Title: The stock assessment of the Spiny lobster (Panulirus argus) in the southeastern Cuban waters

Author(s): Liset Cruz Font
Type:
Final project
Year of publication:
2002
Publisher:
UNU-FTP
Place of publication:
Reykjavík
Number of pages:
51
Supervisors: Einar Hjorleifsson

Abstract

An assessment of the population of spiny lobster (Panulirus argus) living in the southeastern shelf of the Cuban waters is made in this report. The input data were a matrix of catch at age and effort information from the commercial fleet. Three different methods were applied to the data, the catchability tuning VPA, the ADAPT-VPA and the Excel catch at age model. These methods are in principle the same, the only great difference being how they handle error in the catch at age data. They all showed that there is a discrepancy between the two input data sets, the modelled fishing mortality trends only partially following the trend in the observed effort. The results obtained demonstrate that when analysing the same data set with models that use similar assumptions, the conclusions are more or less the same. The catch at age analysis uses some different assumptions, so more variabilities were observed. For the catchability tuning and the ADAPT VPA the fishing mortality rate in the final year was 0.44, while it was 0.63 for the EXCAM model. The recruitment followed the same pattern for the three methods, declining continuously since 1982. The selection pattern obtained by the catchability tuning and the ADAPT VPA showed a bell shape pattern, but for the catch at age method it has to be assumed to follow a logistic curve, where the last age groups are recruited to the fishing gear with a selectivity of one. Additional information is needed to clear the pattern of selectivity. The yield per recruit analysis indicates that the current fishing mortality rate (0.63) is lower than Fmax (0.8). The predictions were made for different reference points like F0.1, FSSB35% and Fmax. A 30% reduction in effort is needed to reduce the fishing mortality to FSSB35%. It is possible to keep fishing the stock at the current level, but a consideration in the recruitment has to be taken into account, as a continuous decline has been observed with this parameter.

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