A comprehensive trial was undertaken to assess the effect of various types of feed on biomass conversion rate as well as on gonad (ovarian) weight in Colisa fasciata, a dual-purpose fish for food and ornamental use. Three groups of juvenile fish (3.0±0.015 g; 10.00±0.75 mm) were fed with three different types of feed: dried earthworm feed, laboratory prepared feed (LPF) and market feed. The LPF made with dried earthworm powder, eggshell powder and plant rhizome (Commelina sp.) dusts proved to be the best and economical feed among the three feed tested. The LPF also increased gonad weight of the cultured fishes indicating a production of more fish offspring’s from a single female fish. The plant rhizome possibly played a role in increasingly appetite among LPF cultured fish, which in turn influenced somatic as well as reproductive growth of those fish.

Wide variation (>10.28 times) of fish yield (Cyprinus carpio Linnaeus, 1758) was obtained in a trial arranged in concrete cisterns (100 l) receiving compost (T-2), Diammonium phosphate (=DAP) (T-3) and vermicompost (T-4) as direct application fertilizer and manure in those systems. Significant (P < 0.005) differences were observed in diversity and abundance of plankton in response to manure application among treatments. Highest phyto- and zooplankton population was found in the cistern treated with vermicompost followed by DAP, compost and control. In all the treatments dry weight and population of both phyto- and zooplankton population were significantly (P < 0.005) higher than control. The highest production of fish was obtained in the cisterns treated with vermicompost (3,970.56 kg ha−1 90 day−1), followed by diammonium phosphate (3,080.45 kg ha−1 90 day−1), compost (1,952.64 kg ha−1 90 day−1) and the lowest in the control (385.92 kg ha−1 90 day−1). Vermicompost might be cost-effective manure in carp culture, replacing the expensive chemical fertilizer diammonium phosphate.

Three hundred adult healthy earthworms (Eudrillus euginae) ranging length and weight from 14–29 cm (mean 21.5 ± 6.8 cm) to 1.6–3.0 g (mean 2.55 ± 1.1 g), respectively, were cultured in three different substrate for 70 days. The substrates were soil alone, (control T-1), cow (Bos taurus) dung and water hyacinth (Eichhornia crassipes) (1 : 1 T-2), and partially dried neem (Azadirachta indica) leaves with kitchen waste (1 : 1 T-3). The earthworms were grown in these substrates in a wooden chamber (0.8 m × 0.5 m × 0.2 m) and these were subjected to monitoring for various growth patterns (length, biomass, number) at every fortnight (five observations) interval. The observations showed that T-2 was the best among the three treatments used. There was significant difference (P < 0.05) between the mean values of growth efficiency in food conversion among the treatments. However, there was no significant difference (P > 0.05) between the mean values of survival rate of earthworm among different treatments.

Qualitative and quantitative analyses of phyto- and zooplankton, and growth performance of Cyprinus carpio Linnaeus were done in earthen vats receiving compost, Diammonium Phosphate and vermicompost as direct application fertilizer were conducted. Significant differences were observed in the diversity and abundance of plankton in response to fertilization. The highest production of fish was obtained in the vats treated with vermicompost (3,970.56 kg/ha/90 days), followed by Diammonium Phosphate (3080.45 kg/ha/90 days), compost (1,952.64 kg/ha/ 90 days) and the lowest in the control (385.92 kg/ha/90 days). Vermicompost might be a cost-effective fertilizer in carp culture, replacing the expensive chemical fertilizer Diammonium Phosphate.

Two laboratory experiments were conducted to evaluate the amount of P utilization from two different types of sparingly soluble phosphate rock by aquatic biotic communities. The first type was Mussoorie Phosphate Rock or MPR (sedimentary in origin) and other was Purulia Phosphate Rock or PPR (igneous in origin). The two trials were with eight different treatment combinations. Among various treatments, fish and Chironomid larvae contributed to some extent in increasing the available sediment phosphate content which in turn increased the soluble reactive phosphate (SRP) of overlying water. Concentration of SRP of overlying water decreased in the treatment with zooplanktons. Depletion of SRP of overlying water due to uptake of orthophosphate by Chlorella was also observed. The sedimentary type phosphate rock proved to be more efficient in releasing phosphate than igneous one.

