Broadbill swordfish:Status of world fisheries

by

Peter Ward and Sue Elscot

Bureau of Rural Sciences

Bureau of Rural Sciencesii

Commonwealth of Australia 2000ISBN 0 642 47584 9This work is copyright. Apart from any use permitted under the Copyright Act 1968, no part may be reproduced by anyprocess without written Permission of the Bureau of Rural Sciences. Requests and inquiries concerning reproduction andrights should be addressed to the Executive Director, Bureau of Rural Sciences, PO Box E11, Kingston ACT 2604.

Published by:

Bureau of Rural SciencesPO Box E11 ph. 612–6272–4253Kingston ACT 2604 fax 612–6272–4747Australia Internet http://www.brs.gov.au

Recommended citation for this publication:Ward, P. and Elscot, S (2000) Broadbill swordfish: Status of world fisheries. Bureau of Rural Sciences, Canberra.

Editing: Green Words & Images.

Printing: Panther Publishing & Printing.

Cover design: Racheal Bruhn (Design), based on a photograph by Mr Peter Ward (Bureau of Rural Sciences).

Publication management: Mrs Barbara van der Linden (Bureau of Rural Sciences).

Line drawing of a swordfish (p. xi) courtesy of Food and Agriculture Organization of the United Nations, from Nakamura,I (1985) FAO Species catalogue volume 5. Billfishes of the world: An annotated and illustrated catalogue of marlins,sailfishes, spearfishes and swordfishes known to date. Food and Agriculture Organization, Rome.

The Bureau of Rural Sciences is a science agency within the Commonwealth Department of Agriculture, Fisheries andForestry – Australia.

The Bureau of Rural Sciences has endeavoured to make the information in this publication as accurate and up to date aspossible. However, it does not guarantee that the information is totally accurate or complete. Therefore you should not relysolely on this information when making commercial decisions.

Swordfish fisheries iii

FOREWORDBroadbill swordfish are a very recent and exciting development for Australia’s fishingindustry. A great-tasting fish, swordfish has excellent storage qualities. During the late 1980sfresh-chill fisheries developed in local ports in Australia and elsewhere, catching tuna andairfreighting the fish to high-priced sashimi markets in Japan. Fishing for swordfish is adiversification of the fresh-chill tuna industry to markets in the United States and Europe.

As a result of prospects for continued expansion in Australia, fishing permits are changinghands for large sums of money and new, larger boats are entering the fishery every week.Several swordfish fisheries in other parts of the world, however, have shown initial rapidexpansion and then declined, prompting concern over the species’ ability to support intensiveharvesting. Views on swordfish status are polarised between the fishing industry andconservation groups, with scientists somewhere in between. Conservation groups, forexample, instigated a boycott of swordfish in restaurants in the United States and are callingfor a complete ban on longline fishing.

In response to the rapid expansion of Australia’s swordfish fishery, the Bureau of RuralSciences (BRS) undertook the present review of the world’s swordfish fisheries. BRS is in anideal position to review swordfish fisheries; being an independent bureau within theCommonwealth Government we have a long history of providing scientific advice in supportof evidence-based decisions for the management of Australia’s natural resources.

Australia’s success in managing swordfish will require the early implementation of firmmanagement measures based on rigorous research and consideration of experiences withsimilar fisheries in other parts of the world.

PETER O’BRIENExecutive DirectorBureau of Rural Sciences

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ACKNOWLEDGMENTSThis report is as much the product of a review of literature as it is a representation of thecollective knowledge of a host of fishery experts. Appendix 1 is a detailed list of the manypeople who provided advice and information for the report. In particular, we are indebted toMr Albert Caton, Mr John Gunn, Dr Jim Joseph, Dr John Kalish and Dr Julie Porter whoprovided detailed comments on drafts of the report.

Our work and the report were funded by the Australian Fisheries Management AuthorityResearch Fund and the Eastern Tuna and Billfish Management Advisory Committee ResearchFund.

