STATUS OF BIGEYE TUNA IN THE EASTERN PACIFIC OCEAN IN 2007 AND OUTLOOK FOR THE FUTURE

摘要: 1. SUMMARY This report presents the current stock assessment of bigeye tuna (Thunnus obesus) in eastern Pacific Ocean (EPO). As last assessment, this was conducted using Stock Synthesis II (SS2; Methot 2005). The reported here is based on assumption that there a single EPO, and no exchange fish between EPO western central Ocean. requires substantial amount information. Data retained catch, discards, catch per unit effort (CPUE), used as indices abundance, size compositions catches from several different fisheries have been analyzed. Several assumptions regarding processes such growth, recruitment, movement, natural mortality, fishing also made. Catch, CPUE, length-frequency data for surface updated to include new 2007 revised 2003-2006. Analyses were carried out assess sensitivity results to: 1) stock-recruitment relationship; 2) use southern longline CPUE only; 3) two time blocks selectivities floating-object fisheries, separated by implementation 2001 IATTC Resolution C-00-08, which prohibited discards tunas EPO. There important changes mortality caused On average, since 1993 less than about 15 quarters old has increased substantially, more slightly. increase younger expansion association with floating objects. Over range spawning biomasses estimated base case abundance recruits appears be unrelated potential adult females at hatching. are features series recruitment. First, estimates recruitment before very uncertain, not catching significant amounts small bigeye. period above-average 1995-1998, followed below-average 1999-2000. recruitments above average 2000, particularly large 2005. most recent due fact recently-recruited represented only few samples. extended