The influence of bioturbation caused by common carp fry in 5L jars (5L each) in the laboratory and in 150L outdoor vats in increasing the fertilizer value of phosphate rock was evaluated. Soluble reactive phosphate (SRP) was determined to quantify the effects of bioturbation, fish excrements and soil. The level of SRP was always lowest in the control series. Introduction of common carp fry resulted in a net increase of 0.09–0.10mgL−1 of SRP attributable to the effect of fish excrement. Bioturbation caused by common carp resulted in a 64.8–90% influx of phosphate from bottom soil in the presence of phosphate rock but only about 6.3–7.2% in the absence of phosphate rock. The bioturbation that occurred in these treatments resulted in a significant release of phosphorous into the overlying water from the apatite source. The results confirm the benefits of the application of environmentally friendly phosphate rock in fish farming ponds at low cost.

The influence of bioturbation caused by common carp fry was treated in 24 transparent polythene jars (5 L each) in the laboratory and in outdoor vats (150 L), increasing the fertilizer value of phosphate rock in eight treatment combinations in triplicate. Input of water soluble reactive phosphate (SRP) was determined to quantify the effects of bioturbation, fish excrements and soil. The level of SRP in water was always lowest in the control series. Introduction of common carp fry resulted in a net increase of 0.009–0.010 mg phosphate g−1day−1 of SRP attributable to the effect of fish excrement. Bioturbation caused by common carp resulted in as high as a 64.8 to 90% influx of phosphate from bottom soil in the presence of phosphate rock but only about 6.3 to 7.2% in the absence of phosphate rock. The bioturbation that occurred in this treatment resulted in a significant release of phosphorous into the overlying water from an apatite source. The results confirm the environment friendly application of phosphate rock in fish-farming ponds at low cost.

Fish community structure and water chemistry of two tropical rivers of West Bengal, an eastern province of India, were studied for two annual cycles (January 2003-December 2004) and a higher degree of pollution was found in one river (the Churni) than in the other river (the Jalangi). This was reflected in the water quality as well as in fish community structure of the rivers. We observed that 63.6% of fish species appeared to have been eliminated from the polluted Churni river since 1983 in 20 years. For the protection of fish biodiversity and enhancement of fish production, a rational management program should be implemented for the Churni river.

Limnological studies in two tropical Indian aquatic habitats showed that macroinvertebrate communities have greater diversity than other biotic communities present there. Sediment redox potential is found to be an important factor for alteration of macroinvertebrate communities in aquatic bodies. Anthropogenic activities have influenced the changing of sediment redox potential values of the studied sites and there by affected the macroinvertebrate communities.

The flow and pattern of energy utilization in two tropical ecosystems where polyculture of fishes was practiced were studied. The rates of organic production made by the two tropical natural aquatic systems (oxbow lakes) were studied for two annual cycles. The study of utilization of energy in two tropical lakes revealed that herbivores were more efficient in energy utilization than autotrophs. The energy available in these systems was supplied by allochthonous source. Silver carp and grass carp were found to be most efficient in conversion of energy in the grazing food chain of the lake. The efficiency of the system to fish production was found to be 0.06 (OL-I) −0.05% (OL-II) of the total available solar radiation. Various forms of life are all accompanied by energy changes, in the studied lakes were found to form a food web.

Physicochemical as well hydrobiological investigations were made in two large tropical ox-bow lakes at monthly intervals during the period of two annual cycles of which the second one experienced an unusual drought. The monthly mean concentrations of total alkalinity, hardness, chloride, phosphate and nitrate of water were greatly increased during the drought-affected second year compared with the first year. Prolonged summer in the region caused about 5-25-fold increases in chlorophyll a concentration of nanoplankton and net plankton, respectively. Phytoplankton peaks were less developed during the first year, whereas the summer peak was greatly enlarged during the drought affected second year. There was about a twofold rise in the numbers of zooplankton during the second year as compared with the first year. Benthic invertebrates, on the other hand, were reduced in numbers. Fish production was relatively less during the drought affected second year than during the first year.

