A linked separable-ADAPT VPA assessment model for western horse mackerel (Trachurus trachurus), accounting for realized fecundity as a function of fish weight

• Published in: ICES Journal of Marine Science
• Main Authors: De Oliveira, José A. A., Darby, Chris D., Roel, Beatriz A.
• Format: Text
• Language: English
• Published: Oxford University Press 2010
• Subjects: Article; Darby; Northeast Atlantic
• Online Access: http://icesjms.oxfordjournals.org/cgi/content/short/fsp290v1; https://doi.org/10.1093/icesjms/fsp290

<qd> De Oliveira, J. A. A., Darby, C. D., and Roel, B. A. 2010. A linked separable–ADAPT VPA assessment model for western horse mackerel ( Trachurus trachurus ), accounting for realized fecundity as a function of fish weight. – ICES Journal of Marine Science, 67: 000–000. </qd>The western horse mackerel stock covers a large area of the Northeast Atlantic and is characterized by the sporadic occurrence of strong year classes. The only fishery-independent data available for its assessments are the estimates of total annual egg production from triennial egg surveys. Horse mackerel are indeterminate spawners, so a direct conversion of total annual egg production to spawning-stock biomass using prespawning-season estimates of fecundity is not viable. There is also evidence that potential fecundity per kg spawning female increases with fish weight. A linked separable–ADAPT VPA (SAD) model was developed that combines data on total catch, catch-at-age, and total annual egg production with data on potential and realized fecundity to provide population estimates for western horse mackerel. The model accounts for potential fecundity as a function of fish weight and for the development of a targeted fishery on the strong 1982 year class. Simulations confirm that the SAD model is able to reproduce population estimates without bias under a range of scenarios, except where there is a trend in realized fecundity. This underscores the need for improved information on realized fecundity, or alternatively the need to develop management plans that are robust to this source of uncertainty.