Title: Life history and stock assessment of the African hind Cephalopholis taeniops (Valenciennes, 1828) in São Vicente- São Nicolau insular shelf of the Cape Verde archipelago

Final project
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Supervisors: Einar Hjorleifsson
Cephalopholis taeniops; life history parameters; cohort splitting; age-based assessment; yield prediction; Fterm; F 0.1.


The African hind Cephalopholis taeniops (Valenciennes, 1828) is one of the most abundant and important demersal species caught in the Cape Verde archipelago. In this report, the life history parameters of C. taeniops are estimated and the status of the stock in the insular shelf from São Vicente to São Nicolau is assessed. Data were collected following a biological sampling scheme established in 1993. Following the changes in the gonadosomatic index it is concluded that the highest reproductive activity period extends from June to October. The maturity ogive is estimated and the mean length at sexual maturity was determined at 26.5 cm, which corresponds to a mean age of sexual maturity of 4.2 years. The weight-length relationship is estimated with α =0.0067 and β=3.2. Von Bertalanffy growth parameters are estimated using the Ford-Walford plot and the Macdonald and Pitcher method. For assessment purposes, the growth parameters L∞= 62.9 cm, Κ=0.12 per year and t0=-0.28, estimated using the Macdonald and Pitcher method, are used. The natural mortality is estimated to be M=0.34 by Pauly’s empirical formula and M=0.38 by Rikhter and Efanov’s formula, the last one being used in the assessment. Age-based assessment methods are applied. The cohort splitting is performed through least squares minimisation, following the Macdonald and Pitcher method of analysing distribution mixtures. A classic VPA and a simplified YpR and SSBpR model of Beverton and Holt were applied and tested for sensitivity using different scenarios of M-values. YpR management targets (Fmax and F0.1) were estimated. A yield forecast for 2001, assuming different values of M, was performed. Assuming the M=0.25 scenario as the most probable one, it is concluded that the fishing mortality since 1997 has been around the F0.1 levels and no increases in fishing effort are recommended. This scenario predicts for 2001 a yield at Fterm around 77 tons and a yield at F0.1 around 74 tons. Finally, some changes are recommended in the sampling scheme in order to improve data collection and to create a basis for applying better and more reliable assessment models.

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