برخي خصوصيات زيست شناختي و ريخت شناسي سياه ماهي (Nikolski, 1897) Capoeta fusca در قنوات شهرستان بيرجند

Some Biological and Morphometric Characteristics of Siah Mahi, Capoeta fusca (Nikolski, 1897) Living in the Qanats of Birjand County (IRAN)

Some morphometric characteristics, feeding regime and reproduction of 600 specimens of Capoeta fusca was studied in qanats of central zone of Birjand county (South Khorasan Province, I. R. IRAN) during November 2006 to October 2007. The mean total length and maximum length of fish were 13.5±1.4 cm and 21.5 cm respectively. The length-weight relationships of this fish was described as BW=0.0101 xTL2.9 (R2=0.9). The mean relative length of the gut (RLG) was 4.42 ± 0.48, suggesting that this species is an herbivore. Likewise, the mean of the vacuity index was 30.95 ± 5.90, so this fish is classified in relatively gluttonous group. Beside plants as primary food, mollusks, aquatic insects, and some times frog eggs, were found as secondary food items. Based on the gonadosomatic index (GSI), the reproduction period of this species begins from March and lasts to May. Variations of gastrosomatic index (GI) showed that, feeding is correlated with reproduction. Measurement of salinity resistance in 96 fish specimen showed that this species can withstand up to 10 ppt of salinity.