Workshop Consensus: International Project on Bigeye Tuna Needed

Transcription

1 Volme 4, Nmber 1 Janary March 1999 Workshop Consenss: International Project on Bigeye Tna Needed 200, , , ,000 Bigeye tna is the mainstay of longline fisheries 120,000 throghot the Pacific Basin. It is the principal target species of the Japanese distant-water longline 100,000 80,000 fleet and a critical component of smaller-scale 60,000 longline fisheries in Hawai i, French Polynesia and Astralia. The landed vale of bigeye tna caght 40,000 in the Pacific has been estimated to be approximately US$1.5 billion. The total landings of bigeye 20,000 0 tna have been relatively constant for the last 10 years at arond 175,000 mt per year (Figre 1). Most of these landings are by longline vessels, bt the proportion harvested by prse seine has been steadily increasing. Prse-seine landings are composed of largely immatre fish, and there are preliminary indications that these harvests may be having a detrimental impact on some longline fisheries. Unfortnately, bigeye tna is the least nderstood of the major tropical species, and in spite of its economic importance, less than 0.1% of its landed vale is expended by the varios research organizations arond the Pacific on stdies of this species. The lack of critical information on mortality rates and movement rates prevent scientists from making definitive evalations of the stats of the bigeye tna poplation in the Pacific. In November 1998, the PFRP coordinated a workshop attended by tna scientists from all major research instittions in the Pacific. The workshop participants discssed crrent and planned research on bigeye tna in their part of the world and identified research priorities and approaches for ftre work. The participants conclded that a well-designed, coordinated, large-scale, international tagging project is necessary to address the critical information gaps. The project they envisaged wold tilize a variety of different tagging methods inclding simple dart tags, acostic tracking devices, data logging archival tags and pop-p tags that transmit data to satellites. The choice of methods wold depend on local circmstances, sch as availability of bigeye tna for tagging, probability of recaptre and scientific hypothesis to be addressed. The workshop participants also conclded that a dedicated tagging vessel is necessary for long-term monitoring of tna pop- Catch Other Prse Seine Pole and Line Longline Figre 1. Total catch in metric tons of bigeye tna in the Pacific Ocean by varios gear types. (Sorce: Report of the eleventh meeting of the standing committee on tna and billfish, 28 May 6 Jne 1998, Honoll) lations in the Pacific. This vessel wold be a scientific asset to be tilized throghot the Pacific on a rotating basis to provide pto-date information on changes in movement, mortality and levels of exploitation. Participants were optimistic that the consenss they achieved will improve the prospects for increasing the general level of fnding for research on this important bt neglected natral resorce. The workshop report is available on the PFRP World Wide Web site ( PFRP CONTENTS Workshop Consenss: International Project on Bigeye Tna Needed 1 Creating the Big Pictre for Pacific Bigeye Tna 2 New Data Fels Old Debate on Blefin Tna 4 Schedle of Upcoming Events 5

2 Creating the Big Pictre for Pacific Bigeye Tna A Pelagic Fisheries Research Program (PFRP) workshop on Pacific bigeye tna, Nov. 9 10, 1998, in Honoll, addressed the spotty natre of crrent regional research on the species. PFRP Director John Sibert, coordinator and chairman of the workshop, noted that some regions are well advanced in the planning or implementation of field research while others are very mch in a conceptal or planning phase. Workshop participants reported on proposed and ongoing fieldwork in their regions. The projects are smmarized below. Astralian Coral Sea In an area where fishing effort has increased significantly in recent years, tagging reslts raise qestions abot assmed growth rates and longevity of bigeye tna. In the early 1990s, the Soth Pacific Commission (SPC, now the Secretariat of the Pacific Commnity) condcted the Regional Tna Tagging Project (RTTP). As part of the project, approximately 3,800 medimsized bigeye tna were tagged in the northwestern Coral Sea. More than 200 of these individals have been recaptred. Contining recaptres of medim-large bigeye tna in the same area of release sggest that bigeye tna may live longer and grow slower than commonly thoght. The SPC s Oceanic Fisheries Program (OFP) in conjnction with the Astralian research organization CSIRO (Hobart) is