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Fish Culture (fish + culture)

Distribution by Scientific Domains

Earth and Environmental Science	90%

Selected Abstracts

ORIGINAL ARTICLE: Echinacea purpurea and Allium sativum as immunostimulants in fish culture using Nile tilapia (Oreochromis niloticus)

JOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 5 2010
S. M. Aly
Summary The study was conducted to evaluate the efficiency of echnicacea (E) and garlic (G) supplemented diets as immunostimulant for tilapia (Oreochromis niloticus). Seven treatments were designed including a control (C). Fish were fed on 35% protein diet at a rate of 3% body weight per day. Echinacea (1.0 ppt) and garlic (3%) were incorporated in the feed, which was administered for periods of 1, 2 and 3 months (summer season), followed by basal diet for 4 more months (winter season). Neutrophil adherence and haematocrit values increased in both supplemented groups with prolonging period of application. The neutrophils adherence was significantly increased in all treatments except group administered echinacea for 1 month. The lymphocytic counts were significantly (p < 0.004) elevated that resulted in a significant increase in the total leucocytic count in groups administered echinacea for 1 and 2 months when compared with the control and/or other treatments. The gain in the body weight and specific growth rate was significantly increased in all supplemented groups (p < 0.004) during summer, but remained without any significant increase after winter. The survival rate was significantly high (>85%) in all the supplemented groups. The percentage of protection, after challenge infection using pathogenic Aeromonas hydrophila was the highest in groups supplemented with echinacea and garlic for 3 months after summer and winter seasons. It could be concluded that echinacea and garlic improve the gain in body weight, survival rate and resistance against challenge infection. Both compounds showed extended effects after withdrawal and improved resistance to cold stress during the winter season. However, a full commercial cost benefit analysis is necessary before recommending their application in aquaculture. [source]

Swimming activity of seabass: comparing patterns obtained in natural environment and in re-circulating tanks under high density

JOURNAL OF FISH BIOLOGY, Issue 2004
M.-L. Bégout Anras
Seabass (Dicentrarchus labrax) swimming activity was compared between natural environments and aquaculture facilities. Behaviour under natural conditions was assessed in a saltmarsh pond (250 m2, 18 × 14 × 0·8 m) using acoustic telemetry. From several surveys, we documented the diel activity rhythm and demonstrated group effects on swimming patterns and amplitudes by comparing activity of solitary fish with that of a fish living in a group of 60. Consequences of weather variability were also analysed and revealed a high sensitivity of fish to atmospheric conditions for both swimming and demand-feeding behaviour. Behaviour in fish tanks was also studied using acoustic telemetry, as part of the EUREKA EU1 960 ,Aqua-Maki 2' project investigating aspects of fish culture in re-circulating tanks under high density. A re-circulating hexagonal tank (5·4 × 5·4 m, 1·8 m depth, 48 m3) was equipped with positioning and demand-feeding systems, oxygen and temperature probes. Initial density was 50 kg m3 in March and rose to 90 kg m3 at the end of the experiment in May. During this period, the movements of nine fish were continuously recorded for 24 h each, reaching a total of six 24 h episode at eight days interval. Swimming activity was analysed in terms of activity rhythms and space occupation specially around feeding events. The two data set and main results will be presented and compared to assess seabass behavioural plasticity and sensitivity to husbandry conditions. [source]

Toward Improved Public Confidence in Farmed Fish Quality: A Canadian Perspective on the Consequences of Diet Selection

JOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 2 2010
Anthony P. Farrell
Marine fish oils (MFO) are used in salmon diets to mimic the natural diet, to ensure that essential fatty acid requirements for good fish growth and health are met, and to provide salmon flesh with an omega-3 highly unsaturated fatty acid content that can benefit human health. However, an extensive use of MFO in formulated salmonid diets is perceived as an unsustainable use of wild marine fish stocks. In addition, MFOs have a background level of persistent organic pollutants (POPs) unrelated to aquaculture practices. This review considers recently completed studies using alternative lipid sources of terrestrial origin as replacements for MFO and shows that the composition of conventional finfish diets can be altered to reduce the reliance on MFO while concurrently maintaining fish health as well as reducing background levels of POPs. A challenge still ahead is the need for a concerted and sustained outreach to ensure that the public is aware of such improvements to seafood quality so that the preoccupation of the news media with presenting negative images of fish culture to the public is combated. [source]