Swordfish fisheries v

CONTENTSpage

FOREWORD............................................................................................................................iii

ACKNOWLEDGMENTS ........................................................................................................ iv

SUMMARY.............................................................................................................................vii

GLOSSARY ...........................................................................................................................xiii

1. INTRODUCTION ................................................................................................................. 1Purpose............................................................................................................................ 1Related studies ................................................................................................................ 1Report structure............................................................................................................... 1Information sources......................................................................................................... 2References....................................................................................................................... 2

2. SUMMARY OF SWORDFISH BIOLOGY.......................................................................... 5Introduction..................................................................................................................... 5Diagnostic features.......................................................................................................... 5Distribution and movement............................................................................................. 5Stock structure................................................................................................................. 6Reproduction and spawning............................................................................................ 8Age and growth............................................................................................................. 10Food and feeding........................................................................................................... 14References..................................................................................................................... 16

3. OVERVIEW OF SWORDFISH FISHERIES ..................................................................... 21Development of swordfish fisheries.............................................................................. 21Fishery distribution ....................................................................................................... 27Global trends ................................................................................................................. 29References..................................................................................................................... 32

4. FISHERY CASE STUDIES................................................................................................ 35The Mediterranean swordfish fishery ........................................................................... 35The North Atlantic swordfish fishery............................................................................ 52Chile’s swordfish fishery .............................................................................................. 83Japan’s north-west Pacific swordfish fishery................................................................ 97Hawaii’s swordfish fishery.......................................................................................... 111Australia’s swordfish fishery ...................................................................................... 126

5. COMPARISON OF SWORDFISH FISHERIES .............................................................. 153The fisheries................................................................................................................ 153Gear and targeting....................................................................................................... 159Assessment.................................................................................................................. 161Management................................................................................................................ 167Concluding remarks .................................................................................................... 170References................................................................................................................... 172

INDEX................................................................................................................................... 175

APPENDIX 1. CONTRIBUTORS TO THE REPORT........................................................ 181

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APPENDIX 2. SPECIES NAMES........................................................................................ 185

APPENDIX 3. AGE, LENGTH AND WEIGHT RELATIONSHIPS.................................. 187

APPENDIX 4. DATA SETS................................................................................................. 191

Swordfish fisheries vii

SUMMARYCoastal nations

depend onswordfish

Swordfish are a high value catch that represent an increasingly important source ofrevenue to many coastal nations in the Pacific and Indian oceans, e.g., Australia and LaRéunion. Optimistic that they can continue to increase swordfish catches, fishers arepurchasing fishing permits and investing in new, larger boats to fish for swordfish.However, several swordfish fisheries in other parts of the world have shown initial, rapidexpansion, then declined, prompting concern over the species’ ability to support intensiveharvesting. We examine established fisheries for swordfish to identify lessons for theassessment and management of developing swordfish fisheries, like Australia’s.

Swordfish differfrom other

species

Like other billfish and tuna, swordfish are highly fecund, migratory fish that grow quicklyin their early years and become apex predators. Tuna and billfish are truly oceanic andthey are difficult to study. Swordfish have a wider geographical distribution (50ºN–50ºS)than other billfish and tuna. They routinely move between surface waters and great depthswhere they tolerate extreme cold (~5ºC). They do not form schools. Results of recentresearch suggest that the Pacific Ocean is comprised of several, semi-independent stocksof swordfish (a northern stock, a south-western stock and two or three eastern Pacificstocks). Swordfish move with prevailing currents and use their highly developed sight tostalk prey. Female swordfish grow faster and live longer than males. They reach theirmaximum size (usually ~350 kg) at about 15 years of age. Male and female swordfishhave different distributions depending on size.

Early activitiestake large

females

Swordfish fishing started as nearshore subsistence activities in subtropical areas,thousands of years ago. The early fishing involved harpooning large, female swordfish asthey were basking at the sea surface. Large swordfish are also a prized catch ofrecreational anglers, although in most areas gamefishing activities tend to focus on otherbillfish, such as blue marlin. Anecdotal reports suggest that large swordfish were moreabundant when commercial fishing commenced in the 1800s than they are in many areasnow. Swordfish fisheries changed dramatically when fishers upgraded to monofilamentdriftnet and longline fishing gear in the 1980s.

