A new high in fish production in India with record yields by composite fish culture in freshwater ponds

Composite fish culture of the Indian major carp, Catla catla, Labeo rohita and Cirrhinus mrigala together with the Chinese silver carp Hypophthalmichthys molitrix and grass carp Ctenopharyngodon idella and the Indonesian strain of common carp (Cyprinus carpio communis) was carried out in experimental ponds in 1971–1972 and 1973–1974. The management techniques adopted aimed at high yields of marketable fish (around 1 kg) in 1 year.In the first year, production varied from 3 889 to 5 600 kg/ha/year and this rose to an average of 8 200 kg/ha/year with a maximum of 9 389 kg/ha/year in the second year. The important changes made to the management schedule in 1973 were increased stocking density, greater use of feed and fertilizers, and provision of more weeds for grass carp.The experimental studies demonstrate the practicability of raising large crops of healthy marketable fish in India.     

Feeding algae to fish

Aquarium-held bigmouth buffalo Ictiobus cyprinellus (Valenciennes) were fed the blue-green alga Spirulina platensis (Nordstedt) at a daily rate of 29 g dry weight/kg body weight for 28 days. Daily growth was 14 g/kg body weight, and food conversion was 2.0. Tilapia aurea (Steindachner) also was fed this blue-green alga; growth and food conversion were similar to those found for bigmouth buffalo. Fresh Spirogyra sp. fed to grass carp Ctenopharyngodon idella Valenciennes resulted in poor growth, and food conversion was about 10.     

Nutrient requirements of ornamental fish

Although fish have been kept for more than three centuries as ornamentals, and the development of manufactured feed since 50 years ago has contributed to the tremendous growth of this hobby, nutrition of ornamental fish is based on extrapolation of results derived from food fishes under intensive farming conditions. Some research on nutrient (protein, minerals) requirements of growing freshwater ornamental species (live-bearers) in a production environment has been conducted, mainly in Singapore, with emphasis on the provision of live feed during the early stages of the life cycle. Protein requirements varied from around 30% dietary protein for growing omnivorous goldfish (Carassius auratus) to 50% for the carnivorous discus (Symphysodon aequifasciata). Whereas mineral (phosphorus, iron, magnesium, zinc) requirements have received some attention in the guppy (Poecilia reticulata), few researches have concentrated on vitamin requirements of ornamental species. Requirements for fatty acids have been conducted mainly on marine ornamentals (damselfish, seahorses), and accentuated the need for dietary supplementation of n-3 highly unsaturated fatty acids. Fish kept in public and home aquaria presents the problem of diversity of species in the same enclosure, each with its own specific requirements and needs. Maintenance energy levels of ornamental fish varied from 0.068 kJ per day for small neon tetras (Paracheirodon innesi) to 0.51 kJ per day for moonlight gouramis (Trichogaster microlepsis) kept at a water temperature of 26 °C. Research on nutrient requirements of ornamental fish urges for suitable measurements other than only growth rate in order to determine optimal dietary inclusion levels.     

Experimental investigation on the transport of different fish species in a jet fish pump

A jet fish pump with a throat of ø60 mm was designed to study its performance in the transport of different fish species and the physiological changes in fish thereafter. Experiments were conducted to investigate the fish transport rate and energy required to transport each ton of fish when transporting Carassius auratus, commonly known as the Chinese goldfish, Megalobrama amblycephala, or Wuchang bream, and Ctenopharyngodon idella, the grass carp. Fish were examined for external injuries as well as for several important enzymes and hormones which are indicators of tissue injury and stress. The results showed that the transport rate for all three species of fish rose dramatically with an increase in the primary stream rate. In this experiment, the transport rates of C. auratus, M. amblycephala and C. idella reached 2357 ± 37.2 kg ∙ h⁻¹, 2888 ± 41.6 kg ∙ h⁻¹, and 2060 ± 40.2 kg ∙ h⁻¹, respectively. However, both injury rate and energy required to transport each ton of fish increased no matter whether the primary stream rate was too low or too high. Considering both transport rate and injury rate, the mean primary stream rate of 80 m³ ∙ h⁻¹ was determined to be the optimal operating condition in this experiment. Fish were stressed and most likely some of their organs were damaged. However, most physiological indexes almost fully recovered after several hours.     

Vitellogenin genes in fish: differential expression on exposure to estradiol

Three types of vitellogenins (Vgs) namely vitellogenin A (VgA), vitellogenin B (VgB) and vitellogenin C (VgC) have been identified in fishes. The existence of VgA and VgB is reported in the Indian freshwater murrel Channa punctatus. Gene-specific primers were designed using available nucleotide sequences in National Centre for Biotechnology Information (NCBI), for amplification of VgA and VgB cDNA. Differential processing of Vgs is evident in many fishes. Adult male murrel expressed both the VgA and VgB genes when estradiol-17β (E₂) is injected in vivo and Vg levels in blood quantified by Enzyme linked immunosorbent assay (ELISA) showed a dose-related response in such treatments. Cultured hepatocytes on treatment with E₂, however, expressed only VgB as detected by RT-PCR, suggesting different regulatory mechanism for the VgA and VgB genes.     

