By-Catch Begone: Changes in the Philosophy of Fishing Technology

FISH and FISHERIES, 2002, 3, 340 ^355

Ghoti

Ghoti papers Ghoti aims to serve as a forum for stimulating and pertinent ideas. Ghoti publishes succinct commentaryand opinion that addresses important areas in ¢sh and ¢sheries science. Ghoti contributions will be innovative and have a perspective that maylead to fresh and productive insight of concepts, issues and research agendas. All Ghoti contributions will be selected bythe editors and peer reviewed.

Etymology of Ghoti George Bernard Shaw (1856^1950), polymath, playwright, Nobel prize winner, and the most proli¢c letter writer in history, was an advocate of English spelling reform. He was reportedlyfond of pointing out its absurdities byproving that `¢sh'could be spelt `ghoti'.That is:`gh'as in`rough',`o'as in`women'and`ti'as in palatial.

By-catch begone: changes in the philosophy of ®shing technology

Steven J Kennelly1 and Matt K Broadhurst2

1NSW Fisheries, Cronulla Fisheries Centre, PO Box 21Cronulla, NSW 2230, Australia; 2NSW Fisheries, Conservation TechnologyUnit, National Marine Science Centre, PO Box J321, Co¡s Harbour, Australia

Abstract Correspondence: Since humans began ¢shing (at least 90 000 years ago), ¢shing technology has devel- Steven J. Kennelly, oped with the objective of trying to catch the greatest quantities of ¢sh possible, of an NSW Fisheries, Cronulla Fisheries ever-increasing variety. Fishing technology has evolved from simple harpoons and Centre, PO Box 21, hooks to the industrial factorytrawlers of the 20th century.After millennia of assum- Cronulla, NSW 2230, ing that seafood resources are inexhaustible, and centuries of somewhat muted con- Australia cerns that advanced ¢shing technologies mayhave detrimental impacts on stocks and Tel.: 61 2 9527 8532 ecosystems, the last centuryhas seenadvances in ¢shing technology blamed as a major Fax: 61 2 9527 8513 E-mail: kennells@ cause of the current over-exploitation of ¢sh stocks. It has mainlybeen during the last ¢sheries.nsw.gov.au few decades that ¢shing technologists have begun to focus on more conservation- orientated goals. This occurred initiallyin response to concerns over the by-catch of Received28 Aug2001 charismatic species (like dolphins in tuna purse-seines), but quicklybroadened to Accepted21June2002 address concerns over the discarding of not-so-charismatic species (like juvenile ¢sh killed byshrimp trawling). To ameliorate these issues, technologists and commercial ¢shers successfullydeveloped various innovative gear-based and operational solutions. The steps involved in successfullyreducing by-catches have tended to follow a certain incremental framework involving identi¢cation of problems using observer pro- grammes, developing technological solution to these problems, experimentallytesting these solutions, implementing these solutions throughout industryand ¢nallygaining acceptance of the solutions from concerned interest groups. Most recentlypublic concern has broadened once again from by-catch issues to encompass a much wider context involving the impacts of ¢shing on entire ecosystems, i.e. the impacts of ¢shing on all species a¡ected ^ not just those species caught, retained or discarded. As a

340 # 2002 Blackwell Science Ltd Changes in the philosophyof ¢shing technology S J Kennelly & M K Broadhurst

consequence, therehave been manycalls forecosystem-based ¢sheries management to ensure that ¢sheries operate under the principles of ecologicallysustainable development. Scientists are gradually¢lling the gaps in our knowledge about how ¢shing a¡ects whole ecosystems but, because of the scales and complexities involved, such studies are usuallydi¤cult, expensive and of long duration.While this descriptive work is di¤cult, ¢nding solutions to anyidenti¢ed problem is an even greater challenge, parti- cularlyfor ¢shing technologists. The easiest solutions to such problems involve rather draconian management strategies like closures. A less extreme alternative involves the development of new technologies that reduce the impacts of ¢shing on ecosystems ^ in a similar wayas that done to reduce by-catch problems. Innovations like altering ground-chains, footropes, sweeps and trawl doors have been suggested as possibleways to ameliorate the environmental damage done bytrawling, but such research is still verymuch in its infancy.Nevertheless, the recent historyof ¢shing technologyis che- quered with successfullymeeting such challenges, giving one con¢dence that solutions to such issues mayeventuallybe developed. Integral to the success of any solutions that strive towards the goal of perfect selectivity, however, is a corresponding improvement inthe adoptionof these methods by¢shers. As our framework shows, this is best achieved byinvolving ¢shers in all aspects of the work.

Keywords by-catch reduction, discards, ecosystems, ¢shing technology, over- exploitation

Sea of Galilee in biblical times involved cast nets and Beginnings ± ®shing technology developed larger dragnets and, whilst these techniques were to exploit an `inexhaustible' supply designed to catch the maximum quantityand diver- In1995,Yellen et al. described the discoveryof barbed sityof ¢sh possible, it is also apparent that the dis- and unbarbed bone fragments in the upper Semliki carding of unwanted, dead ¢sh was commonplace. Valleyin Zaire (Fig. 1). These fragments, dated from One of the ¢rst recorded mentions of the impacts of approximately90 000 years ago, were found in asso- ¢shing on nontargeted species is attributed to Jesus ciation with the remains of large cat¢sh, indicating Christ in his `Parable of the Fishing Net': ``Also, the the use of harpoons to catch ¢sh.This marks the ¢rst kingdomof heaven is like a net thrownout inthe lake, known use of ¢shing technologybyhumans, who no whichcatches all kinds of ¢sh.When it is full, the ¢sh- doubt regarded it as a signi¢cant allyintheir struggle ermen pull it to shore and sit down to divide the ¢sh: to survive. From these beginnings, the primarygoal the good ones go into their buckets, the worthless of ¢shing technologythroughout prehistorywas to ones are thrown away'' (Matthew,13.47). develop better techniques to increase the quantity Despitediscardingpracticesbeinga featureof¢sh- and diversityof ¢sh landed^ agoalthat hasremained ing 2000 years ago, there was still no recognition of the priorityof ¢shers for millennia ^ with little atten- anynegative aspects of such discarding on stocks or tion given to the impacts of such techniques on the ecosystems. Such a philosophy typi¢es the thoughts stocks exploited or their ecosystems (see Pitcher of not only¢shers from ancient times, but also most 2001for a review). ¢shers until recently. That is, for most of recorded By2000 years ago, ¢shing technologyhad devel- history(and prehistory), humans have tended to oped a large diversityof methods. The Bible provides consider ¢shing technologyas a major aid in provid- some of the earliest written descriptions of some of inga seeminglyinexhaustible supplyof seafood.With the basic techniques used at the time: angling with the bene¢t of archaeological evidence, we now know rods and hooks on £axen line; £axen cast nets; ¢sh that technological advances have led to major reduc- traps and pronged tridents (see Wuellner 1967; Nun tions in biodiversityand the progressive depletions 1989,1993). The most common mode of ¢shing in the of many¢sh populations (Pitcher 2001).

