea crabfisheries contributed an additional $50 million loss. Earlier evaluation (NRC 1990)placed the value of non-target removals of crab, halibut, and salmon in Gulf ofAlaska fisheries lost because of regional discards at between $20 million and $30million per year. The aggregate Bering Sea and Gulf of Alaska losses ofcommercially harvested species resulting from discards has thus been in excess of$250 million annually.
These studies provide informative insights into the economic costs ofdiscards. Unfortunately, few such studies exist, and consequently we are left withlittle more than a skeletal picture of the global scope of economic costs imposed byfishery discard. For example, we note:
In the North Sea bottomfish fishery, the discard of marketable species equals thereported landings for the fishery.
Off the Brazilian coast, discards in the trawl and shrimp fisheries arecomparable to the size of the total landed catch.
Off the U.S. East Coast in the Gulf of Maine discards of demersal species rangefrom 35% to 79% of landed catch volume (Chapter 6).
In many of the world's crab fisheries, numbers of discards significantly exceedlanded numbers, and the weight of discards may also exceed the weight oflandings.
If these discard costs are even remotely accurate, the aggregate economiclosses due to discards in many fisheries and regions of the world may easilyapproach the value of landed catches. Unfortunately, a definitive test of thishypothesis 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 havesuggested such costs be aggregated, based on specific criteria. The classificationused by Smith and Lloyd (1989) is particularly informative because it relateseconomic impact to the group bearing the burden of the identified costs. Theauthors indicate discard impact costs are felt by those harvesting, processing,marketing, or consuming any species discarded by the target fishery. Control costsare the costs of measures taken by a fishery to minimize its discards. A finalcategory, management costs, is tied to measures attempting to regulate discards.While we agree the cost categories Smith and Lloyd specify correctly describe thetypes of costs associated with discards, measurement realities make it difficult toassess each of these costs groups separately. Overlap unavoidably ensues.Consequently, in this chapter we have chosen to use a slightly different analyticalparadigm, one aggregating the trilogy of coasts delineated by Smith and Lloyd intotwo broad groups. These two categories, the costs associated with the act ofdiscarding and the costs tied to objectives of monitoring or preventing discards,provide a useful basis upon which to analyze the economic consequences ofdiscards.
Impacts Associated with Discard Mortalities
Discards of Species of Commercial Value to Other Fisheries
In terms of estimates of economic losses imposed by discards, mostpublished studies investigate discard mortalities induced by a fishery on species ofcommercial value to other fisheries. For obvious reasons, these sorts of mortalitiesoften spawn bitter conflict between fisheries and lead to inter-gear battles andpolitical infighting over resource allocation and bycatch removal quotas. Finding asolution minimizing losses to all gear types, or which satisfies society as a whole, isnot an easy task. Complex sets of impacts and counter-impacts occur in allmultigear fisheries.16
Linear programming analysis of various bycatch management strategies forthe Bering Sea multi-species groundfish fishery was used by NRC (1991a) to searchfor an optimal solution to the catch and discard problems of the region. Using theextant fleet size, target species catch quotas, and bycatch rates collected by onboardobserver programs, the NRC study searched for mixes of fishery start dates, quotasfor Alaska pollock, and discard species allocations that would reduce the currentestimated $150 million annual cost to halibut, crab, and salmon fisheries whilemaintaining positive net margins in the groundfish fleet.
The model revealed effecitive vessel-specific incentive or quota systems havegreat potential to reduce bycatch, new and uncomplicated fishery regulations canlower bycatch significantly, and benefits to the fishers and the nation can risesignificantly in conjunction with the additional harvests these changes permit. Italso revealed that crab fishermen in the region were their own worst enemy interms of the bycatch losses they generate and that bycatch can vary tremendouslyfrom one vessel type to another. Furthermore, it became clear the current size andstructure of the groundfish fleet would prevent it from attaining all of the potentialbenefits bycatch reduction could provide. Finally, sensitivity analyses alteringdiscard survival rates demonstrated a reduction in the number of fish or crab thatdie after being taken as bycatch will, in and of itself, make a huge contribution toimproving overall benefits.
