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| Cotter, A; Mesnil, Benoit; Piet, G. |
| A year-class curve is a plot of log cpue (catch per unit effort) over age for a single year class of a species (in contrast to the better known catch curve, fitted to multiple year classes at one time). When linear, the intercept and slope estimate the log cpue at age 0 and the average rate of total mortality, Z, respectively. Here, we suggest methodological refinements within a linear least squares framework. Candidate models may include a selectivity term, fleet-specific parameters, and polynomials in year to allow for gradual variations of Z. An iterative weighting method allows for differing precisions among the different fleets, and a forward (one-step ahead) validation procedure tests predicted cpue against observed values. Choice of the best... |
| Tipo: Text |
Palavras-chave: Year class curve; Plaice; North Sea; Iteratively weighted least squares; Forward validation; Fish stock assessment; Cpue; Analysis of relative residual variance. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2776.pdf |
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| Piet, G; Jansen, H; Rochet, Marie-joelle. |
| This study describes the process of evaluating potential indicators for an ecosystem approach to fishery management in European waters by evaluating these indicators against existing criteria using questionnaires completed by experts. We (i) compare the use of a longer list of simple criteria with a shorter list of elaborate ones; (ii) compare evaluation results when screening criteria are applied to specific indicators vs. high-level headline indicators; and (iii) examine whether detailed questionnaires, with elaborate indicators and elaborate criteria, result in ranked scores that are less influenced by familiarity with the indicators. The results show that the ranked scores of indicators are affected by the level of detail, both in terms of criteria and... |
| Tipo: Text |
Palavras-chave: Questionnaire; Headline indicators; Evaluation criteria; Ecosystem approach. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-4715.pdf |
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