The effects of water retention time and watershed features on the limnology of two tropical reservoirs in Brazil

LAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 4 2008
Maria Carolina S. Soares
Abstract Although reservoirs are similar to natural lakes in many respects, such driving forces as water retention time and watershed features can play important roles in the limnology of manmade lakes. With the goal of investigating how these factors influence the limnology of tropical reservoirs, physical and chemical variables were measured at four sampling sites in two reservoirs in southern Brazil, from June 2002 to June 2003. Funil Reservoir is located in one of the most-populated areas in the country, in the Paraíba do Sul river basin, which drains and drastically influences the water quality of the reservoir. In contrast, Lajes Reservoir is located in a well-preserved area, with its water retention time varying from six to 30 times longer than for Funil Reservoir. Funil Reservoir is a turbid (median euphotic zone = 4.3 m), eutrophic reservoir (median total phosphorus (TP) = 3.1 µm), with a high phytoplankton biomass (median chlorophyll- a concentration = 10.0 µg L,1). In contrast, Lajes Reservoir is a transparent (median euphotic zone = 9.2 m), mesotrophic water system (median TP = 1.0 µm), with a low phytoplankton biomass (median chlorophyll- a = 1.9 µg L,1). Both reservoirs were stratified during the summer months, but isothermy was only observed in Funil Reservoir. Because of its short water retention time, Funil Reservoir is a much more dynamic system than Lajes Reservoir, with a pronounced temporal pattern related to changes in its water column and its phytoplankton biomass. Spatial heterogeneity is more evident in Lajes Reservoir, mainly as a consequence of its location in a preserved area, long water retention time and the presence of net cages for fish culture in the waterbody. The typical spatial zonation found in reservoirs, related to nutrient sedimentation and light availability, however, is more evident in Funil Reservoir than in Lajes Reservoir. Despite the similarities between these two water systems, which are in the same geographical region with similar climate, and are comparable in size, the distinct watershed features and water retention time are responsible for marked differences between these reservoirs. [source]

Effects of water flow velocity and fish culture on net biofouling in fish cages

AQUACULTURE RESEARCH, Issue 10 2010
John Madin
Abstract The effects of water flow, fish feed and cage position on net biofouling was examined in a floating cage fish farm. Fouling of 16 mm mesh net panels suspended inside and outside net cages and exposed to different treatments were monitored weekly until net apertures were completely occluded by the fouling organisms (8 weeks). Results indicate a dramatic reduction in water flow velocity throughout the fish farm due to the cage units themselves and net biofouling. The reduced water flow (<10 cm s,1) inside net cages promoted rapid net biofouling, while rapid water flow outside the net cages (>25 cm s,1) kept the net fouling organisms at bay. Although fish rearing in net cages with inputs of commercial pellet feed increased sessile biofouling (222% higher than outside the net cages) and non-sessile biofouling (570% higher), the type of fish feed used did not significantly affect biofouling development. The study recommends that the geometry of serially arranged net cages, as commonly deployed in tropical tidal estuaries, be reconfigured to improve flow through in order to minimize the impact of fouling. [source]

Performance evaluation of concurrent rice,fish,prawn culture with and without cull harvesting

AQUACULTURE RESEARCH, Issue 9 2010
Rajeeb K Mohanty
Abstract This study was carried out in farmers' fields for three experimental culture cycles to evaluate the performance of rice,fish,prawn culture. The treatments carried out were deepwater rice mono-cropping (R), and rice,fish,prawn culture with cull harvesting (R,FC) and without cull harvesting (R,F). Water pH and total alkalinity were significantly higher (P<0.05) in R,FC than in R,F, while the concentrations of total suspended solids, plankton and chlorophyll a were higher in R,F. Cull harvesting in R,FC had no marked influence on the concentrations of dissolved oxygen, NH4+, nitrite, nitrate and phosphate compared with the R,F treatment. The significantly higher fish and prawn yields (P<0.05) and species-wise faster individual growth performance in R,FC than in R,F were probably due to periodic cull harvesting, which minimized the competition for food and space as well as physiological stress at reduced density. The paddy yield and percentage increase in paddy yield over rice mono-crop was significantly higher (P<0.05) in R,FC (25%), followed by R,F (16.9%), probably due to lower chlorophyll a (36.7 mg m,3) and plankton density (1.4 × 104 L,1), which minimized the competition for nutrients with rice plants. The highest rice equivalent yield (38.5), output value,cultivation cost ratio (1.56) and enhanced net return (28%) in deepwater rice,fish culture were recorded when cull harvesting was practiced. [source]

