Study on the effects of three fishing baits on the catch composition of malian traps in Lake Kainji

The studies on the effects of three fishing baits on the catch composition of Malian traps in Lake Kainji were investigated. The traps were set between Monai and Taafa fishing villages in the Southern basin of the lake, baited with their respective treatment and were inspected daily for twelve days. A total of 218 fish were caught, of which the highest (54.59%) was caught by corn bran, while the lowest (11.01%) was caught by stomach content and rice bran caught 34.4%. The fish caught comprised of 15 species belonging to 8 families. There was no significant different (P>0.05) in the catch of the various baits. The weight also followed the same trend as the number of fish caught. However, both baits showed better efficiency for Alestes baremose. Tilapia zilli, S. galilaeus, Oreochromis niloticus, Labeo coubie and Distichodus rostratus than other species caught. There was a wide range between the inimum and maximum size of species caught, which showed the efficiency of the traps in capturing small size, juveniles and the adult of large fish species due to small mesh size (1") net-cover of the trap. Recommendations were made on the use of corn and rice bran as baits enhancing catch efficiency for fishes such as O.niloticus, T. zilli, T. galilaeus and D. rostratus

Effects of some environmental factors on the fecundity of Tilapia species (Family Cichlidae) in Kigera Reservoir, New Bussa

The effects of some environmental factors on the fecundity of Tilapia species (Family Cichilidae) was carried out at the Kigera dam. Four Tilapia species caught were Tilapia zilli, Hemichromis fasciatus, Sarotherodon galilaeus and Oreochromis niloticus while the environmental factors considered were water temperature, Dissolved Oxygen, pH value, level of rainfall and rate of sunshine and range of time. 43 fish comprising of 25 male with (58.1%) and 18 females having (41.9%) were studied with 74.42% been sexually matured. Both high levels of rainfall and dissolved oxygen favoured fecundity. The spawning peak occurred in (July), environmental factors monitored indicated that dissolved oxygen ranges from 3.7 to 4.45mg/lit rainfall ranges from (34.90mm to 237.80mm) sunshine ranges from (5hrs-8hrs) and pH ranges from (7.35-7.45). The spawning of these species in their natural or hatchery condition is therefore best achieved during the peak of raining season

The changing ecosystem of Lake Victoria, East Africa

Dramatic changes are occurring in the Lake Victoria ecosystem. Two-thirds of the endemic haplochromine cichlid species, of international interest for studies of evolution, have disappeared, an event associated with the sudden population explosion of piscivorous Nile perch (Lates: order Perciformes, family Centropomidae) introduced to the lake some thirty years ago. The total fish yield has, however, increased 5-fold from 1970 to 1990, but this yield is now dominated by just three fish species: the introduced Nile perch (Lates niloticus), Nile tilapia (Oreochromis niloticus), and a small endemic pelagic cyprinid (Rastrineobola argentea); these three have replaced a multispecies fishery. Contemporaneously the lake is becoming increasingly eutrophic with associated deoxygenation of the bottom waters, thereby reducing fish habitats. Conditions appear to be unstable.

Current status of the fish stocks of Lake Victoria (Uganda)

A total of 457 hauls were taken during experimental bottom trawl surveys in the Uganda sector of Lake Victoria between November 1997 and June 1999 to estimate composition, distribution and abundance of the major fish species in waters 4-60 m deep. Fifteen fish groups were caught with Nile perch, Lates niloticus (L.), constituting 94% by weight. Haplochromines and L. niloticus occurred in all areas sampled, while Nile tilapia, Oreochromis niloticus (L.) and other tilapiines were restricted to waters 30 m deep or less. The mean trawl catch rate in the zone where artisanal fishermen operate (i.e. in waters less deep than 30 m was 165 kg hr, of which 93.6% comprised L. niloticus. Species diversity and relative abundance decreased with increasing water depth.

Relative abundance and distribution of fish in Kenyan waters of Lake Victoria

Bottom trawl surveys were conducted in Kenyan waters of Lake Victoria during the period September 1997 and March 1999. The means of fish biomass for the two most important species: Lates niloticus (L.) and Oreochromis niloticus (L.) were estimated at 61.5 kg ha and 4.5 kg ha respectively. There were few L. niloticus greater than 80 cm TL and O. niloticus greater than 50 cm TL, though these species attain maximum sizes of 205 cm and 65 cm respectively. Oreochromis niloticus was mostly found shallower than 5 m though some specimens were encountered deeper than 10 m, suggesting that the species has extended its ecological range. Very low catches were obtained from areas under water hyacinth cover. Water in such areas was turbid with oxygen levels below the critical 3.0 mg L.

Zooplankton - fish interaction in the littoral zone of Nyanza Gulf, Lake Victoria

The zooplankton community of the littoral zone of Nyanza Gulf, Lake Victoria, was studied between June 1998 and June 1999 to identify and quantify various zooplankton groups, and investigate the interactions that occur between them and the littoral fish through the food chain. Zooplankton samples were collected from five stations using a 83 micro-m mesh size plankton net hauled vertically through the water column. Fish samples were obtained by beach seine, except at Gingra (May 1999), where trawl samples were used. Gut/stomach analysis was carried out on the three major commercial species, Lates niloticus (L.), Oreochromis niloticus (L.) and Rastrineobola argentea (Pellegrin).

