Length frequency, sex ratio and relative abundance (CPUE) of Astacus leptodactylus in Arass Reservior (1997-98)

Abstract

The length frequency, sex ratio and CPUE of Arass reservoir crayfish have been studied during a one year research project in 1997-98. Comparison of Arass crayfish with the same species of crayfish dwelling in freshwater habitats of Turkey, Turkamenistan, Caspian sea region and also in Anzali lagoon, The Arass crayfish were higher in length and weight. The average length and weight were 120.50±0.96mm and 54.68±1.53 gr, respectively (n=3219, confidence interval 95%). In the samples, the smallest crayfish measured 78mm and weighted 12.3 gr and the largest crayfish had 186mmlength and 239.6 gr weight. In the crayfish traps 83.2% of catch exceeded the standard commercial size. The sex ratio during spawning period (December-May) dominated by males and in other months the females had superiority in the catch. In general consideration the sex ratio during the project life dominated by males (1:1.33, n=35454). The CPUE in August was the highest and the least in January (in order of 10.32 and 0.15 crayfish per one trap in 24 hours respectively). The catching operation occured in the depth of 2.5-17.5m in the ecosystem, and CPUE were the highest the depth of 75m. Considering the CPUE data, the desirable catch occured in the August, September and October. Positive relationship between water temperature and CPUE observed, and optimum catch were occured when the water temperature ranged between 16-26ᵒc.