Feeding Ecology with Prey Electivity and Growth Performance of Indigenous Asian Striped Dwarf Catfi sh, Mystus Vittatus (Bloch, 1794) in Low Saline Earthen Ponds of Indian Sundarbans

Feeding ecology with prey preferences and fi sh growth of Mystus vittatus (Bloch, 1794) reared in low saline earthen polyculture ponds in Sundarbans were studied for 11th months during July, 2015 to June, 2016. Locally available wild collected mixed bagrid juveniles (4.3±0.14 cm, 1.20±0.99 g) including M. vittatus were stocked @ 1000 juveniles ha-1. No commercial feed or fertilizer was applied following common practice. According to the order of dominance the existing food items in water recorded were Chlorophyceae, Myxophyceae, Bacillariophyceae, Insect parts and larvae, Fish parts &amp; larvae, Rotifers and Cladocera, Copepods and Crustacean larvae. Feeding intensity in terms of stomach fullness upgraded with increasing body weight of fish. The major food constituents in stomach were Copepods followed by Bacillariophyceae, Fish parts and larvae, Insect parts and larvae, unidentified organic matter, Chlorophyceae, Myxophyceae, Rotifers &amp; Cladocera and Crustacean larvae. Prey electivity analysis indicated significantly active selection of Copepods (+0.53±0.05) and Bacillariophyceae (+0.31±0.06). Fish parts and larvae (+0.17±0.11), Insect parts (+0.06±0.07) and larvae and Crustacean larvae (0.02±0.17) were positively selected but not signifi cant. M. vittatus is an omnivorous fi sh and almost prefer zooplanktons. M. vittatus was attained average body weight 26.50±1.20g (13.6±0.19cm) with mean specific growth rate of 0.96±0.19 % day-1at harvest. Bagrid catfi sh performed isometric growth (W=0.012TL2.98) and good condition factor (1.14±0.046) indicating suffi cient of natural food materials in water. Health status of M. vittatus in low saline polyculture ponds is good.</p

Threat Detection Technique in Context to Mangrove Ecosystem of Indian Sundarbans

The mangrove ecosystem in the lower Gangetic delta is one of the most biologically productive and taxonmically diverse ecosystems of the tropics, which is threatened by a variety of stressors. The main threats operating in this fragile ecosystem are erosion, natural disasters (like cyclone, wave actions, tidal surges etc), over exploitation of natural resources, pollution, siltation, sea level rise etc. In this research, we have attempted to develop a mechanism to evaluate and rank the magnitude of threats based through collection of expert opinion from different groups of respondents. The respondents were categorised into five major classes namely policy maker, researcher, fisherman, agriculturist and local inhabitant. About 305 respondents belonging to this 5 categories were asked about the types of threats and their respective magnitude by ranking the threats between 1 to 6. Three different Composite Threat Scales were constructed for three sectors (western, central and eastern) of Indian Sundarbans as these three sectors have contrasting variations with respect to geographical features, salinity, biodiversity, and vulnerability of threats. The present approach of threat analysis can be a road map to identify the types of threats along with their magnitude in the mangrove ecosystem of the world. This scale can also be regulated because of regional settings, which would subsequently lead towards the path of conservation priority of natural resources.</p

Growth Performance, Feeding Ecology and Prey Preference of Bagrid Catfish, Mystus tengara (Hamilton, 1822) in Low Saline Polyculture Ponds of Indian Sundarbans

Growth performances, feeding ecology and prey preferences of Mystus tengara (Hamilton, 1822) reared in low saline homestead traditional polyculture ponds in Sundarbans were studied for 12 months. Mixed carp early fingerlings (4.98±0.61 cm, 1.09±0.26 g) @ 14000 nos ha-1 and wild collected mixed bagrid catfish juveniles (5.09±0.48 cm, 1.38±0.11 g) including M. tengara were stocked @ 5000 juveniles ha-1. Farm yard manure @ 200 kg ha-1 was applied monthly and household dining wastes (11.37±2.08 kg ha-1 day-1) were thrown in the ponds almost daily following traditional practice. Fishes attained 31.56±2.08 g (13.92±0.88 cm) with specific growth rate of 0.95±0.15 % day-1 and exponent value of Length-Weight Relationship (b=2.99) indicated isometric growth. Numeric order of dominance of prey groups in water were Chlorophyceae, Myxophyceae, Bacillariophyceae, Insect parts and larvae, Copepods, Rotifers and Cladoceran, Fish parts and larvae, unidentified materials and Crustacean parts. Whereas, order of dominance of prey groups in stomach were Insect parts and larvae, Copepods, Myxophyceae, Rotifers and Cladoceran, Fish parts and larvae, Bacillariophyceae, Chlorophyceae, Crustacean parts and unidentified materials. Prey electivity analysis indicated significant active selection of Insect parts and larvae (E= +0.36±0.06) and Copepods (E= +0.30±0.12). Crustacean parts, Rotifers and Cladocera and Fish parts and larvae were also positively selected but were not significant. This study reveals that M. tengara is a carnivorous fish mostly preferring Insect larvae and Copepods. M. tengara can be added in low saline polyculture ponds to improve profitability and can be considered as a biological tool for Insect control.</p