SPATIO-TEMPORAL PATTERNS OF ABUNDANCE, BIOMASS AND LENGTH-WEIGHT RELATIONSHIPS OF DASYATIS SPECIES (PISCES: DASYATIDAE) IN THE GULF OF ANTALYA, TURKEY (LEVANTINE SEA)

Spatio-temporal patterns of abundance, biomass and length-weight relationships of Dasyatis species (Pisces: Dasyatidae) 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 Fisheries, Çanakkale Onsekiz Mart University, 17100, Çanakkale, TURKEY
Faculty of Fisheries, Akdeniz University, 07058, Antalya, TURKEY

Abstract

The present paper reports the abundance and biomass of Dasyatis centroura (Mitchill, 1815), D. marmorata (Steindachner, 1892), D. pastinaca (Linnaeus, 1758), and D. tortonesei Capapé, 1975 at various depth levels and seasons in the Gulf of Antalya, and total length-weight (TL-W), disc length–weight (DL-W) and disc width weight (DW-W) relationship of 391 individuals of D. pastinaca, 21 individuals of D. marmorata, and five individuals of D. centroura, caught in trawling surveys. 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. Dasyatis species were sampled from 65 hauls and the frequency of occurrence was 56.03% for D. pastinaca, 11.21% for D. marmorata, 2.59% for D. centroura and 0.86% for D. tortonesei. The overall mean abundance and biomass was 55.32 ind./kmand 107.53 kg/kmfor D. pastinaca; 2.54 ind./kmand 2.56 kg/kmfor D. marmorata, 0.50 ind./kmand 25.97 kg/kmfor D. centroura and 0.25 ind./kmand 1.34 kg/kmfor D. tortonesei. The general TL-W, DL-W and DW-W were described by the equations: W = 0.023*TL2.76 ; W = 0.0999*DL2.74 and W = 0.037*DW2.97 for D. pastinaca; W = 0.002*TL3.23; W = 0.034*DL3.02 and W = 0.0045*DW3.59 for D. marmorata; and W = 0.00001*TL4.04; W = 1.481*DL2.16 and W= 0.141*DW2.59 for D.centroura.

Keywords: Stingray, Dasyatis, seasonal trawl survey, Antalya, Mediterranean Sea