1.1 BACKGROUND TO THE STUDY
In all countries actively involved in mud crab aquaculture development, the national government is taking a key role in aquaculture planning to underpin national aspirations and growth targets for their respective industries (Ji & Huang, 1998). The Federal Ministry of Agriculture, Nigeria, or similar organizations in other countries, all are implementing national policies and regulations, which will flow down to provincial areas. As a result, an individual or organization seeking to develop a mud crab farming venture will need to seek local government advice on correct procedures and processes to follow to obtain the appropriate authorities, licences and permits to undertake the activity. In addition, discussing development plans with government agencies will enable potential farmers to be made aware of any incentives or regional initiatives that may assist the development and operation of their business. Mud crab aquaculture is currently undertaken at relatively low densities compared with other types of pond- or pen-based aquaculture (Bian, 1980). In Nigeria, mud crab is just one species of many being used in integrated mangrove-aquaculture farming systems, which are focused on productive and sustainable use of mangrove ecosystems.
The guidelines for sustainable mud crab aquaculture in mangrove pens have been developed. Environmental assessment of an aquaculture development is undertaken by government agencies in most countries. However, the low risk of any environmental degradation from most forms of crab culture should mean that assessment of mud crabs farms is simple and relatively low-cost. For example, it may be more practical for environmental monitoring of farms based in mangroves to be undertaken in partnership between farmers and government agencies, rather than requiring sophisticated, expensive environmental impact assessments, as required for large pond-based developments involving intensive culture (Anon, 2006). For farms involving pond construction, guidelines on how to mitigate against their environmental impact during construction and operation are provided in both the “Guidelines for constructing and maintaining aquaculture containment structures” (Anon, 2007). Crab farming as a practice is not common in Nigeria.
The crab species Scylla serrata is the biggest and most important member of the family of edible crabs in the Nigeria. Mud crab is considered a delicacy and has become a popular fare in seafood restaurants. It is sought for its very tasty aligue or ripe eggs in the ovary. Crabs abound in estuaries, mangroves, swamps and tidal waters, living both as a scavenger and a cannibal. The mating period of crabs is usually long. When mating, the female is carried by the male, clasping her with three pairs of walking legs. In this condition, it is very easy to catch them. After five days, the female is finally released by the male. Mating usually occurs for four months, during the period May to September. Prior to that, in April, the females develops eggs or aligue. Crabs spawn in the sea. The newly hatched larvae called zoea are free-swimming. They are carried by the tide to the coast where they migrate to live-in estuaries, swamps and mangroves. Fertility is very high among females. As much as a million eggs can be laid but mortality is also high becauseof inclement climatic conditions (Anon, 2006). Molting is an indispensable stage in the life cycle of crabs.
During molting, they shed their covering or carapace. This happens when there is an abrupt increase in the size of their body. After shedding the old carapace, the crab is left with a very soft covering. It becomes an easy prey to other animals and to survive, the crab buries itself under the mud until the soft shell hardens (Guo et al, 2008). For the purpose of culture and cultivation, Small crabs or crab seeds are caught by fishermen in seashores, swamps and other natural habitats. They are gathered and sold to fishponds operators. Crabs are raised in brackish water fishponds. It is, however, not advisable to culture crabs together with prawns, because when prawns undergo molting, crabs eat them.
1.2 STATEMENT OF THE PROBLEM
Crab culture system in Nigeria is not common because it has not gained the required attention from the government in terms of financial support considering the lot of processes involved in developing the farm. First, there should be adequate supply of estuarine water because good and stable salinity is conducive to growth. Smaller ponds are advisable since they are easier to manage. It is important to ensure that the soil is clay or clay loam. This kind of soil is capable of retaining water. If possible, the site should be free from floods. The depth of water is also important. Advisable depth is one meter to prevent exposure of cultured crabs and stop them from boring holes through the dikes.
1.3 OBJECTIVES OF THE STUDY
The following are the objectives of this study:
1. To examine the process of development of improved mud crab culture system in Nigeria.
2. To examine the level of practice of mud crab farming in Nigeria.
3. To identify the limitations in the mud crab culture system in Nigeria.
1.4 RESEARCH QUESTIONS
1. What is the process of development of improved mud crab culture system in Nigeria?
2. What is the level of practice of mud crab farming in Nigeria?
3. What are the limitations in the mud crab culture system in Nigeria?
1.5 SIGNIFICANCE OF THE STUDY
The following are the significance of this study:
1. Outcome of this study will educate fish farmers and the likes in Nigeria on the development of improved mud crab culture system in Nigeria.
2. This research will be a contribution to the body of literature in the area of the effect of personality trait on student’s academic performance, thereby constituting the empirical literature for future research in the subject area
1.6 SCOPE/LIMITATIONS OF THE STUDY
This study will cover the process of mud crab culture system for the purpose of improved production.
LIMITATION OF STUDY
Financial constraint– Insufficient fund tends to impede the efficiency of the researcher in sourcing for the relevant materials, literature or information and in the process of data collection (internet, questionnaire and interview).
Time constraint– The researcher will simultaneously engage in this study with other academic work. This consequently will cut down on the time devoted for the research work.
Anon. 2006. Australian Prawn Farming Manual. Health management for profit. The State of Queensland, Department of Primary Industries and Fisheries. 157 pp.
Bian, B.Z.E.S. 1980. Atkinsiella hamanaensis sp. nov. isolated from cultivated ova of the mangrove crab, Scylla serrata (Forsskal). J. Fish Dis., 3(5): 373–385.
Guo, Z.X., Weng, S.P., Li, G., Chan, S.M. & He, J.G. 2008. Development of an RT-PCR detection method for mud crab reovirus. J. Virol. Methods, 151(2): 237–241.
Ji, R. & Huang, S. 1998. Studies on pathogenic bacteria of “Yellow Body” disease of mud crab Scylla serrata. J. Oceanogr. Taiwan Strait/Taiwan Haixia, 17(4): 473–476.