agmenting research on bigeye tna in the northwestern Coral Sea with a small-scale archival tagging project. John Hampton of SPC OFP explained that the project wold deploy 80 data-logging tags manfactred by Wildlife Compters on medim-sized ( cm) bigeye tna dring December Astralian flag longline vessels wold longline and handline bigeye tna fond on lanternfish (Myctophidae) feeding aggregations that normally occr in the area dring this time of year. Fishing vessel owners have made their vessels, crews and fish available at no cost to the project. A retrn rate of 10% is expected. The CSIRO plans to match the SPC-fnded 1998 tagging with 100 additional archival tags dring the 1999 season. Western Eqatorial Pacific Dring the RTTP (see above), a total of 6,800 bigeye tna were tagged, of which 35% were released in the Western Eqatorial Pacific (WEP) and a frther 3,500 in the Philippines. Overall retrn rates were 8% and 25%, respectively. Tony Lewis of SPC OFP said the experiments provided sefl information on movements, age and growth and estimates of natral mortality of varios sized bigeye tna. The OFP crrently has no plans to ndertake frther conventional tagging of bigeye tna. Opportnities to rotinely tag-and-release large nmbers of bigeye are generally qite limited, Lewis said. However, a recent increase in the se of drifting FADs in the WEP fishery may offer some potential for tagging of small- to medim-sized bigeye tna in this area, provided technical and handling problems cold be overcome. Deployment of archival tags in the region is also a possibility. A proposal has been lodged with the United States Tna Fondation for 300 archival tags to be deployed in as yet ndetermined areas, bt likely to inclde areas adjacent to the main longlining fisheries gronds in the central Pacific. OFP contines to be involved in other areas relevant to bigeye research, sch as age and growth stdies, investigation of environmental determinants of tna prodction, and observer and port sampling work. Western North Pacific Field research on tropical tna condcted by Japan s National Research Institte of Far Seas Fisheries traditionally carried ot on dedicated research crises and dring some observer trips on commercial tna vessels will soon be agmented by operations aboard a longline research vessel. A medim-sized vessel has been chartered for a three-year period, and Western Pacific operations concentrating on swordfish and albacore, bigeye and yellowfin tna research are to begin September 1999, reported Naozmi Miyabe. In addition, prefectral longline training vessels that will be operating near Hawaiian waters dring late 1998 and 1999 provide the possibility for collaborative research, Miyabe noted. Another potential sorce for ftre research on bigeye tna is a large and well-eqipped government research vessel that will become available for pelagic research in the Pacific dring Eqipped with a fll array of sophisticated marine electronics, RV Shoyo Mar will be capable of longline and gillnet operations and acostic tagging of large fish. Hawai i In Hawai i, bigeye tna is one of the two highest dollar-vale pelagic resorces landed by locally based fishermen. It is no wonder then that research on the species is booming. A particlarly ambitios project is the Hawai i Tna Tagging Project (HTTP), which will tag yellowfin and bigeye tna throghot Hawai i s exclsive economic zone (EEZ) for a twoyear period. Kim Holland and David Itano explained that the PFRP project, which began releasing tags in March 1998, is an expansion of a small-scale tagging project at Cross Seamont, which was designed to address interaction and aggregation isses of bigeye and yellowfin tna. HTTP ses commercial and sport vessels as tagging platforms at Cross Seamont, near Midway Atoll and arond the main and Northwestern Hawaiian Islands. Aggregation points sch as seamonts, isolated islands and anchored fish aggregation devices (FADs) are targeted to maximize releases of bigeye tna. The total nmber of releases to date for both projects exceeds 11,000, of which 58% are bigeye tna. Domestic fishing vessels have recaptred 1,100 individals, with recaptre rates for bigeye and yellowfin tna at 8.7% and 13.6%, respectively. Most of the releases and recaptres have been made at Cross Seamont and inshore FADs. An ancillary State of Hawai i tagging project, which targets small yellowfin and bigeye tna 2

