The reproductive biology and artificial breeding of ningu Labeo victorianus (Pisces: Cyprinidae)

Lake Victoria, the largest tropical lake, has faced an unprecedented assault on its ecosystem through a variety of anthropomorphic causes that include the introduction of Nile perch Lates niloticus and over-fishing. As a result there have been species extinctions and declining fish population trends. This thesis explores options for reversing these declining population trends and the restoration of collapsed fisheries based on indigenous non-cichlid species. A candidate species was chosen - the cyprinid fish Labeo victorianus. This thesis studied various aspects of L. victorianus' reproductive biology in two geographically distant populations. These included general reproductive patterns in relation to proximate environmental conditions, gonadal development and recrudescence, sex development, characterisation of genetic and morphological diversity, and induced spawning. Fish from both populations were found to be potamodrometic, and highly fecund, iteroparous spawners. L. victorianus was also shown to be an undifferentiated gonochorist, where all individuals pass through an intersexual juvenile stage prior to differentiation, and maturation to either sex. Sexual maturity was attained at a significantly larger size within the Kagera River than that of Sio River fish – possibly as a response to genotypic and/or phenotypic differences. Spawning seemed to be synchronised with rainfall in Kagera River - a pattern that was not strictly adhered to with the Sio River. Thorough microscopic investigation of recrudescence patterns indicated there was uninterrupted spawning in fish from the Kagera River followed by Type I oocyte atresia. In contrast, there was a 90% spawning failure, as characterised by Type II oocyte atresia, within the Sio River population. Aspects of spermatogenesis and sperm ultrastructure using light- and ultramicrotomic methods are described. Although the populations had varying reproductive biology parameters and were morphologically distinct, they remained undifferentiated at the mitochondrial level. Both populations were characterised by low nucleotide diversity – a feature attributed to a bottleneck event. The option of captive breeding was explored by conducting induced spawning experiments. Success was only achieved with a decapeptide Gonadotropic Releasing Hormone ([D-Arg⁶, Pro⁹-NEt])-sGnRH) in combination with a water-soluble dopamine receptor antagonist metoclopramide. This thesis stresses the importance of a research-oriented approach in the conservation of Lake Victoria's indigenous fish resources. It was concluded that information needed for the development of management policies can be generated within a reasonably short time period, of approximately three years, with modest levels of funding support

Reproductive biology of ningu, Labeo victorianus (pisces: cyprinidae), in the kagera and Sio rivers, Uganda

We investigated aspects of the reproductive biology of the cyprinid fish, Labeo victorianus, locally known as ningu, in the Kagera and Sio Rivers, Uganda. These rivers represent the last remaining refuges for this species within Uganda. L. victorianus is a highly fecund, potamodrometic fish that migrates upstream to spawn. Spawning is generally synchronised with the bimodal water level maxima observed within the rivers. There were, however, some deviations from this pattern. We caught sexually mature fish throughout the year in the Sio River, and noticed that spawing started before the second rainfall peak. Fish from the Kagera matured at significantly larger sizes than fish from the Sio River. Male and female fish, from both rivers, fed intensively during the non-breeding months accumulating significant fat reserves; a probable energy storage mechanism prior to their spawning migrations. The differences between the populations is probably a phenotypic response to differing abiotic factors such as river size, flow velocity and food availability

Evolution of Labeo victorianus predates the Pleistocene desiccation of Lake Victoria: evidence from mitochondrial DNA sequence variation

Geological data show that Lake Victoria dried out some 15 000 years ago. These data suggest that the entire faunal diversity within the lake has evolved since this time. However, mitochondrial DNA sequence diversity in the endemic cyprinid fish, Labeo victorianus, was high (24 haplotypes in 38 individuals; percentage sequence divergence of 0.74%), suggesting that the evolution of this species predates this Late Pleistocene climatological event. This finding is consistent with what has been reported earlier for cichlid fishes in the lake

National Investment Policy for Aquaculture Parks in Uganda

According to the National Development Plan (NDP), fish farming in Uganda presents immense opportunities for socio-economic development, in terms of livelihood, income, and employment. The need  for the National Investment Policy for Aquaculture Parks in Uganda arose out of public demand for guidance on the investment in commercial scale aquaculture. Stakeholders in aquaculture demanded public guidance and support for implementation of the Aquaculture Parks Concept that is prioritized in Development Strategy and Investment Plan (DSIP) within the Ministry of Agriculture, Animal Industry and  Fisheries (MAAIF)

Review and analysis of small-scale aquaculture production in East Africa : Part 4. Uganda

