98F. ALBACORE <strong>TUNA</strong>There are two stocks of albacore in the Pacific Ocean, one occurring in the northern hemisphere and the other in the southernhemisphere. Albacore are caught by longline gear in most of the North and South Pacific, but not often between about 10°N and5°S, by trolling gear in the eastern and central North and South Pacific, and by pole-and-line gear in the western North Pacific. Inthe North Pacific about 60% of the fish are taken in pole-and-line and troll fisheries that catch smaller, younger albacore, whereasabout 90% of the albacore caught in the South Pacific are taken by longline. The total annual catches of North Pacific albacorepeaked in 1976 at about 125,000 t, declined to about38,000 t in1991, and then increased to about 126,000 t in 1999 (Figure F-1a).The total annual catches of South Pacific albacore ranged from about 25,000 to 50,000 t during the 1980s and 1990s, but increasedafter that, ranging from about 55,000 to 70,000 t during 2001-2007 (Figure F-1b).Juvenile and adult albacore are caught mostly in the Kuroshio Current, the North Pacific Transition Zone, and the California Currentin the North Pacific and in the Subtropical Convergence Zone in the South Pacific, but spawning occurs in tropical and subtropicalwaters, centering around 20ºN and 20ºS latitudes. North Pacific albacore are believed to spawn between March and July in thewestern and central Pacific.The movements of North Pacific albacore are strongly influenced by oceanic conditions, and migrating albacore tend to concentratealong oceanic fronts in the North Pacific Transition Zone. Most of the catches are made in water temperatures between about 15ºand 19.5ºC. Details of the migration remain unclear, but juvenile fish (2- to 5-year-olds) are believed to move into the easternPacific Ocean (EPO) in the spring and early summer, and return to the western and central Pacific, perhaps annually, in the latefall and winter, where they tend to remain as they mature. It has been hypothesized that there are two subgroups of North Pacificalbacore, separated at about 40ºN in the EPO, with the northern subgroup more likely to migrate to the western and centralPacific Ocean.Less is known about the movements of albacore in the South Pacific Ocean. The juveniles move southward from the tropics whenthey are about 35 cm long, and then eastward along the Subtropical Convergence Zone to about 130°W. When the fish approachmaturity they return to tropical waters, where they spawn. Recoveries of tagged fish released in areas east of 155°W were usuallymade at locations to the east and north of the release site, whereas those of fish released west of 155°W were usually made atlocations to the west and north of the release site.The most recent stock assessments for the South and North Pacific stocks of albacore were presented in 2008 and 2006, respectively.The assessment of South Pacific albacore, which was carried out with MULTIFAN-CL by scientists of the Secretariat of the PacificCommunity, incorporated catch and effort, length-frequency, tagging data, and information on biological parameters. Althoughuncertainties were found to exist, it appeared reasonably certain that the stock was above the level corresponding to the averagemaximum sustainable yield (MSY), that the effort during 2004-2006 was less than that corresponding to the MSY, and that thespawning biomass was greater than that corresponding to the MSY. There currently appears to be no need to restrict the fisheries foralbacore in the South Pacific Ocean, but additional research to attempt to resolve the uncertainties in the data are recommended.An assessment of North Pacific albacore was conducted at a workshop of the Albacore Working Group of the InternationalScientific Committee for Tuna and Tuna-like Species in the North Pacific Ocean (ISC), held in November-December 2006.The conclusions reached at that workshop were presented to the seventh plenary meeting of the ISC, held in July 2007. Among thesewere the following:• The spawning stock biomass (SSB) in 2006 was estimated to be about 153 thousand t—53% above the long-term average(Figure F-2);• Retrospective analysis revealed a tendency to overestimate the abundance of albacore;• Recruitment had fluctuated about a long-term average of roughly 28 million fish during the 1990s and early 2000s;• The current coefficient of fishing mortality (F), calculated as the geometric mean of the estimates for 2002-2004, was about0.75, which is high relative to several biological reference points to which Working Group compared its estimate for albacore;• The SSB was forecast to decline to an equilibrium level of about 92 thousand t by 2015;• The substantial decline in total catch during recent years is cause for concern;
99• In conclusion, the Working Group recommended that all nations participating in the fishery observe precautionary-basedfishing practices.Additional meetings of the Albacore Working Group took place in February-March 2008 and July 2008. These workshops weredevoted mostly to discussion of data requirements and transition of assessments from Virtual Population Analysis to Stock SynthesisII. Another short meeting will take place in July 2009. An updated stock assessment will be produced at a meeting of the AlbacoreWorking Group in March 2010.FIGURE F-1a. Retained catches of North Pacific albacore, 1979-2007.FIGURA F-1a. Capturas retenidas de albacora del Pacífico norte, 1979-2007.FIGURE F-1b. Retained catches of South Pacific albacore, 1979-2007.FIGURA F-1b. Capturas retenidas de albacora del Pacífico sur, 1979-2007.
Change language