Demographic and Exploitation Parameters of the Blue Shark in the Gulf of Guinea

Demographic and Exploitation Parameters of the Blue Shark, Prionace Glauca in the Gulf of Guinea (Togo-Benin-Nigeria)

Calèbe Midinoudéwa, H.E.; Sohou, Z.; Tulashie, S.K.; Fiogbé, E.D.

ABSTRACT:

Prionace glauca, blue shark is a cosmopolitan species. Together with Carcharhinus falciformis, it co-dominated the landings of carcharhinidae sharks at the Artisanal Fishing Port of Cotonou. The objective of this study is to determine the demographic parameters of the blue shark in Gulf of Guinea marine waters. The different routines of the FISAT II v 1.2 software associated with the empirical equations of Froese and Nohland, allowed the evaluation of the different demographic parameters of the blue shark in Benin’s marine waters. From August to December 2015, 244 individuals shark sizes; ranging from 175cm to 325cm were sampled. The total asymptotic length obtained was 341.25cm with a growth rate of 0.35/year, which indicates that the species is growing rapidly and the optimal total length of the species is 232.01cm. The age of first maturity of the species is 3 years with a longevity of 10 years. The exploitation rate is E= 0.74 with total mortality being 2.4; natural mortality is 0.6 and fishing mortality is 1.8. The sex ratio remains in favour of males throughout the study period. Monitoring programme were suggested with effective management measures established and executed for sustainability of the blue shark’s stock in the Gulf of Guinea.

Preprints 2020, 2020080660, DOI: 10.20944/preprints202008.0660.v1

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