On the relative efficiency of different shaped otter boards

Rectangular, horizontal curved and oval otter boards were tested under identical fishing conditions and their relative efficiency ascertained on the basis of towing tension and the horizontal opening of the boards. While the tension in the warps with the different otter boards was not significant, the horizontal curved board gave increased lateral spread to the net.

Effect of brood source on the growth of rohu (Labeo rohita Ham.) fingerlings reared in glass tanks with formulated diets

A 60 day long feeding trial was conducted in an indoor static water system with rohu fingerlings (Labeo rohita Ham.) originating from wild brood, private and public hatcheries (denoted as A B and C respectively). They were fed on formulated diet having 34% crude protein level using indigenous ingredients. The effect of brood source on growth as well as their responses to formulated diet was observed. On the basis of the observed growth rate, food conversion ratio, protein efficiency ratio, apparent net protein utilization and apparent protein digestibility, fingerling source A showed significantly (p<0.05) higher growth, while the sources B and C produced no significantly different (p>0.05) in terms of these parameters. The results of the present study demonstrated that the fingerlings of wild source were of best quality in terms of growth and food utilization in comparison to those had the sources from hatcheries.

Effects of cowdung application on the production of mud crab (Scylla serrata Forskal) in brackishwater pond

A culture experiment of mud crab for 84 days was conducted in earthen pond at Brackishwater Station, Bangladesh Fisheries Research Institute, Paikgacha, Khulna. The aim of the experiment was to study the effects of cowdung application on crab production and water quality. There were three treatments as without cowdung (T1), 500 kg cowdung/ha/fortnight (T2) and 750 kg cowdung/ha/fortnight (T3) with three replicates for each. The result was evaluated on the basis of growth, production, survival rate etc. The experimental months were mid-April '96 to mid-July '96. To maintain a good water quality, water was exchanged in every spring tide. The range of salinity during the experiment was 8-19 ppt. Trash fish and fresh shrimp head were used as feed on raw basis in every alternate week at a rate of 8% body weight of crab at the same time rice bran and wheat flour were used at a rate of 2% body weight as a source of carbohydrate. The production of T1, T2 and T3, were 720.35 kg, 862.16 kg and 669.19 kg/ha respectively. Though the effects of cowdung on production of crab is insignificant but in terms of production, survival rate and growth, the study suggest that the application of cowdung in addition to feed can be recommended for mud crab culture at a rate of 500 kg/ha/fortnight.

Effects of animal and plant protein diets on growth of Indian major carp (Labeo rohita Ham.) fingerlings

An experiment was conducted with Labeo rohita fingerlings in an indoor static fish rearing water system of glass made aquaria. Five experimental diets A, B, C, D and E were formulated containing 33% dietary protein level in five treatments each having two replicates containing 12 fingerlings of mean total initial weight of 13.00±0.2g. Sixty days of feeding trial in this experiment showed that fish fed on diet 'A' containing fish meal and diet 'E' containing mixed plant sources protein had significantly highest and lowest growth respectively. However, no significant difference of growth was found in fish fed on diets C and D containing meat and bone meal, and mix of animal protein source diets respectively. The result showed that the apparent protein digestibility (APD) of diets 'A' and 'E' had significantly best and least values respectively. Food conversion ratio (FCR) and protein efficiency ratio (PER) ranged between 1.37 to 2.17 and 1.38 to 2.18 respectively. On the basis of observed FCR and PER diets 'A' and 'E' produced significantly highest and lowest growth respectively.

Effect of different feeds on growth, survival and production of African catfish (Clarias gariepinus Burchell)

An experiment was conducted to study the effect of different feeds on growth survival and production of African catfish (C. gariepinus) in six cemented tanks (3m² each) over a period of 120 days. Three different feeds namely Feed A (Saudi-Bangla fish feed, 33.43% protein), Feed B (formulated feed, 40.12% protein) and Feed C (chicken raw intestine, 59.58% protein) were applied to treatments I, II and III respectively. Each of the tanks was stocked with 24 fry with mean initial body weight of 2.56±0.06 g. Feeds were supplied to the fish ad-libitum daily in two instalments. Significantly highest weight gain was obtained in treatment III, however, survival rate was low compared to other treatments. The feed conversion ratio (FCR) values ranged from 2.52-6.4. Survival rate of fish varied between 83 and 96%. Treatment II yielded the highest (5000 kg/ha/120 days) production with the highest survival rate of fish. On the basis of survival rate and production, it is suggested that the formulated feed (Feed B) is suitable for the culture of C. gariepinus in cemented tanks.

