Density, Biomass and Length-Weight Relationship of Brown Trout (Salmo trutta Linnaeus, 1758) Population in the Çoruh River Basin, North-Eastern Anatolia, Turkey

Abstract

This study was conducted to determine density, biomass and length-weight relationship for brown trout (Salmo trutta Linnaeus, 1758) caught from removal method based on single-pass electro fishing. A total area of 2.176 ha was sampled and 167 fishes were caught using electro fishing between May 2012 and June 2013 in Tortumkale Stream of Coruh River, Turkey. Mean density and biomass of brown trout were found to vary between 106-167 fish ha-1 and 4.76-10.64 kg ha-1, respectively. The length-weight relationship exponent b values ranged from 3.0672 to 3.3158 and indicated positive allometric growth. Length-weight relationship in between stations were statistically significant (r2>0.9917, p<0.05). Our results revealed that the density of the brown trout population in Tortumkale Stream is at a level indicating a risk of extinction of this species. Density of brown trout occuring in restricted habitats was reduced in Tortumkale Stream; especially it causes reduction of their population overfishing on adult individuals in reproduction season and lower of recruitment to the population. Also, biotic and abiotic effects of rainbow trout (Oncorhynchus mykiss), aquacultures activities, recreational fisheries, barriers of dam construction and irrigation canals, pollution from domestic, industrial and agricultural waste contribute to the destruction of the habitat of brown trout.