Proteolytic enzymes in fish development and the importance of dietary enzymes

The development of proteolytic enzymes (trypsin, chymotrypsin and aminopeptidase) was studied in three species of fish: Coregonus sp. (hybrids of C. wartmanni and C. lavaretus from Lake Constance), Salmo gairdneri and Rutilus rutilus. Enzyme activity increased more or less with increasing age, particularly in R. rutilus. In this species (a stomachless cyprinid), the level of proteolytic activity was considerably higher than that of S. gairdneri and Coregonus. However, in trout, the low activity of pancreatic enzymes may be compensated by the action of the stomach whereas in coregonids the stomach is not developed until 50 days (body weight without gut content: 65 mg; temperature: 10°C) after hatching. In coregonids this may lead to insufficient digestion of proteins which nevertheless can be compensated by the use of exogenous (dietary) enzymes ingested together with the natural diet. In coregonid larvae fed with Moina sp., exogenous trypsin represents a very high portion of the total tryptic activity. In juveniles older than 60 days (> 150 mg) and in the other two species, the exogenous portion of tryptic activity is less important. Furthermore, a change in the pattern of tryptic isozymes has been found during development of coregonids. It is concluded that low enzyme production as well as the absence of a stomach in the first few weeks after hatching are two important reasons for difficulties in rearing coregonids on an artificial diet.     

Characterization of catalytic efficiency parameters of brain cholinesterases in tropical fish

Brain cholinesterases from four fish (Arapaima gigas, Colossoma macropomum, Rachycentron canadum and Oreochromis niloticus) were characterized using specific substrates and selective inhibitors. Parameters of catalytic efficiency such as activation energy (AE), k _cat and k _cat/k _m as well as rate enhancements produced by these enzymes were estimated by a method using crude extracts described here. Despite the BChE-like activity, specific substrate kinetic analysis pointed to the existence of only acetylcholinesterase (AChE) in brain of the species studied. Selective inhibition suggests that C. macropomum brain AChE presents atypical activity regarding its behavior in the presence of selective inhibitors. AE data showed that the enzymes increased the rate of reactions up to 10¹² in relation to the uncatalyzed reactions. Zymograms showed the presence of AChE isoforms with molecular weights ranging from 202 to 299 kDa. Values of k _cat and k _cat/k _m were similar to those found in the literature.     

The use of lidocaine-sodium bicarbonate as anaesthetic in fish

Lidocaine and lidocaine-sodium bicarbonate mixture were evaluated as anaesthetics for carp (Cyprinus carpio), catfish (Ictalurus punctatus) and tilapia (Tilapia mossambica = Oreochromis mossambicus). Although both induced anaesthesia, the mixture was more effective for induction and recovery, and was able to achieve the required time for the fish to be out of water. The responses varied for the three test species.     

Experiments on rearing exotic carp fingerlings in composite fish culture in India

The results of four field experiments on rearing fry to fingerlings of mainly exotic carp, Hypophthalmichthys molitrix, Ctenopharyngodon idella and Cyprinus carpio var. communis conducted for three- and six-month periods during 1971–1975 are presented. In one experiment Labeo rohita, an indigenous species was also introduced as a compatible species. Fry were stocked at densities of 200 000 and 250 000 per hectare in the three-month period and at 100 000 and 250 000 per hectare in the six-month period.Under pond fertilization and supplementary feeding a high percentage of fingerling survival was recorded; the aggregate percentages ranging between 71.50 and 91.16 in the three-month period and 61.26 and 89.03 in the six-month period.     

Experimental transmission of Saprolegnia and Achlya to fish

Experiments were conducted to determine the mode of transmission of saprolegniasis by Saprolegnia diclina Humphrey-S. parasitica Coker complex and Achlya racemosa in Cyprinus carpio (common carp), Labeo rohita (rohu) and Cirrhina mrigala (mrigal). The fish were exposed to A. racemosa and S. parasitica by direct contact, scale removal or intramuscular injection. The results of these experiments indicate that natural infection is primarily brought about through surface abrasions.     