On the troll line investigations off Cochin during five fishing seasons. Pt. 3. Investigations during 1965-66 and 1966-67 seasons

During these two seasons investigations were carried out with a view to exploring the possibility of this operation on commercial basis and to study the effect of certain meteorological factors on catch.

Use of dopamine antagonists on induced spawning of Indian major carps

To test the efficacy of the technique of using dopamine-antagonists with pituitary extracts, experiments were conducted in July/August '93, at the CIFE Fresh water Fish Farm, Powerkheda. In all, 35 sets (1 female x 2 male in each set) were tried individually. 19 sets were treated with Domperidone (DOM) and Carp Pituitary Extract (CPE) and they constituted the experimental sets, while the rest 16 were treated with CPE and formed the control sets. The breeding, complete ovulation and hatching was 84.2%, 87.5% and 85.7%, respectively in the experimental sets whereas it was 93.7%, 60% and 72.7%, respectively in case of control sets. Experimental sets yielded 1.20 lakh spawn/kg body wt. (female) as compared to 0.83 lakh spawn kg body wt. (female) received from control sets on average basis. When DOM was used at 50-60% there was 100% breeding success but when increased to 70%, breeding rate fell to 66%. In mass breeding of Catla in the circular hatchery DOM mixed with CPE in 50:50 ratio gave excellent results.

Studies on paddy-cum-fish culture under different land situations

Paddy fields can be broadly classified on the basis of land situations viz. Upland - Shallow water (10-30 cm), Medium land-medium deepwater (30-100 cm) and Low land-deepwater (above 100 cm). Three major systems of paddy-cum-fish culture, viz. (A) high yielding paddy varieties (H.Y.V) and air-breathing fish under Upland, (B) H.Y.V./local paddy and Tilapia/common carp under Medium land and (C) deepwater paddy and major Indian carps under Low land situations have been successfully investigated in the farmers' fields and at the Research Stations (1982-92). Effects of low-cost artificial feeding on growth, yield and management practices of different types of fish showed a considerable increase of rice and fish yields and a decrease in insect-pest incidence. Under Upland situation, short duration H.Y.V. in combination with fast-growing air breathing fish was studied thrice a year (summer, winter & autumn seasons). Combined rice and fish culture produced highest yields in all the seasons than in the control.

On the spawning activities of kingfish, Scomberomorous commerson, in Oman waters

The spawning activities of kingfish, Scomberomorus commerson, in Oman waters are traced out for the first time. The possible spawning period and spawning ground are identified on the basis of collection of its eggs and larvae from Oman waters. The eggs and early larval characteristics are described suitably with photographic illustration of 4.9 mm larva. The optimum surface water temperature and salinity recorded for the occurrence of kingfish eggs and larvae are 23.57-26.05°C and 36.0-36.1‰, respectively.

Semi-intensive shrimp farming system of Kerala, India: a production function analysis

An analysis of the factor-product relationship in the semi-intensive shrimp farming system of Kerala, farm basis and hectare basis, we are attempted and the results reported in this paper. The Cobb-Douglas model, in which the physical relationship between input and output is estimated, and the marginal analysis then employed to evaluate the producer behaviour, was used for the analysis. The study was based on empirical data collected during November 1994 to May 1996, covering three seasons, from 21 farms spread over Alappuzha, Ernakulam and Kasaragod districts of the state. The sample covered a total area of 61.06 ha. Of the 11 explanatory variables considered in the model, the size of the farm, casual labour and chemical fertilizers were found statistically significant. It was also observed that the factors such as age of pond, experience of the farmer, feed, miscellaneous costs, number of seed stocked and skilled labour contributed positively to the output. The estimated industry production function exhibited unitary economies of scale. The estimated mean output was 3937 kg/ha. The test of multi-co-linearity showed that there is no problem of dominant variable. On the basis of the marginal product and the given input-output prices, the optimum amounts of seed, feed and casual labour were estimated. They were about 97139 seed, 959 kg of feed and 585 man-days of casual labour per farm. This indicated the need for reducing the stocking density and amount of feed from the present levels, in order to maximise profit. Based on the finding of the study, suggestions for improving the industry production function are proposed.

The deep crab - Geryon quinquedens: first notes on its biology off Mozambique

The deep crab Geryon quinquedens was the objective of an exploratory fishing operation with long lines of baited traps along the slope of southern Mozambique and was caught between 250 and 850 m. Data were analysed from the start of the operation in May, 1979 until March, 1980. The availability of the resource is discussed on the basis of catch rates. Size composition of the catches shows the bigger size of the males and suggests a stratification of the resource by area. Females dominate in shallower waters whereas the interval at which the sex-ratio equals one is identified at 400-450 m. Reproduction is discussed in connection with recruitment and an hypothesis is advanced for an exponential growth rate of about 10 mm per month.

