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Showing papers in "Aquaculture Research in 1995"


Journal ArticleDOI
TL;DR: Bacterial genera isolated from fish intestines vary with salinity, antibiotics, chromic oxide, diet and dietary components such as linoleic acid, and display day-to-day fluctuations.
Abstract: Microflora isolated from fish intestines have been described for a limited number of salmonid fish species. The size of the microbial population of salmonids appears to vary within different regions of the gastrointestinal tract. The genera present in the gastrointestinal tract seem to be those which can survive and multiply in the intestinal tract. The predominant bacteria isolated from the salmonid gut are aerobes or facultative anaerobes. Few investigations have evaluated obligate anaerobes in the digestive tract of salmonids, and these studies have suggested that the population levels of obligate anaerobes are lower than those of facultative anaerobes. The bacterial genera isolated from fish intestines vary with salinity, antibiotics, chromic oxide, diet and dietary components such as linoleic acid, and display day-to-day fluctuations. Acinelobacter spp., Enterobacter spp. and Pseu-domonas spp. are regarded as autochthonous in Oncorhynchus species, while Aeromonas spp., Flavobacterium spp., Pseudomonas spp. and Lactobacillus spp. are suggested as autochthonous in Arctic charr, Salvelinus alpinus(L.).

360 citations


Journal ArticleDOI
TL;DR: This paper reviews the scientific literature published between 1989 and 1994 on the culture of the freshwater prawn Macrobrachium rosenbergii and summarizes earlier work, and a brief summary of the status and characteristics of prawn culture in the major farming locations is presented.
Abstract: Farmed freshwater prawn production globally expanded by a factor of 3.5 in the 7 years from 1984 to 1991 but declined by 17% to 31 235 tin 1992. This was caused by a 53% reduction in the output of Taiwan due to disease and in-breeding problems, partially compensated by increases elsewhere, notably in India and Vietnam. This paper reviews the scientific literature published between 1989 and 1994 on the culture of the freshwater prawn Macrobrachium rosenbergii (De Man 1879) and summarizes earlier work. Broodstock and larval studies, nutrition, grow-out management, genetics, integrated aquaculture and disease and water quality are covered. Finally, a brief summary of the status and characteristics of prawn culture in the major farming locations is presented, together with some comments on the opportunities and constraints for further development.

196 citations


Journal ArticleDOI
TL;DR: The present experiment suggests that a diet containing approximately 9% starch is optimal for salmon growth and feed utilization, taking into account feed utilization and environmental aspects.
Abstract: Five groups of Altantic salmon, Salmo salar L., (80 g postsmolt) were fed moist diets containing increasing levels of starch from 0% to 31% and concomitant decreasing levels of protein. The results showed that feeding a diet containing 22% lipid with no starch or a starch inclusion higher than 22% exerts negative effects on growth and feed utilization. A starch inclusion above 9% resulted in decreased starch digestibility, while protein digestibility was not influenced by the dietary starch content. Undigested starch is suggested to affect lipid digestibility in the same manner as dietary fibre. The reduced digestibility by high levels of dietary starch led to increased loss of particulate matter to the environment. Taking into account feed utilization and environmental aspects, the present experiment suggests that a diet containing approximately 9% starch is optimal.

195 citations


Journal ArticleDOI
TL;DR: Bottom-dwelling common carp were found to exert an influence on the quality and quantity of planktonic food organisms and the growth of other carps including the bottom-feeder mrigal.
Abstract: The effects of introduction of common carp, Cyprinus carpio (L.). in polyculture with major Indian carps and silver carp were studied in fertilized and fed earthen ponds in Mymensingh, Bangladesh. Bottom-dwelling common carp were found to exert an influence on the quality and quantity of planktonic food organisms. The presence of common carp significantly increased (P < 0.05) the growth of other carps including the bottom-feeder mrigal. Cirrhinus mrigala (Hamilton). A significantly higher fish yield (P < 0.05) was observed in the fish ponds containing common carp when the combined yields of all species in three treatments were compared.

