Determination of the Sexual Maturity of Threadfins Polydactylus quadrifilis (Cuvier, 1829), Galeoides decadactylus (Bloch, 1795) and Pentanemus quinquarius (Linné, 1758) of the Artisanal Marine Fishery of Grand-Lahou (Ivory Coast)

Abstract

Reproduction of the threadfins of the costal shelf of Grand-Lahou was studied with a monthly sampling frequencies range from may 2009 to april 2011. 534 specimens of Polydactylus quadrifilis, composed of 315 males and 219 females and 648 Galeoides decadactylus composed of 420 males and 228 females, then 453 individuals of Pentanemus quinquarius composed of 210 males and 243 females were used. The sexual maturity parameters of threadfins fishes indicate a size of first maturity (L50 = 67.5 cm) for females of Polydactylus quadrifilis and (L50 = 55.5 cm) with their males. Concerning  the specimens of Pentanemus quinquarius, females present (L50 = 15 cm) and their males (L50 = 14.5 cm). This parameter has identical values ​​with the females of Galeoides decadactylus (L50 = 15.5 cm) and their males (L50 = 15.5 cm). The individuals of Polydactylus quadrifilis and the specimens of Galeoides decadactylus and Pentanemus quinquarius become mature at 1 year of age. The sex ratio determination show that specimens of Polydactylus quadrifilis show a predominance of males during the warm season, from October (73.68%) to March (64.28%) which weakens during the cold season, from May (30%) to July (58%). For Galeoides decadactylus, the sex ratio shows a predominance of males, from August (88%) to March (94.73%). Concerning specimens of Pentanemus quinquarius, the sex ratio is in favor of the females whose lowest value is during the cold season in July (21.74%). All threafin species reach sexual maturity from their first year of life with different sex ratios variations.