Aquaculture in Jamaica

Jamaica, with its overfish marine resources, has become a major tilapia producer in Latin America led by a small number of large farms practicing tilapia culture with considerable commercial success. Across the country, however, aquaculture is typically practiced by a large number of small-scale fish farmers who own less than 1.0 ha of land. Production is constrained by lack of credit, finite land space and suitable soil type, but larger existing aquaculturists are expanding further for overseas markets. Inspired by pioneering tilapia fish culture demonstration projects funded by the USAID and the goverment of Jamaica, fish culture production rose from a few hundred kg of Oreochromis niloticus in 1977, to about 5000 t of processed fish mainly red hybrid tilapia, in 2000. Most of this quantity was exported to Europe and North America.

Pawpaw seed as fertility control agent on male Nile tilapia

To find out if pawpaw (Carica papaya) seeds can induce sterility in male Nile tilapia (Oreochromis niloticus) and to determine if sterility so induced is reversible or otherwise, mature male tilapia of mean weight 40 g were treated for 30 days with a low dose (4.9 g/kg/day) and a high dose (9.8 g/kg/day) of ground pawpaw seeds incorporated into their feed. Fish of similar sizes in the control experiment were fed with feed that did not contain pawpaw seed. The pawpaw seeds induced permanent sterility in the fish that received the high dose, while sterility in the low dose treatment was reversible. Fish in the control experiment spawned two weeks into the experiment and again in the fifth week. Fish in the low dose treatment spawned three weeks after the treatment had been discontinued. Histological sections of the testes showed that pawpaw seeds produced swollen nuclei in the low dose treatment and disintegrated cells in the high dose treatment. The study showed that pawpaw seeds, which are easy to obtain, can be incorporated into fish feeds and used by farmers to control prolific breeding of Nile tilapia.

Approaches to national fish breeding programs: pointers from a tilapia pilot study

Details are given of a framework for developing breeding programmes using experience from the Genetic Improvement of Farmed Tilapias project which focussed on Nile tilapias (Oreochromis niloticus ). The following aspects are outlined: Analysis of targeted production and marketing systems; Breeding goals; Systematic documentation and evaluation of available genetic resources and choice and genetic base; Number of strains; Breeding strategy; Selection criteria and evaluation; Production and dissemination of improved strains; and, social, economic and environmental impacts.

Pig-duck-fish-azolla integration in La Union, Philippines

Three studies on pig-duck-fish-azolla integration were conducted simultaneously in La Union, Philippines. Growth performance of pigs and ducks as affected by different levels of azolla meal in their feed, and that of tilapia (Oreochromis niloticus) under varying stocking rates are presented and discussed.

From drawing board to dining table: the success story of the GIFT project

As compared to crops and livestock, the genetic enhancement of fish is in its infancy. While significant progress has been achieved in the genetic improvement of temperate fish such as salmonids, no efforts were made until the late 1980s for the genetic improvement of tropical finfish, which account for about 90 percent of global aquaculture production. This paper traces the history of the Genetic Improvement of Farmed Tilapia (GIFT) project initiated in 1988 by the WorldFish Center and its partners for the development of methods for genetic enhancement of tropical finfish using Nile tilapia (Oreochromis niloticus) as a test species. It also describes the impacts of the project on the adoption of these methods for other species and the dissemination of improved breeds in several countries in Asia and the Pacific.

A global experiment on tilapia aquaculture: impacts of the Pond Dynamics/Aquaculture CRSP in Rwanda, Honduras, Philippines and Thailand

The Pond Dynamics/Aquaculture Collaborative Research Support Program (PDA/CRSP) is a global research network to generate basic science that may be used to advance aquaculture development. One of a family of research programs funded by the United States Agency for International Development (USAID), the CRSP focuses on improving the efficiency of aquaculture systems. The PDA/CRSP began work in 1982 in Thailand, and subsequently in the Philippines, Honduras, the US and, until recently, Rwanda. At all the sites, the goal is the same: to identify constraints to aquaculture production, and to design responses that are environmentally and culturally appropriate. The research network's global experiment has focused on tilapia (Oreochromis niloticus), although some sites have devoted attention to marine shrimp and other locally significant species. Impact of the network's investigations with tilapia is examined in this article.

Age and growth of three species of Lake Victoria fish determined by means of otolith daily growth rings

The sagittal otoliths of Lates niloticus, Haplochromis obesus, and Oreochromis niloticus from Lake Victoria were examined for daily growth rings using scanning electron microscopy. In the three species the increments were clear and thick enough to allow future studies with light microscopy. The daily nature of the increments seems supported by the rhythmic growth that were found.

Tilapia breeding in ricefields in Vietnam

Results of the studies undertaken for breeding and nursing Nile tilapia (Oreochromis niloticus) in ricefields in Thai Binh province in Vietnam during the years 1995-96 are briefly presented in this paper.

On-farm trials with rice fish cultivation in the west Kano rice irrigation scheme, Kenya

The viability of integrating rice farming with fish culture was studied in ten (10) rice plots. The on-farm research was done during one rice-growing season starting May 2003. The rice variety used was IR 2793-80-1 while the fish species was the Nile tilapia, Oreochromis niloticus. The fish culture period lasted 77 days. An average fish production of 132.4 kg/ha was obtained. The mean recovery rate of tilapia was 43 per cent. Total rice yield from the fields stocked with fish was lower than from unstocked fields. The net returns were not significantly different.