Aside from the analysis of incentive-based management approaches, somespecific regulatory options were investigated in the modeling effort. Theseuncomplicated scenarios were suggested by fishermen who felt changes, such as ashift in the start date of the Bering Sea groundfish fishery would take advantage ofthe 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 thevalue of bycatch losses by 30% and permitted the harvest of more groundfish perdollar of bycatch loss than any other comparable model.
Another straightforward scenario required the harvest of the entire pollockresource with midwater trawl gear. This alternative lowered bycatch discard to thelowest levels of any model runs but, unfortunately, also reduced harvest and fisheryrevenues dramatically. In terms of bycatch discard reduction, performance of thisoption was exemplary. In terms of accrued economic and food production benefitsto the nation, however, the strategy performed rather poorly.
One of the more interesting work products of the study was the finding thatif effective bycatch management programs are put in place groundfish harvestsalmost reach Acceptable Biological Catch (ABC) limits before reaching bycatchquotas. This ABC-level fishery actually costs less in terms of bycatch losses thandoes the present fishery restricted to the lower Total Allowable Catch (TAC) levels.
Overall, the study demonstrated if fishers were permitted to use theirindividual capabilities to seek out the optimum mix of catch and bycatch,substantial reductions in aggregate bycatch are possible. The most striking resultsof the modeling effort were those showing a significant improvement in the bycatchpicture (a 70% to 80% reduction in bycatch) with neutral side effects for thegroundfisher would be possible if the profit-seeking fisher were given theincentive individually to improve the discard picture. Of course, the modelselected those fishers making the best choices, and one could quite correctly argueexisting management systems do not operate in such a fashion. Instead, undercurrent management regimes, the rational, profit-seeking fisher, recognizingbycatch quotas on the horizon, races to catch as much fish as soon as possible inorder to minimize his loss when those quotas are reached.
Successful incentive programs might emerge if decisions were transferred tothe level of the individual fisher through carefully thought out incentive or ITQprograms. The capacity of incentive programs to reduce discard levels is based onthe ability of the fishers to use their collective experience to avoid areas where highlevels of unwanted species or sizes of species are taken. Furthermore, fishers alsohave a clear understanding of the implications of success or failure of their efforts,with rewards for success and disincentives/punishment for failure. In most currentmanagement systems, such rewards (catch) and punishments (closures) are feltonly 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 beendependent on relatively costly observer programs.
Discards of Non-Legal Individuals
A second set of -induced mortalities carrying obvious economicimplications is what is suffered when a fishery discards immature individuals ornon-legal sexes of the same species group it is targeting. Several examples can befound of the benefits of minimizing such losses. Poffenberger (1982) determinedshrimp 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 Seacrab 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 lossesresulting from discarding of under-aged demersal fishes.
Disincentives for the capture of immature fish are now emerging in somefisheries. For example, in the Bering Sea groundfish fisheries discards and retainedweights are deducted from TAC quotas. The cost to Bering Sea fishermen for thecapture of immature pollock by their vessels and by pollock taken by fisheriestargeting other species in 1992 is established at about $35 million.17 That is, if theimmatures were not taken, the increase in the catch of marketable pollock whichwould have occurred would have raised the value of the harvest by this amount. Asalready mentioned, however, such accountability is more the exception than thenorm in today's fisheries management. Moreover, with the exception of systemslike New Zealand's Individual Transferable Quota, accounting occurs at the fisheryrather than at the individual fisher level, and such aggregated programs may serveless well as economic disincentives than do vessel- or fisher-based systems.
Much more attention needs to be directed at the cost of this form of discardmortality. With the exception of the large reduction fisheries, most commercial andrecreational fisheries are directed at specific size/age classes optimizing economicperformance, 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 inconjunction with the target sizes/sexes has often been ignored in calculating realfishing mortality. Consequently, target quotas are met and fisheries closed onlywhen the tonnage of legal/optimum-sized individuals is reached, despite thepossibility that owing to discards, actual mortalities of the species induced by thefishery may be much higher.