133 citations


Journal ArticleDOI
TL;DR: Fish fed the 20% soybean meal (SBM) diets were not significantly different in body fat content, whilst this was significantly lower in the fish fed the 40% SBM diet, and there were no significant differences between the dietary treatments in body protein content.
Abstract: Diets, containing dehulled, solvent-extracted soybean meal in amounts corresponding to 0. 20 and 40% soybean protein of total protein, were fed for 10 months to duplicate groups of Atlantic salmon, Salmo salar L., weighing about 900 g, held in sea water. Fish fed the diet containing 20% soybean protein grew as well as fish fed the diet with high-quality fish meal as the sole protein source, whilst the fish fed the diet containing 40% soybean protein grew significantly less. No significant differences were found for dressing percentage, condition factor or relative liver weight between the dietary treatments. Fish fed the control or the 20% soybean meal (SBM) diets were not significantly different in body fat content, whilst this was significantly lower in the fish fed the 40% SBM diet. There were no significant differences between the dietary treatments in body protein content. Inclusion of SBM seemed to affect neither carcass calcium, carcass zinc, nor plasma calcium, magnesium or potassium. The plasma zinc content increased and plasma iron decreased by inclusion of SBM in the diets, probably reflecting dietary contents of zinc and iron. Liver iron was not affected. Plasma phosphate was significantly decreased by inclusion of SBM in the diet, whilst plasma glucose, total protein and haemoglobin were not affected. For plasma free amino acids, the only significant differences were a decrease in taurine with increasing SBM inclusion and methionine was significantly higher for the SBM groups than for the control groups.

130 citations


Journal ArticleDOI
TL;DR: The present results show that alcohol-soluble components of soybeans may be responsible for a significant part of the negative effects of standard soybean meal in diets for Atlantic salmon.
Abstract: A commercially available soybean molasses (alcohol extract from soybean meal) was included at levels of 0 5,10,15 and 20% in a fish meal based diet for Atlantic salmon, Salmo salar L, weighing about 75 g These inclusion levels supplied dietary alcohol soluble components corresponding to levels that would have been obtained if a standard soybean meal was included at levels up to about 70% The fish were reared in fresh water at 9oC and with a minimum of 7 ppm O2 at outlet, and fed the experimental diets for 14 days before the faeces were stripped Digestibility coefficients were determined using chromic oxide as an indigestible indicator The digestibility of fat, and particularly the long-chained, saturated-and monounsaturated fatty acids, were significantly reduced by increasing the inclusion level of soybean molasses, whereas digestibility of dry matter, protein (%N x 625) and polyunsaturated fatty acids were not affected significantly The present results show that alcohol-soluble components of soybeans may be responsible for a significant part of the negative effects of standard soybean meal in diets for Atlantic salmon

112 citations


Journal ArticleDOI
TL;DR: The degree of pigmentation in muscle of Atlantic salmon fillets of fish that were fed eight diets fortified with 10, 20, 40, 60, 80, 80.100, 150 and 200 mg astaxanthin kg−1 and a non-supplemented control diet from 3 to 21 months was assessed using different methods.
Abstract: The degree of pigmentation in muscle of Atlantic salmon, Salmo salar L., fillets of fish that were fed eight diets fortified with 10, 20, 40, 60, 80.100, 150 and 200 mg astaxanthin kg−1 and a non-supplemented control diet from 3 to 21 months was assessed using different methods. A tristimulus colorimeter (Minolta Chroma Meter) was used to measure the colour composition of the fillets instrumentally. The colour was also determined using the Roche Colour Card for Salmonids. The concentration of astaxanthin in the muscle was measured by chemical analyses. All measurements for colour were done directly on the epaxial muscle anterior to the dorsal fin. The lightness factor (L *). the red/green chromaticity (a*), the yellow/blue chromaticity (b*) and the saturation C* of the colorimetric readings and the Colour Card scores were compared with the chemical analyses. The astaxanthin concentration in the flesh varied from 1 to 10 mg kg−1 and the visual appearance of the fillets varied from yellowish-white to red. The relationship between the a*, b* and C* values and the astaxanthin concentration in the muscle was non-linear. Non-linear regression lines were found between the a* value and the astaxanthin concentration in the flesh (r2= 0.974) and the b* value and the astaxanthin concentration in the flesh (r2= 0.984). The instrument was not able to detect differences in astaxanthin concentration at astaxanthin levels above 3-4 mg kg−1 using the presented method directly on the fillet. The instrument might be useful for rejecting groups of salmon with poor pigmentation. A good linear regression was found between the Colour Card score and the mean astaxanthin concentration in the flesh (r2 - 0.992). The Colour Card provided a better prediction of the astaxanthin concentration at higher astaxanthin levels than the Chroma Meter. None of the methods provided a satisfactory prediction of the astaxanthin concentration in the muscle of individual fish using the presented methods.

107 citations


Journal ArticleDOI
TL;DR: Challenge testing seems to be a feasible method, with relatively low costs and easy management, and the future response to selection will depend on the relationships between results from a challenge test and mortalities under farming conditions and between disease resistance and other traits in the breeding goal.
Abstract: Genetic variation in susceptibility of Atlantic salmon, Salmo salar L., to furunculosis, bacterial kidney disease (BKD) and cold water vibriosis was studied by challenge testing one-year-old fingerlings. Fish from 81 full-sib families within 32 sire progeny groups were infected with Aeromonas salmonicida, Renibacterium salmoninarum and Vibrio salmonicida. Estimated heritabilities were relatively low, being highest for BKD (h2= 0.23) and lowest for cold water vibriosis (h2= 0.13). Genetic correlations between the ability to survive the diseases were all positive, but the magnitude of the genetic correlation between furunculosis and BKD may be biased upwards because some of the dead BKD fish were also infected with furunculosis. The application of selection to develop resistant populations of Atlantic salmon is advocated. Challenge testing seems to be a feasible method, with relatively low costs and easy management. The future response to selection will depend on the relationships between results from a challenge test and mortalities under farming conditions and between disease resistance and other traits in the breeding goal.

