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.
Highlights
The brown trout, Salmo trutta, is a native species for Iran
The study of weight-length relationship and condition factor are useful because they have been used for the comparison of species growth between regions (Koutrakis and Tsikliras, 2003)
There is a lack of information on biological traits of brown trout in Iran
Summary
The brown trout, Salmo trutta, is a native species for Iran. This species prefers cold upstream and mountain lakes with rich oxygen contents and feeds from small fishes and aquatic insects. The study of weight-length relationship and condition factor are useful because they have been used for the comparison of species growth between regions (Koutrakis and Tsikliras, 2003). There is a lack of information on biological traits of brown trout in Iran. The aim of present study was to provide information about basic biological traits of brown trout in six main rivers in north part of Iran. It was hypothesized that the lengths of brown trout correlate with sizes of their habitats
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