CONSENSUS DOCUMENT: WORKSHOP ON THE BIOLOGY OF BLUEFIN TUNA IN THE MID-ATLANTIC 5-7 MAY 2000, HAMILTON, BERMUDA
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SCRS/00/125 Col. Vol. Sci. Pap. ICCAT, 52 (2) : 803-808 (2001)
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 2001. 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; email mlutcavg@neaq.org
2 Division of Fisheries, P.O. Box CR 2, Crawl CRBX, Bermuda; email bluckhurst@bdagov.bmbesoins 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 2001. 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.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), sizeat 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 22-27° C, phytoplankton biomass levels of 0.1-0.4
mg/m3 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.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, 1998-99. ICCAT, Coll. Vol. Sci.
Pap. SCRS/99/104.
LUTCAVAGE, M., Brill, R. Skomal, G., Chase, B., and P. Howey. 1999. 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. 56:173-177.
RICHARDS, W.J. 1976. Spawning of bluefin tuna (Thunnus thynnus) in the Atlantic Ocean and
adjacent seas. ICCAT, Coll. Vol. Sci. Pap. 5(2):267-278.
RIVAS, L.R. 1954. A preliminary report on western north Atlantic fishes of the family Scombridae.
Bull. Mar. Sci. 1:209-230.3. BERMUDA BLUEFIN WORKSHOP PARTICIPANTS
Dr. Richard Brill Dr. Molly Lutcavage
Honolulu Laboratory New England Aquarium
National Marine Fisheries Service Central Wharf
Southwest Fisheries Center Boston, MA 02110 USA
2570 Dole Street, Honolulu, HI 96822-2396 voice 617 973-5451
voice 808 592-8304 fax 617 723-9705
fax 808 592-8300 email mlutcavg@neaq.org
email rbrill@honlab.nmfs.hawaii.edu website www.marinegis.org
Dr. John Graves Dr. James D. McCleave
College of William & Mary School of Marine Sciences
Virginia Inst. of Marine Science University of Maine
Gloucester Point, Virginia USA 23062 5741 Libby Hall
voice 804/684-7352 Orono, ME 06669-5741 USA
fax 804/684-7157 voice 207/581-4392
email graves@vims.edu fax 207/581-4388
email mccleave@maine.edu
Dr. Scott A. Heppell
Department of Fisheries and Wildlife Dr. Norm B. Nelson
104 Nash Hall Satellite Laboratory
Oregon State University BBSR, Ferry Reach
Corvallis, OR 97331 St. Georges, GE01,Bermuda
voice 541/737-1964 voice 441/297-1880
fax 541/ 737-3590 fax 441/297-8143
email heppells@ucs.orst.edu email norm@bbsr.edu
Dr. Frank Hester Dr. Julie Porter
c/o LMR Fisheries Research Inc. Biological Station
11855 Sorrento Valley Rd., SuiteA 531 Brandy Cove Road
San Diego, CA 92121 St. Andrews, NB Canada E5B 2L9
voice 619/792-6515 voice 506 529-5902
fax 619/792-6519 fax 506 529-5862
email Fhester52@aol.com email porterjm@mar.dfo-mpo.gc.ca
Bruce Ker Richard Ruais
12 Hudson St. East Coast Tuna Assoc.
PO Box 42 PO Box 447, Salem, NH 03077 USA
Marlboro, NJ 07746 voice 603/898-8862
voice 732/303-8328 fax 603/898-2026
or 732/899-6458 email rruais@aol.com
Robert Lambe Dr. Greg Stone
2 Aphilipolis Hill Drive New England Aquarium
Somerset Central Wharf, Boston, MA 02110 USA
51301 Bermuda voice 617 973-5229
voice 441/ 234-1071 fax 617 723-9705
cell 441/754-9244 email gstone@neaq.org
Dr. Brian Luckhurst Dr. Steve Turner
Senior Fisheries Officer, Division of Fisheries National Marine Fisheries Service
P.O. Box CR 52, Southeast Fisheries Science Center
Crawl CRBX, Bermuda 75 Virginia Beach Drive, Miami, FL 33149
voice 441/293-1785 voice 305/361-4482
fax 441/293-2716 fax 305/361-4562
email bluckhurst@bdagov.bm email steve.turner@noaa.govVous pouvez aussi lire