3 (20 35 cm) fond in association with state-anchored FADs, began in November 1998 and is an integral part of HTTP. Additional bigeye tna stdies in Hawaiian waters are being condcted by Honoll Laboratory. Michael Lars said the National Marine Fisheries Service (NMFS) laboratory has, nder a PFRP-sponsored project, committed 80 archival tags to bigeye tna, with 24 deployments and one captre recorded to date (see Archival Tags A Worthy Reward, PFRP Newsletter, Jly 1998). Meanwhile, conventional tagging of longline-caght bigeye contines on an opportnistic basis from the NMFS RV Townsend Cromwell, which also condcts in sit fisheries oceanography in the Hawai i EEZ and adjacent seas. A major initiative of Honoll Lab in recent years is the stdy of pelagic fish habitat and ecology in relation to offshore fisheries throgh direct fieldwork, remote sensing and validation, habitat stdies and large-scale ecosystem research and modeling. Jeffrey Polovina, who leads these efforts, said se of satellite altimetry data to detect crrent eddies, seamonts and vertical temperatre strctre, sch as shoaling of the thermocline, is encoraging. Several research proposals involving bigeye tna have been sbmitted to PFRP and are crrently nder scientific review. Eastern Pacific Ocean In the Eastern Pacific Ocean (EPO), a FAD-based prse-seine fishery has recently developed. It takes significant qantities of jvenile bigeye tna in an area where a longline fishery targets large, high-valed individals. The ensing interaction isses are of dominant concern in the area. The Inter-American Tropical Tna Commission (IATTC) has imposed a limit of 45,000 mt of bigeye tna from the EPO srface fishery, which if exceeded wold sht down prse-seining on floating objects. Robin Allen explained the importance of obtaining better age-specific estimates of natral mortality, as yield assessments and interaction estimates rely significantly pon these parameters. The IATTC intends to mont a large-scale tagging project, focsed on conventional tagging of bigeye tna fond in aggregation with floating objects, bt no firm plans are crrently in place pending the identification of a fnding sorce. However, there is a distinct possibility of condcting a pilot tagging project in early 1999 to tag bigeye, yellowfin and skipjack tna in the EPO prseseine fishing gronds. The objectives of this project are to estimate movements, interaction between srface and sbsrface fisheries, and rates of natral mortality in bigeye, bt the opportnity wold be sed to gain a better nderstanding of the relationship between sothern (soth of 5 N) and northern grops of yellowfin in the EPO. There is also an interest to deploy archival tags in the sothern region in conjnction with conventional tags. The intention of the IATTC is to realize an ongoing tagging project for bigeye tna in the EPO region over the next several years. Krt Schaefer otlined plans for the IATTC to begin life history research on EPO bigeye tna, which will inclde stdies on the age, growth and reprodctive biology of the species in different geographic regions of IATTC jrisdiction. Otoliths and vertebrae will be sampled from tagged bigeye tna of cm fork length that have been chemically marked for age validation prposes. Size and age-specific reprodctive characteristics from srface and sbsrface fisheries will be determined sing histological analyses of gonad material. Spatio-temporal distribtions in spawning, length at matrity, spawning freqency, batch fecndity and sex ratios will be determined. French Polynesia In an area strategically located for basin-wide bigeye tna research, French researchers are winding down on the ECOTAP program two years of fieldwork investigating the pelagic resorces of the French Polynesian zone (see Tna Telemetry in Tahiti, PFRP Newsletter, October 1997). Stephen Yen and Larent Dagorn described the reslts of the stdy, which involved pelagic longlining, echo sonding, sonic tracking of tna and pelagic trolling. Utilizing the RV Alis, researchers investigated behavior and habitat of bigeye tna and longline characteristics in relation to catch rates. ECOTAP will conclde in the smmer of 1999, leaving the ftre of this type of research in qestion. However, cooperation between researchers and local fisheries has been excellent, and reslts of direct relevance to local fishermen have been obtained. The legacy of ECOTAP, Yen said, incldes a willingness and interest of local commercial vessels to work with researchers and the mechanisms and staff to facilitate this type of collaboration. PFRP PFRP Technical Reports For a copy of these recent or other PFRP technical reports, please contact PFRP Administrative Assistant Dodie La Tel.: (808) Fax: (808) dla@soest.hawaii.ed or contact Joint Institte for Marine and Atmospheric Research University of Hawai i at Mānoa 1000 Pope Road, MSB 313 Honoll, HI Tel.: (808) Fax: (808) Sociology of Hawaii Charter Boat Fishing, by Jlie Walker, SOEST 97-02, JIMAR Design of Tag-Recaptre Experiments for Estimating Yellowfin Tna Stock Dynamics, Mortality, and Fishery Interactions, by Peter Bills and John Sibert, SOEST 97-05, JIMAR Cost-Earnings Stdy of Hawaii s Small Boat Fishery, , by Marcia Hamilton and Stephen Hffman, SOEST 97-06, JIMAR An Assessment of Bigeye (Thnns obess) Poplation Strctre in the Pacific Ocean, Based on Mitochondrial DNA and DNA Microsatellite Analysis, by Peter M. Grewe and John Hampton, SOEST 98-05, JIMAR

