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The study of the age and growth of fish is fundamental for understanding the general biology of the species and in particular its population dynamics. The age and growth of two Carangid species Carangoides bajad and Caranx melampygus from the Egyptian Red Sea, Shalateen region (Elba National Park) were studied based on the scale readings using a non-linear back-calculation method. A total of 1103 specimens (145-515 mm in SL) of C. bajad and 795 specimens (145-631 mm in SL) of C. melampygus were aged and their maximum life span was 8 and 12 years, respectively. The most dominant age group in the catch was age groups II (45.36%) for C. bajad, and age group 0for C. melampygus (21.6%). The von Bertalanffy growth parameters were L∞ = 576.88 and 701.08 mm for C. bajad and C. melampygus respectively, while K = 0.24 and 0.17 year-1 for the two species respectively. It was found that C. melampygus was heavier and characterized by a higher growth rate than C. bajad for the same length and age. These data are the inputs of the analytical models used to achieve the wise management of this potential fishery. [ABSTRACT FROM AUTHOR]

The present work has been suggested to screening and documenting the diversity of scale characteristics of three Epinephelus species, namely: E. bleekeri, E. coioides and E. latifasciatus from the Arabian Gulf at Kuwait. Scale characteristics, its detailed structure and superficial ornamentation were studied in terms of morphology and Scanning Electron Microscopic techniques. A wide spectrum of size-free interspecific variations was recorded concerning the surface morphology, shape of interradial tongues and the first circulus, the interradial circuli, most outer lateral circuli, inner lateral circuli, denticles, interradial and intercircular grooves, segmentation and granulation pattern of the caudal field and the shape of ctenii. The results of the present study has clearly indicated the potential application of scale shape variation in identification of Epinephelus species; and also, revealed that the qualitative characters of the scales of the three Epinephelus species studied exhibited species-specific valuable taxonomic characters for each species and indicated that such qualitative characters are genetically fixed and more stable. [ABSTRACT FROM AUTHOR]

The fishery status of two carangid species; Carangoides bajad and Caranx melampygus from Shalateen fishing area, Red Sea, Egypt has been evaluated. Yield per recruit of the two species as a function of different values of fishing mortality coefficient, age at first capture and natural mortality coefficient was estimated. For C. bajad it is found that, the current fishing mortality coefficient (1.34 / y), age at first capture (0.35 y) and natural mortality coefficient (0.34 / y) give a yield of (304.8 g) per recruit. While for C. melampygus, the current fishing mortality coefficient (1.75 / y), age at first capture (0.35 y) and natural mortality coefficient (0.25 / y) give a yield of (675.63 g) per recruit. Yield per recruit for C. bajad and C. melampygus showed that, the maximum (Y/R) was obtained at Fmax = 0.5 and 0.8 for C. bajad and C. melampygus respectively. For management purposes, the fishing mortality which is related to the fishing effort of C. bajad and C. melampygus should be reduced by at least 50% as well as the length at first capture which is related to the mesh size should be raised to the length at first maturity to maintain this valuable fishery. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the genotoxic potential of chemicals present along the course of the river Nile using frequencies of micronuclei (MN) and nuclear lesions (NL) in erythrocytes of Nile tilapia Oreochromis niloticus niloticus and African catfish Clarias gariepinus, as biomarkers. Results showed that most of the physicochemical parameters detected and heavy metal concentrations were significantly higher in the water collected from the estuaries of the river Nile compared to other sites of the upper Nile. The frequencies of MN and NL in peripheral blood erythrocytes of Nile tilapia and African catfish were significantly higher in estuary sites in Damietta and Rosetta compared to upper sites. The lowest level of genotoxicity was observed at two sites (Aswan and Kena), considered to be less contaminated. Our results suggested that higher frequencies of MN and NL determined at Damietta and Rosetta sites may be indicative of damage produced by pollutants in these areas. The most remarkable result was that MN and NL frequencies appear to be strongly related to water quality at different sites examined, indicating that MN frequencies may serve as a reliable biomarker for testing genotoxicity in situ. The positive correlation between MN and NL induction suggested that NL may be a useful complementary assay for genotoxicity analyses when fish are used as experimental animals. It was also found that seasonal variations in MN and NL frequencies might contribute to a better understanding of genotoxic responses in the field. The use of fish as indicator organisms for monitoring the presence of genotoxic-inducing contaminants in the environment seemed justified because the effects of exposure to a complex mixture such as river water were obtained. Nile tilapia appears to be a more suitable bioindicator species than African catfish in studying genotoxic chemical pollution in the river Nile attributed to a higher sensitivity. [ABSTRACT FROM AUTHOR]