Discards of Non-target Species of Little Commercial Value
A third and often overlooked stream of economic costs is associated withdiscards of non-target species having no economic value to a fishery. While at firstglance one might question whether any economic cost can be associated with suchremovals, failing to account for such losses would neglect the often interdependentnature of species with and without commercial value.
Catching an unwanted species represents an economic loss because of (a) thecost 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 separateand return prohibited or unwanted species to the water. For at-sea processors,lower factory throughput efficiencies and higher processing crew costs due to theadditional time required to separate discards from the retained catch are the directresult of the presence of discards in the catch.
In our review of the discard literature, few studies of the actual costs suchinefficiencies impose on a fishery have been identified. An index of such lossescould be derived by an estimate of “wasted” effort units in a fishery. The value ofeach unit of wasted effort would reflect harvesting and processing costs and wouldbe some function of the value of “effective” effort units.
While such an index would require scaling to a per-vessel level, ballparkfigures 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 relatedlinearly to CPUE for retained individuals, then discard effort is a linear function ofdiscard rate and total effort. Thus, for example, one can suggest 6.2% of the effortexpended to harvest pollock in the Bering Sea in 1992 was wasted, since it wasexpended on pollock later discarded. Since data are available on the variable costsof factory trawl operations in the Bering Sea, it can be assumed the entire BeringSea pollock harvest was taken by such vessels. (Actually, 1992 factory trawlcatches accounted for 68% of pollock harvests.) Under these assumptions,“wasted” effort in the 1992 fishery represented an economic operating cost of $1.03million. While not a definitive response to interest in the inefficiency costs ofdiscards, such an index does demonstrate such inefficiencies should not beoverlooked in a rational assessment of total economic costs associated with discards.
If a discard species can be exploited by other sectors, such as turtle watchingor another fishery, the value of discard losses depends on how much alternativeusers are willing to pay. There are also benefits when species take advantage ofdiscards to proliferate. Discarded fish may bring profits to the cephalopod orshrimp industry by increasing food availability and abundance of the targetresources.
In many cases, species of commercial value prey upon each other and onthose with no commercial value. Removals of a prey species as a discard mortalitymay have measurable effects on the growth, survival, and reproductive conditionsof the exploited species. If negative, these impacts can introduce costly economiceffects into the fishery. Conversely, economic benefits may ensue if discardmortalities “fine-tune” the ecosystem, improve prey species populationscharacteristics, or remove predators which constrict survival of the commerciallyvaluable species. Given our understanding, or lack thereof, of real between-speciesdependencies in the marine system, these potential economic costs have beenlargely unknown to date. As this knowledge grows, we should attempt to conductever more critical analyses of the extent of such costs.
A special case of the set of costs associated with the discarding of specieswith and without commercial value bears some mention. This unique situation is ofgrowing concern, is often accompanied by changes to traditional bycatch usepatterns, and involves the redistribution of income and landings from artisanal tolarger, more mechanized vessels. Pauly and Neal (1985) in their discussion ofSoutheast Asia shrimp fisheries, notes one of the definitive characteristics of themodernization 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 ofshrimp compared to other species in the catch, a significant portion of the catch offinfishes is discarded. An unfortunate artifact of this trend is the reduction inlandings of low-valued species which have historically served as a cheap source ofprotein for coastal populations and supported animal husbandry. Perhaps as thescarcity of such discarded fish worsens, their value will increase until a newequilibrium is established between landings, demand, and per-unit cost. However,the new unit cost of the bycatch fraction will undoubtedly be higher than it wasprior to the modernization of the fleet. Such higher costs may well result in one oftwo possible scenarios for low-income or impoverished populations of SoutheastAsia and other developing regions of the world--an increase in family expendituresto meet protein needs or a reduction in protein consumption.
Costs Associated with Monitoring andPreventing or Reducing Discard Levels
The second category of economic costs associated with discards is tied to theobjective of preventing or monitoring discards. Included within this category aremanagement and enforcement costs and costs involving required modifications togear and changes in fishing patterns in order to reduce bycatch.
