Age, growth and sex ratio of the Catfish Malapterurus electricus (Gmelin, 1789) from the Large Reservoir, Lake Nasser, Egypt

The Electric Catfish, Malapterurus electricus, a species from order Siluriformes is widely distributed in Africa and occurs in all freshwater systems. It is a commercial species in Nasser Lake fisheries, with an average annual catch of about 130 MT. Limited biological data are available on this species.  In the present study, random samples of M. electricus were monthly collected from the commercial catch of the lake's main landing sites during 2019. A total number of 538 specimens of M. electricus were collected for biological investigations. Results revealed that the total length ranged from 24.0 to 51.5cm, and the total weight ranged from 192.4 to 2785.9g. The length-weight relationship, with a statistically highly significant coefficient (R²= 0.9127) showed a tendency of the b-value (2.89) towards negative allometric growth. The estimated mean condition factor (Kc) was 1.483 ± 0.238 for combined sexes. Vertebrae were used for age determination, and six age groups were identified. Age groups III⁺ and IV⁺ were the most dominant in the catch since they constituted about 54.3% and 30.7%, respectively.  The sex ratio revealed that the male percentage was higher than that of females (60% males to 40% females) in all samples. The spawning season of M. electricus extended from July to October during the study period. This study afforded biological data about electric catfish in Lake Nasser to sustain the catch and provide necessary information to benefit the exploitation of its resources.