Exploratory assessment of the penaeid shrimp fisheries off the Atlantic coast of Nicaragua using length cohort analysis
Portocarrero, A.H. (1993). Exploratory assessment of the penaeid shrimp fisheries off the Atlantic coast of Nicaragua using length cohort analysis. MSc Thesis. Departement voor Zeevisserij: Oostende. 33, 66 pp.
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Documenttype: Doctoraat/Thesis/Eindwerk
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| Abstract |
The landings and the catches per unit effort (CPUE) of the Nicaraguan shrimp fisheries in the Caribbean Sea, have shown considerable fluctuations over the period 1980-91. with peaks in the early and late 1980s and minima in the mid 1980s and the early 1990s. Both landings and CPUEs were very closely related with fishing effort. Length frequency data of the shrimp catches were available for the years 1989-91 only, and this period was chosen as the reference period for the analytical assessments. Two species, viz. Penaeus notialis and Penaeus schmitti appeared to be of particular importance for the fisheries. The numbers of shrimp caught for each sex and species, varied considerably from one year to another, but their size distributions remained roughly stable. Analytical assessments were carried out, using a modified version of Jones' Length Cohort Analysis (LCA). The results of these assessments are discussed with respect to their sensitivity to the input values of the growth parameters K and Linf, the natural mortality rate M, and the input value of the fishing mortality rate F on the largest size class in the length distributions. The choice of Linf appeared to be of particular importance, since it had a major effect on the estimations of the fishing mortality rates at length and on the prediction of the yields-per-recruit produced by the LCA. The investigations showed that there is little or no immediate danger of over-exploitation in the Nicaraguan shrimp fisheries. The results of the LCAs, however, should be considered with caution, because of the many uncertainties on the data base and on the input values for K, Linf, and M. Finally a number of recommendations is formulated, to improve the overall quality of the data collecting system. |
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