A comparative study on the effect of commercial fish feeds on the growth of Thai pangas, Pangasius hypophthalmus

A 70 day long experiment was carried out to evaluate three commercial pangas feeds available in Bangladesh viz. Quality Feeds Ltd. (QF), Aftab Bohumukhi Farm Ltd. (ABF) and Saudi-Bangla Fish Feed Ltd. (SBFF) (designated as treatment_T1 T2 and T3) on the growth of Pangas, Pangasius hypophthalmus. Each treatment had two replicates using six experimental ponds of each 80m2 size. The stocking density was 250 fish/80m2. At the beginning, the fish were fed twice daily at 15% of their body weight which was gradually reduced to 10 and 6%, respectively for the rest of the period. The ranges of water quality parameters observed were: temperature 29.0°C- ~5.1 °C, pH 6.85 - 8.52, DO 1.71 - 7.65 mg/1 and transparency or Secchi depth 14.5 - 30.0 em. The mean weight gain of fish was significantly (~<0.05) higher in T3 followed by T2 and T. The specific growth rate (SGR) ranged. between 4.09 and 5.06, feed conversion ratio (FCR) values between 1.54 and 1.61 with treatment T1 showing the lowest FCR. Protein efficiency ratio (PER) values ranged between 2.03 and 2.11. The survival of fish varied between 90.4 and 91.6%. The significantly (P<0.05) highest production of fish (kg/ha/70 days) and profit (Tk/ha/70 days) was observe in T3 (SBFF) followed by T2 (ABF) and T1 (QF), respectively. The result of the study showed that on the basis of nutritive value and growth performance of pangas, feed from Saudi-Bangla Fish Feed Ltd. is the best.

Marketing of value-added products from silver carp and involvement of rural people in the production and marketing chain

Cost-profit analysis and market testing of some value-added products from silver carp such as fish mince block, fish sausage, fish ball, fish stick and fish burger were analyzed during April 2001 to March 2002. The study also explored the possibility to involve rural low-income people in the production and marketing of such products. The production of silver carp was higher in greater Jessore and Mymensingh districts but the price remained low during the peak-harvesting season in October to November. The price varied with size of the fish, season, market characteristics and effective demand of the buyers. Price of about 500 g size fish was found to be Tk. 20-25/kg in the rural markets. The average size of fish in the rural markets was 3S0-550 g while that in the urban markets it was 700-1,200 g. The cost of production of the value added products and profit margin were assessed on the basis of market price of the raw material as well as that of the finished products, transportation, storage and marketing costs. The profit margins of 34%, 39%, 81% and 31% of their sales price were obtained for fish sausage, fish ball, fish stick and fish burger, respectively. Actual production cost could be minimized if the fish is purchased directly from the farmers. Consumer's acceptance and marketability tests showed that both rural and urban people preferred fish ball than fish sausage. However, response towards the taste, flavor and color of fish ball and fish sausage was found to vary with occupations and age of the consumers. A correlation was observed between age group and acceptance of new products. Fish ball, fish stick and fish burger were found to be the most preferable items to the farmers because of easy formulation process with common utensils. Good marketing linkage and requirement of capital had been identified as the prerequisites for operating small-scale business on value-added fish products.

On the comparative efficiency of trawls made of cotton, polyethylene and combination of both the materials

The merits and demerits of cotton, polyethylene and combination of the two materials ascertained on the basis of cost, wear and tear, maintenance, total catch and qualitative analysis of the catch are discussed by making comparative fishing experiments with the three trawl gears made of these materials. The study can be concluded with a suggestion for switching over to polyethylene twisted monofilaments for better, in case of bottom trawls without in any way adversely affecting the catch of shrimps and at the same time for enhanced fish catch. Even though the combination net is found to be equal in efficiency as the polyethylene net this idea cannot be conveniently adopted from the point of view of economy.

Report on the occurrence of one subspecies of Scylla serrata (Forskal) in Cochin backwaters

The taxonomy of the mud crab, Scylla serrata has become a topic of interest. Alcock (1899) described this species from Indian waters. It was considered that under the genus Scylla, only one species, namely, Scylla serrata was valid. But Estampador (1949) revised the genus and reported the occurrence of four sorts, Scylla serrata, S. tranquebarica, S. oceanica and a variety S. serrata, var paramarnosain in Philippine waters. He established his claim based on the morphology such as colouration, relative length of chelae and also on the cytological events during gametogenesis. Serene (1952) pointed out that two distinct categories under this genus were demonstrable on the basis of colouration. But Stephenson & Campbell (1960) concluded them as only synonyms, but pointed out the need for further investigations.