Silver Warehou (Seriolella punctata) stock assessment based on data up to 2014

[摘要] This document presents a quantitative Tier 1 assessment of silver warehou (Seriolella punctata) in the Southern and Eastern Scalefish and Shark Fishery (SESSF) using data up to 31 December 2014.The last full assessment was presented in Day et al. (2012). The 2015 assessment updates all data inputs (catch, discard, length, ageing error, age and catch rate data) and is performed using thestock assessment package Stock Synthesis (SS-V3.24U).Changes to the last stock assessment include: using discards in the assessment; splitting the trawl fleet into eastern and western components; separating length frequencies into onboard and portcollected components; time blocking retention to allow for changes in discarding practice since 2002; including FIS abundance indices; weighting length frequencies by shots and trips rather than fish measured; and using a new tuning method.Results show reasonably good fits to the catch rate data. However, when comparing the observed and expected catch rate data points for the last 2 years in the series, the model may be overly optimistic and the stock could break out again in a relatively short time period (potentially requiring a further Tier 1 update if it is placed on a multi-year TAC).This assessment estimates that the projected 2016 spawning stock biomass will be 40% of virgin stock biomass. The RBC from the base case model for 2016 is 1,958t for the 20:35:48 harvest control rule, with a long-term yield of 2,281t. In comparison, the last assessment estimated the 2013 depletion to be 47%, with corresponding RBCs of 2,544t, with a long-term yield of 2,618t. However, these scenarios assume recruitment will return to average levels. If future recruitmentcontinues at a similar level to recruitment since 2003, then depletion could fall to around 30% before 2020. However, if landed catches continue at levels well below the TAC, then the depletion is likely to remain between 35% and 45% for the next 5 years.

[发布日期] 2015-11-17 [发布机构] CSIRO

[学科分类] 地球科学(综合)