School whiting (Sillago flindersi) stock assessment based on data up to 2016 – development of a preliminary base case

[摘要] This document presents a suggested base case for an updated quantitative Tier 1 school whiting (Sillago flindersi) assessment for presentation at the first SERAG meeting in 2017. The last full assessment was presented in Day (2009). The preliminary base case has been updated by the inclusion of data up to the end of 2016, which entails an additional eight years of catch, discard, CPUE, length and age data and ageing error updates since the 2009 assessment and incorporation of an additional trawl CPUE index from 1995-2016. This document describes the process used to develop a preliminary base case for school whiting through the sequential updating of recent data to the stock assessment, using the stock assessment package Stock Synthesis (SS-V3.30).Changes to the last stock assessment include: separating length frequencies into onboard and port collected components; weighting length frequencies by shots and trips rather than fish measured; and using a new balancing method.Results show remarkably good fits to the catch rate data, length data and conditional age-at-length data. This assessment estimates that the projected 2018 spawning stock biomass will be 42% of virgin stock biomass (projected assuming 2016 catches in 2017), compared to 50% at the start of 2010 from the last assessment (Day 2009).

[发布日期] 2017-09-21 [发布机构] CSIRO

[学科分类] 地球科学(综合)