Standard gill net survey date on the distribution and abundance of the inshore fishes of Lake Kariba along the Zimbabwe shore showed that the Mochokid SYNODONTIS ZAMBEZENSIS (squeaker) contributed 40% of the total catch (fresh weight). Special emphasis is placed on analysis of biological data of this catfish, which unlike the other inshore fishes, inhabits deep as well as shallow waters and has increased in abundance since the establishment of the lake. Results also showed that S. ZAMBEZENSIS as well as some smaller species such as BRYCINUS LATERALIS, BARBUS UNITAENIATUS and PSEUDOCRENILABRUS PHILANDER contributed significantly in terms of index of relative importance (IRI). Along the shore between fished and unfished areas, species relative abundance was found to be more or less the same but mean lengths of species caught in commencial nets were significantly lower in the fished areas.

The abundance of S. ZAMBENZENSIS was seasonally correlated (0.78). Seasonal depth changes in distribution were observed and a peak in abundance occurred in April in the shallower waters. Size distribution was however inversely related to depth, with the largest squeakers occurring in the 0-3 meter depth zone. Oxygen depletion in the hypolimnion and breeding behaviour seem to cause the seasonal migration that affected distribution.

Aspects of fish stock assessment such as fecundity, growth and mortality were evaluated for S. ZAMBEZENSIS. Selectivity analysis showed that the gear used (Lundgren monofilament gill nets) for sampling covered the whole population size range enabling the data to be used for growth analysis. There were no large differences in growth parameter results obtained using LFA and vertebrae growth rings. The L-Infinity (L-i) for males is 33.6 centimeters (cm) and 31.1 cm, and L-i for females is 38.3 and 38.2 cm respectively, while the K values are 0.19 and 0.21 males, and 0.24 and 0.26 for females. S. ZAMBEZENSIS females were found to be very fecund and attained fifty percent maturity (L-50%) when they are around three years of age. The breeding activity for males was very low, never exceeding 10% throughout the year and as a result they never attained a fifty percent maturity, as shown on the maturity ogive where the L-50% length was beyond the L-i.

Stomach contents analysis confirmed that S. ZAMBEZENSIS is euryphagous and fed on the benthos as well as the surface water depending on the availability of preferred food. It is an omnivorous species, preferring the gastropod Lymnaea Natalensis (59% IRI) and Chironomidae larvae (33% IRI) mostly. S. ZAMBEZENSIS diet is elastic, evidence showed that it switched its preferred food to certain insects and this was related to the emergence of those insects. Fish and plants were fortuitous in the diet.

The concept of biological interaction between species, covering predation and food consumption were modelled for Lake Kariba using ECOPATH II. All findings pointed to a large biomass of S. ZAMBEZENSIS which is very much under-exploited commercially. Hence its low total mortality of 0.55 - 0.86 per year.

Results from the study suggest that the observed pattern of distribution and size is due to a complex interaction of biotic factors such as food distribution and abiotic factors such as oxygen and rise in water level. In conclusion, the success of S. ZAMBEZENSIS was attributed to its wide niche, increase in gastropod populations, anti-predatory mechanisms and currently negligible fishing mortality.