The 1992 budget for marine fisheries management in the U.S. ofapproximately $200 million represented $0.045 of management expenditures perpound of landed harvest weight. It is difficult to determine just how much of thismanagement budget was spent directly or indirectly on bycatch management,monitoring, or prevention. Let us assume, however, that 10% of U.S. costs werespent on discard concerns and that discard budgets in other nations are themselvesjust 50% of the U.S. allotment for discards. Doing so generates a global tab fordiscard-related costs of $4.5 billion. Even under conservative assumptions ofexpenditure allocations, costs associated with the management, monitoring, orprevention of discards are staggering.
Lost fishing opportunity constitutes another area of economic costsassociated with discarding. For gear types discontinued because of discard impacts,losses to the involved fishery will be complete. Further, if alternate harvestingsystems cannot be introduced for such fisheries, the economic loss to society is alsocomplete, even though ethical and biological/ecological concerns may have beenaddressed. In fisheries where discard quotas exist, large quantities of target speciesharvests will be lost when these discard quotas are reached. Attainment of thediscard quotas triggers selective species closure or generic, area-wide, across-speciesbans on fishing. Although such closures can limit the operation of all geartypes, equity considerations typically result in restrictions on the offending geartype.
Potential economic costs associated with the closure of fisheries prior to theattainment of the target species quotas are neither trivial nor infrequent. In theBering Sea in 1991, discard quotas contributed to the closures of the bottom trawlfishery for rock sole, pollock, cod, and flatfish, as well as crab pot fisheries forbairdi Tanner crab. Similarly, in 1990, discard quotas closed eight major fisheriesin the region. In the Gulf of Alaska, the halibut bycatch quota has served as abarrier to the development of a large and economically valuable resource. Thepotential yield of flounders in this region is set at 442,000 mt, but less than 10% ofthe take is normally harvested. Access to these economically important flounderstocks are currently dependent on the evolution of more selective gear types or therelaxation of current prohibited species quotas. In addition to curtailing access tothese species, in an open-access fishery such closures can complicate discardmanagement in the region. As closure in one fishery push effort into other areas,the race for fish intensifies, and as closures approach, selective fishing practicesminimizing discards may be ignored. Fishers frequently believe fish they don'tcatch today may not be available for the taking tomorrow. Clearly, biological, ifnot economic, wastage is encouraged.
Of course, different management institutions use quotas in different ways.In the multi-species Northeast Atlantic groundfishery, for example, quotaattainment for a species requires that species to be discarded overboard. Sincemany of these discarded individuals die, the management significance of suchquotas is drawn into question. Perhaps a more biologically and economically soundapproach is reflected in New Zealand's ITQ system. Here, quotas for discardspecies are subdivided among participating vessels and can be traded. Economiccosts of quota attainment for a specific vessel are embodied in the costs associatedwith the purchase of additional discard quota. Presumably, as the supply of suchunused discard quota dwindles, the per unit cost of the discard quota rises. Whenall such quota is exhausted, vessels without remaining quota are forced out of thefishery. Their costs become the value of their remaining inaccessible target quotaless variable and discard quota costs that would have been expended had theyharvested the quota. Such a system perhaps better reflects the true cost ofdiscarding.
Observer costs are another item for which total expenditures should beprorated across discards and other fisheries management costs. However, given thepresence of operational observer programs in the Northeast Pacific and elsewhere,per-unit observer costs are much more tangible than other management costs. Afternearly four years of operation, observer costs associated with full-time coverage ofvessels participating in the U.S. Bering Sea and Gulf of Alaska groundfish and crabfisheries range from $3,500 to over $5,000 per month. These costs are paid toobserver contractors who hire qualified individuals and place them on contractedvessels.18 Observe costs can clearly be substantial, and this in large part explainswhy observer programs have not been implemented more comprehensively. Facedwith such costs, marginal vessels or even low-marging operations could be forcedout of the fishery.
Enforcement costs associated with wild harvest commercial and recreationalfisheries are substantial. In the North Pacific alone, U.S. fisheries enforcementcosts total $80 million annually. Unfortunately, given the number of stockscurrently overfished in global fisheries, ongoing problems with illegal fishing onthe high seas and emerging concerns over high-grading and other means ofeconomic poaching, current enforcement capabilities are not real deterrents to suchactions. While some of the problems concerned with documenting discard levelscan be dealt with through the use of observers, in many fisheries they may beimpractical.
