CHAPTER ONE
INTRODUCTION
1.0. BACKGROUND OF THE STUDY
Aquaculture is the fastest growing food producing sector; this is in contrast to other food producing sectors (FAO, 2009). This is a sector that is most likely to benefit from the application of appropriate reproduction biotechnologies to increase food production.
According to CGIAR (2006) aquaculture contributes to the increase in supplies of crustaceans, mollusks and some other aquatic animals, total by weight 3.9% in 1970, 271.%in 2000 and 32.4% in 2004. Aquaculture growth is impeded due to lack of adequate attention to selective breeding and genetics consideration, leading to inadequate yield. Catfish (family clariidea) are very popular in Nigeria. The fish is hardy and can grow to a size of about 10kg which are very attractive to consumers, but the production of fish larvae of the right quality and quantity remain a major challenge facing aquaculture in Nigeria. With global population expansion, the demand for high-quality protein, especially from aquatic sources is rising dramatically. Increased aquaculture production is clearly needed to meet this demand in the new millennium, because captured fisheries are at declining capacity or showing precipitous declines due to overfishing and habitat destruction. Further increases in capture fisheries are not anticipated under the current global conditions (Dunham et al., 2000).
Since the end of the 19th century, a large number of studies has been devoted to hybridization in fish, with descriptions of “hybrid-like” individuals among natural populations or including results of artificial insemination of eggs from one species by sperm from another one (Chevassus, 1983).
During the recent decades remarkable improvement of productivity has been achieved for all important species of livestock. In the growing aquaculture industry future development will also largely depend on the potential of the stock used. It is surprising that up to now integrated breeding and selection programs rarely have been practiced even though in some regions fish farming has a long tradition. The main reasons for failure in aquaculture breeding strategies have been unsuccessful artificial reproduction of some farmed species, technical difficulties in applying sophisticated testing procedures, and also inflexible aquaculture tradition Banzoussi, 1995).
This contribution deals with the encouraging prospects for selective improvement of aquaculture candidate species and sets out principles for developing advanced breeding and selection strategies in fresh water fish. Hence, Chevassus, (1983) defined hybridization as the union of gametes from two different species, resulting on a new organism. Hybridization therefore, is one of the methods used to introduce new fish species into intensive fish production (Klaus, 1987). Simple hybridization may also help sometime to bring in some improvements in the hybrid progeny. Hybrids are the progeny of parents from different lines, strains (intraspecific hybrids), or species (interspecific hybrids). The mean phenotypic value of hybrids is often greater than the value of either parent line.
This study was conducted to proffer solution to this problem. A good supply of fry is essential for successful aquacultural production. The process of hybridization helps the fish farmer to select for desirable characteristics such as fast growth, food conversion, resistance to diseases etc which can increase the profitability of the farmer. The clariid catfish from wild and farmed source are economically important food fish in Nigeria, like other parts of the world. The catfish species of the family Clariidae have gained much prominence as important food fish.
1.1. STATEMENT OF THE PROBLEM
The purpose of hybridization is to recombine useful and desirable traits from selected parents with the aim of producing offspring of superior quality. In this way intraspecific and intergeneric hybrids of clariid catfishes have been produced but have not been thoroughly screened and adopted as to their suitability for aquaculture (Madu et al 1993; Salami et al 1993; Nwadukwe, 1995; and Aluko et al (2003).
Heterobranchus species do not have the same survival rate as Clarias and Clarias species do not grow to a large size as Heterobranchus Furthermore, there is the problem of low fecundity of Heterobrachus compared to high fecundity of Clarias. The decline in production has been a consequence of scarcity and high cost of fingerlings. These fish also does not readily breed in captivity.
Therefore to profer solution(s) to these problems and improve their productivity for commercial culture, artificial hybridization using induced hormonal spawning become necessary. Thus this project when fully accomplished will lead to increase production and supply of fingerlings through popularizing among fish farmers this technique of fish breeding under pond culture condition.
1.2. JUSTIFICATION OF THE STUDY
The African catfish is a favourite cultured fish in many parts of Africa and Asia because of its hardiness and fast growth rate Aquaculture is fully recognized as a major contributor to gross domestic product (GDP) in many countries, fisheries and aquaculture production is an important contributor to many national economies across Asia and the Pacific region. FAO recommends greater emphasis on legislation and policy that support the poor and advocates: (i) financing aquaculture production for enhanced poverty alleviation programmes; (ii) making market work for the poor; (iii) better management that includes managing small-scale aquaculture. (iv) Appropriate information, research and communication to strengthened foreign exchange for countries (FAO 2014). Furthermore, aquaculture contributes significantly to employment or job creation, and income generation.
Nutritionally, fish is a high-protein, low-fat food that provides range of health benefits. It provides nutrients and micronutrients that are essential to cognitive and physical development, especially in children and are important part of healthy diet. Fish is a low-fat high quality protein which is high in omega-3 fatty acids and vitamins such as D and B2 (riboflavin). Fish is rich in calcium and phosphorus and is a major source of minerals, such as iron, zinc, iodine, magnesium, and potassium. Economically, fish contributes to the Gross domestic products GDP through export trade.
Biotechnological innovations which include in vitro reproduction methods have shown a lot of positive impacts in improving aquaculture production most especially in breeding and in the larval production of catfish towards producing a desired healthy and fast growing industry.
Having seen the enormous importance of fish to man, its nutritional value, and its contribution to GDP, the application of biotechnological innovations which include in-vitro reproduction, larval rearing methods etc. attested to have a lot of positive impacts in improving aquaculture production the world over is much welcome development and justifiable.
1.3. AIM AND OBJECTIVES OF THE STUDY
The main aim and objectives of this project are:
To Crossbreed Heterobranchus longifilis x Clarias gariepinus for the production of improved hybrids
Specifically, to evaluate the growth performance of the larvae raised with formulated feeds.
1.4. SCOPE
The scope of this project work is limited to in vitro hybridization, hatching and rearing of hybrids larvae for fingerlings production.
