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Asymptotic size and natural mortality of long-lived fish for data poor stock assessments

2012; Elsevier BV; Volume: 127-128; Linguagem: Inglês

10.1016/j.fishres.2012.04.005

1872-6763

Kate I. Andrews, Marc Mangel,

Fish Biology and Ecology Studies

An assessment of the California sheephead (Semicossyphus pulcher) was conducted in 2004 despite the lack of critical data to estimate life history parameters, as often occurs for other species in need of assessment. Among other parameters, natural mortality, M, and the parameters of the von Bertalanffy growth equation were estimated using data poor methods. We assess the difference between those results and the results of applying a more recent set of data poor methods to the same data. We use a Bayesian model with only sheephead length data to estimate asymptotic size; our estimate is similar to previous work using the von Bertalanffy growth equation but includes statements about uncertainty in asymptotic size. We use weight-based methods for calculating age-specific mortality and compare the estimate to the constant of 0.2 used in the sheephead assessment. Finally, since the sheephead is a long-lived fish, we determine the age at which fish must recruit to the fishery in order for a constant M to be appropriate. Our estimate of constant mortality stabilizes if the fish recruit after age two.