CONSENSUS DOCUMENT: WORKSHOP ON THE BIOLOGY OF BLUEFIN TUNA IN THE MID-ATLANTIC 5-7 MAY 2000, HAMILTON, BERMUDA

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1 SCRS/00/125 CONSENSUS DOCUMENT: WORKSHOP ON THE BIOLOGY OF BLUEFIN TUNA IN THE MID-ATLANTIC 5-7 MAY 2000, HAMILTON, BERMUDA Molly Lutcavage, 1 and Brian Luckhurst 2 SUMMARY An international workshop was held in Hamilton Bermuda, 5-7 May 2000, to discuss the distribution and biology of north Atlantic bluefin tuna (Thunnus thynnus) in the central Atlantic. Participants included academic and government fisheries scientists and oceanographers, ICCAT delegates, and members of the commercial fishing industries of the U.S. and Bermuda. The goal of the workshop was to review scientific information that portrays spawning size class bluefin in the central Atlantic during their presumed spawning period. The Working Group (attachment 1) identified gaps in knowledge of the biological and reproductive status of this adult bluefin assemblage, and produced a Consensus Document that identified research steps, with timeline, that should be undertaken to fill these gaps. The stimulus for the Bermuda workshop was to focus attention on compelling new scientific information that differs broadly from prevailing views of bluefin biology. Since 1981, Atlantic bluefin tuna have been managed by ICCAT as two biological units separated by a management line at 45 deg. W. The biological basis of this management division is based on presumed separate and exclusive spawning grounds (in the Gulf of Mexico and the Mediterranean Sea), different ages of first reproduction, and an assumed low transfer rate (2-7% annually). But since 1997, new fishery-independent popup satellite tagging efforts targeting adult and spawning size fish in New England, Canada, and North Carolina showed that about 30% of bluefin each year were located in the eastern management zone when their tags reported. Further, none of the spawning size fish were located in either known spawning ground when their tags reported their location, raising the possibility of a previously unknown spawning area in the central Atlantic. The management implications of possible spawning of bluefin tuna in the central Atlantic would be enormous. Consequently, the Bermuda working group s consensus document recommended that an exploratory research cruise for sampling of larvae and spawning size bluefin tuna be conducted and implemented in May - July Specific recommendations call for participation by at least one oceanographic research vessel and two longline vessels, and full financial support for oceanographic data collection and analysis of samples. RÉSUMÉ Un atelier international a eu lieu à Hamilton, aux Bermudes, les 5-7 mai 2000 pour aborder la distribution et la biologie du thon rouge (Thunnus thynnus) nord -atlantique dans l Atlantique central. Les participants comprenaient des scientifiques et des halieutes des universités et du gouvernement, des délégués de l ICCAT et des représentants d entreprises de pêche commerciale des Etats-Unis et des Bermudes. L objectif de l atelier était d examiner l information scientifique qui mentionne la présence de thons rouges de la taille de géniteurs dans l Atlantique central pendant leur période supposée de frai. Le groupe de travail (Pièce jointe 1) a décelé des lacunes dans les connaissances sur l état biologique et reproductif de ce groupe de thons rouges adultes, et a rédigé un document de consensus établissant les étapes de la recherche, avec leur calendrier d exécution, qu il convient d entreprendre pour combler ces lacunes. La raison d être de l atelier des Bermudes était d attirer l attention sur de nouvelles informations scientifiques intéressantes qui diffèrent amplement des opinions qui prédominent quant à la biologie du thon rouge. Depuis 1981, le thon rouge de l Atlantique est géré par l ICCAT en tant que deux unités biologiques délimitées à 45º de longitude ouest pour les 1 Edgerton Research Lab, New England Aquarium, Central Wharf, Boston, MA 02110, USA; mlutcavg@neaq.org 2 Division of Fisheries, P.O. Box CR 2, Crawl CRBX, Bermuda; bluckhurst@bdagov.bm

