Growth and mortality of brown trout, Salmo trutta fario in Lar dam, Iran

    The length-weight relationship, age, growth parameters, sex ratio, mortality and exploitation rate of Salmo trutta fario were determined in Lar dam. The sex ratio (male: female) was 1:1.84 which differed significantly from the expected 1:1. The length-weight regression was (females) and (males) indicating a negative allometric growth for both sexes. Growth parameters were estimated as L∞ = 45.0 cm, K = 0.27 yr-1, t0 = -0.23 yr. The instantaneous coefficients of natural, total and fishing mortality were estimated as 0.40 yr-1, 0.75 yr-1 and 0.35 yr-1. The results showed that S. trutta fario is moderately a rapidly-growing species in Lar dam. The exploitation rate was 0.47. Therefore, the population appeared to be in good condition in 2004.