Observations on the fish and prawn seed resources of the Gulf of Kutch and their utilization in aquaculture

The characteristics of the fish and prawn seed resources of the Gulf of Kutch are described. Results of experiments conducted in a primary low saline reservoir of a solar salt works to study their utility for aquaculture are reported. The prospective role of aquaculture in augmenting fish production along the coast is also discussed.

Observations on the artificial fertilization of eggs and larval rearing of the grey mullet, Mugil cephalus L.

The results are presented of attempts to artificially fertilize Mugil cephalus eggs in the Philippines. Embryonic development is outlined and rearing of the larvae described. Mass mortality occurred during week 3 of rearing.

Some observations on the growth and cyst production characteristics of the brine shrimp Artemia sp. (Gujarat strain) in pond culture and its potential for import substitution

Experimental culture of the brine shrimp Artemia sp. (Gujarat strain) and production of cyst is discussed. The qualitative and quantitative aspects of the cyst and its economic potential for import substitution are highlighted.

Observations on the taxonomy and biology of Lates (Cuvier 1828) in Lake Albert

Both in terms of commercial landings and biological importance, the Nile Perch is one of the most prominent fish in Lake Albert. It can bear considerable further exploitation, is the source of stockings elsewhere, and it is, therefore, important to know whether more than one species is being dealt with, and, if so, what differences there are in the ecology of the different species.

Observations on the influences of codend mesh size on bottom trawl catches in Lake Victoria, with emphasis on the Haplochromis population

Codends of four different mesh size" were compared during exploratory bottom trawling on Lake Victoria. Small mesh sizes (19 and 38 mm) generally caught greater quantities of fish than large mesh sizes (64 and 76 mm) with haplochromis species responsible for the difference. The differences in catch rates were most pronounced where dense concentration of small haplochromis were found. This was generally in shallow water since the average size of haplochromis tends to increase with depth. Catch rates for species other than haplochromis were fairly similar for the codends tested, although there were indications of lower catches in small mesh coderlds fished through dense haplochromis concentrations. For haplochromis fished with 64 and 38 mm eodends, the estimated 50% retention lengths were 13.6 and 8.0 cm, respectively. The predicted value for the 19 mm codend was 4.5 cm.

Observations on the biology of Nothobranchius guentheri (Pfeffer) (Cyprinodontidae), an annual fish from the coastal region of East Africa

Nothobranchius guntheri is found in seasonal pools and streams in the coastal region of Tanzania. A population recurring annually in a pond near Kilosa has been studied. Growth in length was rapid and maximum mean lengths were attained within 11-12 and 7-8 weeks of hatching by males and females respectively. Males grew larger and exhibited wider variation in length than females. N. guentheri shows clear sexual dichromatism. No significant inequality in the sex ratio was found. Females with ripe eggs were found 7-8 weeks after hatching. Spawning continued throughout adult life and fecundity increased markedly with increasing length. In laboratory aquaria, aggressiveness between adult males was noted and females were actively driven on to the substratum preparatory to spawning. The diet of the fish pond consisted chiefly of aquatic and terrestrial insects, of which midge larvae and pupae were the most common. N. guentheri is exploited by man in the aquarist trade and for the biological control of mosquitoes. An extended redescription of the species is appended which includes N. melanospilus (Pfeffer) as a synonym.

Preliminary observations on the feeding of Tilapia nilotica Linn. in Lake Rudolf

Tilapia nilotica is commercially very important throughout the Ethiopian region including the major rivers in West Africa, the Chad basin, the Nile and its associated lakes. The Tilapia fishery of Lake Rudolf is at present small, but potentially important, particularly on the eastern shores of the lake where fishing intensity is low. Preliminary results from observations on the feeding of Tilapia nilotica in Lake Rudolf are presented. The fish exhibit a regular diurnal feeding rhythm, commencing between 05.00 hours and 08.00 hours and ceasing between 14.00 hours and 18.00 hours. The largest fish appear to feed longer. Quantitative estimates of the daily food intake indicate less material to be ingested than by populations in other lakes. The lysis of algae, intestinal pH and food material are also investigated.