4 New Data Fels Old Debate on Blefin Tna New findings sggest the distribtion of spawning-size giant Atlantic blefin tna (Thnns thynns) is mch broader than previosly considered. These findings, reported by Molly Ltcavage, a research scientist at the New England Aqarim, add to the intense debate over the poplation of a species that is very valable (with individal fish worth $10,000 each) yet whose harvest is strictly reglated. Information obtained by Ltcavage and her colleages highlights the possibility that blefin tna that travel throgh New England waters spawn, or lay eggs, between Bermda and the Azores. Since blefin tna are managed nder the theory that there are two different stocks or grops (western and eastern Atlantic), these findings arge for reconsideration of crrent assmptions abot migration, spawning habitats and stock strctre. In September and October 1997, researchers tagged 20 blefin tna of reprodctive size, inches long (estimated ages 8 18 years), off the New England coast sing tags that detach from the fish and transmit data to a satellite. The tags were pre-programmed to release or pop-p monthly from March to Jly The tags are abot the size of a cigar, with a 5-inch long antenna. Once released, the tags not only transmit location bt also reveal historical data abot water temperatre dring the tna s travels. Seventeen ot of 20 tags reported after being on the blefin tna for as long as 9 1/2 months, a span of time that is nprecedented with pop-p tags (Figre 1). Five of the tags popped p on the eastern side of the western Atlantic management line at 45 W longitde, the international fisheries management bondary established by the International Commission for the Conservation of the Atlantic Tna (ICCAT). Tna clearly have a very complex and broad migration pattern, Ltcavage says. Since the 1980s, scientists conclded that Approx. areas of deployment l n l l n n Eastern Management Area l l Unpblished data from Glf of Maine pop-p satellite tagging program investigators: M. Ltcavage, R. Brill, G. Skomal, B. Chase, P. Howey Sponsors: New England Aqarim, East Coast Tna Association n l March n May Jne Jly Western Management Area Figre 1. Release locations for pop-p satellite tags deployed on giant blefin tna in the Glf of Maine, 24 Sept. 6 Oct there were two, separate blefin tna stocks. Now it looks as thogh the same tna that travel throgh New England waters also swim near the Azores. We now have an opportnity to qickly gain a better nderstanding of blefin migration and potential spawning areas, and pop-p tag technology is proving to be a very effective research tool to gather data. Giant Atlantic blefin tna are the largest living species of tna, A giant blefin tna is broght alongside reaching p to 10 feet in the FV Cookie Too for application of a length and weighing pop-p tag. Recent research reslts from more than 1,400 these tags have rekindled debates on the ponds. Blefin tna management of the species. are at the center of a heated debate becase they are commercially valable (fetching p to $120/lb) and believed by many to be depleted in the eastern Atlantic. Fishery reglators have been recommending increasingly stricter qotas, while fishermen claim they see more blefin tna in a week than reglators say exist in the entire North Atlantic all year. In fact, the last two stock assessments for the western Atlantic zone reveal that the poplation of blefin tna is on the rise. Crrently, blefin tna are managed by fishing area qotas, size limits and spawning area protection measres. However, compliance with these reglations occrs only in the western Atlantic fishing gronds and srronding seas off the coasts of the United States and Canada. Understandably, New England fishermen are eager to take part in the scientific research of blefin tna to learn whether or not adhering to restrictions in the western Atlantic is worthless becase of the lack of management compliance in the eastern Atlantic. In another first, Ltcavage and colleages have ndertaken an international collaboration with Canadian Department of Fisheries and Oceans researcher Jlie Porter and Canadian blefin tna fishermen. The new partnership targeted both New England and Canadian giant Atlantic blefin tna dring the 1998 season. In late Agst, the first of five Canadian blefin tna was tagged with pop-p technology. The tags are schedled to pop p in 9 1/2 months. The 1998 tagging stdy was fnded by the East Coast Tna Association and throgh donations by cooperating fishermen. Ongoing collaborations with fishermen contribte priceless information abot blefin tna, a sorce of knowledge that has ntil now been ntapped as a research resorce, said Rich Rais, 4

