Some Observation on the Age and Growth of Tilapia zillii (Gervais, 1848) in Umhfein Lake (Libya)

Original article


A. A. Hadi

Biology Department, Faculty of Science, Omar El-Mukhtar University, Tobruk, Libya

Journal of Science and Its Applications Vol 2, No 1:12-21 (March 2008)


Age determination and annual increase in both length and weight of Tilapia zillii (Gervais, 1848) were investigated. Specimens studied ranged from 15 to 27 cm in total length and aged from one to four years. Age determination and annual increases in both length and weight were made by examination and measurements of scales. A linear
relationship between the body length and the anterior radius of scale has been established with an intercept of 5.1683, where the annuli first appeared on the scales in April. The length-weight relationship was estimated by the equation W = 0.011 L3.2279. The condition factor, K for the different size groups ranged between 1.9336 and 2.3646. The
maximum growth in length was attained in the first year, while an intensive growth in weight was observed in the fourth year. The theoretical growth in length and weight was accurately described by Von Bertalanffy’s model, using the back-calculated lengths. Values of L∞ = 28.81 cm, W∞ = 565.78 gm, K = 0.23458 & t0 = – 1.73748 were

Keywords: Age; growth; Tilapia zillii; length; weight; condition factor; growth performance.