Population dynamics of Carasobarbus luteus in Shadegan International Wetland, Iran

Abstract

Estimation of length at maturation and spawning time and determination of fishing prohibition time and optimum length for catch are of important information about a fish species. Seasonal samplings were conducted over a year to study population dynamic of Carasobarbus luteus in Shadegan wetland. Samples were collected from five sampling stations in Shadegan wetland (Salmane, Rogabe, Khoroosi, Mahshahr and Atish) from April to March, 2014-2015. From total number of 1600 samples, 269 individuals were male and 1331 individuals were female. Length-weight relationships were W=0.0136L3.0124 (R2=0.92) for males; W=0.0136L3.0117 (R2=0.91) for females, showing isometric growth pattern. Condition factor (K) was calculated to be 1.308±0.15 and 1.368±0.17 for the males and females, respectively, showing significant difference between the genders (P<0.05). Overall, K coefficients of the males were lower than those of the females, which the highest and lowest values were related to winter and spring, respectively. Also, the results show that this species spawns in April-July with a long spawning period and sexual dormant period in autumn to early winter. Length at maturation was 152, 139 and 150 mm for males, females and whole specimens; whereas, weight of matured fish was 42 and 100 g for the males and females, respectively. Growth indices including L∞, growth coefficient and t0 was 305 and 301 mm, 0.67 and 0.55 per year and 0.23 and 0.29 for the males and females, respectively. Natural mortality, fishing mortality, total mortality, Munro Ф' and coefficient of exploitation was 1.22 and 1.02 per year, 1.61 and 1.45 per year, 2.83 and 2.47 per year, 2.79 and 2.72, and 1.61 and 1.45 per year respectively for the males and females. Von-Bertalanffy equation for the males and females was Lt =305(1- exp (-0.67(t +0.23))) and Lt =310(1- exp (-0.55(t +0.29))).