Another area of costs imposed when seeking to prevent discards is tied togear or fishing pattern modifications mandated by bycatch regulations. Griffin and Hendrickson (1992) estimated the present value of the use of bycatch reductiondevices in the U.S. Gulf of Mexico shrimp fleet would represent a cost to thefishery of $16.4 million to $27 million over a ten-year period. Fishery closuresmandating 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 bottomfishermen in the Bering Sea costs the industry and the nation from $30 million to$120 million per year.19
In many fisheries, current fishing practices and gear riggings producediscards carrying with them an assortment of economic costs. Gear modificationsor alternative fishing approaches have the potential of reducing the catch ofunwanted fish or shellfish, but at what expense to target catch and processing orhandling rates? Break-even results may not be good enough to induce fishers toshift fishing practices; that is, unless real financial benefits can be associated withthe new gear type/method, fishers will not voluntarily modify their behavior.Although regulations mandating the use of new gear have been imposed in certainfisheries, their effectiveness may be negated if there is strong user-group resistanceto employing the new gear. The alternative then becomes the development of geartypes, fishing strategies, or fishery management options that encourage fishers toadapt low discard rate practices.
Chapter Summary
Economic impacts flowing from discarding include (1) foregone catch as aresult of mortalities imposed on recruits to the target fishery, (2) foregone catchresulting from mortalities imposed on target fisheries by fisheries targeting otherspecies, (3) loss of fishing operations resulting from bycatch quotas forcing fisheryclosures when attained, (4) costs of purchasing new technology, (5) loss of catchwhen a gear type is outlawed, and (6) loss of catch due to capture of immaturessubtracted from the TAC. Other economic losses result from required observedprograms and sorting costs. In total, the loss of potential catch resulting fromdiscarding or discard regulations amounts to billions of U.S. dollars, and in manyfisheries the losses due to discard mortalities are noted to equal or exceed landedcatches.
Much more work is needed to assess adequately the true economic cost ofdiscards on fishers and the benefits and costs of potential solutions to society as awhole. We should not forget, however, that discarding is not all bad. Mortalitiesassociated 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 costeffective. Currently, society views the benefits of such continued viability asoutweighing the potential costs imposed on marine ecosystems. Only in the lastfew years have environmental groups begun to use political pressure to promotecommercial embargoes or trade barriers to overcome this problem. Much morework is needed to assess adequately the true economic costs and benefits of discardson fishers and the societies of which they are a part. Revised cost/benefitaccounting procedures and better natural resource economics may offer the basis formore rational alternatives.
CHAPTER 4 SOCIO-CULTURAL IMPACTS
The nature of most economic, biological, and ecological variables is suchthat if an effect is suspected, measurement and evaluation of the underlying datacan usually confirm or reject its presence. If confirmed, the effect can be furtherparameterized 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 itsremoval as discards in the groundfishery is one measure of the economic effect ofdiscards on the halibut fisher. Likewise, a reduction in population abundance dueto the growth overfishing of a given species is an index of a biological impact andthe elimination of a predator due to excessive discard mortality a reflection ofecological change.
Although disagreements over the presence or absence of an economic,biological, or ecological discard effect may occur due to debates over properanalytical methods or measurement errors, the described impact can usually berecognized by the participants in the fisheries of concern. However, the perceptionof the consequence of a discard impact or its importance may vary sharply betweencountries as the result of socio-cultural differences or their dependence on marineresources as a source of protein for their population, religious beliefs, and historicalcustoms. Thus, the success of a proposed international fishery managementstrategy designed to reduce discard mortality will benefit from an understanding ofthe distinct attitudes of separate societies towards the biological, economic, esthetic,and ethical aspects of discards. To date, efforts to understand socio-culturaldistinctions or different national dependencies upon marine resources as proteinstaples appear to have played little or no role in regional or international discardpolicy evolution. Instead, the issue of discards and the “correct” attitude towardsthem is clouded because each society clings tightly to the vision they believeappropriate. This is particularly true for the emerging bycatch policies that haveimpacted or will impact bycatch discarding in the ETP purse seine tuna fishery andthe high seas driftnet fishery as well as the use of TEDs in world tropical shrimpfisheries.
