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Reproductive biology of 803 specimens of Chrysichthys auratus from Damietta branch of the River Nile, Egypt was studied between January and December 2010. The overall sex ratio (M:F = 1:1.18) was significant at P

The present study sheds light on the growth pattern of the elephant snout fish (Mormyrus kannume, Mormyridae) in the Damietta branch of the Nile during the period from January to December 2010. This is done through studying the biometric characters, length–weight relationship, condition factors, growth performance index as well as the natural mortality. The linear regression for 15 morphometric characters in total length and 4 morphometric characters in head length was applied. The higher coefficient of the characters’ determinations which fit best was also applied. Five meristic characters were determined (dorsal fin rays, 49–69; pectoral fin rays, 12–15; ventral fin rays, 6; anal fin rays, 17–21 and vertebrae, 49–52). Fish length varied between 14.0 cm and 43.0 cm TL with a modal length range from 19 to 22 cm representing 61.36% of the fish sample. A length–weight relationship using the total weight was found to be LogW = −2.2218 + 3.063LogL (R2 = 0.997) and using the gutted weight was LogW = −2.1549 + 3.003LogL (R2 = 0.995) hence exhibiting isometric growth. The average condition factors for different lengths were 0.76 ± 0.06. The chi-square of the overall sex ratio (male:female = 1:0.42) was significant at P

This article aimed to assess the species composition, seasonal distribution, length–weight relationships (LWRs); age composition and the non-indigenous species (Lessepsian species) of the non-target catch obtained by commercial bottom trawlers operated between Al Agamy and Abu Qir (west and east off Alexandria, Egypt). A total of 44 economic species and 45 non-economic species were recorded forming 51.2 % and 48.8 %, respectively of the total examined catch weight during the whole year 2014. The high diversity indices were recorded in spring and summer for economic species. The recruits of nine mostly important economic species in the region were recorded. Four species namely: Spicara maena; Pagellus acarne; Trachurus picturatus and Nemipterus japonicus had lengths between 8.5 and 10.9 cm appeared in spring while other five species namely: Pagellus erythrinus; Boops boops; Serranus hepatus; Spicara smaris and Mullus barbatus had lengths ranged between 7.00 and 11.00 cm appeared in summer. The exponent “b” of the length–weight relationship for 22 species varied between 2.1316 and 3.2415 for economic species and ranged between 2.6341 and 3.4406 for non-economic species. Age analysis showed that the life span of the majority of economic species is two years. The number of Lessepsian species recorded in this area was 22 species of which eleven were economic.

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.