2 besoins de la gestion. La base biologique de cette délimitation de la gestion se fonde sur l existence supposée de lieux exclusifs de frai (dans le golfe du Mexique et en Méditerranée), Un âge différent de première reproduction, et un taux jugé faible d échange (2-7% par an). Mais, depuis 1997, de nouveaux marquages avec marque pop-up satellitaire, indépendants de la pêche, portant sur des poissons adultes et de la taille de géniteurs en Nouvelle-Angleterre, au Canada et en Caroline du nord ont révélé que chaque année environ 30% des thons rouges se trouvaient dans l unité est de gestion au moment où leur marque émettait. Aussi, aucun des poissons de la taille de géniteurs ne se trouvait dans l un ou l autre des lieux de frai connus au moment où leur marque signalait leur position, ce qui soulève la possibilité de l existence d un lieu de ponte non connu jusqu à maintenant dans l Atlantique central. Les implications pour la gestion d un frai éventuel de thon rouge dans l Atlantique central seraient énormes. Par conséquent, le document de consensus du groupe de travail des Bermudes recommandait d organiser et de mener en mai-juillet 2001 une campagne de recherche exploratoire pour l échantillonnage de larves et de thons rouges de la taille de géniteurs. Des recommandations spécifiques prévoient la participation d au moins un navire de recherche et de deux palangriers, et le financement intégral de la collecte des données et de l analyse des échantillons. RESUMEN Los días 5 a 7 de mayo de 2000 se celebraron unas Jornadas de Trabajo internacionales en Hamilton, Bermuda, destinadas a discutir la distribución y la biología del atún rojo (Thunnus thynnus) del Atlántico central norte. Entre los participantes había científicos académicos y otros que pertenecían a departamentos gubernamentales de pesquerías, oceanógrafos, delegados de ICCAT y miembros de la industria comercial pesquera de Estados Unidos y Bermuda. El objetivo de las Jornadas era examinar la información científica relativa a la clase de talla del atún rojo reproductor en el Atlántico central durante su supuesto período de desove. El Grupo (documento adjunto 1) halló lagunas en el conocimiento de la biología y reproducción de este grupo de atunes rojos adultos y redactó un documento de consenso identificando los pasos a dar en la investigación para colmar dichas lagunas, estableciendo también un calendario de tareas. La intención de la reunión de Bermuda era centrarse en la nueva información científica que difiere ampliamente de los puntos de vista que hasta ahora prevalecen sobre la biología del atún rojo. Desde 1981, el atún rojo, en lo que respecta a su ordenación, ha sido gestionado por ICCAT como dos unidades biológicas separadas por una linea establecida a 45ºW. Las bases biológicas de esta división de ordenación se basan en zonas de desove supuestamente separadas y exclusivas (Golfo de México y Mediterráneo), diferentes edades de primera reproducción y una tasa de intercambio que se supone baja (2-7% anual). Pero a partir de 1997, se hicieron nuevos esfuerzos de marcado con marcas pop up conectadas a un satélite, independientes de la pesquería y dirigidos a peces adultos de talla apta para la reproducción en Nueva Inglaterra, Canadá y Carolina del Norte, que demostraron que cada año alrededor del 30% del atún rojo se encontraba en la zona este de ordenación cuando sus marcas transmitieron los datos. Además, ninguno de los peces reproductores estaba situado en ninguna de las zonas de desove conocidas cuando sus marcas señalaron su posición, lo cual plantea la posibilidad de que exista una zona de desove hasta ahora desconocida, en el Atlántico central. Las implicaciones en cuestión de ordenación de la posibilidad de que el atún rojo desove en el Atlántico central serían enormes. En consecuencia, en el documento de consenso del grupo de trabajo de Bermuda se recomendaba que se llevase a cabo una campaña de exploración científica para hacer muestreo de larvas y de atún rojo de talla apta para la reproducción entre los meses de mayo y julio de Se recomendaba en particular la participación de al menos un barcos oceanográficos y dos palangreros y una total financiación para la recogida de datos y análisis de muestras.