Combined production of fish and plants in recirculating water

A pilot plant of ca 2000 l of recirculating fresh water for intensive fish production was constructed in a controlled-environment greenhouse. The feasibility was examined of using nutrients from fish waste-water, mainly oxidized nitrogenous compounds, for plant production, combined with an activated sludge system for water purification.The reduction of nitrates, formed during the extended aeration process by nitrifying bacteria, was not sufficient by higher plants and unicellular algae alone to reduce the nitrate concentration in our system significantly. An additional microbial denitrification step had to be included to effect maximal decrease in nitrogenous compounds.For fish culture in the pilot plant Tilapia mossambica and Cyprinus carpio were chosen as experimental fishes. Both fish species showed significant weight increases during the course of the experiment.Ice-lettuce and tomatoes were tested both in recirculating water and in batch culture. The unicellular algae Scenedesmus spp. were grown in a non-sterile batch culture. All plants grew well in the waste-water without additional nutrients.Determination of the physical and chemical parameters for optimum water purification, the most suitable ratio of denitrification by plants and by microorganisms, and the most favourable fish and plant species for combined culture in recirculating water are important and of current interest in view of the increasing demand for clean, fresh water, and the pressing need to find new ways of producing protein for human nutrition under prevailing conditions of an exponentially expanding world population.     

Molecular mechanism regulating axoneme activation in marine fish: a review

River Gomti, a tributary of river Ganga in northern India, is being polluted due to indiscriminate disposal of domestic sewage and industrial wastes that contain genotoxic chemicals. The study was conducted to evaluate the genotoxic potential of polluted water of river Gomti in two fish species, namely Channa punctatus and Mystus vittatus. The fishes were exposed in situ in nylon cages to the polluted water of river Gomti fixed near a distillery outlet located in Lucknow. The induction of DNA damage and micronuclei were determined in blood erythrocytes using comet assay and micronucleus test, respectively. The induction in micronuclei frequencies and DNA damage were found to be significantly elevated (p?<?0.01) in exposed specimens after 3?days post-exposure as compared to the control, i.e. from laboratory-acclimatized fish specimens. The comparison of DNA damage between the two species indicated that C. punctatus is more sensitive to aquatic pollutants. Thus, this fish could be used as a bio-indicator of genotoxicity for bio-monitoring of water bodies. The results further revealed that the river Gomti is being contaminated with potential genotoxic and mutagenic chemicals produced from industrial and domestic activities; therefore, immediate measures are needed to reduce the inflow of pollutants in the river.     

Flat fish eggs,larvae and their development

Studies on development of eight species of flat fishes (Psettodes erumei, Brachypleura novae-zeelandiae, Pseudorhombus arsius, Bothus myriaster, Synaptura albomaculata, S. commersoniana, Cynoglossus arel and C. monopus) were carried out with plankton collections and with laboratory reared larvae. The development stages of Cynoglossus arel and C. monopus from egg to metamorphosis are described.     

Characteristics of marine vibrios isolated from fish farm tanks

Twenty-five cultures of organisms (grouped into presumptive V. parahaemolyticus and V. alginolyticus strains) isolated from tank water used to farm marine fish were subjected to a series of preliminary tests for the identification of V. parahaemoliticus. None were positively identified as this organism. Consequently the isolates, following their characterization as Gram-negative, motile, oxidase-positive rods which were fermentative without the production of gas, together with ten named Vibrio spp., were subjected to various tests and the results were subjected to computer analysis.They were sorted into clusters and it was found that both the presumptive V. parahaemolyticus and V. alginolyticus groups were largely homogeneous. The analysis also showed that the presumptive V. parahaemolyticus strains and one presumptive V. alginolyticus strain were best classified as V. parahaemolyticus and that all but one of the presumptive V. alginolyticus strains would have been best classified as V. anguillarum. The named V. alginolyticus strains proved to be a heterogeneous group and were not closely related to any other group of organisms. The significance of the occurrence of Vibrio spp. in tank water used to farm marine fish, especially when this water is heated power station effluent, is discussed.     

Experimental integrated aquaculture of fish and red seaweeds in Northern Portugal