# 2002 Blackwell Science Ltd, F I S H and F I S H E R I E S, 3, 340 ^355 341 Changes in the philosophyof ¢shing technology S J Kennelly & M K Broadhurst

Figure 1 Bone fragments from the Upper SemlikiValley, Zaire,90 000 y ears ago (fromYellenet al. (1995) ).

¢shermen take such quantityof small ¢sh that The 14th to 19th centuries ± beginning to theyknow not what to do with them; and they see a problem feed and fat their pigs with them, to the great It was not until the14th centurythat we begin to see damage of the Commons of the Realm and the anymentionthat ¢shing technologycould be leading destruction of the ¢sheries' (as cited in Dyson to negative impacts on stocks and ecosystems (see 1977). Dyson1977 for a summary). In the River Thames, for A royal commission reported that the wondyrch- example, the capture of immature ¢sh was illegal as oun was 3 fathoms long and10 feet wide, had a beam earlyas 1320; in 1349 it was recorded that 15 nets 10 feet long and a leaded rope weighted with big were con¢scated that contained three bushels of ¢sh stones ¢xed on the lower part of the net ^ which com- `which, byreason of their smallness, could be of no prised meshes the length and breadth of two thumbs. use to anyone'. The commissionadvised that the net ought to be used Fishers of this era were particularlyconcerned onlyin deep waterand not in estuaries, but nolegisla- abouta`newand subtlycontrived instrument' known tion was enacted. The 14th centuryoutcryagainst as the `wondyrchoun' (meaning `wondrous ability') this technologybegan a battle that was repeated in (Dyson 1977). This early beam trawl had been in use the 1620s when Charles I considered the impacts on for about 7 years when Edward III was petitioned stocks bythe net that was, bythen, called the `trawle'. in 1376 about the declines of ¢sh it mayhave been It is a con£ict that has, of course, continued to the causing: present day. The great and long iron of the wondyrchoun The 19th centurysaw a dramatic increase in the runs so heavilyand hardlyover the ground use of most of the major methods of ¢shing applied when ¢shing that it destroys the £owers of the today. Previously, longlines and drift nets were the land below the water, and also the spat of main gears used, although beam trawls, beach seines oysters, mussels and other ¢sh upon which the and trap nets had also been used to a lesser extent great ¢sh are accustomed to be fed and nour- for centuries (see above). The ¢rst recorded use of the ished. Bywhich instrument in manyplaces the purse-seine was in the USA in1826, the Danish seine

342 # 2002 Blackwell Science Ltd, F I S H and F I S H E R I E S, 3, 340 ^355 Changes in the philosophyof ¢shing technology S J Kennelly & M K Broadhurst

was invented byJens LaursenVaever in Denmark in seafood resources were inexhaustible. This is an 1848 and the modern-dayotter trawl was ¢rst used assumption that we now know is false. in England or Ireland around 1860. The arguments A particularlywell-documented example of the against trawling and other contemporarymethods consequences of allowing ¢shing technologyto of ¢shing continued throughout that centurywith develop unchecked is found in the ground¢sh ¢sh- several parliamentarycommissions appointed to eries o¡ the north-eastern USA (see NOAA 2001for a consider the issue. However, the e¤ciencyof these summary). Fishing for cod, haddock, red¢sh and methods (and in particular, the trawl) in catching £ounders initiallyinvolved baited lines ¢shed from large quantities of ¢sh always prevailed, establishing schooners and their dories (Fig. 2), but these were them as the prime tools used to catch ¢sh up to the replaced bysteam-powered trawlers in around1906. present day. At this time, there were considerable warnings that the new technologycould threaten the productivity of stocks, but these had no e¡ect on ¢shing practices. Into the 20th century ± unchecked Demand quicklygrew as improvements in storage, technology, over®shing and impacts on marketing and distribution occurred and this led to ecosystems even greater landings. By1930, there were clear signs The warnings from the 14th to 19th centuries about that ¢shing e¡ort had grown too large for sustainable the negative impacts that advances in ¢shing tech- yields and the ¢shing methods used were quite non- nologymight be having on stocks and ecosystems selective (e.g. in 1930 the ¢sherywas estimated to were realized in the 20th century, particularly dur- have landed 37 million haddock at Boston and owing ing the second half, when major declines occurred to the small mesh size used, another 70^90 million in the world's ¢shing stocks. The unchecked con- small haddock were estimated to have been discarded struction of bigger vessels (culminating in huge fac- dead at sea). Landings began to fall and scientists torytrawlers) combined with advances in electronic recommended increasing mesh size, but no formal equipment and netting materials and designs, all led agreements occurred. The beginning of the 1960s to a strong test of the millennia-old assumption that saw the controversial arrival of large high-seas

Figure 2 Schooners and dories line-¢shing on the Grand Banks (byH.W.Elliot and Capt. J.W.Collins).

# 2002 Blackwell Science Ltd, F I S H and F I S H E R I E S, 3, 340 ^355 343 Changes in the philosophyof ¢shing technology S J Kennelly & M K Broadhurst

