Scientific Report on Stock Assessments of Yellowfin Tuna (Thunnus albacares), Bigeye Tuna (Thunnus obesus) and Skipjack Tuna (Katsuwonus pelamis) in Sulu and Sulawesi Seas by ASPIC

Abstract

Results of stock assessments should be looked at with caution because of following reasons, i.e., (a) Stock assessments (YFT: yellowfin, BET: bigeye and SKJ: skipjack tuna) in the SSS water, may not be meaningful because they are small parts of Western and Central Pacific stocks (see Fig. 2), thus catch in SSS are about 19% (YFT), 12% (BET) and 14% (SKJ) of the catches in WCPFC water. But results may represent the stock status in the local (SSS) situation in some extent if emigration and immigration between the SSS water and WCPFC water are constant, (b) there are 23 years of catch in SSS, which are long enough for stock assessments. But aggregated catch of various species are often disaggregated to catch by species using average species compositions, which may produce biased in the estimated catch by species, (c) stock assessments were conducted by ASPIC without biological data and stock-recruit relationship, which may mask real population dynamics which may mislead the Kobe plot (stock status trajectories) and (d) results are highly relied on CPUE that is available only for 10 years, thus results are very sensitive by trends and/or jumps of CPUE series.