86 citations


Journal ArticleDOI
TL;DR: Values for energy digestibilities indicated a much greater variation, from 6% to 80%.
Abstract: A number of raw materials were tested to obtain the in vivo apparent digestibility coefficients of protein, lipid and gross energy for gilthead bream. Sparus auratus L., under controlled conditions. In the case of protein digestibility assessment, a standard in vitro method was also included for comparison. Protein digestibility coefficients were generally high, with values between 60% and 96% being observed for most of the materials studied. However, some exceptions were apparent in materials of both animal and plant origin. Lipid digestibilities also ranged between 50% and 90%. Values for energy digestibilities indicated a much greater variation, from 6% to 80%. These observations are discussed in relation to the nature and source of ingredients and to the type of processing technology employed.

85 citations


Journal ArticleDOI
TL;DR: An analysis showed that the system is labour orientated, technically reliable and economically feasible when the fingerlings can be sold for USS 0.07 apiece.
Abstract: In order to obtain an appropriate and reliable method for the mass production of Clarias gariepinus (Burchell) fingerlings. experiments on artificial reproduction and pond rearing were carried out in the Republic of Congo in 1987-1991. Reproduction could be induced throughout the year using common carp pituitaries (3 mg kg−1 female). The average relative fecundity of females varied between 1.3%± 0.3 (SEM) and 14.3%±1.3 (SEM). The average hatching percentage of the eggs varied between 28.4%± 4.5 (SEM) and 59.1%± 3.7 (SEM) respectively, in the dry and rainy season. The fluctuation of the relative fecundity as well as the fluctuation of the hatching percentage follows the seasonal fluctuation in rainfall and temperature. The use of a net cage made of mosquito netting (1 m3, 0.5 mm mesh size) and the roots of water hyacinth (E. crassipes) as an egg incubator proved to be reliable. In ponds not protected against frogs an average of 5.0 ± 2.9 (SEM) fingerlings m−2 per 40 days cycle were obtained, whereas in ponds completely surrounded by a wall of aluminium roof plates (0.8 m high) the average production was 32.3 ± 3.3 (SEM) fingerlings nr- per 40 days cycle, when they are stocked with approximately 100 larvae m−2. Increasing the larval stocking density or extending the rearing period did not improve the final production. The main causes of low production in unprotected ponds are competition for food resources due to the presence of phytophagous frog larvae and cannibalism among the fingerlings of Clarias gariepinus. An analysis showed that the system is labour orientated, technically reliable and economically feasible when the fingerlings can be sold for USS 0.07 apiece.

84 citations


Journal ArticleDOI
TL;DR: Some of these field techniques were found to be reliable indicators of stress in fish and have potential for use in aquaculture facilities and field monitoring programmes.
Abstract: While physiological stress in fish can be assessed by several laboratory-based methods, many of those methods use very sensitive and expensive instruments, which make them impracticable under field conditions. The objective of this study was to determine the feasibility of detecting stressed states in fish, under Held conditions, using simple but reliable methods. The first set of experiments were conducted in the laboratory, where a standard handling stressor was applied to juvenile coho salmon, Oncorhynchus kisutch (Walbaum). Results of blood samples analysed by both laboratory-based and portable methods (e.g. glucometers for diabetic patients) were in good agreement. The second set of experiments focused on field-testing the most promising methods based on the laboratatory tests. Production lots of Atlantic salmon. Salmo salar L., at commercial fish farms were sampled to assess stress and health status with the selected field techniques, from the swim-up to smolting stages. The measured variables included: blood glucose, protein, haemoglobin concentrations: haematocrit: erythrocyte and lymphocyte numbers: and an autopsy-based health profile, which involved the internal and external examination of the body for texture and colour. In addition to establishing resting, or normal, values for each variable under field conditions, blood glucose levels were observed to increase significantly at 4 h after a stressful event (e.g. grading, handling) using these field methods. Some of these field techniques were found to be reliable indicators of stress in fish and have potential for use in aquaculture facilities and field monitoring programmes.