This publication reports the results of a study of the small-scale aquaculture producers’ situation in Uganda that was carried out in March-April 2018. The study was commissioned by Msingi East Africa. The study comprised two main parts: a desk study and a field study. The latter consisted of visits and interviews with fish farmers, fish feed producers and importers, fish traders, service providers and other key informants and served as validation of the results of the desk study. The methodology for field data collection was semi-structured interviews. Three small-holder aquaculture segments have been identified. Segment I comprises of small-holders producing Nile tilapia (ponds and cages) and/or African catfish (ponds). Production varies from 1- 5 tonnes/year. They lack affordable and high quality inputs, knowledge and capital. Segment II includes small-holders producing Nile tilapia (ponds and cages) and/or African catfish (ponds). Production varies from 6 to 40 tonnes/year. They have some degree of knowledge on farm management and some capital to invest. Access to affordable and high quality inputs is problematic. Segment III consists of small-holders with higher education and on-job-skills. Production varies from 41 to 50 tonnes/year. They import high quality feed and have access to family capital. Their business is expanding and they will soon be medium-scale farmers. Opportunities for development support consist of better coordination and an integrated approach within a new aquaculture platform in which lead-farmers train farmers via a training-of trainers approach. The platform should concentrate on segment I and II farmers; they urgently need better feed, improved knowledge, skills and access to capital. Segment II farmers need better local feed of affordable prices and improved knowledge and skills for farm management. Models to link farmers to markets and support services include cluster farming (joined buying of inputs and distribution), aquaparks (improved production infrastructure) and empowering investors with access to capital and organised markets

Review and analysis of small-scale aquaculture production in East Africa : Summary and Recommendations

This report describes the findings of literature studies and of interviews with fish farmers and key informants in Kenya, Rwanda, Tanzania and Uganda as well as recommended actions that result from the findings. The studies were commissioned by Msingi East Africa in collaboration with Stichting BoP Innovation Centre and have been reported in four separate reports, covering each country. This final report provides a summary of all country reports. Extensive to semi-intensive production of Tilapia and to a lesser extent, African Catfish in small ponds is the most common production system in the region. However, there is a rapidly expanding culture of tilapia production in floating cages taking place in Lake Victoria and in other lakes. The situation of small-scale aquaculture producers as well as support services in the four countries differs but most small-scale fish farmers in the region are confronted with a shortage of essential inputs (especially fish feed, fingerlings and credit) of good quality and affordable price. The level of knowledge about better farm management practices, of related skills and application of more advanced technology (needed to increase productivity and income) is low for most farmers. For most countries the opportunities for the more advanced segment of small-scale farmers to grow are good. The study recommends a number of actions which it is believed will contribute to growth of smallholders’ production and income for all the countries surveye

Effectiveness of African catfish pituitary extracts, dagin and water flow for optimising egg production, fertilisation and hatchability in artificial spawning of Barbus altianalis

Fish inducing hormones are widely used in commercial aquaculture to facilitate continuous supply of sufficient seed required on regular basis by the farmers. The objective of this study was to optimise production of viable eggs for improved hatchability during artificial spawning in Barbus altianalis. Two experiments were conducted, namely (i) experiment I evaluated the efficiency of using catfish pituitary extracts in spawning of second generation broodstocks compared to that of Dagin and water flow. (ii) experiment II examined ripe running females facilitated to spawn by running water only. Fish treated with pituitary extracts performed much better than those treated by Dagin with respect to fertilisation rates at 80.27 ± 39.57% (U = 66.5, p < 0.001) and working fecundity at 2314.40 ± 882.04 (U = 59.5, p < 0.05). However, the difference in hatchability was not significant (p > 0.05). In experiment II, hatchability and working fecundity were significantly higher when fish were striped after 4 hours (100 degree hours at 25 oC) of running water than those striped after 10 hrs (250 degree hours) but fertilization rates were not different. The findings indicate that catfish pituitary extracts are more effective in inducing B. altianalis to spawn than those treated with Dagin. However, the observations made on ripe running females in both experiments suggest that they should not be induced with any hormone. Hence, the cost of spawning could further be reduced using running water, especially in wet seasons when the majority are ripe.Key words: Eggs, hatchability, hormone, spawnin

Morphology and functional ontogeny of the digestive tract of Barbus altianalis larvae