3 1. WORKSHOP RECOMMENDATIONS The goals of the meeting were to: 1. Review historic and recent information on the mid-atlantic distribution and biology of north Atlantic bluefin tuna; 2. Identify gaps in knowledge concerning their status and activities in this region; and 3. Identify research steps that could fill these gaps. Results from recent pop-up tagging studies in the west Atlantic were reviewed, and showed that a total of 35 tags jettisoned from bluefin tuna of spawning size reported from the mid-atlantic in late January through late July (Lutcavage et al., 2000). Of those, 15 reported in April through June, the presumed spawning period in the western Atlantic. Similarly, in another study (Block et al. 2000) 20 pop-up tags jettisoned from bluefin tuna outside of the Gulf of Mexico from April to June. Although individual sizes were not reported, some spawning-sized fish were tagged. These results support the hypothesis that some Atlantic bluefin tuna may spawn in subtropical regions of the mid-atlantic, possibly along frontal areas north and east of Bermuda and west of the Azores. It is unlikely in the extreme that 11 fish aged 8 and above whose tags popped-up in April and May (Lutcavage et al., 2000) would be on the same reproductive schedule such that none returned to the presumed exclusive Gulf of Mexico or Mediterranean spawning areas proposed by Rivas (1954) and Richards (1976). Alternative explanations for the observed April and May bluefin tuna distribution patterns (Lutcavage et al 2000) for age 8+ (11 fish) and 10+ (4 of the 11 fish) bluefin tuna were considered. For example, the possibility that age at maturity is substantially older than that currently used in assessments was discussed. However, it was considered to have a low probability, given the size composition of Japanese and U.S. longline catches in the Gulf of Mexico in the late 1970's and early 1980's. Secondly, the size composition of rod and reel catches for post-spawners in Cat Cay, Bahamas during the 1940's and early 1950's (Rivas 1954) consisted of fish that were generally over 220 cm or 400 lb, which corresponds to ages 10+. Finally, recent U.S. Gulf of Mexico bluefin size compositions are fish over about 200 cm, which corresponds to ages 8+. Fishery-independent popup tagging studies show that spawning-sized fish are in the central Atlantic at about the time they would be spawning. Based on these compelling new observations, combined with the presence of oceanographic conditions associated with spawning in the Gulf of Mexico, the group concluded that the null hypothesis that no substantial bluefin spawning occurs in the central Atlantic region should be tested using a variety of approaches. If indeed substantial spawning occurs in the central Atlantic, or if spawning size fish that do not spawn in that year occur there, then the implications for management are enormous. Using existing data and samples, the group agreed to: 1. Compile an inventory of historical plankton collections from the central Atlantic and include such data as when, where, what samples taken, how preserved, where stored, etc. If suitable samples are available, we will seek funding to sort and identify bluefin tuna larvae. 2. Compile an inventory of historical fishing cruise data from the central Atlantic which document the presence or absence of spawning-sized fish and related biological data during the time when conditions are considered suitable for bluefin spawning. 3. Review existing tagging data from pop-up and archival tags to better define the timing and location of spawning sized fish. This would be facilitated by a common database for high-tech tags. The data base should include tag number, date of release and recapture (or pop-up), size

4 at tagging and recapture, etc. This should in no way compromise the publication of original results from these high-tech tagging programs, but it would allow the basic data to be made available to the scientific community. 4. Identify the appropriate time(s) and area(s) in the central Atlantic where bluefin tuna spawning could occur, based on knowledge of environmental conditions associated with spawning in the Gulf of Mexico and the Mediterranean. In addition, we have identified new research needs and strongly encourage the following actions: 1. Exploratory research sampling of larvae and spawning-sized bluefin in the central Atlantic in 2001 as outlined below. On behalf of this group, a letter of intent will be drafted by the meeting co-chairs and widely distributed to national governments with bluefin tuna fishing interests in the central Atlantic, the fishing industry, and private and government foundations. The elements of the initial exploratory research survey would be: May to July 2001 implementation; 2 long-line vessels and one research vessel; 2 trips per vessel of about 15 longline sets per trip; In areas that have temperatures of C, phytoplankton biomass levels of mg/m 3 of chlorophyll a at the surface, and oceanographic features such as eddies, Gulf Stream rings and fronts; Charter costs will be in the order of $5000/day in order to attract good fishermen at the time of the commercial fishery. Additional resources are required for lab-based costs associated with sampling. Note that already approximately 2 million dollars has been spent on high-tech tagging; Ensuring an appropriate scientific quota (i.e., 15 MT) for sampling is set aside by ICCAT. 2. Expand popup archival satellite tagging (PSAT) of bluefin tuna to the central Atlantic. 3. Develop appropriate technology for PSATs that could detect spawning. Calibration should take place in known spawning areas on mature fish. A telemetry device that could detect spawning behavior would be a valuable tool. 4. Use ships of opportunity to collect biological samples and encourage fleets fishing in the central Atlantic to provide detailed samples and to tag bluefin where possible, consistent with responsibilities associated with the FAO Code of Conduct for Responsible Fisheries. For instance, the Japanese 2000 research cruise in tropical Atlantic waters should be approached to conduct/initiate appropriate biological sampling. Sampling of bluefin tuna catches from northeast of the Bahamas should occur. This is the suggested initial research plan. Modifications and future research will take place based upon the results of the work specified above.

