Temporal changes in some Rajiformes species of cartilaginous fish (Chondrichthyes) from the west coast of İskenderun Bay (northeastern Mediterranean)


Abstract: Some Rajiformes species among the cartilaginous fish (Chondrichthyes) that are distributed on the west coast of the Gulf of İskenderun were seasonally obtained by bottom trawling from 2 different depth layers between the years 2004 and 2011. The spatiotemporal changes in catch per unit effort (CPUE) values were investigated by considering 2 depth contours (10 and 20 m). Six species belonging to 6 different Rajiformes families were identified during the sampling period, including Dasyatis pastinaca (common stingray), Gymnura altavela (spiny butterfly ray), Rhinobatos rhinobatos (common guitarfish), Raja radula (rough ray), Myliobatis aquila (common eagle ray), and Torpedo marmorata (marbled electric ray). A general linear model was used to analyze the changes in the total and separate weights of cartilaginous fish. For this purpose, the logarithms of CPUE values in weight were classed according to the depth, season, and years. Seasonal variations and year–season 2-way interactions were found to be highly significant for total cartilaginous CPUE values (P < 0.01). The annual changes in R. rhinobatos were the only significant annual difference (P < 0.05), while the year–season interactions of D. pastinaca were found to be significant (P < 0.01). The seasonal variations of D. pastinaca and G. altavela were also highly significant (P < 0.01).

Keywords: Cartilaginous fishes (Chondrichthyes), İskenderun Bay, biomass

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