Stock assessment of albacore Thunnus alalungain the Indian Ocean

Albacore Thunnus alalungais one of the main tuna species in the Indian Ocean(IO).The stock status of IO albacore was uncertain due to the lack of reliable data.We assessed the albacore based on the most recent available fishery data and biological information using an age-structured assessment program(ASAP).The estimated fishing mortality(F), spawning stock biomass(SSB)and biological reference points were sensitive to the assumed steepness(h)in stock-recruitment relationship.At the assumption of h=0.7,0.8(base-case) and 0.9,the maximum sustainable yield(MSY)was 25 268t,27 414tand 51 924t;the ratio of current(year 2010)Fto FMSYwas 2.85,2.32and 1.11;and the ratio of current catch to MSY was 1.65,1.52and 0.80,respectively.The Fvalue has been increasing and SSB value has been decreasing since 1984.At the base-case(h=0.8),the current stock status wasover-fishingand approaching tooverfished.At the sensitivity analyses of h=0.7and 0.9,the current stock status wasoverfishedandoverfishing,respectively.