Age, growth and reproduction of largemouth bass, Micropterus salmoides, in Lake Manyame, Zimbabwe

Abstract

A total of 478 largemouth bass, Micropterus salmoides (Lacépède, 1802), was sampled between September 1997 and July 2001 using hook-and-line in Lake Manyame, a water supply reservoir situated outside Harare, Zimbabwe. Male fish dominated the samples, possibly an effect of aggressive behaviour towards the sampling gear used. Ages, determined from sectioned sagittal otoliths, ranged from one to nine years with 94% of the sample being between one and four years of age. An annulus was deposited in late-winter/early spring. Female fish, despite being the largest fish sampled, were found to grow at a significantly slower rate than males. Growth was modelled with the von Bertalanffy model as  L(t) = 37.22(1–exp(–0.66t)) cm SL for males, and L(t) = 48.16(1–exp(–0.41t)) cm SL for females. All fish matured after one year, thereafter they spawned over a four-month period between July and October. Reproductive activity peaked in August. Largemouth bass has successfully colonized freshwater bodies in southern Africa where it has been introduced, causing significant ecological damage to the indigenous ichthyofauna. Given its ability to grow to a large size, and live to an old age and to breed successfully, further introductions should be viewed with extreme caution.

Keywords: annulus formation, von Bertalanffy growth model, periodic regression, invasive bass species