Journal ArticleDOI
TL;DR: The simulation result indicates that reduced ration is not effective strategy for minimizing nutrient discharges from fish farms, and it is better to adjust the biomass on the farm and to feed the fish to appetite, at which growth rate is maximum and FCR is minimum.
Abstract: Nutrient discharges from fish farms can be determined retrospectively, simply and with a high degree of accuracy from records of fish production and feed conversion ratios (FCR), combined with chemical analyses of feed and fish. Prospective prediction of the inputs (via feed and outputs) via production and discharges) of given chemical elements, on a daily basis and over longer periods of time, would represent a valuable management tool for farmers, and for regulatory and planning authorities. A dynamic model is presented for Atlantic salmon, Salmo salar L., which integrates biomass, growth rate. FCR. and nutrient retention and discharges in relation to feeding rate, diet composition and environmental factors. In view of the importance of feeding rate on growth, FCR and nutrient discharges, three simulation alternatives were modelled; namely, feeding 50%. 75 or 100% of the estimated maximum daily ration of a specified diet to salmon smolts of 80 g initial weight over a period of one year in sea water. The 50 and 75% rations, in comparison with 100% ration, showed dramatic reductions in fish weight after one year (0.4 and 1.4 kg versus 3.3 kg). The discharges of nitrogen (N) and phosphorus (P) per unit biomass production were reduced to some extent in the first months of the simulation period, and thereafter, there were no clear differences in discharges of N and P per unit biomass at the three ration levels. However, the accumulated N and P discharges per unit weight gain were slightly increased on the 75% ration, and two-fold higher on the 50% ration compared to the 100% ration. The FCR was also higher in fish fed the lower rations. The simulation result indicates that reduced ration is not effective strategy for minimizing nutrient discharges from fish farms. In order to control discharges within any limits and to utilize the resources optimally, it is better to adjust the biomass on the farm and to feed the fish to appetite, at which growth rate is maximum and FCR is minimum.

Journal ArticleDOI
TL;DR: It is suggested that a diet with an all-plant protein source (SBM) can totally replace fish meal in a diet for blue catfish, without adverse affects on weight gain or body composition, when the dietary protein level is 35% and fish are fed to satiation.
Abstract: A 12-week feeding trial was conducted in aquaria with juvenile (8.9 g) blue catfish, Ictalurus furcatus (Lesueur), to examine effects of totally replacing fish meal with a high (65%) percentage of soy bean meal (SBM) in prepared diets. Five isonitrogenous (35% protein) and isocaloric (10.5 kJ digestible energy g−1 of diet) diets were formulated. Diet 1 was similar to a high-quality commercial channel catfish diet, containing 15% fish meal and 42% SBM. Diets 2-5 contained 0% fish meal and 70% SBM with various amounts (0.0%. 0.3%, 0.6% and 0.9%) of L-methionine added. After 12 weeks, individual weight, weight gain, survival, specific growth rate, feed conversion ratio, protein efficiency ratio and food intake were not significantly different (P > 0.05) among treatments and averaged 36 g, 302%, 100%, 1.6% day−1. 2.4,1.3, and 3.4% body weight, respectively. Whole-body compositions of fish were not significantly different (P > 0.05) among treatments and averaged 75%, 61% and 27% for percentage moisture, protein and fat, respectively. These data suggest that a diet with an all-plant protein source (SBM) can totally replace fish meal in a diet for blue catfish, without adverse affects on weight gain or body composition, when the dietary protein level is 35% and fish are fed to satiation.

Journal ArticleDOI
TL;DR: Preliminary results indicate that the optimal dietary vitamin E level is 120 mg dl-α-tocopheryl acetate per kg dry diet, or more, and further research is necessary to confirm this hypothesis.
Abstract: The minimum requirement of vitamin E for Atlantic salmon, Salmo salar L., at first feeding was found to be 60 mg dl-α-tocopheryl acetate per kg dry diet. The dry diet contained 5.6% polyunsaturated fatty acids, which is similar to that used in practical diets at first feeding. Preliminary results indicate that the optimal dietary vitamin E level is 120 mg dl-α-tocopheryl acetate per kg dry diet, or more. Further research is necessary to confirm this hypothesis.

Journal ArticleDOI
TL;DR: The results lead to the conclusion that, in rainbow trout, feeding time has an effect on both feed intake and feed utilization.
Abstract: The effect of the time of delivery of a single daily meal was studied in immature rainbow trout, Oncorhynchus mykiss (Walbaum). In a first experiment, fish were fed 1.5 % of their body weight once a day at dawn. 1200 h, dusk or 2400 h and no attempt was made to monitor uneaten food. The best growth performance was observed for fish fed at dawn, while lowest performance was achieved by fish fed at 2400 h. During a second experiment, fish were fed at dawn or 2400 h at 0.9%, 1.2 % or 1.5% of their body weight, and the proportion of uneaten pellets was measured. Fish fed at 2400h showed lower growth performance, and feed intake was 10% lower than that of fish fed at dawn. Protein, lipid and energy retention (nutrient gain/ nutrient intake) was also the lowest in fish fed at 2400 h. These results lead to the conclusion that, in rainbow trout, feeding time has an effect on both feed intake and feed utilization.

