Fishery biology of Catfish (Chrysichthys auratus, Family: Bagridae) from Damietta branch of the River Nile, Egypt

The study of fishery biology of Chrysichthys auratus from Damietta branch, Egypt showed that the population has SL range of 7–20 cm, L′ = 11.85 cm. Males represent 45.90% and females 53.98% of the population. Length–length and length–weight relationships were analyzed for males, females and combined sexes. It was: SL = −0.6231 + 0.8402 TL and Log W = −1.6253 + 2.9832 Log SL for combined sexes, respectively. The highest values of condition factor were obtained in July, August and September for both sexes. The mean value of (K) for males was higher than those of females in all different lengths. Age was assessed by Bhattacharya’s (1967) method from length frequency data to estimate the von Bertalanffy growth parameters (L∞ = 26.53 cm, K = 0.214 and to = −1.569). The individuals of this species live for about 4 years and the first age dominates the population. The growth performance index in length (ФL) and weight (Фwt) was estimated as 2.18 and 1.11, respectively. The mortalities were computed as: Z = 1.44, M = 0.60 and F = 0.84. The exploitation rate was estimated as Ecur = 0.58. Length at first capture (Lc) was 9.66 cm at age 0.54 years. Length at recruitment (Lr) was 8.49 cm and age 0.35 years. It was found that the stock of Chrysichthys auratus in Damietta branch was rationally exploited.