Population structure, growth, length-weight relationship, mortality and stock size of tench, Tinca tinca (L.), was studied in Lake Beys¸ehir, Turkey in 2005. Totals of 3360 tench (1865 males; 1795 females) were captured with gill-and trammel-nets of various mesh sizes. Male to female ratio was 1.04 : 1. The study covered length year classes. Fork lengths and total weights ranged from 9 to 37 cm and 13 to 815 g. For all individuals, the von Bertalanffy growth equation and lengthweight relationship were L t = 54.2[1)exp()0.1350(t + 1.0281)] and W = 0.0151 L 2.9993 , respectively. Growth performance index and mean condition factor of the tench population were 2.598 and 1.513, respectively. Mortality rates were Z = 1.97 year )1 , M = 0.29 year )1 and F = 1.68 year )1 for total, natural, and fishing mortality, respectively. The exploitation rate was E = 0.85, and the percentage of surviving fish was 13.9%. Tench stock was assessed as about 6-7 million individuals and 1450-1500 tonnes in biomass. It was determined that maximum sustainable yield could be obtained with an 80% level of the current fishing effort.

This paper was carried out from 15 June to 24 December in 2000 in Lake İznik of Turkey, to determine catch per unit effort (CPUE) and size composition of crayfish, Astacus leptodactylus Eschscholtz 1823, captured by fyke-nets of local fishermen. The average CPUE of all size groups was found as 1.65 crayfish/fyke-net/night for fishing season in 2000, but 26.4% of which was below the legal minimum size (crayfish<90 mm). The average CPUE of legal-sized (crayfish≥90 mm) crayfish was 1.10 crayfish/fykenet/night. The annual catch of crayfish was estimated as 2990 tonnes. The length and weight compositions of crayfish captured in the fyke-nets have varied between 60 and 130 mm, and 6 and 71 g, respectively. The mean length and weight were found as 95.5 mm and 28.8 g for all size groups and 100.1 mm and 33.0 g for legal-sized individuals.

The aim of this study was to investigate the combined effects of two stocking densities (650 and 1300 juveniles/m 2) and diets (live feed-Daphnia magna and commercial trout feed) on survival rate and growth performance of Astacus leptodactylus juveniles. Juveniles in the second developmental stage were used in the experiment. Final survival rate and growth paremeters of juveniles were evaluated at the end of experiment (90 days). The results of this study indicated that diets were not found effective on survival rates, though increasing stock densities reduced survival rates. The best final survival rate as 21.99 %, was achieved in the group fed with live feed and kept under the 650 juveniles/m 2 stocking density, whereas the lowest survival rate values as 10.84 % was obtained in the group fed with trout pellet and kept under the 1300 juveniles/m 2 stocking density. At the end of experiment, the highest final body weight was found in group of at 650 juveniles/m 2 stocking density and fed with trout feed. The result of our study also revealed that stocking density had a significant effect on survival rates of crayfish juvenile fed with both feeds.

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