Failure tocontain fleetovercapacity

Distant-water longliners started to target swordfish early in the 1950s. Theytypically spend several months at sea and freeze their catches. In the 1960s manydistant-water longliners started targeting sashimi tuna, such as yellowfin. In themid-1980s fishers realised the potential for smaller (10–25 m) longliners to makeshorter fishing trips, store tuna and swordfish on ice and airfreight the fish todistant markets. Unit prices paid for fresh-chilled swordfish in the United Statesand Europe are generally lower than those paid for sashimi tuna in Japan.However, boats can undertake longer fishing trips for fresh-chilled swordfishbecause it has good storage qualities and its price is less sensitive to productquality. Fresh-chill longline fleets quickly developed in many of the world’sports. Driftnet boats also target swordfish and distant-water tuna longliners take asubstantial bycatch of swordfish. During the 1980s and 1990s longliners anddriftnet boats increased swordfish catches to high levels. Examples of rapid expansion in swordfish catches:

Area Initialannual

catch(t)

Peakannual

catch(t)

Period ofincrease

(yrs)

Mediterranean 5 000 20 000 11 North Atlantic 12 000 21 000 9 South Atlantic 5 000 21 000 15 Chile 500 7 000 6 Hawaii 300 6 000 3 North-west Pacific 2 000 5 000 3

In each area fishingeffort continued toexpand for severalyears after the peakin catches,highlighting theinability of fisherymanagers to controlgrowingovercapacity in thefleets.

Fisheries expandgeographically

Fresh-chill longline fisheries for swordfish exhibit a development pattern where the risk-takers in the fleet progressively move further offshore, initially taking high catch rates.Other longliners follow and the fleet ranges further offshore for longer trips, toleratingmore extreme weather conditions. Hawaii-based longliners, for example, regularly maketrips of more than 30 days. They venture 1000–2000 nm from port and average about250 days at sea per year. Such expansion shows the potential for increases in effort in

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SUMMARYother fresh-chilled fisheries like Australia’s. To allow informed decisions on economicefficiency, fishers and fishery managers require an understanding of the limits thatdistance and boat size place on the commercial feasibility of swordfish fisheries.

Expansionconcealsdeclines

The introduction of longline gear increased swordfish catch levels and resulted in theexpansion of fishing into offshore waters and to lower latitudes where small, juvenileswordfish were typically more abundant. The expansion of fishing grounds alsobroadened the size range of swordfish in catches. However, expansion often concealeddeclines in swordfish abundance and degradation of size composition on the originalfishing grounds.

Flexibilityhampers

management

Longliners are able to switch between target species (e.g., from targeting swordfish tosashimi tuna) or to relocate to distant ports in response to declining prices, poor catchrates or the imposition of management regulations. Many of Spain’s swordfish longliners,for example, started to target tuna or shark or relocated to the South Atlantic whenswordfish catch rates declined in the North Atlantic. Fishery managers need to establishmeasures that encompass the ability of longliners to switch between target species and torelocate to distant areas.

Prone to localdepletion

Within populations a proportion of the swordfish associate with underwater features, suchas banks and seamounts. Such features were often the focus of fisheries when they firstbegan to develop. Modern longliners are potentially capable of removing the ‘resident’components of swordfish populations at a greater rate than growth and immigration canreplace them. Swordfish may thus be inclined to local depletion around underwaterfeatures.

Fishing removeslarge swordfish

Very large swordfish (250–500 kg) weremost abundant when commercial fishingbegan to develop in the 1800s. In theMediterranean the size composition ofcatches has declined so that the fisherynow relies almost exclusively on one-,two- and three-year-old swordfish. Thesize at maturity is smaller in theMediterranean than in other fisheries (itmight be a characteristic of theMediterranean stock or it might havedeclined there in response to increasedexploitation). However, swordfish areremarkably fast-growing in their earlyyears and, in the Mediterranean, seem tosupport relatively heavy fishing pressure.

No stock collapseapparent

There is no clear evidence of swordfishstocks or their fisheries collapsing fromoverfishing. Their broad distributioncombined with prolonged spawningperiods might contribute to the apparentresilience of swordfish stocks to intensiveharvesting. Nonetheless, inadequatescientific advice and fishery managementare failing to realise the considerable

Special research needsThe unique biology of swordfish requirescomplex age and spatially structured stockassessment models. Swordfish stockassessment needs knowledge of stockstructure and mixing, age and growth andnatural mortality. Tag–recaptureexperiments are often used to obtain such