Journal ArticleDOI
TL;DR: Simulation results provide strong support for the oxygen limitation theory and can be used for the analysis of fish growth as affected by feed amount, feed composition, as well as environmental conditions (temperature, dissolved oxygen concentration).
Abstract: Fish need oxygen for aerobic generation of energy for body maintenance, locomotion, feeding and biosynthesis. The rate of oxygen uptake of most fish is limited by diffusion through the gills, and gill surface area grows at a slower rate than body mass. We hypothesize, therefore: (1) that the maximum rate of feed intake is related to the capacity to take in oxygen for processing of this feed; and (2) that the maximum rate of feed intake relative to body size decreases with increasing body size to a point where growth is zero. An oxygen limitation module based on this theory was incorporated into an existing dynamic simulation model for the Nile tilapia, Oreochromis niloticus (L.). The module calculates the maximum potential oxygen supply to the fish on the basis of Fick's law of diffusion and the allometric relationship between body weight and gill surface area. Total oxygen demand of the fish is computed as the sum of routine metabolism, feeding metabolism and energy needed for biosynthesis. In the module, the feeding rate is limited to a level where total oxygen demand does not exceed the potential supply. The model is used to simulate feeding and growth of O. niloticus. Simulation results provide strong support for the oxygen limitation theory. Hence, the model can be used for the analysis of fish growth as affected by feed amount, feed composition, as well as environmental conditions (temperature, dissolved oxygen concentration). It also explains differences in final size between fish species, and within species under different conditions.

Journal ArticleDOI
TL;DR: In fish receiving protein rations equal or below rations resulting in maximal growth, protein ration and protein gain were almost linearly related and the model showed that the portion of the dietary protein which is digested decreases with increasing protein ration.
Abstract: Three size groups of Colossoma macropomum were submitted to a 4-week growth trial. Five nearly isocaloric (18.8-21.0 kJ g−1) diets with protein concentrations ranging between 17 and 64% were administrated at a fixed, near satiation level. Maximum growth was 6.6, 3.6 and 1.9 g protein kg−0.8 day−1 for 5, 50 and 125 g fish, respectively. The protein requirement to achieve maximum growth decreased from 28.9 g protein kg−0.8 day−1 for 5 g fish to 11.7 g kg−0.8 day−1 for 125 g fish. Possibly because of its high growth rate. C. macropomum needs a slightly higher dietary P/E ration (25.4-27.9 mg protein kJ−1) to obtain maximal growth than most other fishes. The relation between protein ration and protein gain was studied by a quadratic regression model. In fish receiving protein rations equal or below rations resulting in maximal growth, protein ration and protein gain were almost linearly related. The model showed that the portion of the dietary protein which is digested decreases with increasing protein ration. Body protein content increased and body lipid content decreased with feed protein level. Fish fed a 17% protein diet deposited as much as 18% lipid.

Journal ArticleDOI
TL;DR: Heritability estimates derived from the dam component of variance corresponded in general to the sire estimates, indicating the absence of non-additive genetic and environmental effects common to full sibs.
Abstract: Data on two year classes of Atlantic salmon, Salmo salar L., reared for 2 years in sea water, were analysed. Records were obtained on 1271 offspring of 58 sires and 171 dams mated hierarchically. Medium-high sire heritabilities (0.30-0.38) were found for ungutted and gutted body weights, body length, body circumference and condition factor (whole-body traits). Corresponding estimates for height and width of cutlet and average thickness of the abdominal wall ranged from 0.23 to 0.27. The latter measurements were made on a transversal section anterior to the dorsal fin. Heritability estimates derived from the dam component of variance corresponded in general to the sire estimates, indicating the absence of non-additive genetic and environmental effects common to full sibs. Estimated phenotypic and genetic correlations among the traits were all positive. With regard to the likely breeding goal of a commercial selection programme, the genetic correlations of ungutted and gutted body weights with condition factor (rG=0.36-0.37) were judged unfavourable. The results revealed substantial impact of sex and sexual maturation status on growth. The need is stressed for proper adjustment for these effects when assessing growth or growth-related data.