Discard Conflicts Based in Socio-Cultural Differences
As a consequence of competing socio-cultural visions, the intensity ofconflicts over the discard issue should not be surprising. From the perspective ofmany conservation/environmental groups in the U.S. and elsewhere, it seemsappropriate and necessary to demand an embargo on shrimp from Indonesia due toturtle discards in these fisheries (Seattle Post-Intelligencer 1992). On the otherhand, to the Indonesian shrimp fisherman whose principal source of income comesfrom 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 todisregard the interests of commercial netters who have operated in the fishery forgenerations (Fiorillo 1991). Dolphin-safe tuna marketing programs are lauded bymany environmental/conservation groups on ethical grounds they protect marinemammals (Kronman 1992). Persuading these groups to take into account thediffering concerns of impacted participants or to change their attitudes andmanagement tactics based on technological advances may be difficult, if notunlikely. For example, a significant reduction in dolphin mortality has occurred intuna fisheries setting on porpoise schools, making such gear theoretically moreacceptable. Although the bycatch of juvenile yellowfin (Thunnus albacares),skipjack (Katsuwonus pelamis), and other pelagic fishes has been shown to be veryhigh in some alternative seine fishing modes, efforts to outlaw the use of purseseines or ban sets on porpoise schools in tuna fisheries continue. Dr. Martin Hallof the IATTC (seminar, University of Washington 1994) noted:
Many attempts have been made to solve the tuna-dolphin problem rangingfrom embargoes to consumer actions…. With dolphin mortality reduced97% since 1986 and a projected mortality of 3,500 individuals for 1993, thisis no longer a conservation issue. This question is now how to harmonizethe different priorities and concerns, economic interests, cultural views,etc., of the countries involved in the fishery, in a solution that takes intoaccount 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 beenencouraged to use them because of their reported conservation properties. Datademonstrates some driftnets have relatively low discard ratios. Furthermore,although the thrust of much of this volume is the documentation of bycatch discardquantities and the excessive nature of these losses, at the same time it is noted thatsome fishers encourage the development of shrimp trawls that take more fishbecause 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 afunction of vantage point. After reviewing much of the literature describing thesocio-cultural impasses resulting from discards, it appears such national andinternational standoffs are frequently driven by ethics, esthetics, or societal attitudestoward the consumption of various marine products.
Attitudes Toward Non-Consumptive Usesand 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; thedynamics and ecological social importance of artisanal fisheries are ignored.” Suchbias towards first-world interests goes much deeper than just management issues.Conservation and environmental protection attitudes are frequently seen as drivenby U.S. and European societies. The 1992 Roper survey on U.S. NationalResource Conservation attitudes in the 1990s (National Research Council 1992)offers some insights into the nature of these attitudes. About 80% of Americansconsider themselves active environmentalists or sympathetic to environmentalconcerns. Two-thirds of the populace state they think environmental regulationshave not gone far enough. Sixty to seventy percent of Americans also rankenvironmental concerns before economic ones when compromises between the twocannot 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 ofthe least wealthy Americans, as opposed to only 21% of the most well off, believeeconomic issues outweigh environmental onces. Given the continuum of economicstatus across socio-economic groups in the U.S., we would not be surprised towitness the steadily increasing concern for economic considerations in manydeveloping countries.
Environmental/conservation concerns date back to the first recitations of theconcept of “Public Trust” in English Common Law (Everitt et al. 1980). Publictrust precepts simply assert all fish (and wildlife, for that matter) are held incommon by all people. In such a context, consumptive and non-consumptive usesof these resources are equally legitimate. As the number and diversity of non-consumptiveuses of fish have increased in recent decades, the relevance of theseinterests to environmental decision-making has also grown. Due largely to theireconomic well-being, the developed states have witnessed the fastest growth in non-consumptiveuses. Given the international influence of these states, their role inpromoting 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 marinemammals, Kellert's (1979) review is enlightening. In 1979, issues including DDTand bird survival, leg-hold traps, the Endangered Species Act, the killing oflivestock by coyotes, and the Tellico snail darter controversy were majorenvironmental topics. Nevertheless, the issue most widely recognized and opposedby the U.S. public at that time was the commercial and subsistence hunting of harpseals for fur.