Swordfish fisheries ix

SUMMARYeconomic benefits that would be derivedfrom optimum use of the swordfishresources. Three fisheries—theMediterranean, South Atlantic and NorthAtlantic—have been fished at levels thatare above the estimated maximumsustainable yield (MSY). It is unclearwhether the combined effects of harpoon,driftnet and longline fishing or juvenilecatches by longline alone were the maincause of the decline in the parent stocks.Swordfish abundance in the NorthAtlantic has shown a continuous declinesince about 1980 with the stockeventually falling below the estimatedoptimum level. Catch rates declinedduring 1990–96 and there were fewerolder-age swordfish in the population.The most recent (1999) assessmentsuggested that the decline in abundancehas slowed and that there were strongrecruitments of young swordfish in1997 and 1998. The status of swordfish inthe South Atlantic is more uncertain.There, swordfish catches are believed tohave been above the maximumsustainable yield in most years since1989. In the Mediterranean the number ofnew recruits produced in 1994 wasestimated to be 10–20 per cent of thatwhich an unfished stock would haveproduced. The fishery’s reliance on smallswordfish and the fluctuations inrecruitment reflect significant reductionsin the size of the parent stock.

information for other marine fish. However,swordfish are notoriously difficult to tag.New technology ‘archival’ and ‘pop-up’tags might provide information on swordfishmovement and behaviour.

Swordfish distribution and abundance areclosely linked to ocean temperature andproductivity. Knowledge of inter-annualvariability in swordfish abundance, theeffects of broad-scale oceanographic events,like El Niño, and changes in oceanproductivity might aid the interpretation ofcatch rates and the management of severalswordfish fisheries, such as those off Chileand Australia.

The accuracy of stock assessments dependson data quality and coverage. A recentanalysis suggests that size may be a moresensitive indicator of swordfish stock statusthan catch rates. For most swordfishfisheries, stock assessment relies onprograms that sample catches when they arelanded at ports. However, female swordfishgrow faster than males and the size and sexcomposition of swordfish catches varyconsiderably between areas and seasonally.Longliners that supply United Statesmarkets often discard small and damagedswordfish, creating further gaps in the datacollected through port sampling.Consequently, swordfish stock assessmentrequires a detailed breakdown of catches bylocation, size and sex that can only begathered by at-sea programs.

Regionalmanagement

has lacked power

Swordfish are a highly migratory species. Nations and regional organisations have notbeen particularly successful in managing swordfish fisheries. They have been unable toestablish the necessary data collection and research programs early in the fishery’sdevelopment. They have allowed fleets to overcapitalise and have not alwaysimplemented restraints recommended by scientific advisers. Where restraints have beenimposed, they have proved inappropriate (e.g., size restrictions) or difficult to enforce(e.g., quotas). The North Atlantic stock seems to have recovered quickly in response tothe application of strict management action. Apart from those cooperating in theInternational Commission for the Conservation of Atlantic Tunas (ICCAT), however,most nations have taken unilateral approaches, attempting independently to research andmanage swordfish within their waters. In the Mediterranean there is virtually nocoordination of regulations; neither is there an overall limit on fishing effort or catchlevels. Several nations have inadequate enforcement arrangements and many fleets do notto comply with those regulations. In the Atlantic, ICCAT has no regulatory authority andmember nations are not legally bound to accept its recommendations. Several membershave ignored the national quotas allocated by ICCAT and catches have regularlyexceeded the total allowable catch, thereby contributing to the continuing decline of theSouth Atlantic swordfish stock and, in the past, the North Atlantic stock. Nations thathave developing swordfish fisheries need to cooperate in regional approaches to fisherymanagement and assessment.

Mostly anincidental

catch of tunalongliners

Globally, swordfish catches are increasing. More than half of the world’s swordfish istaken as an incidental catch of longliners targeting tuna. Most of that swordfish catch isfrozen and sold for low prices. Bycatch presents problems to fishery management andassessment. With stock assessment, it is difficult to collect catch, effort and sizecomposition data on bycatch species and it is difficult to control catches of bycatchspecies when the fishery is targeting other species. Japan’s longliners, for example, do nottarget swordfish in the North Atlantic. They are, however, the second largest harvester of

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SUMMARYswordfish there, landing more than ten per cent of the total catch.

Control effortbefore expansion

commences

Several nations have managedtheir swordfish fisheries bylimiting the entry of newparticipants. Yet, inadequatesupport measures (e.g., boatsize limits) for limited entryregulations have oftenallowed latent effort to buildup in the fishery. Limitedentry has not restrainedfishing effort because fishershave been able to upgrade tolarger fishing boats, set morefishing gear or spend moredays at sea. Longliners wereable to leave the NorthAtlantic swordfish fisheriesbefore they were restrained bymanagement regulations.Many nations have beenunable or unwilling to preventthe relocation of their fleets tonew areas. An importantlesson from our review is theneed to put in placemechanisms to control fishingeffort before expansioncommences and to activatethose measures in aprecautionary manner.

