Length-frequency data collected from fish landings on Lake Naivasha were used to estimate the growth parameters: total mortality (Z), growth performance index (¢'), exploitation rate and recruitment pattern in Oreochromis leucostictus. The asymptotic length (Lee) was 38 em and K 0.48 yr -I. Z was estimated as 3.5 yr -I, M was 0.19 yr -I, F was 2.6 yr .1 and E of 0.74. Recruitment occurs throughout the year, with a peak in January to March, while entry into the fishery occurs at a mean length of 15.9 cm.
Existing restriction on the maximum number of gill nets allowed per fishing licence (10 per boat) and a minimum mesh size (10 cm) inthe lake are not adhered to. Poaching using illegal mesh size nets as small as 5 em and use of more than 10 nets per boat are common in the lake.