Effects of artificial feeds on production of fishes in polyculture

A study on the effects of artificial feeds on the growth and production of fishes in polyculture in 6 ponds along with some limnological conditions was conducted. Species of Indian and Chinese major carps (Labeo rohita, Catla catla, Cirrhinus mrigala, Hypophthalmicthys molitrix) and catfishes (Clarias batrachus, Clarias gariepinus) were stocked in 6 ponds. Stocking rate in both cases were 32044 fingerlings per hectare. Ratio of species of Rui:Catla:Mrigal:Silver carp:African Magur:Local Magur=25%:25%:5%:25%:14%:6%. Fertilization and artificial feeds were given in 3 ponds (treatment I) and only fertilization was done in other 3 ponds (treatment II). Average yield/ha/yr was 7.903 m.ton in case of fertilization and artificial feeding application and 3.374 m.ton in case of only fertilization application. Urea, TSP and cow dung were applied fortnightly at the rates of 400 kg/ha/yr, 2000 kg/ha/yr and 4000 kg/ha/yr respectively. Wheat bran, rice bran and mustard oil cake were given daily as an artificial feed in treatment I. Whereas treatment II was conducted without any artificial feed. Ratio of artificial feed was wheat bran:rice bran:oil cake=2:2:1 (by wt). Absence of artificial feed in 3 ponds under treatment II seriously affected the growth and production of fish

Integration of aquaculture into the farming systems of the floodprone ecosystems of Bangladesh: an evaluation of adoption and impact

This report presents the results of studies undertaken for incorporating low-external input aquaculture practices into the farming systems of a complex floodprone ecosystem in Bangladesh and the impacts of integration on income, nutrition and resource use in rural households. The study shows that multi-purpose ponds which were underutilized or unutilized because of risk of flooding could be made productive through proper management and incorporation into the existing farming systems. Farmers with minimal external inputs were able to increase fish production and consumption by 5 to 8 times.Integrated farming, Farming systems, Technology transfer, Fish culture, Impact assessment, Bangladesh,

Enrichment of rotifer Brachionus rotundiformis with calcium

Possibility of enrichment of rotifer (Brachionus rotondiformis) with calcium (Ca) for feeding the fish fry was investigated. Rotifer was kept for 24 h with aeration in normal seawater (Treatment 1), seawater with 400 mg/l supplemental Ca from Ca-lactate (Treatment 2) and seawater with 400 mg/l supplemental Ca from Ca-chloride (Treatment 3). After the experimental period, Ca contents of rotifer were 0.20, 0.29 and 0.39% of dry weight in T-1, T-2 and T-3, respectively. Ca content of media did not affect phosphorus, zinc and manganese contents of rotifer. Results revealed that rotifer can be enriched with Ca for feeding fish fry and Ca-chloride might be a better source for Ca enrichment

Is soil organic carbon underestimated in the largest mangrove forest ecosystems? Evidence from the Bangladesh Sundarbans

Globally, mangroves sequester a large amount of carbon into the sediments, although spatial heterogeneity exists owing to a wide variety of local, regional, and global controls. Rapid environmental and climate change, including increasing sea-level rise, global warming, reduced upstream discharge and anthropogenic activities, are predicted to increase salinity in the mangroves, especially in the Bangladesh Sundarbans, thereby disrupting this blue carbon reservoir. Nevertheless, it remains unclear how salinity affects the belowground soil carbon despite the recognised effect on above ground productivity. To address this gap, research was undertaken in the Bangladesh Sundarbans to compare total soil organic carbon (SOC) across three salinity zones and to explore any potential predictive relationships with other physical, chemical properties and vegetation characteristics. Total SOC was significantly higher in the oligohaline zone (74.8 ± 14.9 Mg ha-1 23 ), followed by the mesohaline (59.3 ± 15.8 Mg ha-1), and polyhaline zone (48.3 ± 10.3 Mg ha-1 24 ) (ANOVA, F2, 500 = 118.9, p <0.001). At all sites, the topmost 10 cm of soil contained higher SOC density than the bottom depths (ANOVA, F3, 500= 30.1, p <0.001). On average, Bruguiera sp. stand holds the maximum SOC measured, followed by two pioneer species Sonneratia apetala and Avicennia sp. Multiple regression results indicated that soil salinity, organic C: N and tree diameter were the best predictor for the variability of the SOC in the Sundarbans (R2 = 0.62). Despite lower carbon in the soil, the study highlights that the conservation priorities and low deforestation have led to less CO2 emissions than most sediment carbon-rich mangroves in the world. The study also emphasised the importance of spatial conservation planning to safeguard the soil carbon-rich zones in the Bangladesh Sundarbans from anthropogenic tourism and development activities to support climate change adaptation and mitigation strategies

Study on fish hatchery and nurseries in Mymensingh, Bangladesh

In generally, fish hatchery and nursery owners having both hatchery and nursery facilities were financially stronger, well-educated and well-trained than only nursery ponds owners in Mymensingh aquaculture region. On the other hand, only nursery pond owners were more experienced in fish seed business than only hatchery owners. Most of the owners were satisfied with existing communication facilities. Lack of technical knowledge was one of the major constraints which could be solved by ensuring proper training. This business can be made more profitable providing loan to poor farmers and improving law and order situation