Figure 3 The launch of theAtlantic Dawn, in February,2000 (from Fishing News International, March 2000). factorytrawlers from the USSR, East Germany, and ¢shers tried to develop techniques that permit Poland, Spain, Japan and othercountries. Inthe early the exploitation of ¢sh stocks in a more sustainable 1970s, continued declines in stocks eventuallyled to manner.The ¢rst major impetus for this change was the US Magnuson Act in 1976, which took control of the issue over `by-catch' (the capture and discard of the exclusive economic zone and established a sys- untargeted individuals and species). Concern over tem to regulate the domestic industry. This led to this issue surfaced periodicallythroughout history great expectations in the industryand, aided by (see above), but recentlyreached a maximum due to subsidyprogrammes, manynew, modern trawlers declining ¢sh stocks and widespread publicityover were built. Fishing e¡ort therefore continued to the incidental capture of charismatic species like dol- increase and manyof the most productive stocks in phins and turtles. These factors led to commercial the region declined. In the late 1980s, various envir- and recreational ¢shers, conservationists, environ- onmental groups sued the US government for not mentalists, politicians, ¢sheries managers and scien- adequatelyenforcing laws mandating against the tists, all identifying by-catch as a key problem and over¢shing of resources. This led to new manage- calling for ways to reduce it (for reviews seeAlverson ment plans to control ¢shing e¡ort and rebuild et al. 1994; Kennelly1995). In response to this chal- stocks. lenge, ¢shing technologists have been successful in The above example is just one of the many developing technologies to protect manyorganisms accounts of increasing demand and unchecked while still allowing target species to be caught. Two technologyleading to stock collapses in manyparts examples are described below. of the world throughout the 20th century. The trend Interestingly, despite centuries of concernover the for bigger, more powerful vessels continues today, discarding of small ¢sh from nets (especiallytrawls), with the largest ¢shing vessel in the world launched one of the ¢rst attempts to resolve by-catch issues in February2000 (Fig. 3). This 14 000-t ship (the did not address trawling but the more selective `Atlantic Dawn') was built in Norwayfor an Irish method of purse-seining (for a full description of this company, is 145 m long, cost »50 m, has a crew of example, see Hall 1994,1998). Concern over the inci- 100 and can hold enough ¢sh to feed14 million peo- dental mortalityof dolphins in tuna purse-seines ple for a day. Given recent history, one must wonder has been one of the world's most infamous by-catch how long such vessels can remain pro¢table. issues since the 1960s with dramatic outcries from various environmental and conservation organiza- tions. The most common waypurse-seiners ¢sh in The last few decades ± a change in the eastern Paci¢c Ocean is to encircle groups of dol- philosophy phins to catch the tunathat theyswimwith. During So, after tens of thousands of years developing better the1960s, the incidental mortalityof dolphins using techniques to catch ¢sh, centuries of concern that this method was an average of approximately such techniques maybe causing signi¢cant damage 350 000 dolphins yearÀ1, which is believed to have tostocks and ecosystems, and half acenturyofrealis- caused signi¢cant declines in their populations. But ing that such impacts were occurring, the last two through the development of a series of technological decades have seena majorchange in focus inthe ¢eld and other modi¢cations, dolphin mortalities were of ¢shing technology. This has occurred as scientists reduced in this ¢sheryto negligible levels (Hall1994,

344 # 2002 Blackwell Science Ltd, F I S H and F I S H E R I E S, 3, 340 ^355 Changes in the philosophyof ¢shing technology S J Kennelly & M K Broadhurst

1998). These modi¢cations included di¡erent mesh this ¢sheryshowed that it was possible to save sizes incertain sections of the nets, modi¢ed methods bycaught dolphins without closing a major ¢shery. for tying the cork line, a manoeuvre termed `back- Another, virtuallyglobal, example of how ¢shing down' after dolphins were encircled (see Fig. 4 and technologybecame an allyin minimising impacts of Medina 1994), using speedboats to `herd'dolphins to ¢shing is the success that various types of by-catch the rear of the net, and avoiding areas containing reduction devices (BRDs) have had in decreasing the populations of particularlyprone dolphins. Once unwanted by-catch of large numbers of juvenile ¢sh these modi¢cations were developed, a large-scale from shrimp trawls (for a recent review, see Broad- education programme trained skippers and crews in hurst 2000). Much of this work began in the Gulf of the new techniques. The success of the work done in Mexico and Europe more than 20 years ago, but the

Figure 4 The`backdown' manoeuvre used in tuna purse-seining.

# 2002 Blackwell Science Ltd, F I S H and F I S H E R I E S, 3, 340 ^355 345 Changes in the philosophyof ¢shing technology S J Kennelly & M K Broadhurst

example that we will use to illustrate it comes from ¢sheryo¡shore from this river in the same year, it work done in New SouthWales (NSW), Australia. was estimated that in catching 288 tons of shrimp, In NSW, high-pro¢le by-catch problems in shrimp 4 022 tons of by-catchwas caught, of which725 tons ¢sheries have occurred since the late 19th century was landed for sale as `byproduct' (including various (see Dannevig 1904; for review see Kennelly1995) species of slipper lobsters, squid, octopus and large but reached a maximum in the late 1980s with ¢sh) while the rest (some 3 297 tons) was discarded. threats to close certain ¢sheries to stop the by-catch After a series of experiments (see Broadhurst 2000 of juvenile ¢sh. An observer programme estimated for details), two gear modi¢cations proved successful large by-catches of juvenile ¢sh in these ¢sheries at reducing by-catch while maintaining and some- (Kennelly et al. 1993, 1998; Liggins and Kennelly times even enhancing catches of shrimp. Because 1996). For example, in the Clarence River in1991^92, the targeted shrimp in the estuarine ¢sherywere it was estimated that in catching 270 tons of shrimp, smaller than the by-catch to be excluded, a modi¢ed 123 tons of by-catch was discarded, including NordmÖre-grid (Isaksen et al. 1992) was found to be 0.8 million individuals of the recreationallyand com- most e¡ective (Fig. 5). For the oceanic ¢shery, a commerciallyimportant yellow¢n bream. In the oceanic posite square-mesh panel anterior to the codend (see

Figure 5 The NordmÖre-grid used in the NSWestuarine shrimp trawl ¢sheryand an example of the catches from paired comparisons using a conventional codend (a) and one with a NordmÖre-grid (b).

346 # 2002 Blackwell Science Ltd, F I S H and F I S H E R I E S, 3, 340 ^355 Changes in the philosophyof ¢shing technology S J Kennelly & M K Broadhurst

Figure 6 The composite square- mesh panel tested in the NSWoceanic shrimp-trawl ¢sheryand an example of the catches from paired comparisons using a conventional codend (a) and one with a composite square-mesh panel (b).

Fig. 6) was developed that allowed small ¢sh to swim involves ¢ve keysteps: (i) quantifying by-catches; (ii) out of the codend, while commerciallyimportant identifying the main by-catch species of concern; shrimp, slipper lobsters, squid and octopus were (iii) developing modi¢cations that minimize mortal- retained. The sizes of ¢sh excluded could be selected ityof these species; (iv)testing the alternatives in¢eld byadjusting the mesh size in the square-mesh panel. experiments; and (v) gaining acceptance of the new Both these modi¢cations are now among the BRDs technologythroughout the particular ¢sheryand that are mandatoryin NSW'sshrimp ¢sheries. ¢nallyto interested groups. The logic and methods for completing steps (i), (ii), (iv) and (v) are common among many¢sheries and A framework for solving by-catch problems have been described in detail byKennellyand Broad- The case studies above illustrate that technological hurst (1996), Kennelly(1997), (1999) and Broadhurst solutions can be employed to address successfully (2000). The development of new ¢shing technologies the issue of by-catch in di¡erent ¢sheries. Further, it that minimize by-catches (step iii) is a more compli- has been shownthat this has generallyoccurred only cated step and largelydepends on the characteristics when an incremental protocol or framework is of the ¢sheryin question. For example, in the case of employed (Fig. 7) (Kennelly and Broadhurst 1996; active ¢shing gears, like trawls and seines, this has Kennelly1997; Broadhurst 2000). This framework nearly always involved di¡erent types of physical