Six lessons for developing fisheries1. Control fishing effort. Catch rates and average size

will not be maintained at initial levels. Withoutcontrols, fishing effort will expand and overshootthe optimum level.

2. Control geographical expansion. The fishery willexpand to a size that threatens the commercialviability of boats comprising the fleet.

3. Establish appropriate data collection programs.Swordfish are different to tuna; stock assessmentrequires more robust size-monitoring and at-seaprograms to collect data on the sex composition ofswordfish catches.

4. Take a multispecies approach. Management andresearch must deal with the ability of longliners toswitch between target species in response tofluctuations in abundance and price.

5. Monitor and mitigate bycatch. Fishing affectsother components of pelagic ecosystems thatswordfish depend on. Environmental concerns overbycatch may also damage markets and attract harshregulation.

6. Adopt a regional approach. Modern longliners areable to relocate to distant areas. Nations must worktogether through appropriate regional bodies toeffectively manage and assess highly migratoryspecies like swordfish.

Externalinfluencesdetermine

catches

Swordfish is a global commodity. Markets in Europe and the United States tend to dictateswordfish prices. Catch levels declined in the 1970s in response to mercury restrictions inthe United States and Canada, then increased when the restrictions were eased. In1998 swordfish prices fell in response to a restaurant boycott and oversupply of theUnited States market. Further health restrictions or fluctuations in global demand willdirectly influence the commercial viability of many swordfish fisheries. A significantdecline in the value of the United States dollar, for instance, might suddenly make severaldeveloping swordfish fisheries unprofitable.

Concern overshark

Longliners that target swordfish often take large, incidental catches of shark, particularlyblue shark. Finning—the practice of removing the shark’s fins and discarding thecarcass—is common in many swordfish fisheries. The wastage associated with finningand the broader effects of longlining on shark populations are a growing concern tofishery managers and the wider public. Fishery managers require reliable estimates of thecatch levels of shark and the status of shark populations. Simple techniques, such as theuse of monofilament leaders, might also be available to mitigate shark bycatch.

Environmentalconcerns drive

management

There is scant information about the catch levels of other bycatch species becauseobservers are rarely placed on longliners targeting swordfish. Compared with longliningfor tuna, swordfish longlining is more likely to interact with marine wildlife, such asseabird, seal and turtle, because it usually involves shallow-sets beginning in the lateafternoon, at high latitudes where those species are often active. Many fishing nationshave agreed to the Food and Agriculture Organization (FAO) International Plan of Actionto reduce the incidental take of seabird by longline. At a national level, fishery managersare also responding to concern over the bycatch of seabird and other species in swordfish

Swordfish fisheries xi

SUMMARYfisheries. The potential for incidental catches of seal and turtle, for instance, resulted insignificant area closures around the Hawaiian Islands. Fishing for swordfish in the pelagicenvironment is simultaneously taking predators, competitors and prey. There is littleunderstanding of fishing’s effects on the wider ecosystem. Those effects will, in turn,affect swordfish population dynamics. In addition to robust assessments of swordfishstatus, the fisheries need multispecies assessments and ecosystem approaches to theirmanagement.

Unexploitedresources in

southernhemisphere

Swordfish distribution is closely linked to ocean temperature and the abundance of preyspecies. Deep-sea bathymetry and oceanographic conditions suggest that there may beunexploited or lightly exploited resources of swordfish in several locations of thesouthern hemisphere: the south-eastern Indian Ocean, southern Tasman Sea, across thesubtropical convergence zone of the South Pacific and associated with seamounts andbanks south of French Polynesia, Fiji and Tonga. Feasibility fishing is required toevaluate the resources of those unfished areas. The development of commercially feasiblefisheries in unfished areas will also depend on the proximity of fishing grounds to portsand airfreighting links and markets.

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Science arrangements xiii

GLOSSARYADAPT a stock assessment modeling

framework

AFMA Australian Fisheries ManagementAuthority (Australia)

AFZ Australian fishing zone

ASPIC A Stock-Production modelIncorporating Covariates

BRS Bureau of Rural Sciences(Australia)

convergence The earth’s rotation deflectscurrents to the right in thenorthern hemisphere (and to theleft in the southern hemisphere).In the northern hemisphere,surface waters tend to accumulateand sink between an eastwardflowing current that is north of awestward flowing current. Suchan area is called a convergencezone. There are convergencezones in both hemispheres.

