Age and Growth of the Mozambique Tilapia, Oreochromis mossambicus Introduced into the Genka River on Okinawa Island

Abstract

The Mozambique tilapia, Oreochromis mossambicus is a species intentionally introduced as a source of low cost protein or as bait fish for skipjack angling in Okinawa Prefecture. This species has recently been found to breed widely in natural rivers of the Ryukyu Islands. The growth and life history of O. mossambicus were studied between May 1996 and August 1997 at the Genka River on Okinawa Island, Japan. Analysis of the marginal increments of 263 otoliths showed an annulus was formed between May and July, corresponding to the reproductive periods. Maximum ages of 14 years for females and 8.5 years for males were obtained for the Genka River population, and patterns by the von Bertalanffy formula growth were described as Lt=276.9 {1-exp (0.63 (t-0.38) ) } for males and Lt=237.6 {1-exp (-0.26 (t+1.32) ) } for females, respectively.