Stock assessment of the Pick Perch (Stizostedion lucioperca) in the southern coastal waters of the Caspian Sea

Pick Perch is one of the most valuable fish species of the Caspian Sea, caught commercially each year. During the fishing season of the years 2000-2001, 18 tons of the fish comprising 11% of the total commercial catch was caught in the southern Caspian Sea. Of this around 12 tons was caught using beach seine (12 tons) in the coastal waters and another three tons in Anzali Lagoon and the rest is calculated to be the amount of the fish caught without license and recording.
The mean fork length, weight and age of the species as 28.11±3.12cm, 253±91.1 grams and 3.09±0.72 years respectively. Also the length-weight relationship calculated as W= 0.035*L2.65 (R2 = 65.66%, N= 106). The range of age groups in the catch was 2 - 5 years of which the age groups 2 and 3 comprised 78.5% of the catch. I calculated the Von Bertalanffy growth equation for the fish as:Lt =52.5*[1-exp-0.158*(t+1.852) ].
The instantaneous rate of total, natural and fishing mortality coefficients were 0.95 year-1, 0.31 year-1 and 0.64 year-1 respectively. The calculated exploitation ratio was 0.67. Using the cohort analysis, I estimated the biomass of the species as 31.56 tones.
The Gulland's formula used to assess the minimum sustainable Yield of the fish as 13.89 tones which is lower than the total catch of the fish. Fishery return coefficient of the fish was measured as 2.87%.