# 2002 Blackwell Science Ltd, F I S H and F I S H E R I E S, 3, 340 ^355 347 Changes in the philosophyof ¢shing technology S J Kennelly & M K Broadhurst

Figure 7 The framework for solving by-catch problems. modi¢cations to improve selectivity(Fig. 8). Depend- being used to improve selectivityof passive ¢shing ing on the species to be excluded and retained, these gears. As an example, the size, morphology, condition modi¢cations range from simple changes to existing and behaviour of ¢sh have been shown to be impor- mesh sizes and materials (e.g. Broadhurst et al. 2000; tant factors in£uencing the selectivityof traps (e.g. Gray et al. 2000; Kennellyand Gray2000) to the Stewart and Ferrell 2002) and gillnets (e.g. Hay et al. application of speci¢c and often complicated BRDs 1986; HovgÔrd 1996; Poulsen et al. 2000). Similarly, (Fig. 8; Broadhurst 2000). These BRDs separate species-speci¢c variabilities in feeding behaviour catches either mechanicallyaccording to their sizes and preferences for di¡erent sizes and types of baits (e.g. rigid devices like the NordmÖre-grid) or via dif- have been shown to in£uence the composition, size ferences in physiology and/or behaviour (e.g. like the and quantityof ¢sh caught bylonglines (LÖkkeborg composite square-mesh panel). In some cases, by and Bjordal1992;Broadhurst and Hazin 2001). Other combining devices that incorporate the principles of successful solutions to reduce by-catch have simply both mechanical separation (as primaryBRDs) and involved subtle changes to the operation of tradi- behavioural separation (as secondaryBRDs), it is pos- tional ¢shing gears, such as di¡erent setting methods sible to allow a large range of di¡erent species and of longliners to reduce by-catches of sea birds (LÖkke- sizes to escape nets (Fig. 8; Broadhurst 2000). borg1998) or the backdown procedure used to reduce BRDs are generallylimited to active ¢shing gears; by-catches of dolphins from tuna purse-seines (see however, the underlying factors governing their above). e¡ectiveness (i.e. di¡erences in the behaviour and The various studies described above serve to illus- physiology of target and nontarget species) are also trate that manyby-catch problems can be resolved

348 # 2002 Blackwell Science Ltd, F I S H and F I S H E R I E S, 3, 340 ^355 Changes in the philosophyof ¢shing technology S J Kennelly & M K Broadhurst

Figure 8 Summaryof the logic used for developing and testing modi¢cations in shrimp-trawl ¢sheries. via technological solutions, but that this must be regard for anyof the likelyenvironmental impacts. done ona ¢shery-speci¢c basis. Further,it is apparent But in recent times, attention has shifted towards that the successful adoption and use of these techno- some of the more obvious environmental issues con- logical solutions will onlyoccur when ¢shing indus- nected with ¢shing, beginning with concerns over tries are involved in all stages of the framework the by-catch, discard and wastage of charismatic spe- (Kennelly1997,1999). cies and expanding to concerns over not-so-charismatic species like the small ¢sh killed during shrimp and ¢shtrawling. In response to these issues, ¢shing Current issues technologists and commercial ¢shers developed var- The brief historyof ¢shing technologysummarized ious gear-based and operational solutions (like those above shows how the focus of the ¢eld has changed. discussed in the previous section) that ameliorated For most of the time since humans began catching manyof the problems. ¢sh, ¢shing methods were developed to maximize During the past decade, public concern has broa- catches of an ever-increasing diversity, with little dened once again to encompass a much wider con-

# 2002 Blackwell Science Ltd, F I S H and F I S H E R I E S, 3, 340 ^355 349 Changes in the philosophyof ¢shing technology S J Kennelly & M K Broadhurst

Table 1 Summaryof a brief review of the literature examining ecological impacts of ¢shing

(a) Papers assessing impacts Sainsbury (1991) Sainsbury et al. (1997) Simboura et al. (1998) Eleftheriou and Robertson (1992) Auster (1998) Thrush et al. (1998) Brylinsky et al. (1994) Brailovskaya (1998) Tuck et al. (1998) Kaiser and Spencer (1994) Collie (1998) Auster and Langton (1999) Witbaard and Klein (1994) Dorsey and Pederson (1998) DeAlteris et al. (1999) Dayton et al. (1995) Gilkinson et al. (1998) Freese et al. (1999) Thrush et al. (1995) Gordon et al. (1998) Friedlander et al. (1999) Auster et al. (1996) Jennings and Kaiser (1998) Hall-Spencer et al. (1999) Currie and Parry (1996) Kaiser (1998) Hill et al. (1999) Kaiser (1996) Kaiser et al. (1998) Jennings et al. (1999) Kaiser and Spencer (1996) Lindeboom and de Groot (1998) Kaiser et al. (1999) Kaiser et al. (1996) Pilskaln et al. (1998) Lindeman and Snyder (1999) Morton (1996) Poiner et al. (1998) Prena et al. (1999) Ramsay et al. (1996) Pranovi et al. (1998) Tegner and Dayton (1999) Collie et al. (1997) Ramsay et al. (1998) Hansson et al. (2000) Jennings and Polunin (1997) Rogers et al. (1998) Lindegarth et al. (2000a) Kaiser and Ramsay (1997) Schwinghamer et al. (1998) Lindegarth et al. (2000b)

