The preservation of some Indian freshwater fish

Quality changes in Labeo rohita, Cirrhinus mrigala and Tilapia mossambica were studied during storage in ice and at ambient temperature (29-32°C). After 10h at ambient temperature L. rohita and T. mossambica were completely spoiled, while C. mrigala became unacceptable within 11h. Organoleptic examination, total volatile base nitrogen and total bacterial counts showed that L. rohita (0.5 kg and above) and C. mrigala (0.5 kg and above) were acceptable up to 7 to 8 days of storage in ice in popular container (Bamboo basket) lined with palmyrah mat) at ambient temperature while T. mossambica (30-40 g) was acceptable up to 6 days. Influence of size of fish on shelf life in ice studied with reference to L. rohita showed that fishes below 500 g were acceptable up to 6 days of storage in ice in popular container at ambient temperature while those above 1000 g size were acceptable up to 8 days. Provision of an alkathene lining to the popular container extended the storage life of L. rohita from 6 days to 8 days. Pre-chilled and iced L. rohita had a longer shel flife (9 days) than merely iced sample (7 days).

A mesocosm analytical study on the impact of freshwater mussel (Lamellidens marginalis Lamarck) mediated bioturbation and biodeposition on some ecological factors of a freshwater lake

The biotic potential of the benthic filter feeding freshwater bivalve mollusc Lamellidens marginalis (Lamarck) influencing the nutrient dynamics of the bottom sediments of the lake by means of biodeposition and bioturbation activities were analysed using a lake mesocosm experiment. Five control as well as experimental mesocosms was maintained up to 60 days (d). The factors studied included the percentage of water content of the sediment, percentage of total nitrogen, percentage of organic matter along with the total phosphorus and humic acid content. While total phosphorus and humic acid content of the experimental mesocosoms showed gradual and significant increases from 30d of the experiment to reach the maximum levels after 60d, the percentage of organic matter registered significant increases right from 15d onwards and reached the maximum values after 60d. On the other hand, while the percentage of water content of the sediments of the experimental mesocosoms increased only up to 30d experiment, percentage of nitrogen was increased during the first half and at the fag end of the experiment. All the investigated ecological factors were found to be significantly influenced by the presence of L. marginalis in the experimental mesocosms. The study indicated that the mussel influence the nutrient dynamics of the inhabitant ecosystem through the processes of excretion, biodeposition of pseudofaeces and faeces, along with the bioturbation of the sediments brought about by their ploughing movements. KEYWORDS: freshwater mussel, Lamellidens marginalis, bioturbation, biodeposition, mesocosms.