Reproductive biology and fishery of ailia coila (hamilton-buchanan) (siluriformes: schilbeidae)

Abstract

Fish and fisheries play a vital role in the economy of our nation. Bangladesh is endowed with unique aquatic resources for fisheries development. Though Bangladesh is a small country of only 147, 570 square kilometers, it contains an abundance of rivers, streams, canals, ponds, tanks and ditches. Bangladesh is the richest country in the world in terms of water resources. The Rajshahi Division in the Northwest Region (NWR) of the country covers an area of about 3.5 million hectares and accounts for about 25% of Bangladesh's land area. The population of this region is about one fourth of the total population of Bangladesh. The people of this area suffers more from malnutrition than those in other parts of the country. The per capita protein intake in Bangladesh is about 50 g/day of which only 7-8 g comes from animal protein (Haque, 1982). To raise the animal protein production for human consumption we need to increase the production of fish, poultry and cattle. In Bangladesh fish play a vital role in meeting the requirements for protein. One of the most complex problems facing the world today is the capacity of the environment to support human life. Bangladesh, as a nation, is faced not just with the problem of sufficient food production but also with the quality food production to improve the general health of the rapidly increasing population. Blessed with innumerable bodies of freshwater, the nation has the potentiality to become self sufficient in the production of protein food of superior quality- the fish.

Bangladesh is rich in fish wealth, which is the second staple food of the people. It is not only a food product but also a cash product, as a good amount of foreign money is earned by exporting fish. Thus fish plays an important role in the economy and dietary habits of the people. Development of fisheries means the development of the country. Millions of landless people are engaged in fishing, fish processing, marketing, transportation, preservation, fish by products and other aspects of the fish industry. The people of our country are fond of fish and it is an established fact that fish has been the most preferred and major source of animal protein in the diet of the people of our country. Production of fish from inland waters in Bangladesh has declined. substantially. Consequently to the decline in fish production from inland waters and increase in population fish consumption per capita per day has droped from 33 g. The per day fish consumption per capita was 21 g in 1963- 1964, which decreased to 12 g in 1985. As a result animal protein is very low in daily diet of our rural people, which is among the lowest in the world. However, the large fishes are preferred more, though the catch deficit is being supplemented by the small fishes, which are more nutritious than the large fishes. The total protein intake in Bangladesh per capita per day is about 57 g of which 7.8 g are of animal origin as reported by nutrition survey 1963- 1964. Out of which 6.38 g i.e. about 80 percent come from fish alone (Rabbani and Hussain, 1970; Mannan, 1977; Ali, 1982). Fish diet mainly provides proteins, fats, vitamin A and D, and phosphorus. According to FAO-report 1991, fish contains 72% water, 19% protein, 8% fat, 0.5% calcium, 0.25% phosphorus and 0.1% vitamin A, D, B and C. The institute of Nutrition and Food Science (INFS) of Dhaka University has recommended that to arrest any further decline in the nutritional level of food of the people, an increase in the consumption of fish as 33.6 g/person/ day would be desirable. In this context, it would be well to examine how the recommended rate of the INFS will meet. A study made by the Bangladesh Bureau of Statistics (1985) indicates that inland fisheries contribute as much as 30.52 percent to the overall fish Production of the country. It has been shown that the proportion of the contribution of the capture (open water) and culture (closed water) fisheries to inland fisheries stand at 95 percent and 5 percent respectively. On the other hand, among the total capture fisheries 22.9 percent contribution was made by the small indigenous fish species (Nabi, 1987). Recently we are getting fish 36% from culture water and 64% from open water. In the 1930s and 1940s, capture fisheries contributed more than 90% of the total fishery resources while culture fisheries contributed 10% or less. Since then there has been a sharp decline in the capture fisheries and a gradual increase in culture based fisheries. The indiscriminate use of insecticides has drastically affected the fish population. With the increase in human population and their high demand for fish and other aquatic resources came the necessity for an increased production of fish. So we should concentrate our attention on better production of fish and fishery resources. The small indigenous fish species, thus make a very significant contribution to the fisheries of Bangladesh. In Bangladesh about 80 percent population is poor and they mainly depend on small size fish for their daily supply of animal protein (Siddique, 1985). Another advantage of small size fish is that they could easily breed and grow in a water bodies, where culture of the other major fishes are impossible. Bangladesh, being an agriculture country and rich in fishery, a number of potential water bodies remain neglected even up to these days. Only by proper culture of these fishery resources the country can overcome the problem of protein deficiency. In realizing this condition several research programs are being organized on different indigenous species by different research institutions of the country. The present thesis is a step in the direction of an effort to amass of information as much as possible on one of the hither to less known species Ailia coila (Hamilton-Buchanan). The freshwater A. coila a member of cat fish family is excellent as food and a rich source of protein in the common people. It is caught largely from the river Padma. A. coila carries its local name as Kajuli, Baspata (Rahman, 1989). This genus is represented by two species such as A. coila and A. punctata.