Bayesian assessment of Northeast Atlantic spurdog using a stock production model, with prior for intrinsic population growth rate set by demographic methods

• Main Authors: T. R. Hammond, J. R. Ellis
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2005
• Subjects: Key words; age; assessment; biomass; catch; effort; fecundity; growth; population; spurdog; McAllister; Schaefer; Northeast Atlantic; Squalus acanthias
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.553.2380; http://journal.nafo.int/35/hammond/8-hammond.pdf

Schaefer-model stock assessments can be imprecise when they are fitted to catch rate data (CPUE) because a large, unproductive stock can often explain CPUE trends as well as a small, productive one. However, consideration of life-history characteristics can improve parameter estimates by constraining maximum productivity. Therefore, we applied the methods of McAllister et al. (2001) to Northeast Atlantic spurdog (Squalus acanthias) by using demographic techniques to convert prior distributions for age-specific fecundity and natural mortality (the latter based on published estimates from tagging studies) to prior distributions for the intrinsic rate of population growth (r). The priors for r generated in this manner were then used in a Bayesian, Schaefer-model assessment of spurdog, fitted to bottom trawl survey CPUE data. Results suggest the stock is depleted to about 5 % of virgin biomass.