Three potentially valuable red seaweeds, Chondrus crispus Stackhouse, Gracilaria bursa pastoris (S.G. Gmelin) P.C. Silva and Palmaria palmata (L.) O. Kuntze, collected in northern Portugal, were cultivated using the nutrient-rich effluents from a local turbot (Scophthalmus maximus Linnaeus) and sea bass (Dicentrarchus labrax Linnaeus) farm. The algae were cultivated in a two level cascade system. Several arrangements of the cascade system, stocking densities (3, 5, 7 and 8 kg m^− 2) and water fluxes (140 and 325 l h^− 1) were tested to optimize biomass yield and nitrogen uptake rate and efficiency. The yield and the total ammonium nitrogen (TAN) uptake of the three species were highly seasonal. Palmaria could not survive culture conditions during the summer when water temperature was above 21 °C. In the spring, Palmaria had an average yield of 40.2 (± 12.80) g DW m^− 2 day^− 1 and a nitrogen uptake efficiency (NUE) of 41.0% (± 17.26%). NUE expresses, in percentage, the average reduction in TAN concentration between the inflows and the outflows of the tanks. Chondrus performed better in summer with an average yield of 37.0 (± 11.10) g DW m^− 2 day^− 1 and removing 41.3% (± 17.32%) of nitrogen. Gracilaria grew year round, but also performed better during spring/summer, producing an average of 29.1 (± 2.90) g DW m^− 2 day^− 1, and only 7.3 (± 5.08) g DW m^− 2 day^− 1 during autumn. Yield of C. crispus did not differ significantly when grown at two different stocking densities (5 kg m^− 2 and 8 kg m^− 2). On the other hand, Gracilaria had significantly higher yields at 5 than at 7 kg m^− 2. Better NUE, on average 76.7% (± 22.13%), was also obtained with 5 kg m^− 2 stocking density and only 63.8% (± 24.62%) with 7 kg m^− 2. The yield of Gracilaria increased significantly with the increase of water flux from 140 to 325 l h^− 1 and more nitrogen was removed from the water. However, NUE decreased from 48.4% to 33.4% at 140 and 325 l h^− 1, respectively. Biofiltration was highly improved by a cascade system with a NUE as high as 83.5%.     

Truncation selection for BLUP-EBV and phenotypic values in fish breeding schemes

We have compared rate of inbreeding (ΔF) and genetic gain (ΔG) in truncation selection schemes for fish on best linear unbiased prediction (BLUP) estimated breeding values (EBVs; BTS) or phenotypic values (PTS) with one constraint on the number of tanks (100 or 200) to rear the families, e.g., until tagging size, and one constraint on the total number of selection candidates (3200 or 6400). Single trait selection was practiced for a trait with heritability of 0.1, 0.4 or 0.7 and 5, 10, 20, 50, 100 or 200 selected sires and dams were selected. When going from PTS to BTS, we found an overall increase of ΔG and ΔF of a factor of 0.07 and 1.45, respectively; that is, the increase of ΔG was moderate and accompanied by a dramatic increase of ΔF. In general, ΔF was reduced by increasing the number of tanks at a given number of selection candidates and by decreasing the number of selection candidates at a given number of tanks. ΔF was also reduced for schemes with high heritability because BLUP breeding value estimation then increases the weight on the individual's phenotype, which leads to a reduced correlation between BLUP estimated breeding values within a family, and fish from more families become selected. In practical fish breeding schemes, PTS seems preferable over BTS because BTS generally give unacceptable high ΔF (≫0.01) for these schemes with few but large families. PTS can, however, only be used for traits measured on the selection candidate, which makes PTS less valuable for schemes with comprehensible breeding goals, including, for example, growth, disease resistance, maturity and fillet quality traits. Several traits are measured today on sibs only.     

The role estrogens play in sex differentiation and sex changes of fish

Using genetically controlled all-female and all-male tilapia (Oreochromis niloticus), the role steroid hormones play in the sex differentiation was analyzed histologically, ultrastructurally, immunohistichemically and experimenntally. The results strongly suggest that endogenous estrogen acts as an ovarian inducer, and that the lack of steroid hormone including androgen is important for testicular differentiation. Moreover, the roles of steroid hormones in protogynous sex change of three-spotted wrasse (Halichoeres trimaculatus) and saddleback wrasse (Tharassoma duperrey) were examined. The results strongly support the hypothesis that the endogenous estrogen plays an important role in protogynous sex change.     

Identification and expression analysis of two HSP70 isoforms in mandarin fish Siniperca chuatsi

Heat shock protein 70 (HSP70) plays important roles in multiple cellular stress responses. Two HSP70 isoforms, ScHSP70a and ScHSP70b, were identified from Siniperca chuatsi in this study. ScHSP70a and ScHSP70b shared all but one of their 639 amino acids and showed a remarkable homology to HSP70s of other species. Expression profile analysis by qRT-PCR revealed that both isoforms were detected throughout embryonic development, and a striking feature of ScHSP70a was its significant up-regulation during the crystal stage. ScHSP70a and ScHSP70b were expressed ubiquitously and at a low level in tissues under non-stressed conditions. However, they were dramatically induced by heat shock at different levels, and their induction was positively correlated with the increasing rate of temperature. Although insensitive to hypoxia in the heart, both genes were greatly induced by hypoxia in the liver, and the induction was returned to the basal level after re-oxygenation for 24 h. Additionally, Aeromonas hydrophila infection also markedly augmented ScHSP70a and ScHSP70b expression in a time-dependent manner in the head kidney and spleen, and the ScHSP70a induction levels were much higher than those of ScHSP70b. These results suggest that ScHSP70a and ScHSP70b contribute differently to embryonic development and protection against damage from high temperature, hypoxia and bacterial infection.