Response of African Catfish, <i>Clarias gariepinus</i>(Burchell 1822), Fingerlings Fed Diets Containing Differently Timed Wet-Heat-Treated Sesame (<i>Sesamum indicum</i>) Seedmeal

The response of catfish fed differently timed wet-heat-treated sesame seedmeal was evaluated in the diet of Clarias gariepinus using growth performance, nutrient utilisation and apparent digesti-bility coefficient as indices. Three batches of sesame seed, which were cooked for 10, 20 and 30 minutes, dried, milled, and mechanically defatted using locally made screw press. Each of these differently processed seedmeals was included in the diet of African catfish at varying replacement levels, 15, 30 and 45% with soybean meal. There was good growth performance and nutrient uti-lization by Clarias gariepinus fed with differently timed wet-heat-treated sesame seed that was not significantly different (p > 0.05) from fish fed control diet. More so, the apparent digestibility coef-ficient for organic matter, protein, energy, lipid, fibre, carbohydrate in Clarias gariepinus fed with differently timed wet-heat-treated sesame seedmeal based diets in this study were comparable with the results obtained for fish fed control diets.

Influence of Bleaching Powder on the Quality of Giant Freshwater Prawn (<i>Macrobrachium rosenbergii</i>)

Calcium hypochlorite commercially known as bleaching powder is used as a bleaching agent in shrimp processing industries in many countries and known to effect biochemical alteration in shrimp muscle. Studies were, therefore, undertaken to determine their effect in different concentrations viz., 10, 20, 30, 40 and 50 ppm with different time intervals on the quality of head-on, headless shell-on and peeled giant freshwater prawn (Macrobrachium rosenbergii) by determining biochemical and organoleptic aspects. Myofibrillar protein solubility of fresh head-on, headless shell-on and peeled samples were 90.5%, 90% and 88%, respectively indicating a gradual decrease in protein solubility with increasing concentration of bleaching powder. Decrease in protein solubility was also higher in samples kept at longer duration in different concentration of bleaching powder. At a given concentration of 50 ppm for 30 min treatment, the loss of myofibrillar protein was higher (26.14%) in peeled samples than those of head-on and headless shell-on samples (20.44% and 21.11%). Shelf life of bleaching powder treated prawn samples was found to be reduced to 4 - 5 days in iced condition compared to 6 - 7 days for control samples. Peeled samples were also found to be more susceptible to bleaching powder than that of head-on and headless shell-on samples.

Chemical and Microbiological Hazards of Dried Fishes in Bangladesh: A Food Safety Concern

Food safety along with nutrition is an important issue in the present word. Only nutritionally safe food can ensure a healthy balanced diet to consumers. Dried fish is a popular processed fishery product not only in our country, but also in many countries of the world. It is a very good source of dietary protein, lipid and minerals necessary for a healthy body. The consumers of dried fish in national and international level are losing their interest to buy dried fish due to poor quality and safety of the products. Therefore, we reviewed the state of knowledge regarding the contamination level of dried fish by heavy metals, harmful pesticides, amount of lipid oxidation, and microbial quantity and quality from several districts in Bangladesh. The data reviewed in this article revealed that several dried fishes contaminated with excess amount of heavy metals (Pb, Cd, Cr etc.), pesticide residue (dichlorodiphenyltrichloroethane, heptachlor, endrin, aldrin, dieldrin), higher degree of lipid oxidation, excess amount of total plate count and presence of highly pathogenic E. coli, Salmonella sp. Vibrio sp. were found in few dried fish that may cause substantial human health hazard after consumption. The possible factors of these hazards are traditional drying, use of illegal pesticides with higher dose, lack of maintaining proper hygiene, sanitation, packaging, storage, distribution as well as water pollution. These findings will be helpful to develop an effective quality control and assurance program for producing safe dried fishery products for domestic consumption as well as earning foreign currency.

The Ecotoxicological Effects of Microplastics on Primary Producers in the Marine Environment

Plastic debris is an emerging environmental threat all over the world.But its effect and distribution in the marine ecosystem is barely known.Microplastics abundance in the marine vegetated area is about 2 to 3 times higher than the bare site in the ocean.Although seagrass meadows trap huge amount of microplastics over the ocean floor,a considerable amount of microplastics are also sink incorporating with the marine aggregates from the epipelagic zone of the ocean.Scavenging of microplastics by diatom aggregation decreases the sinking rate of them rather than cryptophyte.As we know,marine snow is the leading carbon source for zoobenthos,but the ubiquitous presence of microplastics damages cell of different microalgae which may alter the food webs of marine ecosystems.Additionally,microplastics releases immense amount of dissolved organic carbons(DOC)in the surrounding seawater that stimulates the growth of heterotrophic microorganisms as well as their functional activity.Plastic debris result in outbreaks of disease in the marine environment and coral reefs are highly affected by it.When coral reef comes in contact with microplastics,the disease infestation rate of the reef increases massively.Three major disease viz.,skeletal eroding band,white syndrome and black band of coral reef causes approximately 46%of reef mortality due to microplastics consumption.Due to complex structure and size,the corals accumulates huge amount of microplastics that increases growth of pathogens by hampering the coral immune system.Existing scientific evidence presents that exposure of microplastics in aquatic environments triggers a wide variety of toxic insult from feeding disruption to reproductive performance,disturbances in energy metabolism throughout the ocean.The present review focused on the ecotoxicological effect of microplastics on primary producers of ocean,its uptake,accumulation,and excretion,and its probable toxicity with risk assessment approaches.