Journal ArticleDOI
TL;DR: Marked differences in the response to handling stress among stocks of coho and spring chinook smolts were evident, and the results point to the importance of screening hatchery salmonid stocks to assess differing capabilities of dealing with stress.
Abstract: This study examined whether rapid recovery from stress-induced impairment in predator evasion, observed in previous studies on coho salmon, Oncorhynchus kisutch (Walbaum), was a general characteristic of different stocks of the same species and different species of Pacific salmon. We monitored stress-induced non-predator mortality, predator evasion and Cortisol concentrations of smolts of coho and spring Chinook, O. tshawytscha (Walbaum), after administration of standardized single and multiple handling stresses. Marked differences in the response to handling stress among stocks of coho and spring chinook smolts were evident, with recovery from impaired predator evasion occurring within 24 h of a 30-s handling stress for coho smolts and 24 h of a 1-min handling stress for spring chinook smolts. Differences in stress-induced non-predator mortality among stocks were also observed. The results point to the importance of screening hatchery salmonid stocks to assess differing capabilities of dealing with stress.

Journal ArticleDOI
TL;DR: Feeds formulated with 5.7, 11.4 and 22.7% spray-dried blood powder, also called blood flour, were compared with a control diet with 49% herring meal and no blood powder for rearing juvenile rainbow trout to investigate apparent digestibility and increases in phosphorus concentrations in the water in which trout were fed diets with blood powder.
Abstract: Feeds formulated with 5.7, 11.4 and 22.7% spray-dried blood powder, also called blood flour (88.1% protein, 0.2% total phosphorus), were compared with a control diet with 49% herring meal (64% protein, 2.1% total phosphorus) and no blood powder for rearing juvenile rainbow trout. Oncorhynchus my kiss (Walbaum). Diets with 5.7, 11.4 and 22.7% blood powder contained 1.22,1.03 and 0.84% phosphorus, respectively, compared with 1.36% phosphorus in the control diet. Over 12 weeks, differences in mean specific growth (range 2.23-2.35 day−1) or feed conversion (range 1.04-1.09) among the four diets were not significant (P > 0.05). Apparent digestibility of phosphorus in the diet with 22.7% blood powder was greater (45.2%) than that in the control diet (31.6%). Increases in phosphorus concentrations in the water in which trout were fed diets with blood powder (range 16-20 μg−1 total phosphorus) were 33-47% less (P<0.05) than in tanks where trout were fed the control diet (30μg−1 total phosphorus). Feed formulations for rainbow trout prepared with 22.7% blood powder and 17.0% fish meal would contain 65.3% less fish meal and 38% less total phosphorus than present in the control diet, which was a representation of a modern feed formulation for rainbow trout.

Journal ArticleDOI
TL;DR: It was found that 2-phertoxyethanol was most effective, followed by quinaldine sulphate, in decreasing the excretion of metabolic wastes by the fish, and metomidate had no effect in the control of waste production.
Abstract: An experiment was carried out to study the effects of anaesthetics (2-phenoxyethanol, quinaldine sulphate, metomedate and MS-222) on water parameters during simulated air transport of platyfish. Xiphophorus maculatus (Gunther). The platyfish were put in sealed plastic bags, one-quarter full of water, to which a required amount of anaesthetic was added. The rest of the bag was filled with oxygen. The water in the bag was tested for pH. total ammonia and carbon dioxide at intervals of 4 and 8 h for a period of 48 h. Mortality rates within this period and the post-packaging period were also noted. It was found that 2-phertoxyethanol was most effective, followed by quinaldine sulphate, in decreasing the excretion of metabolic wastes by the fish. Metomidate had no effect in the control of waste production. MS-222 reduced ammonia excretion but not carbon dioxide. None of the anaesthetics used had any effect on the pH of the water.

Journal ArticleDOI
TL;DR: Macrobenthic infaunal responses were considered to provide the best measure to date of determining the impacts of organic wastes from cage fish farming and a possible way forward in developing benthic Environmental Quality Standards (EQS) for aquaculture.
Abstract: Benthic macrofaunal community changes are used extensively to monitor the impact of polluting discharges to the marine environment. Regulatory and pollution control authorities have recognized the particular value of the well studied and reported responses of infaunal communities to organic pollution including wastes from aquaculture. Benthic systems are embraced in both the consent (licence) to discharge and monitoring procedures for marine cage fish farms in the Clyde River Purification Board's (CRPB) area. The relevant protocols of the CRPB are described and data are presented from impact studies throughout west central Scotland, focussing on the sedimentary environment (macrobenthos, organic carbon and redox: Eh). Macrobenthic infaunal responses, though not fully understood, were considered to provide the best measure to date of determining the impacts of organic wastes from cage fish farming and a possible way forward in developing benthic Environmental Quality Standards (EQSs) for aquaculture. Some patterns in physico-chemical data were identified, but frequently, the relationship both with benthic infaunal data and each other were inconsistent. Grossly impacted faunal communities varied little between sites and could readily be described by the simple community determinands of abundance (A), species richness (S) and Shannon Weiner diversity index (H). Moderate to lightly impacted zones were less easily defined but detailed faunal studies have allowed the selection of some widely distributed marker species. However, site-specific observations emphasized the site individuality and difficulties of setting EQSs across the industry. Using the principles of enhanced species populations and by identifying marker species, measurable impacts were found to extend further than previously reported. In naturally enriched systems, like the Firth of Clyde and some sea lochs, difficulty in separating slight effects from background was experienced. Continued monitoring and impact assessment, as well as building a better biological data base, may help develop appropriate benthic EQSs relating to aquaculture.

