| Abstract: |
Bagrid catfish, family Bagridae form a well defined group comprising seven species belonging to four genus.Bagrus bayad and Bagrus docmac are the only representatives of genus Bagrus in the River Nile waters.The present study deals with the biology (systematics, biometrics, growth, reproduction and feeding) of Bagrus species (Bagrus bayad and Bagrus docmac) from the Egyptian Nile waters of Beni-Suef area. In addition, the analysis of commercial catch of BagruAnalysis of morphometric regressions of both species indicated that Bagrus bayad and Bagrus docmac are more related species.Concerning the meristic characters, the present results showed that the confusion may cause in the identification of both species since the comparison between Bagrus bayad and Bagrus docmac show approximately no differences in the meristic characters.Concerning the age and growth of Bagrus species, it was found that the calculated lengths at age obtained for Bagrus bayad (combined sexs) were 29.3, 37.5, 44.3, 50.6, 55.8, 60.4 and 64.6 cm for the first to seventh age group respectively. For Bagrus docmGenerally for both Bagrus species, the annual increments of growth in length are larger in the first year of life. This increment shows a tendency to decrease as fish grows older.From the study of the length-weight relationship for Bagrus species, a curvilinear relationship was represented by the following formulas:Log W = - 2.3188 + 3.0776 Log L (for Bagrus bayad)Log W = - 2.1549 + 3.0489 Log L (for Bagrus docmac)Investigation of coefficient of condition of Bagrus bayad and Bagrus docmac revealed that coefficient of condition of Bagrus bayad (0.6498) is lower than that of Bagrus docmac (0.8461). For both species, coefficient of condition recorded higher values in Estimation of the calculated weights at age was occurred by using length-weight relationship for both species as follows:For Bagrus bayad, the calculated weight at age obtained were 159.1, 335.4, 559.4, 853.2, 1141.6, 1457.6 and 1788 gm for the first to the seventh age group respectively.For Bagrus docmac, the calculated weight at age obtained were 194.6, 385.45, 656.98, 989.75, 1364.63, 1754.65 and 2166 gm for the first to the seventh age group respectively.Theoretical growth was calculated by applying von Betalanffy equation. For Bagrus bayad L∞ was 92 cm, where W∞ was 5308 gm, while for Bagrus docmac L∞ was 97.6 cm, where W∞ was 8142 gmMales attain first sexual maturity at length slightly smaller than those of females for both species. For Bagrus bayad, Males attain first sexual at 56 cm (3 years) while that of females was 61 cm (4 years). For Bagrus docmac, males attain first sexual maFor studying monthly variation of maturity stages and gonadosomatic index it was found that for Bagrus bayad the spawning season extends from April to August with a peak in July. On the other hand, the spawning season of Bagrus docmac extends from April tThe absolute fecundity of Bagrus bayad ranged from 47202 to 180830 eggs for fishes of 36 to 72 cm forked length, while for Bagrus docmac it varied between 27250 and 92205 eggs for fish ranging between 41 and 67 cm forked length.Concerning food and feeding habits of Bagrus species, it was found that the intensity of feeding was high in spring for both Bagrus species since they had maximum filling index in that time. Analysis of the food ingestion for Bagrus bayad and Bagrus docmaAnalysis of the size composition of Bagrus bayad and Bagrus docmac shows that the average length for Bagrus bayad was found to be 43.47 cm, while that of Bagrus docmac was found to be 47.99 cm.Analysis of the age composition of Bagrus bayad and Bagrus docmac shows that both species were predominated by the fishes of age group III followed by fishes of age group II.The study of basic assessments of fish stock for Bagrus bayad and Bagrus docmac showed that Bagrus bayad had survival rate of 49 % while Bagrus docmac had survival rate of 51 %. The values of natural mortality of Bagrus bayad was comparatively higher (M =
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