Age and Growth of Brown Trout (Salmo trutta) in Six Rivers of the Southern Part of Caspian Basin

Abstract

Problem statement : Because of dramatic declines in stocks of brown t rout in southern part of Caspian basin, the population's structure of bro wn trout ( Salmo trutta ) in several rivers were studied to provide data for conservation programs. Approach: The structure of the populations in the six rivers of the southern part of Caspian basin including: Ke liyare, Khojirood, Lar, Shirinrood, Rig cheshme and Pajimiyane, were studied. Results: Five age classes, ranged from 0 + -4 + years, were determined. The most frequent age classes belong to 1 + and 2 + . The length ranged from 78-305 mm and weight ranged from 3.6-390 g. Also, the condition factor ranged f rom 0.58-1.47. The highest and lowest length, weight and condition factor were observed in Lar an d Rig cheshme, respectively. In 5 out of 6 rivers, females were dominant over males. The highest and lowest female: Male ratios were observed in Pajimiane (6.75:1) and Khojirood (0.8:1), respectiv ely. Significant relationships were found between total length of brown trout with depth (r = 0.6, p< 0.0001) and width (r = 0.68, p<0.0001) of habitats in these studied areas. Conclusion: According to our knowledge, this is the first repo rt of brown trout from Kelyare and Khojirood rivers. Since size of po pulations in studied areas are small and majority o f these rivers located in low protected locations, it is essential to apply serious measures to protect these vulnerable habitats.