Journal ArticleDOI
TL;DR: The results showed that salmon lice were able to survive for up to 3 weeks, in contrast with previous published information that the parasite is quickly shed when the fish enters fresh water.
Abstract: The survival of salmon lice. Lepeophtheirus salmonis (Kroyer) on Arctic charr. Salvelinus alpinus (L.). in fresh water was studied. The results showed that salmon lice were able to survive for up to 3 weeks, in contrast with previous published information that the parasite is quickly shed when the fish enters fresh water.

Journal ArticleDOI
TL;DR: A new type of extender is presented and experiments demonstrating that warming of frozen/thawed semen to 20°C prior to fertilization significantly increases the fertilization rate are demonstrated.
Abstract: The present study describes a uniform method for cryopreservation of semen of Salmonidae (Oncorhynchus mykiss (Walbaum), Salmo trutta f. fario L., Salmo trutta f. lacustris L., Coregonus sp.). It presents a new type of extender and experiments demonstrating that warming of frozen/thawed semen to 20°C prior to fertilization significantly increases the fertilization rate. Freezing is performed in straws in the vapour of liquid nitrogen and for insemination a diluent technique is used. The consistency of the method was tested by repeating the experiments with different batches of semen and eggs. The following fertilization rates (% of control) were obtained: Oncorhynchus mykiss: 89.6 ± 16.0% (mean ± standard deviation, n= 25, n of control = 20, sperm/egg ratio of 1.6 ± 0.2 × 106 spermatozoa/ egg). Salmo trutta f. fario: 93.8 ± 6.4% (n= 12,9.9 ± 1.2 × 106spermatozoa/egg), Coregonus sp.: 92.8 ± 2.4% (n= 6, 0.5 × 106 spermatozoa/egg), Salmo trutta f. lacustris: 85.0 ± 8.4% (n= 12, 4.8 ± 1.4 × 106 spermatozoa/egg).

Journal ArticleDOI
TL;DR: The view that fish can be fed alternately with animal- and plant-protein-based diets of varied protein levels is supported, which would help to reduce protein input, and would contribute to the efficient utilization of low-quality, plant- protein-based dinners.
Abstract: A 90-day growth trial was conducted with common carp, Cyprinus carpio L., to test the suitability of mixed feeding using a plant-based low-protein diet (16% -diet A), and two fish-meal-based diets of 26% protein (diet B) and 31% protein (diet C). Three mixed feeding schedules were tested: 1A/2B, 2A/2B and 2A/2C; numerals refer to number of days each diet (A, B or C) was offered continuously. Fish fed diets A, B or C continuously served as controls. Fish grown on diet A grew the least, while there was no significant difference between those fed on diets B or C. Of the three mixed schedules, 2A/2C produced the highest growth, which was better than that on control diets B or C. Specific growth rate (%) and food conversion ratio and protein retention were found to be good for all mixed feeding schedules. The plant protein diet resulted in poor-quality flesh as indicated by carcass composition. The study supports the view that fish can be fed alternately with animal- and plant-protein-based diets of varied protein levels. This practice would help to reduce protein input, and would contribute to the efficient utilization of low-quality, plant-protein-based diets.

Journal ArticleDOI
TL;DR: It was shown that rapidly developing eggs and the larvae that hatched from them contained greater triacylglyceride lipid reserves than those which developed more slowly and hatched later and that fouling organisms became attached to larvae was related to feeding regime but not to development rate.
Abstract: The viability of batches of larvae reared to produce lobsters, Homarus gammarus (L.), for stock-supplementation experiments varied widely and rendered the timing and numbers of juveniles available for release unpredictable. Egg lipid reserves, time of hatching, exposure to low salinity during incubation and the influence of feeding regimes on water quality during larval culture were among the factors judged most likely to have affected viability. There was considerable variation in the lipid content of eggs from different females captured in 1989 and 1990. The proportion of lipid in eggs from females caught in 1990 was higher (10-20%) than that in eggs from females caught in 1989 (6-11%). The fatty acid content of eggs declined 72-80% during development although the overall proportions of fatty acids remained similar. Analysis of eggs and larvae from a single brood showed that rapidly developing eggs and the larvae that hatched from them contained greater triacylglyceride lipid reserves (by 49% and 15% respectively) than those which developed more slowly and hatched later. Exposure to reduced salinity (below 29 psu) prolonged development (by 30%), increased losses (to > 50%) and reduced the ratio of n-3:n-6 fatty acids (from 35-48 to 18-29) of eggs being incubated by captive, wild-caught, female lobsters. Larvae hatching from eggs held in reduced salinity (23 psu) survived less well (3% compared with 15%) than those incubated in sea water of 29 psu. The rate and degree to which fouling organisms became attached to larvae was related to feeding regime but not to development rate. A diet of mysids supplemented with mussel produced most fouling, generally poorer growth and a higher incidence of moulting abnormalities than a diet of mysids supplemented with Artemia nauplii. Among larvae fed Artemia, those developing early were significantly larger at instar 4 than late developers (56.4 mg cf. 49.8 mg, P < 0.05), but such differences in weight were not maintained by juveniles during the following 31 days of culture. The ecological and aquacultural implications of the results are discussed.