5 exective director, East Coast Tna Association. Throgh this joint research with the New England Aqarim, some light will be shed on critically important qestions which might allow ftre development of a fair and efficient long-term, Atlantic Ocean wide conservation program for Atlantic blefin tna. Reglators need to have better information on exactly where blefin tna spend their time and where they reprodce to ensre that tna stocks are properly managed and not overfished. A highly migratory and fast-swimming species, blefin tna spend mch of their time foraging off the continental shelf and then probably disperse to spawning areas to lay eggs. It has been assmed that blefin tna spawn primarily in the Mediterranean and in the Glf of Mexico. Before these recent reslts from pop-p tagging research, there was little reason to qestion these assmptions. Despite the intense interest in blefin tna, their travels and behaviors are not well nderstood or docmented, and their life cycles are believed to be exceedingly complex. By nderstanding the whole cycle of the blefin tna s life, fisheries managers can make informed decisions abot appropriate management and conservation measres. Agmenting these tagging efforts, New England Aqarim researchers also condct aerial srveys and remote-sensing and hydro-acostic tracking stdies of blefin tna. Throgh a new stdy with Johns Hopkins Applied Physics Laboratory in Baltimore, the National Marine Fisheries Service, the National Environmental Satellite Distribtion and Information Service of NOAA and Areti Associates of Tcson, Ariz., Ltcavage is testing ctting-edge LIDAR and synthetic apertre radar technology to learn more abot blefin tna. In a process similar to radar, LIDAR emits a laser light that bonces off an object creating a three-dimensional image. In this manner, researchers hope to Pelagic Fisheries Research Program Newsletter Volme 4, Nmber 1 Janary March 1999 Editor Writers Layot Printing John Sibert Sylvia Spalding and John Sibert May Izmi PRINTER NAME For more information Pelagic Fisheries Research Program Joint Institte for Marine and Atmospheric Research University of Hawai i at Mānoa 1000 Pope Road, MSB 313 Honoll, HI TEL (808) FAX (808) jsibert@soest.hawaii.ed WWW (contined on page 6) Upcoming Events Janary Interim Scientific Committee Meeting Honoll, Hawai i (619) fax (619) Febrary Mltilateral High-Level International Conference IV Honoll, Hawai i (808) fax (808) Febrary Seabird Bycatch: Trends, Roadblocks and Soltions Blaine, Washington (206) emelvin@.washington.ed March International Symposim on Geographic Information Systems in Fishery Sciences Seattle, Washington (81) fax (81) tnishida@enyo.affrc.go.jp Jne 7-11 Standing Committee on Tna and Billfish Tahiti (687) fax (687)

6 New Data Fels Old Debate (contined from page 5) learn how many blefin tna are swimming below the ocean s srface, therefore gaining a more accrate cont of the total poplation. Synthetic apertre radar technology may be sed to detect the distribtion of srface-swimming blefin tna over a broad geographic area. New England Aqarim Conservation Director Greg Stone is a U.S. Senate-appointed member of ICCAT, a 23-member-contry organization charged with determining all legal qotas of North Atlantic blefin tna and other large open-ocean fish. Ltcavage serves as scientific technical adviser to the Blefin Working Grop of the Scientific Advisory Committee of ICCAT. Her colleages on the blefin tna stdy inclde Richard Brill of the Pelagic Fisheries Research Program at the University of Hawai i, Greg Skomal and Brad Chase from the Massachsetts Division of Marine Fisheries, and Pal Howey from Telemetry 2000 in Colmbia, Md. PFRP Anthony Mendillo Jr., mate on the FV Cookie Too, holds the tagging applicator that he and Cookie Mrray designed and constrcted. Attached to the applicator is a tag that is pre-programmed to detach from a fish at a predetermined date to transmit data to a satellite. Pelagic Fisheries Research Program Joint Institte for Marine and Atmospheric Research University of Hawai i at Mānoa 1000 Pope Road, MSB 313 Honoll, HI 96822