Morphometric and Meristic Analysis of Lates niloticus (Linnaeus, 1758) (Teleostei: Latidae) from Lake Nasser and the River Nile, Egypt

The present study aimed to provide data on the effect of the High Dam on the morphological and meristic characteristics of Lates niloticus from two different Egyptian freshwater environments; Lake Nasser in Aswan City and the River Nile in Assiut City, Egypt. Therefore, twenty-six specimens of L. niloticus were collected from each site. The morphological characteristics and related index ratio to the standard length were determined. The results showed that the fish specimens from Lake Nasser were longer (mean 30.5± 8.8cm TL) than those from the Nile River (27.6± 4.2cm TL), and a strong correlation was detected between the different morphometric parameters to the standard length with different morphometric indices. The t-test showed significant differences between the total length, predorsal fin distance, postdorsal fin distance and prepectoral fin distance (P< 0.01). The means of indices related to the standard length, total length, predorsal fin distance, postdorsal fin distance, and prepectoral fin distance of L. niloticus collected from Lake Nasser are about 118.2, 44.2, 81.6, and 32.9 % SL, respectively, and are larger than the same indices of L. niloticus collected from the Nile River in Assiut City (109.3, 40.5, 77.0 and 26.7% SL, respectively). On the other hand, the other morphometric and all meristic parameters for the two locations showed insignificant differences. These findings suggest that differences in some morphometric characters may be due to the biometry of the species being influenced by the differences in the environments of Lake Nasser and the River Nile. Therefore, the continuous study of morphological features, that are related to the dams' constructions, environmental changes, as well as genetic confirmation, is recommended.