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TL;DR: Alfalfa meal as a source of organic fertilizer was used in a series of pond, enclosure and laboratory experiments to determine its effect on bacteria, algae and water quality, and bacteria and flagellate algae were increased, whereas nonflagellated algae were not significantly affected by organic loadings.
Abstract: Alfalfa meal as a source of organic fertilizer was used in a series of pond, enclosure and laboratory experiments to determine its effect on bacteria, algae and water quality. Bacteria and flagellate algae were increased, whereas nonflagellate algae were not significantly affected by organic loadings. Bacterial and algal turnover rates we re 1.9-2.7 times daily and 0.18-0.22 times daily at 20-25oC, respectively. Oxygen consumption rates were enhanced by increasing organic input or temperature. Dissolved oxygen in ponds with organic fertilizer was significantly lower than that in ponds without organic input. Because of low N and P content and high oxygen consumption, organic fertilizer alone is unlikely to provide adequate nutrients for algae and sufficient oxygen for fish. To stimulate the growth of food organisms for fish in aquaculture ponds, a combined use of inorganic and organic fertilizer is recommended, but the amount of organic fertilizer should be determined with care to avoid water quality deterioration. The amount of 10mg alfalfa 1−1 wk−1 is considered the upper safety limit for organic fertilization. The nitrogen and phosphorus ratio should be kept weekly at 20:1 by weight to promote the development of food organisms in ponds.

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TL;DR: The optimum P/DE ratio in purified diets for Mozambique tilapia for rapid growth, efficient feed conversion and maximum retention of protein and energy appears to be approximately 23.8 mg of protein kJ−1 of DE.
Abstract: A 3 × 3 factorial experiment was conducted with Mozambique tilapia. Oreochromis mossambicus (Peters), using satiate feeding with 25%, 30% or 35% dietary protein concentrations each with three energy concentrations 10.5,12.6 or 14.7 kJ per g of purified diets. Protein-to-energy ratios (P/DE ratio) ranged from 17 to 33.4 mg protein kJ−1 of digestible energy (DE). Diets were fed to triplicate random groups of 15 fingerlings for 62 days in glass aquaria. Improvement in both weight gain and feed conversion rate (FCR) was achieved when dietary protein increased (P < 0.05), while increasing dietary energy concentration reduced feed consumption and increased mortality (P < 0.05). Protein efficiency ratio (PER) increased as dietary protein decreased and as dietary energy increased (P < 0.05). P/DE ratio correlated positively with gain, energy retention (ER) and feed consumption (r= 0.96,0.96 and 0.73 respectively) and negatively with feed conversion rate (FCR), protein productive value (PPV), protein efficiency ratio (PER) and mortality (r= -0.93, -0.95. -0.91 and -0.84 respectively). Weight gain had a positive relation with feed consumption (r= 0.82). The optimum P/DE ratio in purified diets for Mozambique tilapia for rapid growth, efficient feed conversion and maximum retention of protein and energy appears to be approximately 23.8 mg of protein kJ−1 of DE.

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TL;DR: Protein and lipid of diets containing more soybean flour seemed to be more digestible than those of poultry meat meal while the reverse was the case for ash.
Abstract: Nutrient digestibility and amino acid availability were assessed in tilapia, Oreochromis niloticus (L), fingerlings fed diets containing soybean flour (SF): poultry meat meal (PMM) blends (25:75, 50:50 and 75:25), and 05 or 10% Cr2O3 Although there was variability in individual amino acid availability, average availability was in agreement with the pattern of overall protein digestibility The best lipid, protein digestibility and amino acid availability values were obtained in the 75:25 SF:PMM blend and 05% Cr2O3 treatment, which corresponded to the lowest level of faecal crude protein while the best ash digestibility was observed with 25:75 SF:PMM blend and 10% Cr2O3 Chromic oxide inclusion level appeared to affect nutrient availability Increased marker level might have resulted in decreased nutrient digestibility coefficients Protein and lipid of diets containing more soybean flour seemed to be more digestible than those of poultry meat meal while the reverse was the case for ash