Spatio-temporal patterns of abundance, biomass and length-weight relationships of Gymnura altavela (Linnaeus, 1758) (Pisces: Gymnuridae) in the Gulf of Antalya, Turkey (Levantine Sea)
Elif Özgür Özbek, Mine Çardak, Turhan Kebapçioğlu
Turkish Marine Research Foundation (TUDAV), P.O. Box: 10, Beykoz, Istanbul, TURKEY
Faculty of Marine Science and Technology, Çanakkale Onsekiz Mart University, TURKEY
Faculty of Fisheries, İzmir Katip Çelebi University, Çiğli Ana Yerleşkesi, 35620, İzmir, TURKEY
The present paper reports the abundance and biomass of Gymnura altavela (Linnaeus, 1758) at various depth levels and seasons in the Gulf of Antalya, Mediterranean cost of Turkey. A total of 116 hauls were carried out between August 2009 and April 2010 seasonally in the Gulf of Antalya at six stations and six depth levels (25, 50, 75, 100, 150, 200 m) using a commercial bottom trawl. From 40 hauls, 172 individuals were sampled and the frequency of occurrence was 41.67% at the depths between 25 and 100 m, but absent at 150 and 200 m. The overall mean abundance and biomass was 27.98 ind./km2 and 167.76 kg/km2. Total length-weight (TL-W), disc length–weight (DL-W) and disc width–weight (DW-W) relationship were described as W= 0.031*TL2.93 ; W= 0.064*DL2.94 and W= 0.007*DW3.03, respectively. The highest TL, DL and DW values in the Mediterranean Sea are reported.
Keywords: Spiny butterfly ray, Gymnura altavela, seasonal trawl survey, Antalya, Mediterranean Sea, length-weight relationship