Revision of the life history parameters (proportion of mature and mean weights at age) for the Iberian (south) sardine stock (ICES 8c and 9a)

Abstract

Maturity and stock weights at age used in sardine assessment up to 2012 were obatined from (Portuguese and Spanish) spring acoustic surveys biological data. Following a recommendation of the WGANSA, the possible alternative use of the Daily Egg Production Method (DEPM) surveys to estimate maturity at age was evaluated, and a revision of these maturity ogives was undertaken for the last benchmark assessment (Silva et al. 2011, WKPELA 2012), the WG having decided that DEPM maturity ogives should be used in the assessment, and for years with no DEPM survey, 80% of fish mature would be assumed at age 1 (corresponding approximately to the historical mean of DEPM ogives), and for simplicity, 100% of fish are mature at age 2. But these estimates were obtained including information from both DEPM and acoustic surveys: maturity data from the DEPM for each stratum and year were combined to obtain stock estimates, using abundances at age from acoustic surveys as weighting factors; however, in most years, 1-2 months lagged between the two surveys in W and S strata. Revision of weights at age could not be carried out in 2012 due to time constraints, but the WGHANSA believes that it makes more sense that both life history parameters be derived from the same surveys. This WD describes the revision of both maturity and stock weights at age estimates, based uniquely on the DEPM surveys.