Appraisal of surface water quality for irrigation collected from Sadar upazila of Jamalpur district, Bangladesh

An attempt was made to assess surface water quality for irrigation collected from Sadar upazila of Jamalpur district, Bangladesh. Total 22 water samples were collected from the study area and analyzed for various physicochemical parameters following standard protocols at the Department of Agricultural Chemistry, Bangladesh Agricultural University, Mymensingh. Major cation and anion chemistry showed their dominance in order of Ca &gt; K &gt; Na &gt; Mg and HCO3&nbsp;&gt; Cl &gt; SO4&nbsp;&gt; BO3&nbsp;&gt; PO4&nbsp;&gt; CO3, respectively. The study revealed that 18, 14 and 6 samples were unsuitable for irrigation in respect of HCO3, K and BO3&nbsp;contents in water, respectively. Among the heavy metals, the concentration of Pb, Mn, Cd and Cu in water were comparatively higher than the standard limits, which makes 22, 14, 10 and 3 samples problematic for long term irrigation in the study area. Electrical conductivity (EC) and sodium adsorption ratio (SAR) reflected that surface water samples were low to very high salinity (C1-C4) and low alkalinity (S1) hazards classes. As regards to hardness, out of 22 water samples, 2 were very hard, 8 were hard, 11 were moderately hard and only one was soft in quality. The study results concluded that HCO3, BO3, K, Pb, Mn, Cd and Cu were the major contaminants in the surface water of Sadar upazila of Jamalpur district, Bangladesh. Finally, the study suggested that the surface water in this area needs to treat to minimize the amount of contaminants before use for irrigation

Induction of mitotic and meiotic gynogenesis and production of genetic clones in rohu, Labeo rohita Ham.

Studies were undertaken to produce genetic clones derived from all homozygous mitotic gynogenetic individuals in rohu, Labeo rohita Ham. ln view of this, attempts were made to interfere with the normal functioning of the spindle apparatus during the first mitotic cell division of developing eggs using heat shocks, there by leading to the induction of mitotic gynogenetic diploids in the F1 generation. Afterwards, viable mitotic gynogenetic alevins were reared and a selected mature female fish was used to obtain ovulated eggs which were fertilized later with UV-irradiated milt. Milt was diluted with Cortland’s solution and the sperm concentration was maintained at 10⁸/ml. The UV-irradiation was carried out for 2 minutes at the intensity of 200 to 250 µW/cm² at 28± 1°C. The optimal heat shock of 40°C for 2 minutes applied at 25 to 30 minutes a.f. was used to induce mitotic gynogenesis in first (F1) generation and at 3 to 5 minutes a.f. to induce meiotic gynogenesis in the second (F2) generation. The results obtained are presented and the light they shed on the timing of the mitotic and meiotic cell division in this species is discussed

Estimation of maximum sustainable yield (MSY) of hilsa (Tenualosa ilisha Ham.) in the Meghna river of Bangladesh

MSY per recruit of Tenualosa ilisha in the Meghna river was predicted as 112 g per recruit at the F(msy)=0.6/yr and at T(c)=0.6/yr. But Y/R=95 g per recruit was obtained at the existing fishing level, F=1.14/yr and at T(c)=0.6/yr. Existing F level was nearly double than the F(msy) level. Fishing pressure should be reduced immediately from F=1.14/yr to F(msy)=0.6/yr. F(msy)=1.14/yr was the same at first capture, T(c)=1.0, 1.2 and 1.4/yr, and MSY could be obtained as 142 g, 162 g and 176 g per recruit respectively. It is easier to change the first capture age (Tc) rather than changing off level. So, hilsa fishery manager may adopt F(msy)=1.14/yr while age at first capture must be increased from T(c)=0.6/yr (3 cm size group) to T(c)=1.4/yr (25 cm size group), by which 1.8 times production could be increased than the present production. MSY also possible to obtain as 201 g and 210 g per recruit at F(msy)=2.0/yr and 4.0/yr at T(c)=1.7/yr and 1.9/yr respectively. Under both the situations, hilsa production could be increased 2 times than the present production. To obtain the MSY=210 g per recruit the fishing level could be increased up to F=4.0/yr at T(c)=1.9/yr (34 cm size group). Economic point of view, hilsa fishery managers may choose to obtain the economic MSY as 201 g per recruit at F(msy)=2.0/yr and T(c)=1.7yr (31 cm size group) in the Meghna river of Bangladesh

Studies on the food habits of three species of Mastacembelidae

To identify the food habits of three species of Mastacembelidae namely Mastacembelus armatus, Mastacembelus pancalus and Macrognathus aculeatus, the gut content analysis was performed by three methods i.e. occurrence method, points method and index of fullness method. All three species were found to consume prawn, molluscs, insects, earth warm, debris and plant materials. M. armatus and M. pan cal us were found to feed mainly on animal food items and 84.68% of different types of animal food were taken by M. armatus and 62.72% by M. pancalus. M. aculeatus was found to consume 44.86% of different types of animal food items, 53.51% of debris and plant materials which indicated that this fish feeds almost equally on animal and plant food. Analysis of the food habits showed that both M. armatus and M. pancalus are carnivore in nature with higher feeding preference for animal food namely prawn, crabs, fishes, molluscs etc. On the other hand, M. aculeatus is an omnivore in nature feeding almost equally on animal and plant food