(b) Papers suggesting technological solutions Seidel (1969) Watson (1976) Carr and Milliken (1998) text involving the impacts of certain ¢shing methods on the ecological impacts of ¢shing and ¢nding solu- on whole ecosystems (Pitcher 2001). One of the most tions that will minimize it. pressing issues facing the world's¢sheries todaycon- In recent years, there has been a substantial e¡ort cerns the impacts of ¢shing on all species a¡ected ^ byscientists to increase our knowledge of these not just those that are caught, retained or discarded, issues, but because of the scales and complexities but also the ecological implications of disrupting involved, such studies are usuallydi¤cult, expensive habitats and the manyuncaught species a¡ected and of a long duration. In a reasonablythorough (see Kaiser et al.1998;Watling and Norse1998; Freese (but byno means exhaustive) examination of this lit- et al. 1999; Lindegarth et al. 2000a,b).While the spe- erature (Table 1), a signi¢cant number of studies (51) cies that comprise the biodiversityof these systems have attempted to measure the ecological impacts of (sponges, ascidians, byrozoans, polychaetes, micro- ¢shing (especiallyusing active gears like trawls), but scopic organisms, juveniles of commercially veryfew (3) have addressed such impacts via techno- exploited species, etc.) have little charisma, public logical solutions. The solutions suggested so far in appeal orcommercial priority, their role is seenas cri- this debate usuallyinvolve stopping ¢shing in sensi- tical because theyunderpin much of the local ecol- tive areas and times ^ not to develop technological ogy. Add this to the fact that most ¢sheries rely on solutions to ameliorate problematic impacts. It is the continued normal functioning of these ecosys- interesting that this initial consideration of closure tems and it becomes obvious that the ¢shingindustry strategies ^ instead of technological solutions ^ itself is, or at least should be, concerned about these repeats the pattern that characterized earlystrate- issues. gies on ways to deal with by-catch issues before As a consequence of this latest stage in humans' advances in ¢shing technologies were developed. perceptions of ¢shing, there have been several initia- tives calling for ecosystem-based approaches to ¢sh- The next challenge eries management. Further, issues concerning biodiversityand ecosystem-wide e¡ects of ¢shing The above discussion places us in the midst of the are now central to most management plans where next major challenge for ¢shing technologists: to there are policies to manage in an ecologicallysus- address the ecological impacts of ¢shing so that ¢sh- tainable manner. A corollaryis that there are now ing can continue in an ecologicallysustainable fash- signi¢cant demands for more scienti¢c information ion. It is this challenge that should now be adopted

350 # 2002 Blackwell Science Ltd, F I S H and F I S H E R I E S, 3, 340 ^355 Changes in the philosophyof ¢shing technology S J Kennelly & M K Broadhurst

by¢shing technologists. Attempts to address this to disturb it more than anyother component of trawl issue will logicallybegin with the infamous ¢shing gear. One wayto reduce this disturbance maybe to technique of trawling and, as those European and use rollers or wheels set into universal joints on the American ¢shing technologists found decades ago base of the boards or to have their basal shoes o¡set as theybegan developing BRDs for shrimp trawls, at an angle from the main part of the board (Fig. 9). we have verylittle research available on this issue This would allow the shoe to slide over the substra- with which to build. tum in the direction of the towand so reduce the con- One concept that comes to us from work done tact of the board to the width of the shoe; up to 90% manyyears ago examines an alternative to the use less than the length of the board. of ground chains on demersal trawls. Seidel (1969) While it is encouraging that there are several tech- and Watson (1976) describe the utilityof electric nological options available for reducing impacts of ¢elds as a replacement for ground chains in making trawl gears on habitats, it is disappointing that so shrimp `jump' into the path of an oncoming net but, few have actuallybeen tested. This is the challenge despite its potential, no further development of this now facing ¢shing technologists and commercial concept occurred. Carr and Milliken (1998) summar- ¢shers throughout the world as theytryto continue ized several options for minimising impacts of trawl ¢sheries on a sound, ecologicallysustainable footing. gear on the sea £oor. One was to rig trawls so that We believe that such a challenge can be met optimis- foot-ropes were raised when targeting ¢sh that ticallybythis ¢eld because its recent historyin deal- school slightlyabove the bottom. Others involved ing with by-catch issues illustrates a successful shift modifying the con¢guration of sweeps using various in philosophyand paradigms to meet environmental types of rollers,`rock hoppers'and `street sweepers'to challenges ^ after manymillennia of ignoring them. minimize impacts of trawls on benthic assemblages. Several quite simple but e¡ective solutions have been The future discussed at recent meetings and workshops on this subject, including: (i) decreasing the warp length-to- There is no doubt that the worldwide demand for sea- depth ratio as much as possible to decrease the food will continue to rise and, whilst increased pro- weight of trawl gear on the bottom; (ii) reducing the duction from aquaculture maymeet some of this lengths of sweeps and bridles as much as possible; demand, there will always be increasing pressure to (iii) maintaining net spread to reduce the likelihood harvest wild stocks. For this to occur in a sustainable that the net bellycontacts the bottom; and (iv) using fashion, the techniques used to harvest ¢sh will have £oats on BRDs and codends to avoid them hitting to become increasinglyselective.We believe that ¢sh- the bottom (Whyte, personal communication). ing technologywill evolve considerablycloser to the Some of the more promising ideas to surface in point where onlythose species and sizes/ages of spe- recent years concerns the operation of otter boards cies are caught whose removal can be withstood and (Whyte, personal communication) which are sustained ^ not onlybythe exploited populations, dragged along the substratum and have the potential but bythe ecosystems which support them.

Figure 9 Two options that may reduce the ecological impacts of otter boards ^ using wheels and angled sleds on the base of boards.

# 2002 Blackwell Science Ltd, F I S H and F I S H E R I E S, 3, 340 ^355 351 Changes in the philosophyof ¢shing technology S J Kennelly & M K Broadhurst