Media attention to tuna-dolphin concerns, high seas driftnets, manatees,whale stranding, and sea lion declines has greatly fostered the recognition of marinemammal issues since 1979. Lynge (1992) argues whales (and presumably othermarine mammals) have been ascribed a “uniquely special” status by Westerncultures that segregate biological life into three bundles: humans, whales and allother biological life. Marine mammal intelligence, social organization,communication, and presumed “innocence” has broad appeal in many Westernsocieties, but at the same time, such views have formed a fertile ground for thegrowth of international socio-cultural conflicts. Lynge (1992) raises the relevantquestion: Are these attitudes toward marine mammals as universal as perceptionssuggest? Does Western thought and attitude supersede that of cultures whererespect for an animal and the killing of it go hand in hand?
Contrary to perhaps common belief, marine mammals are not viewedequally by every nation. They are hunted for meat in Peru, Chile, Sri Lanka,Greenland, the U.S. (aboriginal harvest), and many other nations (Northridge1991b). Regardless, most countries would appear to agree to agree it is better not to kill amarine mammal or sea turtle through incidental contact with a net, trawl, or otherpiece of fishing gear if such contact and mortality can be avoided. Also, it appearsto be agreed it is better to avoid discards whenever possible and have nationalpolicies which seek to minimize such waste. However, achieving these goals mayrequire some scientifically documented evidence that a real conservation,ecological, or economic problem exists. When significant ideological differencesinvolving the use of resources occur, efforts to recognize and work within theboundaries of such socio-cultural distinctions must be made.
Discard Conflicts Spawned by Socio-Cultural Differencesbetween Developed and Developing Countries
Recognition of cultural differences between developed and developingcountries is particularly critical when addressing resource use issues. Much of thedeveloping world encounters conditions differing starkly from those in developednations. In the U.S., less than 3% of total protein is derived from fish. Incontrast, 60% of the remaining world population receives over 40% of its animalprotein from fish, and nearly one billion people in Asia depend on fish for theirentire supply of protein. Reduction of fish available for consumption in manydeveloping countries would push the average level of protein consumption in thesecountries into the “deficiency” category. To replace fish with, say, beef proteinwould require 200 million more beef cattle per year, a quantity in itself associatedwith obvious environmental consequences (Strand et al. 1992).
Fish also represent a significant source of export earnings for manydeveloping nations. In 1985, fish accounted for at least 20% of export earnings in21 countries (Strand et al. 1992). Such earnings permitted developing countries topurchase grain, foodstuffs, and other goods and services otherwise unavailable tothem.
On a smaller scale, fish are important in many developing nations. In astudy of six villages around the Bay of Bengal, 34% of the households in thevillages were completely dependent on fishing for their income, while another 25%depended jointly on fishing and fish marketing (Bay of Bengal News 1992). Fishingformed at least part of the household income in 28% of the remaining 41% of thehouseholds. Loss of the fisheries on which these villages depend would have direconsequences.
Socio-Cultural Attitudes Toward Discards Basedon Different Dependencies on Marine Resources
Although many ideological confrontations associated with bycatch existbetween developed and developing countries, a great many consequential disputesrelated to discards have occurred between developed nations, such as the whalingand driftnet issues. As a result, a more useful paradigm for the analysis of discardconcerns inspired by socio-cultural disputes emerges if one considers these disputesin the light of national dependencies on marine resources as a protein staple.Within such a context, discard attitudes of developed nations with a highdependence on marine protein sources are more closely aligned with those of manydeveloping nations than they are with other developed countries for which marineprotein sources are less critical components of the national diet.