To estimate the rate of organic production, two solar powered tropical natural aquatic systems (Oxbow lakes) have been studied for 24 months. The study of utilization of energy in those two tropical lakes has revealed that herbivores were more efficient in energy utilization than autotrophs. Silver carp and grass carp were found to be most efficient in conversion of energy in the grazing and detritus food chain of these lakes. The efficiency of the system to fish production was found to be 0.05 % of the total available solar radiation. Various forms of life are all accompanied by energy changes, even though no energy is created or destroyed in the studied system.

Limnological studies in two tropical Indian aquatic habitats showed that macroinvertebrate communities have greater diversity than other biotic communities present there. Sediment redox potential is found to be an important factor for alteration of macroinvertebrate communities in aquatic bodies. Anthropogenic activities have influenced the changing of sediment redox potential values of the studied sites and thereby affected the macroinvertebrate communities. A positive correlation has been established between rH and Margelef index in our study.

Growth performances of advanced fry of Indian major carps. Labeo rohita (Hamilton). Catla catla (Hamilton) and Cirrhinus mrigala (Hamilton), were examined in simulated pond systems using monthly application of the following fertilizers in six treatments: Mussoorie rockphosphate (MPR) in low (100 kg P2O5 ha−1) and high doses (200 kg P2O5 ha−1), single superphosphate (SSP) (50 kg P2O5 ha−1), single superphosphate mixed with rockphosphate (1:1 by weight: 50 kg P2O5), compost (C) (water hyacinth and cattle manure) and composted rockphosphate (MPR-C). The amount of available P in surface sediment of MPR-C did not differ from that in either the SSP or the MPR + SSP treatment, whereas the total and available N contents differed greatly. There was an inverse relationship between the time to reach phosphate peak of water and the retention time of fertilizer in surface sediments. It is evident that total P of surface sediment was the most significant contributor to fish growth in exclusively MPR treatments, whereas total P and total N of surface sediments are involved in the MPR treatments in combination with compost or SSP.

Pikovskaia's-and modified Pikovskaia's-broth media were used to assess the power of phosphate solubilization, and P-release from tank waters treated with composted phosphate rock (PR) after incubation of the samples both in situ and laboratory conditions for varying periods of 3 to 36 days. The fertilizer value of the composted phosphate rock was maximum during day 3 and then declined to a marginally low value on day 17 of PR treatment. The natural power of P-release from PR treated samples as well as ammonia level from the medium declined with passage of incubation period. The power of P-solubilization, on the contrary, showed a rising trend as the days of incubation increased and showed the maximal values on day 9 to 12 after which a distinct plateau was exhibited. The ratio of PO4-P/NH4-N in the culture medium was highest during day 3 and then declined.

Thirty-two glass jars (3 L each) in the laboratory and outdoor tanks (300 L) were used to examine the influence of common carp (Cyprinus carpio L.) in increasing the fertilizer value of phosphate rock in eight treatment combinations in quadruplicate. Input of water soluble phosphate was determined to quantify the effects of bioturbation, fish excrements and soil. The level of orthophosphate in water was always lowest in the control series. Introduction of common carp fry resulted in a net increase of 0.1 to 0.114 mg . L-1 of orthophosphate attributable to the effect of fish excrement. Bioturbation caused by common carp resulted in as high as a 72 to 100% influx of phosphate from bottom soil in the presence of phosphate rock but only about 7 to 8% in the absence of phosphate rock.

A comprehensive trial was undertaken to assess the effect of various types of feed on biomass conversion rate as well as on ovary weight in Kolisa Kholisa, a fish for food and ornamental use. Three groups of Juvenile fishes (3.0±0.015 g; 10.00±0.75 mm) were fed with three different types of feed. The special prepared food (SPF) made with dried earthworm dust eggshell dust and a plant rhizome dust proved to be best and economical feed for such fishes.