We see this rather optimistic view as not a hopeful gladius) and other species in an artisanal sub-surface desire but as an inevitable consequence of the state of longline ¢sheryo¡ northeastern Brazil. Fisheries the world's exploited ¢sh populations and the ever- Research 53,169^179. increasing pressure on them. Quite simply, if ¢shing Broadhurst, M.K., McShane, P.E. and Larsen, R.B. (2000) E¡ects of twine diameter and mesh size in the bodyof technologydoes not develop to an almost `utopian' prawn trawls used in Gulf St.Vincent, Australia. Fishery point of perfect selectivity, the ¢sheries of the world Bulletin 98, 463^473. willcontinue todecline at its current (ora faster) rate. Brylinsky, M., Gibson, J. and Gordon, D.C. (1994) Impacts of However, as ¢shing technologists work towards £ounder trawls on the intertidal habitat and community this ultimate goal, there also needs to be a correspon- of theMinas Basin, Bayof Fundy. CanadianJournal ofFish- ding increase in the willingness of the commercial eries and Aquatic Sciences 51, 650 ^661. and recreational ¢shing sectors to adopt such tech- Carr, H.A. and Milliken, H. (1998) Conservation engineer- nologies. Whilst legislation bygovernments can ing: options to minimize ¢shing'simpacts to the sea £oor. provide some impetus for ¢shers to adopt selective In: E¡ects of Fishing Gearon the Sea Floorof New England ¢shing practices, recent historyhas shown that the (eds E.M. Dorseyand J. Pederson). Conservation Law most e¡ective uptake requires the involvement of Foundation, Boston, Massachusetts, pp.100^103. Collie, J. (1998) Studies in New England of ¢shing gear ¢shers at all stages of development. As our frame- impacts on the sea £oor. In: E¡ects of Fishing Gear on the work (Fig. 7) shows, this should occur from the origi- Sea Floor of New England (eds E.M. Dorseyand J. nal identi¢cation and quanti¢cation of particular Pederson). Conservation Law Foundation, Boston, by-catch and selectivity issues, through the design Massachusetts, pp.53^62. and testing of new gears, to the education, adoption Collie,J.S.,Escanero,G.A.andValentine,P.C.(1997)E¡ectsof and advertising of resultant solutions. Unless this bottom ¢shing on the benthic megafauna of Georges engagement and involvement of ¢shers is as fully Bank. Marine Ecology Progress Series155, 159^172. developed as the ¢shing technologyitself, perfect Currie,D.R.andParry,G.D.(1996)E¡ectsofscallopdredging selectivityof ¢shing practices will never occur ^ no on a soft sediment community: a large-scale experimen- matter how perfectlyselective ¢shing technologists tal study.Marine Ecology Progress Series134,131^150. make them. Dannevig, H.C. (1904) Preliminaryreportupontheprawning industry in Port Jackson. W A Gullick, NSW Government Printer,17pp. References Dayton,P.K.,Thrush,S.F.,Agardy,M.T.andHofman,R.J. (1995) Environmental e¡ects of marine ¢shing. Aquatic Alverson, D.L., Freeberg, M.H., Murawski, S.A. and Pope, J.G. Conservation: Marine and Freshwater Ecology 5,205^232. (1994) A global assessment of ¢sheries by-catch and dis- DeAlteris, J., Skrobe, L. and Lipsky, C. (1999) The signi¢cance cards. FAO Fisheries Technical Paper 339.FAO,Rome, of seabed disturbance bymobile ¢shing gear relative to 233pp. natural processes: a case studyin Narragansett Bay, Auster, P.J. (1998) A conceptual model of the impacts of ¢sh- Rhode Island. American Fisheries Society Symposium 22, ing gear on the integrityof ¢sh habitats. Conservation 224^237. Biology12,1198^1203. Dorsey, E.M. and Pederson, J., eds (1998)E¡ects of ¢shing gear Auster, P.J. and Langton, R.W.(1999) The e¡ects of ¢shing on onthesea£oorofNew England. Conservation LawFounda- ¢sh habitat. American Fisheries Society Symposium 22, tion, Boston, MA,160pp. 150 ^187. Dyson, J. (1977) Business in Great Waters: the story of Auster, P.J., Malatesta, R.J., Langton, R.W. et al. (1996) The British Fishermen. Angus & Robertson (UK) Ltd., UK, impacts of mobile ¢shing gear on sea£oor habitats in the pp.37^39. Gulf of Maine (Northwest Atlantic): implications for con- Eleftheriou, A. and Robertson, M.R. (1992) The e¡ects of servation of ¢sh populations. Reviews in Fisheries Science experimental scallop dredging on the fauna and physical 4, 185^202. environment of a shallow sandycommunity. Netherlands Brailovskaya,T. (1998) Obstacles to protecting marine biodi- Journal of Sea Research 30,289^299. versitythrough marine wilderness preservation: exam- Freese, L., Auster, P.J., Heifetz, J. andWing, B.L. (1999) E¡ects ples from the New England region. Conservation Biology of trawling on sea£oor habitat and associated inverte- 12, 1236^1240. brate taxa in the Gulf of Alaska. Marine Ecology Progress Broadhurst, M.K. (2000) Modi¢cations to reduce bycatch in Series182, 119^126. prawn trawls: a review and framework for development. Friedlander, A.M., Boehlert, G.W., Field, M.E., Mason, J.E., Reviews in Fish Biology and Fisheries10,27^60. Gardner, J.V.and Dartnell, P.(1999) Sidescan-sonar map- Broadhurst, M.K. and Hazin, F.H.V.(2001) In£uences of type ping of benthic trawl marks on the shelf and slope o¡ and orientation of bait on catches of sword¢sh (Xiphias Eureka, California. Fishery Bulletin 97, 786^801.

352 # 2002 Blackwell Science Ltd, F I S H and F I S H E R I E S, 3, 340 ^355 Changes in the philosophyof ¢shing technology S J Kennelly & M K Broadhurst