The cultural ideologies of a nation more heavily dependent upon marineresources as a source of protein for its own population may have positive effects onbycatch management. For one thing, its domestic fisheries may be far lesswasteful. The management policies of that nation may clearly reflect an ideologyseeking to maximize the long-term protein yield from the entire resource complex.For example, because utilization of the entire complex of harvested species is morebalanced, regulations can be adjusted to reduce effort on one component of thatcomplex that is overexploited without sacrificing efficiency in utilization of theentire complex. Short-term attitudes leading to widespread overexploitation and adeterioration of the viability of the protein resource cannot co-exist with suchphilosophies.
Under such systems, be they in developed or developing countries, bycatchis not wasted. Bycatch is utilized because the nation itself is dependent upon alarger component of the resource complex for its protein needs. Although differentfishermen fish different gear types and, of course, have distinctive bycatch discardconcerns, conflicts which could emerge from these differences are subjugated forthe greater good. Because the community to which the various groups of fishermenbelong is directly dependent upon the resource for food, fishermen give way to acultural ideology that places wise, yet maximum, use benefiting the community as awhole ahead of inter-gear allocation squabbles.
The many island communities of the world are examples of the culturalideologies heavily dependent upon marine resources for their own domesticconsumption. The geography of island communities in many instances has dictateda food culture distinct from what has developed on Asian, European, and Americancontinents. Compared with the early continental inhabitants who relied uponagriculture and land animals for their food, island communities have turned toanimal and plant life from highly productive coastal waters for their main source ofprotein and vitamins.
The link between the sea and the consumer is much more remote in nationssuch 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 highdependencies on marine resources may look askance at the attitudes of suchcountries toward marine resource use and management, considering such attitudeswasteful and greedy (Ludwig et al. 1993).
Within-Culture, Social Differencesthat Drive Discard Conflicts
Clearly, discard problems also offer competing fishers a lever to improvetheir financial/allocative position in the name of what is right in terms ofconservation and the environment. An unfortunate truth of the Olympic fishingsystem20 is that all too often the arguments on all sides are at least partially correctand worthy of attention. Intensive trawling operations conducted under theconstraint of short seasons induce discard mortalities that might otherwise beavoided if more rational systems were in place. But the same can be said of everyother gear type. Thus, addressing the discards in Olympic style fisheries willrequire close attention to the spectrum of fisheries involved, taking into accountfishery-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 opportunitiesfor marketing discards, but the role discards play in the allocation of target speciesis still relatively insignificant. As these fisheries continue to develop and shortagesof available resources become more acute, we would expect to see an expansion ofthis problem. Whether the problem reaches the extent now observed in manydeveloped states may be largely a function of whether or not the developing worldmoves away from the open-access, free-for-all characteristics of Olympic fisheriesprevailing in many of today's developed nations' fisheries.
Development of Discard PoliciesRecognizing Socio-Cultural Differences
Because of the critical importance of fisheries to many developed anddeveloping nations, the evolution of global bycatch and discard strategies should bedesigned to minimize social conflicts and, to the degree possible, be independent ofideological differences and be based on sound conservation principles. Many of theenvironmental/conservation programs designed to reduce the catch and discard ofmarine mammals, turtles, and seabirds have their origins in developed countries.This subset of the world community should be careful to not foist ideological use-basedethics summarily on other nations, be they developed or developing. Instead,if they are sensitive to the socio-cultural and socio-economic circ*mstances of thedeveloping world in the application of emerging environmental and conservationstandards, global acceptance of world bycatch and discard policies will be muchmore feasible.
The recently signed UNCED agreements and Agenda 21 are excellentexamples of instruments of change in our treatment of living ocean resources andthe environment. Rather than unilateral pronouncements, these agreementsrepresent months of multi-lateral negotiations attempting to deal with the manyrights, beliefs, and obligations of the diverse cultures on this planet. It is hopedthis will be more the rule than the exception in our approach to ocean managementin the future.
Chapter Summary
Discarding creates a number of problems broadly recognized by theinternational community. However, stands on ethical issues are not equallyappreciated in all countries. Further, solutions to resolve some conservationproblems are not fully understood or accepted by various sectors of the worldcommunity. Recognition of socio-cultural differences and efforts to bridge currentconflict arenas are seen as important to an international effort to promote thereduction in fisheries discarding.
