PhD Thesis

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Start date: 1990End date: 1999

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    Fish and Fishery of Aspidoparia (Cypriniformes: Cyprinidae) of the River Padma
    (University of Rajshahi, 1997-11) Sultana, Nasrin; Hossain, Md. Altaf
    Bangladesh has vast fishery resources. The inland water areas of the country comprises 1.03 million hectares of rivers, canals and estuaries; 1,14,161 hectares of natural depressions such as the beals' and 'haors'; 1,61,943 hectares of ponds and tanks, 5,488 hectares of ox-bows; 68,800 hectares of Karnafuli reservior; 2.8 million hectares of flood plains and 87,300 hectares of brackish water aquaforms (Rahman, 1989). A total of 260 species of indigenous species of fin fishes are found in the freshwater habitats of Bangladesh and majority of these fishes are small sized (Rahman, 1989). The small indigenous fishes (SIS) form an important human food item, rich source of complete proteins containing all the essential aminoacids in right proportion. Fish protein is said to be more healthier and cholesterol free and also contains fatty acid which help in cholesterol absorption in the body tissues. The people are advised to take much smaller fish than meat. According to FAO report, (1991), fish contain 72% water, 19% protein, 89% fat, 0.15% calcium 0.25% phosphorus and 0.10% vitamin A,B,C and D. National Household Expenditure Survey (NHES) shows that anmel fish consumption in Bangladesh peaked in 1985 at 13.2 kg/person, had declined to 12.6 kg/person by 1992. This is in the same agreement with the information developed by North West Area Development Study (NWADS), which shows that overall fish supply has stagnated, resulting in price increase in real terms of over 2.8% per annum in the Northwest Region (Interim Report Vol-5 ADB February, 1997). The SIS fishes thus, make a very significant contribution to the daily intake of fish. Moreover, Siddiqui (1985) reported that in Bangladesh about 80 percent of the population is poor and they mainly depend on small size fish for their daily supply of animal protein at a reasonable price. Another advantages of small size fish is that they could easily breed and grow in water bodies, where culture of other major fishes are impossible. However, the ever expanding programme of flood control, drainage and irrigation is interfering with the whole ecological system in fishery resources, thereby causing both loss and degradation of their habitats. Which will inevitably lead to diminution and even disappearance of 95 percent of inland fish production. The present species 4. morer is mostly available in the river systems of Bangladesh. The biology of this species had been reported by Sultana (1991), Bhuiyan et al. (1992) compared the past and present data on the landing of the species together with the market price found that the natural production of the species is decreasing due to construction of the Farakka Barrage and oder FCD projects which caused detremental effect on the national aquatic system. Moreover, over exploitation of fish population and indiscriminate use of agrochemicals also adversely affected the fisheries resources. A. morar is an important species due to its high nutritional value in terms of protein content. Inspite of its usefulness as a source of protein, no detailed studies on the chemical and biochemical investigation has so far been reported. This is a small sized fish with a maximum size of 145 man, feiches the hightest market price due to its taste and flavour. This fish generally live in shallow water of the sandy bottom and medium current areas of the rivers. We hope the present finding may help to increase its population in the river Padma near Rajshahi
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    Ecology, Biology and Fishery of Clupisoma Atherinoides (Bloch) (Cypriniformes:Schilbeidae)Ecology, Biology and Fishery of Clupisoma Atherinoides (Bloch) (Cypriniformes:Schilbeidae)
    (University of Rajshahi, 1999) Begum, Mahbuba; Bhuiyan, M. Abdus Salam
    The juvenile and adult of C. atherinoides is mainly a carnivorous fish. Its food consists mainly of crustaceans, insects, rotifers, protozoans, algae, debris and detritus. The juvenile and adult C. atherinoides are surface feeders. Monthly variations in the percentage composition of the food items in the different stages of the fish were recorded. The fish changed its food and feeding habit seasonally. The feeding intensity was very poor in mature fishes during the spawning period. The immature fishes fed actively throughout the year. The ratio of the total length and alimentary canal length of the juvenile and adult stages of the fish is I :0.56 and 1: O. 61 and it has a shortened alimentary tract. The relationships between the total length and alimentary canal length of the juvenile and adult showed strong linear relationship. The ovaries of C. atherinoides were classified into ten stages. Immature stage, maturing-I ( early developing), maturing-II (late developing), mature, ripe, pre-spawning, spawning, post spawning, spent and resting stage.----
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    Bionomics Of The Sugarcane Top Shoot Borer, Tryporyza Nivella ( Fab. ) ( Pyralidae: Lepidoptera)
    (University of Rajshahi, 1990) Sirajuddin, Md.; Rahman, Mustafizur
    The bionomics of the top shoot borer, Tryporyza nivella (F.) of sugarcane have been carried out as follows: i) The systematics has been reviewed and the identi­fication has been confirmed. ii) The biology of the pest was studied both in the field and under laboratory condition. The female lays eggs in masses on the undersurface of sugarcane leaves. Newly­hatched larva bores through the midrib and enters into the spindle causing 'dead heart' or 'shot-holes'. A single larva infests a single cane only and there it passes its larval and pupal stages. The moth comes out of the cane through the exit hole. The top shoot borer passes five instars during its larval stage. The instars were identified by regular sampling of the infested canes and confirmed by the application of Dyar's law. Occurence of five broods in a year was confirmed. :i:H.) Seasonal and regional (11 north-western sugarmills zones of Bangladesh) incidence of the pest have been surveyed. The incidence in all the mills zones was always minimum in the first brood. It increased up to brood number four anddecreased in the last or fifth brood. The incidence was the highest at Panchagarh among all the eleven study areas. It is also evident that the relationship between temperature and humidity is not independent but the two variables inter­act on the percentage of infestation. iv) Varietal behaviour (succeptibility to pest attack, reducing ability for loss in yield and recovery)of the four promising varieties Isd-16, Isd-17, Isd-2/54 and L.J.C. has been assessed. Variety Isd-16 was the least succeptible to top shoot borer while L.J.C. was the most succeptible one. Infestation of the top shoot borer produces a remarkable reduction in the length, circumference and weight of all the varieties. It has also a detrimental effect on the sucrose recovery in all the varieties studied. The loss was highest (35.598%) and the lowest (6.28%) in Isd-17 and L.J.C. respec­tively. v) Efficiency of mechanical control practice has been evaluated. Without mechanical control the incidence of T • nivella was 4.80 - 55.80% in the grower's field and it was 4.64-13.45% in all other study areas where usual mechanical control practice was adopted. But this practice adopted properly in the present investigation efficiently reduced the incidence and it was 4.20-6.60% only. vi) The natural enemies (parasites) of top shoot borer prevailing in the study areas have been identified and their effectiveness in controlling the pests in different broods at di-fferent sugarmill zones have been observed. Biology of the most common three parasites (Elasmus, Stenobracon and Topobracon sp. ) has been studied. --------