Gilkinson, K., Paulin, M., Hurley, S. and Schwinghamer, P. contrasting life histories. Journal of Animal Ecology 68, (1998) Impacts of trawl door scouring on infaunal 617^627. bivalves: results of a physical door model^dense sand Kaiser, M.J. (1996) Star¢sh damage as an indicator of interaction. Journal of Experimental Marine Biology and trawling intensity. Marine Ecology Progress Series 134, Ecology 224,291^312. 303^307. Gordon, D.C., Schwinghamer, P., Rowell, T.W. et al. (1998) Kaiser, M.J. (1998) Signi¢cance of bottom-¢shing distur- Studies in eastern Canadaonthe impact of mobile¢shing bance. Conservation Biology12, 1230^1235. gear on benthic habitat and communities. In: E¡ects of Kaiser,M.J.andRamsay,K.(1997)Opportunisticfeedingby FishingGearontheSeaFloorofNewEngland (eds E.M. Dor- dabs within areas of trawl disturbance: possible implica- seyand J. Pederson). Conservation Law Foundation, Bos- tions for increased survival. Marine Ecology Progress Ser- ton, MA, pp.63^67. ies152,307^310. Gray, C.A., Larsen, R.B. and Kennelly, S.J. (2000) Use of Kaiser, M.J. and Spencer, B.E. (1994) Fish scavenging beha- transparent netting to improve size selectivityand viour in recentlytrawled areas. Marine Ecology Progress reduce by-catch in ¢sh seine nets. Fisheries Research 45, Series112,41^49. 155^166. Kaiser, M.J. and Spencer, B.E. (1996) The e¡ects of beam- Hall, M.A. (1994) By-catches in purse-seine ¢sheries. In: By- trawl disturbance on infaunal communities in di¡erent catches in Fisheries and their Impact on the Ecosystem,Vol. habitats. Journal of Animal Ecology 65,348^358. 2 (1) (eds T. J. Pitcher and R. Chuenpagdee) ISSN 1198^ Kaiser,M.J.,Cheney,K.,Spence,F.E.,Edwards,D.B.and 6727. Fisheries Centre Research Reports. Universityof Readford, K. (1999) Fishing e¡ects in northeast Atlantic British Columbia, Canada, pp. 53^58[see appendix for shelf seas: patterns in ¢shing e¡ort, diversityand com- availabilityof unpublished reports (1)]. munitystructure. PartVII.The e¡ects of trawling distur- Hall, M.A. (1998) An ecological view of the tuna^dolphin bance on the fauna associated with the tubeheads of problem: impacts and trade-o¡s. Reviews in Fish Biology serpulid worms. Fisheries Research 40, 195^205. and Fisheries 8,1^34. Kaiser, M.J., Edwards, D.B., Armstrong, P.J. et al. (1998) Hall-Spencer, J.M., Froglia, C., Atkinson, R.J.A. and Moore, Changes in megafaunal benthic communities in di¡er- P.G. (1999) The impact of Rapido trawling for scallops, ent habitats after trawling disturbance. ICES Journal of Pecten jacobaeus (L.), on the benthos of the Gulf of Venice. Marine Science 55, 353^361. ICES Journal of Marine Science 56, 111^124. Kaiser,M.J.,Hill, A.S., Ramsay, K.et al. (1996) Benthic distur- Hansson, M., Lindegarth, M., Valentinsson, D. and bance by¢shing gear in the Irish sea: a comparison of Ulmestrand, M. (2000) E¡ects of shrimp-trawling on beam trawling and scallop dredging. Aquatic Conserva- abundance of benthic macro-fauna in Gullmarsfjorden, tion: Marine and Freshwater Ecology 6,269^285. Sweden. Marine Ecology Progress Series198, 191^201. Kennelly, S.J. (1995) The issue of by-catch in Australia's Hay, D.E., Cooke, K.D. and Gissing, C.V.(1986) Experimental demersal trawl ¢sheries. Reviews in Fish Biology andFish- studies of Paci¢c herring gillnets. Fisheries Research 4, eries 5,213^234. 191^211. Kennelly, S.J. (1997) A framework for solving by-catch pro- Hill, A.S.,Veale, L.O., Pennington, S.G.,Whyte, S.G., Braund, blems: examples from New South Wales, Australia, the A.R. and Hartnoll, R.G. (1999) Changes in Irish sea eastern Paci¢c and the northwest Atlantic. In:Developing benthos: possible e¡ects of 40 years of dredging. Estuar- and Sustaining World Fisheries Resources: the State of ine, Coastal Shelf and Science 48,739^750. Science and Management (eds D.A. Hancock, D.C. Smith, HovgÔrd, H. (1996) E¡ect of twine diameter on ¢shing power A. Grant and J.P.Beumer). 2nd World Fisheries Congress of experimentalgill netsused inGreenlandwaters. Cana- proceedings. ISBN 0^643^05985^7. CSIRO Press, Aus- dian Journal of Fisheries and Aquatic Sciences 53, 1014 ^ tralia, pp.544^550. 1017. Kennelly, S.J. (1999) The development and introduction of Isaksen, B.,Valdemarsen, J.W., Larsen, R.B. and Karlsen, L. by-catch reducing technologies in three Australian (1992) Reduction of ¢sh by-catch in shrimp trawl using a prawn-trawl ¢sheries. Marine Technology Society Journal rigid separator grid in the aft belly.Fisheries Research13, 33,73^81. 335^352. Kennelly, S.J. and Broadhurst, M.K. (1996) Fishermen and Jennings, S. and Kaiser, M.J. (1998) The e¡ects of ¢shing scientists solving by-catch problems: examples fromAus- on marine ecosystems. Advances in Marine Biology 34, tralia and possibilities for New England. In: Solving By- 201^352. catch: Considerations forToday and Tomorrow.Alaska Sea Jennings, S. and Polunin, N.V.C. (1997) Impacts of predator Grant College Program Report no. 96^03. Universityof depletion by¢shing on the biomass and diversityof non- Alaska Fairbanks, pp.121^128. target reef ¢sh communities. Coral Reefs16,71^82. Kennelly, S.J. and Gray, C.A. (2000) Reducing the mortality Jennings, S., Greenstreet, S.P.R. and Reynolds, J.D. (1999) of discarded undersize sand whiting sillago ciliata in an Structural change inanexploited ¢shcommunity: a con- estuarine seine ¢shery. Marine and Freshwater Research sequence of di¡erential ¢shing e¡ects on species with 51, 749^753.

# 2002 Blackwell Science Ltd, F I S H and F I S H E R I E S, 3, 340 ^355 353 Changes in the philosophyof ¢shing technology S J Kennelly & M K Broadhurst