Influence of net cage fish cultures on the diversity of the zooplankton community in the Furnas hydroelectric reservoir, Areado, MG, Brazil

AQUACULTURE RESEARCH, Issue 7 2009
Renata M Dos Santos
Abstract The aim of this study was to examine the influence of the net cage system of fish culture on the composition, abundance and diversity of the zooplankton community. Comparisons were made between three collection points located near a group of 30 net cages, with individual volumes of approximately 4 m3, containing newly hatched, young and adult Nile tilapia, positioned in an arm of the Furnas hydroelectric reservoir; point 1 was in the limnetic region and points 2 and 3 were upstream and downstream of the cages, respectively, near the bank. The sampling was carried out at all three points from July to December, 2005. The composition of the zooplankton community differed among the points analysed. The lowest diversity was recorded at point 1. Point 2, upstream of the cages, was characterized by greater species richness and higher density of organisms pertaining to the Rotifera group. The results of the study suggest that variations in the composition and abundance of Rotifera and Cladocera are a consequence of the impact of net cage fish culture, although the magnitude of the variations is small. [source]

Eugenol as an efficacious anaesthetic for tambaqui, Colossoma macropomum (Cuvier)

AQUACULTURE RESEARCH, Issue 11 2005
Rodrigo Roubach
Abstract Anaesthetics are important in fish culture to reduce handling stress and mortality. Eugenol is a promising anaesthetic because of its low cost, efficacy, safety margin for fish and lack of toxicity to humans. The goal of this study was to establish a protocol using eugenol as a fish anaesthetic for tambaqui Colossoma macropomum (Cuvier), and provide information for regulating authorities on establishing safety dosage protocols for its use. Juvenile and sub-adult tambaqui were first individually exposed to doses of 35, 50, 65, 85, 100 or 135 mg L,1 eugenol for 10 min. A second experiment examined the effect of the duration of exposure to eugenol on the time required for recovery and survival of tambaqui. A eugenol dose of 65 mg L,1 was adequate to induce fish of both sizes into a surgical anaesthetic state, and recovery time was similar for dosages up to 100 mg L,1. Exposure to the ideal dose (65 mg L,1) for up to 30 min did not cause fish mortality. Fish blood glucose values were similar for all the tested eugenol doses as well as with the benzocaine control. The results show that eugenol is an efficient and safe anaesthetic for tambaqui. [source]

Swimming activity and energetic expenditure of captive rainbow trout Oncorhynchus mykiss (Walbaum) estimated by electromyogram telemetry

AQUACULTURE RESEARCH, Issue 6 2000
S J Cooke
Rainbow trout Oncorhynchus mykiss (Walbaum) are usually cultured at high densities to maximize production, but little is known about the physiological and behavioural consequences of high-density fish culture. The purpose of this study was to develop quantitative correlates of activity for fish held under conditions of increasing density. Fifteen hatchery-reared rainbow trout (mean fork length = 432.3 ± 9.2 mm) were implanted with activity (electromyogram; EMGi) transmitters and randomly assigned to each of three replicate tanks. Original tank densities (15 kg m,3) were then increased to 30 and finally to 60 kg m,3 at weekly intervals by adding additional fish. Remote telemetry signals indicated that activity increased with increasing stocking density. Fish were relatively inactive during the middle of the day, with diel activity patterns not differing among treatments. Fish were more active during periods of darkness, with activity increasing with increasing stocking density. Relationships between swimming speed, EMGi activity and oxygen consumption were developed using a respirometer and used to estimate oxygen consumption of the fish in the density treatments. Average oxygen consumption estimates increased with increasing density treatments as follows: low density = 75.6 mg kg,1 h,1; medium density = 90.0 mg kg,1 h,1; and high density = 102.6 mg kg,1 h,1. Telemetry permits quantification of the effects of increasing density on fish activity. Physiological telemetry devices may provide a useful tool for remotely monitoring animal welfare correlates under controlled conditions for fish exposed to different husbandry conditions and may prove a valuable tool for the aquaculture industry. [source]