Spatiotemporal variation of shallow water fish assemblages along the coastline of Çanakkale,Turkey

Objective:To determine the shallow water fish species richness ofÇanakkale and to analyse the spatiotemporal variations of these fish assemblages.Methods:Samplings were carried out monthly with a beach seine between January and December 2007.Samples were collected from 6 stations(No.1,2,3,4,5,6).Stations 1 and 4 located in theÇanakkale Strait,2 and 5 in North Aegean Sea,3 and 6 in Sea of Marmara.Results:A total of 112 fish species were sampled and the two most common species were Atherina boyeri and Pomatoschistus marmoratus.A total of 93 species were sampled in theÇanakkale Strait,85 in the Aegean Sea,and 77 in the Sea of Marmara.Shannon diversity index was the highest in the Aegean Sea.Dominant species were caused significant differences of both regional and seasonal fish assemblage fluctuations.Species richness and abundances decreased significantly in winter.Although more species were caught at night and a greater abundance of fishes was obtained during the day,no significant differences were found between day and night in terms of species richness and abundance.Conclusions:The results supported the biogeographical differences between the Aegean Sea,theÇanakkale Strait and the Sea of Marmara in terms of the shallow water fish community.The inventory in the current study can serve as baseline data prior to management strategies to ensure sustainable conservation of the area.

Safety dose of three commercially used growth promoters:nuricell-aqua,hepaprotect-aqua and rapid-grow on growth and survival of Thai pangas(Pangasianodon hypophthalmus)

Objective:To optimize the dose of 3 commonly used growth promoters,viz.,Nuricell-Aqua(composition:glucomannan complex and mannose polymer),Hepaprotect-Aqua(composition:β-glucan,mannose polymer and essential oil)and Rapid-Grow(composition:organic acid and their salt,β-glucan,mannose oligosaccharide and essential oil),using Thai pangas(Pangasiandon hypophthalmus)as cultured species.Methods:Thai pangas fingerlings with an average length and weight of 11 cm and 10 g were reared under laboratory condition and growth promoters were fed after incorporating them with a test diet at a ratio of 10%of their body weight for a period of 28 d.Estimation of data on growth such as weight gain(g),specific growth rate,survivability(%)test in each aquarium were conducted and data were analyzed using statistical software.Results:After 28 d of feeding with Nutricell-Aqua,10 mg/(20 g feed·day),which was the dose recommended by the manufacturer,was found better.When Hepaprotect-Aqua and Rapid-Grow were employed,performance was found to be better with the dose of 60 mg/(20 g feed·day)which was 1.5 times higher than the dose recommended by the corresponding manufacturer.Conclusions:These results suggest that chemicals and feed additives marketed in Bangladesh Fish Feed Market need further testing under Bangladesh climatic condition before being marketed.

Effectiveness of oxytetracycline in reducing the bacterial load in rohu fish(Labeo rohita,Hamilton)under laboratory culture condition

Objective:To observe the effectiveness of most widely used antibiotic,oxytetracycline(OTC)in reducing the bacterial load in rohu fish under artificial culture condition in the laboratory.Methods:The experiment was conducted in the Faculty Fisheries,Bangladesh Agricultural University,Mymensingh-2202.The fish were reared in 8 aquaria where fish in 5 aquaria were used for replication of the treatment(experimental group)and fish in remaining 3 aquaria were considered as a control(Control group).OTC was fed to the fish in the experimental aquarium at the rate of 2 g/kg through diet twice daily whereas fish reared under control condition was given feed without antibiotic for 20 d and bacterial content in the aquarium water,gills,skin and intestine of fish were estimated at every alternative day after onset of the experiment.Results:Rearing the fish with OTC treated feed resulted in gradual decrease of bacterial load in the aquarium water,gills,intestine and skin of the fish whereas the content remain unchanged Or little increased in the control group.W ater quality parameters such as dissolved oxygen,pH and total hardness were within the suitable range in the experimental aquarium but not in control aquaria throughout the experimental period.Conclusions:These results suggest that OTC could be a potential antibiotic to reduce the bacterial load in fish and can be used commercially for maintaining the fish health in aquarium conditions.

Effects of antibiotic on the bacterial microflora in two commercially important catfish species,Clarias batrachus and Heteropneustes fossilis in Bangladesh

Objective:To assess the effects of a widely used antibiotic,oxytetracycline(OTC)on the bacterial microflora in two catfish species under artificial culture conditions in the laboratory.Methods:The experiment was conducted in the Faculty of Fisheries,Bangladesh Agricultural University,Mymensingh-2202.The fish were reared in six aquaria(size 37 cm×30 cm×60 cm)where three aquaria served as replicates of the antibiotic treatment groups and the remaining three aquaria served as an untreated control group.Each aquarium was stocked with 25 fish on an average body weight 15 g.OTC was administered to the fish in the treatment groups at the rate of 2 g/kg in-feed twice daily upto ad libitum,whereas fish in the untreated control groups were given the same feed without antibiotics for 20 d.During the experiment,bacterial loads were estimated as colony forming unit(CFU/g)by every alternate day in the aquarium water,gills,skin and intestine of fish.Results:The administration of OTC in feed resulted in gradual decrease of bacterial loads in the gills,intestine and skin of the two catfish species tested.In contrast,the bacterial loads remain unchanged or slightly increased in the control groups not fed with OTC.Water quality parameters such as dissolved oxygen,pH and total hardness were found to be within suitable range in the test aquaria but not in control aquarium throughout the experimental period.Conclusions:The results of this experiment showed that in-feed antibiotic OTC for a period of 20d reduced the bacterial loads in the gills,intestines and skin of treated fish.