Growth of juvenile tilapia, Oreochromis niloticus L. from Lakes Zwai, Langeno and Chamo (Ethiopian rift valley) based on otolith microincrement analysis

Age and growth of juvenile tilapia, Oreochromis niloticus, from Lakes Zwai, Langeno and Chamo (Ethiopia) were studied from microincrements in otoliths . Growth in length was best described by the Gompertz model. Average growth rate of the fish was most rapid in Lake Chamo (0.39 mm . day(-1), 1.14% . day(-1)), intermediate in Lake Zwai (0.20 mm . day(-1), 0.72% . day(-1)) an d slowest in Lake Langeno (0.16 mm . day(-1), 0.62% . day(-1)). Similarly, back-calculation from otolith increment widths gave growth rates of 0.28 to 0.43 mm . day(-1), 0.15 to 0.32 mm . day(-1) and 0.11 to 0.28 mm . day(-1) for Chamo, Zwai and Langeno fish, respectively. In addition, Fulton's cond ition factor was largest for Chamo tilapia and smallest for Langeno tilapia ; the difference between fish from Langeno and Zwai was small. Rapid growth of juvenile O. niloticus in Lake Chamo was attributed to warm temperature and better food quality.