The ontogenetic development of digestive structures in Ripon barbel (Barbus altianalis) larvae was investigated using standard histological and histochemical procedures from hatching up to 60 days after hatching (DAH). The study was conducted to determine the best period of exogenous feeding and the stage when the digestive tract is able to digest processed microdiets. Results indicated that at hatching, the digestive tract, mouth and anus were closed. The opening of the mouth and anus were observed 3–4 DAH, whereas complete separation of the entire gut was observed on 5 DAH. Exogenous feeding started 5–6 DAH, but complete yolk exhaustion occurred 7–8 DAH, indicating a period of mixed feeding. Mucosal epithelial folds were first noted 3 DAH in the anterior intestine and became profound with some goblet cells (mucous cells) by 6 DAH. At 7 DAH the mucous cells had started secreting both neutral and acid glycoconjugates. The first intestinal single loop occurred at 28–30 DAH and a double loop at 45–50 DAH. Each coiling was proceeded by larval weight increase. By 7 DAH the buccopharyngeal cavity was lined by a layer of squamous epithelial cells with scattered goblet cells and tastebuds that became numerous by 15 DAH. At hatching, the liver and the pancreas were undifferentiated, but on 3 DAH the hepatocytes and zymogen granules of the pancreas became clear. By 7 DAH both organs enlarged, making extensions into the posterior. Intestines coiling at 28–30 DAH coincided with the beginning of external dressing of the scales, a period when B. altianalis started transforming into a juvenile. By 7–8 DAH the digestive structure showed all the necessary digestive features that could enable the larvae to digest any compound diet suggesting that it may be feasible to substitute or offer a complete microdiet during larvae nursing with reduced larval mortality.Keywords: digestive structures, exogenous feeding, microdiet, mucins, ontogenetic development, Ripon barbe

Review and analysis of small-scale aquaculture production in East Africa : Part 4. Uganda

This publication reports the results of a study of the small-scale aquaculture producers’ situation in Uganda that was carried out in March-April 2018. The study was commissioned by Msingi East Africa. The study comprised two main parts: a desk study and a field study. The latter consisted of visits and interviews with fish farmers, fish feed producers and importers, fish traders, service providers and other key informants and served as validation of the results of the desk study. The methodology for field data collection was semi-structured interviews. Three small-holder aquaculture segments have been identified. Segment I comprises of small-holders producing Nile tilapia (ponds and cages) and/or African catfish (ponds). Production varies from 1- 5 tonnes/year. They lack affordable and high quality inputs, knowledge and capital. Segment II includes small-holders producing Nile tilapia (ponds and cages) and/or African catfish (ponds). Production varies from 6 to 40 tonnes/year. They have some degree of knowledge on farm management and some capital to invest. Access to affordable and high quality inputs is problematic. Segment III consists of small-holders with higher education and on-job-skills. Production varies from 41 to 50 tonnes/year. They import high quality feed and have access to family capital. Their business is expanding and they will soon be medium-scale farmers. Opportunities for development support consist of better coordination and an integrated approach within a new aquaculture platform in which lead-farmers train farmers via a training-of trainers approach. The platform should concentrate on segment I and II farmers; they urgently need better feed, improved knowledge, skills and access to capital. Segment II farmers need better local feed of affordable prices and improved knowledge and skills for farm management. Models to link farmers to markets and support services include cluster farming (joined buying of inputs and distribution), aquaparks (improved production infrastructure) and empowering investors with access to capital and organised markets

Optimizing selection of sexually mature Barbus altianalis for induced spawning: determination of size at sexual maturity of populations from Lake Edward and Upper Victoria Nile in Uganda

Abstract Sexual maturity (L50), the length at which 50% of fish in a size class are mature, is a key aspect of domestication of new fish species because it guides the procedure for identification of appropriate broodstock size for artificial spawning. In this study, the L50 was determined for 1083 Barbus altianalis samples obtained from Lake Edward and the Upper Victoria Nile. Gonads of freshly killed samples were examined macroscopically and verified with standard histological procedures for the maturation stages that were used to determine L50. Oocytes and spermatogenic cell sizes were compared for fish obtained from both water bodies. Results indicated that there were no variations in macro gonad features observed for fish from Lake Edward and Upper Victoria Nile. Similarly, there were no significant differences in oocyte sizes (P > 0.05) between the two populations but significant differences in spermatogenic cell sizes were noted (P  0.05). This however did not suggest peculiar differences between the two populations for staging the gonads. Consequently, no staging variations were suggested for both populations in determination of L50. Sexual maturity was found in the same class size of fork length (FL) 20–24.9 cm and 35–39.9 cm for males and females from both water bodies, respectively. At this FL, however, males were too small, and for good selection of vigor broodstocks for spawning and conservation purposes, they are better picked from class size of 30–34.9 cm FL and above. These findings were crucial for integration of appropriate breeding size in spawning protocol by farmers and fisheries scientists conserving wild B. altianalis populations