Estimation of biological parameters for the common dolphin (Delphinus delphis) and its importance on dynamic models. An approximation of the mortality-at-age and the influence of the bycatch
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AuthorsSaavedra, C. (Camilo); Howell, D. (Daniel); Cerviño-López, S. (Santiago); Pierce, G.J. (Graham John); Read, F.L. (Fiona); Santos, M.B. (María Begoña)
The short-beaked common dolphin (Delphinus delphis) is the most abundant small cetacean in the north eastern Atlantic and in some regions by-catch is considered to be unsustainable. To help inform conservation measures, population models are needed to explore how the population will react under different scenarios. In order to build a population model, mortality-at-age curves derived from stranding data were constructed, using a Siler model fitted to the total observed dataset. Due to the paucity of data for the youngest age classes, a separate model was fit to a subset of the data that did not include the youngest age classes. Finally, a Heligman-Pollard model was fitted to the second subset of data as well, taking into account the proportion of by-caught dolphins in the sample. The survivorship curves for the Siler models reported that a median of 30% of the females achieve maturity when we used the total observed data set but only the 18% if we remove the youngest ages. The Heligman ...