5 2. LITERATURE CITED BLOCK, B.A., Dewar, H., Blackwell, S.B., Williams, T., Prince, E., Farwell, C., Boustany, A., and A. Seitz. Archival tagging of Atlantic bluefin tuna.. ICCAT, Coll. Vol. Sci. Pap. SCRS /99/103. LUTCAVAGE, M., Brill, R.W., Porter, J., Skomal, G.B., Chase, B., Howey, P.W., and E. Murray, Jr. Preliminary results from the joint US-Canadian pop-up satellite tagging of giant bluefin tuna in the Gulf of Maine and Canadian Atlantic Region, ICCAT, Coll. Vol. Sci. Pap. SCRS/99/104. LUTCAVAGE, M., Brill, R. Skomal, G., Chase, B., and P. Howey Results of pop-up satellite tagging on spawning size class fish in the Gulf of Maine. Do North Atlantic bluefin tuna spawn in the Mid-Atlantic? Can. J. Fish. Aquat. Sci. 56: RICHARDS, W.J Spawning of bluefin tuna (Thunnus thynnus) in the Atlantic Ocean and adjacent seas. ICCAT, Coll. Vol. Sci. Pap. 5(2): RIVAS, L.R A preliminary report on western north Atlantic fishes of the family Scombridae. Bull. Mar. Sci. 1:

6 3. BERMUDA BLUEFIN WORKSHOP PARTICIPANTS Dr. Richard Brill Honolulu Laboratory National Marine Fisheries Service Southwest Fisheries Center 2570 Dole Street, Honolulu, HI voice fax Dr. John Graves College of William & Mary Virginia Inst. of Marine Science Gloucester Point, Virginia USA voice 804/ fax 804/ Dr. Scott A. Heppell Department of Fisheries and Wildlife 104 Nash Hall Oregon State University Corvallis, OR voice 541/ fax 541/ Dr. Frank Hester c/o LMR Fisheries Research Inc Sorrento Valley Rd., SuiteA San Diego, CA voice 619/ fax 619/ Bruce Ker 12 Hudson St. PO Box 42 Marlboro, NJ voice 732/ or 732/ Robert Lambe 2 Aphilipolis Hill Drive Somerset Bermuda voice 441/ cell 441/ Dr. Brian Luckhurst Senior Fisheries Officer, Division of Fisheries P.O. Box CR 52, Crawl CRBX, Bermuda voice 441/ fax 441/ bluckhurst@bdagov.bm Dr. Molly Lutcavage New England Aquarium Central Wharf Boston, MA USA voice fax mlutcavg@neaq.org website Dr. James D. McCleave School of Marine Sciences University of Maine 5741 Libby Hall Orono, ME USA voice 207/ fax 207/ mccleave@maine.edu Dr. Norm B. Nelson Satellite Laboratory BBSR, Ferry Reach St. Georges, GE01,Bermuda voice 441/ fax 441/ norm@bbsr.edu Dr. Julie Porter Biological Station 531 Brandy Cove Road St. Andrews, NB Canada E5B 2L9 voice fax porterjm@mar.dfo-mpo.gc.ca Richard Ruais East Coast Tuna Assoc. PO Box 447, Salem, NH USA voice 603/ fax 603/ rruais@aol.com Dr. Greg Stone New England Aquarium Central Wharf, Boston, MA USA voice fax gstone@neaq.org Dr. Steve Turner National Marine Fisheries Service Southeast Fisheries Science Center 75 Virginia Beach Drive, Miami, FL voice 305/ fax 305/ steve.turner@noaa.gov