WCPFC Scientific Committee Recommends Reduction in Fishing Mortality for Bigeye Tuna

The seventh regular session of the Scientific Committee (SC7) of the Western and Central Pacific Fisheries Commission (WCPFC) was held from August 9 to 17, 2011 in Pohnpei, Federated States of Micronesia. In attendance were committee members from Australia, China, Cook Islands, Federated States of Micronesia, Fiji, French Polynesia, Indonesia, Japan, Kiribati, Korea, Republic of the Marshall Islands, Nauru, New Caledonia, New Zealand, Palau, Papua New Guinea, Philippines, Samoa, Solomon Islands, Chinese Taipei, Tonga, Tuvalu, USA, Vanuatu and Vietnam. The U.S. delegation was led by PIFSC scientist Keith Bigelow. He was joined by Jon Brodziak and Darrell Tagami of PIFSC, Valerie Chan of the NOAA Fisheries Pacific Islands Regional Office, Steve Teo of the NOAA Southwest Fisheries Science Center, David Itano of the University of Hawaii, and Paul Dalzell of the Western Pacific Fishery Management Council.

Bigeye tuna.
Bigeye tuna.

The Scientific Committee is responsible for providing scientific advice to the WCPFC relating to the Commission's management of valuable fisheries for tuna and billfish in the western and central Pacific. Although tuna catches were lower in 2010 than in 2009, a record year, average prices for fish increased. In 2010, the catch by the multi-national purse seine fleet was valued at $2.5 billion (second highest on record) and the catch by the longline fleet was worth $1.5 billion.

The committee reviewed 5 scientific assessments of fish stocks in the region; all showed results similar to those reported in previous assessments. The stock of bigeye tuna is experiencing overfishing, and may also be in an overfished state. Stocks of yellowfin, skipjack tuna, and albacore (separate North and South Pacific assessments) are not experiencing overfishing, nor are they in an overfished state.

Based on the stock assessment results, the Scientific Committee recommended a 32% reduction in fishing mortality on bigeye tuna from the average levels of mortality during 2006–2009, returning the fishing mortality rate to the level producing the maximum sustainable yield, FMSY. Because levels of exploitation and fishing mortality differ between regions (tropical regions account for 88% of the total bigeye tuna catch), the Scientific Committee suggested that the Commission consider a spatial management approach.

In reviewing the stock assessment for yellowfin tuna, SC7 noted the high exploitation rate for this species in the western equatorial Pacific and recommended there be no increase in fishing mortality for yellowfin in this area.

In addition to addressing critical issues like status of stocks, scientists at SC7 investigated a diverse array of topics under the meeting's Ecosystem and Bycatch Mitigation Theme. Research papers were presented on sharks, seabirds, and animals encircled incidentally in purse seines (such as cetaceans and whale sharks). The SC7 approved a process for identifying which shark species should be considered key species, warranting particular attention for research and stock assessment. Eight 8 key shark species are currently being assessed under the WCPFC's Shark Research Plan, Longline fishery catch rates of one of these species, oceanic whitetip shark, have declined considerably in all data sets examined (including observer data from the Hawaii-based longline fisheries). Based on catch rate data, there also appear to be declines in abundance of blue shark and silky shark, but the trends in catch rates for these species are less consistent.

The Scientific Committee does not anticipate that any tropical tuna assessments will be carried out in 2012, but agreed to conduct assessments on South Pacific albacore and southwest Pacific striped marlin. In addition, there will be assessments for oceanic whitetip shark and silky shark as scheduled in the Shark Research Plan.

U.S. delegate Paul Dalzell was honored by SC7 as he retired as Chair of the Ecosystem and Bycatch Mitigation Theme after serving a 10-year tenure in the position. His efforts were much appreciated by the Scientific Committee.