Biometric assessment and reproductive biology of common carp (Cyprinus carpio var. communis) in Lake Arekit, Ethiopia: fish management implication

Biometric measurement provide crucial information on fish growth and aquatic habitat well-being. This study offers the first comprehensive elucidation on biometric indices and reproductive biology of Cyprinus carpio var. communis in Lake Arekit (Ethiopia). A total of 209 fish were collected (ranging between 8.8 and 51.3 cm in total length (TL), while 16.99–2,498.3 g total weight (TW)) using gillnets during June 2022 to May 2023. The overall sex ratio (male, M; female, F) was 1:0.66 and significantly varied from the hypothetical sex ratio (1:1) (χ2 = 8.85, p < 0.05). The length-weight relationship of C. carpio var. communis was TW = 0.0392 × TL2.792 with a ‘b’ value of 2.792, which indicated a negative allometric growth pattern with r2 values of 0.99. The condition factor of C. carpio showed significant variations between sex and months, with a mean value of 4.01 ± 0.49 (p < 0.05) while the Fulton condition factor showed no significant difference between sexes and months. Fecundity variation was better correlated with length (AF = 152.06 × TL1.879, r2 = 0.795; p < 0.05) than with weight (AF = 1541.2 × TW0.651, r2 = 0.6523; p < 0.05). The fecundity ranged between 46,214 and 210,271 eggs/fish, with a mean of 127,516.6 ± 53,447.1 eggs/fish. Breeding activity peaks in March and June, coinciding with a rise in water temperature. The size at first maturity (Lm50) was found to be 32.28 cm and 28.83 cm of total length for females and males, respectively. Our findings would be very beneficial in planning the sustainable management of C. carpio in Lake Arekit and nearby ecosystems.