Kennelly, S.J., Kearney, R.E., Liggins, G.W. and Broadhurst, Nun, M. (1993) Cast your net upon the waters: ¢sh and M.K. (1993) The e¡ect of shrimp trawling by-catch on ¢shermen in Jesus' time. Biblical Archaeology Review other commercial and recreational ¢sheries ^ anAustra- 19.6,70. lian perspective. In: International Conference on Shrimp Pilskaln, C.H., Churchill, J.H. and Mayer, L.M. (1998) Resus- By-catch, May 24^27,1992, Lake BuenaVista, Florida (ed. pension of sediment bybottom trawling in the Gulf of R.P. Jones). Southeastern Fisheries Association, Maine and potential geochemical consequences. Conser- Tallahassee, FL, pp.97^114. vation Biology12,1223^1229. Kennelly, S.J., Liggins, G.W. and Broadhurst, M.K. (1998) Pitcher,T.J. (2001) Rebuilding ecosystems as a new goal for Retained and discarded by-catch from oceanic prawn ¢sheries management: reconstructing the past to sal- trawling in New South Wales, Australia. Fisheries vage the future. Ecological Applications11,601^617. Research 36,217^236. Poiner, I., Glaister, J., Pitcher, R. et al. (1998) Final Report on Liggins, G.W. and Kennelly, S.J. (1996) By-catch from prawn E¡ects of Trawling in the Far Northern Section of the Great trawling in the Clarence River estuary, New SouthWales, Barrier Reef: 1991^96. CSIRO Division of Marine Australia. Fisheries Research 25,347^367. Research, Cleveland. Lindeboom, H.J. and de Groot S.J., eds (1998) The E¡ects of Poulsen, S., Nielsen, J.R., Holst, R. and Stñhr, K. (2000) An Di¡erent Types of Fisheries on the North Sea and Irish Sea Atlantic herring (Clupea harengus) size selection model Benthic Ecosystems. Netherlands Institute for Sea for experimental gill nets used in the Sound (ICES Subdi- Research (NIOZ). Netherlands Institute for Fisheries vision 23). Canadian Journal of Fisheries and Aquatic Research (RIVO-DLO), the Netherlands,404pp. Sciences 57, 1551^1561. Lindegarth, M., Valentinsson, D., Hansson, M. and Ulmes- Pranovi, F., Giovanardi, O. and Franceschini, G. (1998) Reco- trand, M. (2000a) Disturbances bytrawling changes lonization dynamics inareas disturbed bybottom ¢shing temporal and spatial structure of benthic soft-sediment gears. Hydrobiologia 375/376,125^135. assemblages in Gullmars-fjorden, Sweden. ICES Journal Prena, J., Schwinghamer, P., Rowell,T.W. et al. (1999) Experi- of Marine Science 57, 1369^1376. mental otter trawling on a sandybottom ecosystem of Lindegarth, M., Valentinsson, D., Hansson, M. and Ulmes- the Grand Banks of Newfoundland: analysis of trawl by- trand, M. (2000b) Interpreting large-scale experiments catch and e¡ects on epifauna. Marine Ecology Progress on e¡ects of trawling on benthic fauna: an empirical test Series181,107^124. of the potential e¡ects of spatial confounding in experi- Ramsay,K.,Kaiser,M.J.andHughes,R.N.(1996)Changes ments without replicated control and trawled areas. in hermit crab feeding patterns in response to traw- Journal of Experimental Marine Biology and Ecology 245, ling disturbance. Marine Ecology Progress Series 144, 155^169. 63^72. Lindeman, K.C. and Snyder, D.B. (1999) Nearshore hardbot- Ramsay,K.,Kaiser,M.J.andHughes,R.N.(1998)Responses tom ¢shes of southeast Florida and e¡ects of habitat bur- of benthic scavengers to ¢shing disturbance bytowed ial caused bydredging. Fishery Bulletin 97,508^525. gears in di¡erent habitats. Journal of Experimental LÖkkeborg, S. (1998) Seabird by-catch and bait loss in long- Marine Biology and Ecology 224,73^89. lining using di¡erent setting methods. ICES Journal of Rogers, S.I., Kaiser, M.J. and Jennings, S. (1998) Ecosystem Marine Science 55,145^149. e¡ects of demersal ¢shing: a European perspective. In: LÖkkeborg, S. and Bjordal, Ð. (1992) Species and size selec- E¡ectsofFishingGearontheSea FloorofNewEngland (eds tivityin longline ¢shing: a review. Fisheries Research13, E.M. Dorseyand J. Pederson). Conservation Law Founda- 311^322. tion,Boston,MA,pp.68^78. Medina, H. (1994) Reducing by-catch through gear modi¢- Sainsbury, K.J. (1991) Application of an experimental cations: the experience of the tuna^dolphin ¢shery. In: approach to management of a tropical multispecies ¢sh- By-catches in Fisheries and Their Impact on the Ecosystem erywith highlyuncertain dynamics. ICES Marine Vol. 2 (1) (eds T.J. Pitcher and R. Chuenpagdee) ISSN Science Symposia193,301^320. 1198^6727. Fisheries Centre Research Reports, Univer- Sainsbury, K.J., Campbell, R.A., Lindholm, R. andWhitelaw, sityof British Columbia, Canada, p. 60[see appendix for A.W. (1997) Experimental management of an Australian availabilityof unpublished reports (1)]. multispecies ¢shery: examining the possibility of trawl- Morton, B. (1996) The subsidiaryimpacts of dredging (and induced habitat modi¢cation. In: GlobalTrends: Fisheries trawling) on a subtidal benthic molluscan community Management (eds E.L. Pikitch, D.D. Huppert and M.P.Sis- in the southern waters of Hong Kong. Marine Pollution senwine). American Fisheries SocietySymposium 20, Bulletin 32,701^710. Bethesda, MD, pp.107^112. NOAA (2001) Brief historyof ground¢shing. NOAA NMFS. Schwinghamer, P., Gordon, D.C., Rowell, T.W. et al. (1998) Available at: http://www.noaa.gov/nmfs/ground¢sh/ E¡ects of experimental otter trawling on sur¢cial sedi- grndfsh1.html. ment properties of a sandy-bottom ecosystem on the Nun, M. (1989) The Sea of Galilee and Its Fishermen in the New Grand Banks of Newfoundland. Conservation Biology12, Testament.Ein Gev, Kibbutz Ein Gev. 1215^1222.

354 # 2002 Blackwell Science Ltd, F I S H and F I S H E R I E S, 3, 340 ^355 Changes in the philosophyof ¢shing technology S J Kennelly & M K Broadhurst

Seidel,W.R. (1969) Design, construction and ¢eld testing of Tuck, I.D., Hall, S.J., Robertson, M.R., Armstrong, E. the BCF electric shrimp trawl system. Fishery Industrial and Basford, D.J. (1998) E¡ects of physical trawling Research 4, 213^231. disturbance in a previouslyun¢shed sheltered Simboura, N., Zenetos, A., Pancucci-Papadopoulou, M., Scottish sea loch. Marine Ecology Progress Series 162, Thessalou-Legaki, M. and Papaspyrou, S. (1998) A base- 227^242. line studyon benthic species distribution in two neigh- Watling, L. and Norse, E.A. (1998) Disturbance of the sea bed bouring gulfs, with and without access to bottom bymobile ¢shing gear: a comparison to forest clearcut- trawling. Marine Ecology19,293^309. ting. Conservation Biology12, 1180 ^1197. Stewart, J. and Ferrell, D.J. (2002) Mesh selectivityin the Watson, J.W. (1976) Electrical shrimp trawl catch e¤ciency New South Wales demersal trap ¢shery. Fisheries for Penaeus duorarum and Penaeus aztecus. Transactions Research in press. of theAmerican Fisheries Society105,135^148. Tegner,M.J. and Dayton, P.K. (1999) Ecosystem e¡ects of ¢sh- Witbaard, R. and Klein, R. (1994) Long-term trends on the ing.Trends in Ecology and Evolution14,261^262. e¡ects of southern North Sea beamtrawl ¢sheryon the Thrush, S.F., Hewitt, J.E., Cummings, V.J. and Dayton, P.K. bivalve mollusc Artica islandica L. (Mollusca, bivalvia). (1995) The impact of habitat disturbance byscallop dred- ICES Journal of Marine Science 51,99^105. ging on marine benthic communities: what can be pre- Wuellner, W. (1967) The Meaning of `Fishers of Men'. New dicted from the results of experiments? Marine Ecology Testament Library, Westminster Press, Philadelphia, Progress Series129, 141^150. 256pp. Thrush, S.F., Hewitt, J.E., Cummings,V.J. et al. (1998) Distur- Yellen, J.E., Brooks, A.S., Cornelissen, E., Mehlman, M.J. and bance of the marine benthic habitat bycommercial ¢sh- Stewart, K. (1995) A middle stone age worked bone indus- ing: impacts at the scale of the ¢shery. Ecological tryfrom Katanda, Upper Semliki Valley,Zaire. Science Applications 8, 866^879. 268,553^555.

# 2002 Blackwell Science Ltd, F I S H and F I S H E R I E S, 3, 340 ^355 355