CPUE Catch-per-unit-effort or catchrate.

CSIRO Commonwealth Scientific andIndustrial Research Organisation(Australia)

divergence The earth’s rotation deflectscurrents to the right in thenorthern hemisphere (and to theleft in the southern hemisphere).Between an eastward flowingcurrent that is south of awestward flowing current in thenorthern hemisphere, surfacewaters are displaced, drawing upnutrient-rich water from below.Such an area is called adivergence zone. There aredivergence zones in bothhemispheres.

DFO Department of Fisheries andOceans (Canada)

DMP Dockside Monitoring Program(Canada)

DWFN distant-water fishing nation

EC European Council (EuropeanUnion)

EFL Length measurement, from theposterior margin of the eye orbitto the caudal fork.

ENSO El Niño – Southern Oscillation

EU European Union

EEZ 200 nautical mile exclusiveeconomic zone

EPO Eastern Pacific Ocean

Dwt dressed weight (the weight offillets and trunks afterbutchering)

FAO Food and AgricultureOrganization (United Nations)

Fwt fillet weight

GFCM General Fisheries Council for theMediterranean

halocline strong salinity gradient

IATTC Inter-American Tropical TunaCommission

ICCAT International Commission for theConservation of Atlantic Tunas

IEO Instituto Español deOceanografía (Spain)

IFOP Instituto de Fomento Pesquero(Chile)

IOTC Indian Ocean Tuna Commission

isolume The boundary between light anddark. In the open ocean, thedepth of the isolume depends ontime of day, season and waterturbidity.

isotherm A line drawn on a map or graphconnecting points with the sametemperature.

IUCN World Conservation Union(formerly International Union forthe Conservation of Nature)

LJFL Length measurement, from the tipof the lower jaw to the fork in thecaudal fin.

MSY maximum sustainable yield

NAO North Atlantic Oscillation

NFRIFS National Research Institute of FarSeas Fisheries (Japan)

nm nautical miles

NMFS National Marine FisheriesService (United States)

NOAA National Oceanographic andAtmospheric Administration(United States)

NSW New South Wales (Australia)

OFP Oceanic Fisheries Programme(Secretariat of the Pacific

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Community)

OTC Calciphilic fluorochromeoxytetracycline hydrochloride—an antibiotic injected in a fish toleave a mark on skeletalstructures, such as otoliths. If thefish is later recaptured, the markleft by the OTC can be used tovalidate age estimates.

population A group of interbreedingindividuals of the same species.Mixing may occur betweenpopulations but no significantinterbreeding occurs (see also‘stock’).

ppm parts per million

ROK Republic of Korea (also referredto as ‘South Korea’ or simply‘Korea’)

sashimi Japanese cuisine of fresh fish orshellfish, served raw.

SCRS Standing Committee for Researchand Statistics (InternationalCommission for the Conservationof Atlantic Tunas)

SERNAP Servicio National de Pesca(Chile)

SOI Southern Oscillation Index

SFRs statutory fishing rights

SPC Secretariat of the PacificCommunity (formerly SouthPacific Commission)

SST sea surface temperature

SSP Sub-Secretaría de Pesca (Chile)

STCZ subtropical convergence zone

stock A fishery management unitconsisting of a population orpopulations of individuals of thesame species occupying a definedspatial range independent ofother stocks of the same species.Movement and migrations mayoccur within the stock. Such agroup can be regarded as anentity for management orassessment purposes (see also‘population’).

t metric tonnes

TAC total allowable catch

TDR time–depth recorder

thermocline The depth zone where watertemperature decreases rapidlywith depth. The depth of the15°C isotherm is often used as anindicator of the lower boundaryof the thermocline in tropicalwaters.

Twt Trunk weight. The weight of thecarcass after removal of the head,gills, viscera and caudal fins.

UN United Nations

USA United States of America

VMS Vessel monitoring system,involving a satellite-basedtracking system.

VPA Virtual population analysis. Astock assessment technique thatreconstructs the age-structure of apopulation from catch-at-age dataand information on mortalityrates.

Wwt Whole weight. The weight of afish before butchering;sometimes also termed ‘green’ or‘round’ weight.