Showing papers in "Aquaculture Research in 2001"
TL;DR: Feed practices thatminimize feed wastage should be adopted since feedwastage can have a very significant impact onwaste outputs from aquaculture operations, and is a key factor in insuring long-term sustainability of the Aquaculture industry.
Abstract: Significant efforts should be devoted to reducingwaste outputs from aquaculture operations in orderto lower the environmental impacts of aquaculturein many parts of the world. Since most aquaculturewastes are ultimately from dietary origin, reductionof waste outputs should first be through improve-ments of diet formulation and feeding strategies.The first step in the production of feeds producingless solid waste is to eliminate poorly digestibleingredients (such as whole grain or grain by-products used as binders and fillers in the feedformulae) and to use highly digestible ingredientswith good binding properties. Further reduction ofsolid waste can then be achieved through carefulselection of the ingredients to improve apparentdigestibility and the nutrient balance of the feed.Nitrogen waste outputs can be reduced through thereduction of the digestible protein to digestibleenergy (DP/DE) ratio of the diet. Phosphorus wasteoutputs can be reduced through careful selection ofthe ingredients and optimization of the digestiblephosphorus content of the diet to meet therequirement of the fish but avoid greatly exceedingthis required level. Finally, feeding practices thatminimize feed wastage should be adopted since feedwastage can have a very significant impact onwaste outputs from fish culture operations.Keywords: aquaculture, waste, feed, feedingIntroductionOvert the past decade, the environmental impacts ofaquaculture operations have become a matter ofconcern for the public, the various levels ofgovernment and the aquaculture producers them-selves. Minimizing environmental impacts is there-fore a key factor in insuring long-term sustainabilityof the aquaculture industry.Containment and collection of wastes, both solidand dissolved, is very difficult and costly inaquaculture, as the wastes are rapidly dispersedinto the surrounding waters. The release of solidwastes, phosphorus (P) and nitrogen (N) fromaquaculture operations may have significant eutro-phication effects on receiving waterbodies andassociated ecosystems (Persson 1991). P wasteoutputs are a greater concern in freshwater sinceP is generally the most limiting factor for plant(algae) in that environment. N waste outputs aregenerally a greater concern in the marine environ-ment for the same reason (Persson 1991). Solidwastes (faecal material and wasted feed) settling tothe sediment can have an impact on the benthicecosystem of inland and marine waters (Gowen,Weston & Ervik 1991). Degradation of organicwaste by bacteria and other organisms leads to theconsumption of oxygen (O
303 citations
TL;DR: Results show that high-energy diets where 50%−60% of the fish oil is replaced by other lipid sources can produce similar results to diets containing 100% fish oil during the grow out phase of Atlantic salmon in sea.
Abstract: The present study investigates the impact of replacing at least 50% of the fish oil in high-energy salmon diets with other types of oils. Triplicate groups of Atlantic salmon (Salmo salar L.) were fed six diets differing only in dietary lipid source for 12 months in sea water. The experimental oils were combinations of fish oil and one or two of the following oils: rapeseed, soybean, linseed, palm or poultry oil. Fish oil constituted 40%−50% of the oil mixtures. The fish grew from an average weight of 120 g to 2000 g during the 12 month trial. Except for minor differences in the lipid concentration of trimmed fillets, no significant effects of dietary lipid source were found on growth, survival, body traits or fillet quality. The main dietary effect was observed in the muscle fatty acid composition, which clearly reflected that of the diets. These results show that high-energy diets where 50%−60% of the fish oil is replaced by other lipid sources can produce similar results to diets containing 100% fish oil during the grow out phase of Atlantic salmon in sea. The importance of fillet fatty acid composition on processing and sensory characteristics requires further evaluations.
280 citations
TL;DR: Phytase supplementation increased the apparent absorption of phosphorus, nitrogen (protein), ash, calcium, magnesium, copper, iron, strontium and zinc in low-ash diets containing soybean meal, but had little effect in high-ASH diets containing both soybean and fish meal.
Abstract: Effects of thermal and enzymatic treatments of soybean meal on apparent absorption of total phosphorus, phytate phosphorus, nitrogen (protein), ash, calcium, magnesium, copper, iron, manganese, strontium and zinc were examined using rainbow trout, Oncorhynchus mykiss (Walbaum), as the test species. Absorption of the test nutrients was estimated using yttrium as an inert non-absorbable indicator. Thermal treatments (microwaving, dry roasting, steam heating, cooking) had no measurable effect on the apparent absorption of phosphorus and other minerals. Phytase supplementation increased the apparent absorption of phosphorus, nitrogen (protein), ash, calcium, magnesium, copper, iron, strontium and zinc in low-ash diets containing soybean meal, but had little effect in high-ash diets containing both soybean and fish meal. In low-ash diets, the apparent absorption of phosphorus increased in accord with the level of phytase added to the diet, from 27% (no phytase added) up to 90% (phytase added, 4000 units kg−1 diet) or 93% (predigested with phytase, 200 units kg−1 soybean meal). In high-ash diets, dietary acidification with citric acid decreased the effect of phytase, whereas in low-ash diets, acidification markedly increased the effect of the enzyme. Excretion of phosphorus in the faeces of fish fed a low-ash diet containing phytase-treated soybean meal was 0.32 g per kg diet consumed, a 95%−98% reduction compared with phosphorus excretion by fish consuming commercial trout feeds.
215 citations
TL;DR: Tactics for the rearing of salmonids for specific purposes should take into consideration the fact that the level of proximate constituents in the whole body as well as the fillet are readily manipulated by feed composition and feeding strategies, whereas the sensory parameters are less affected by these variables.
Abstract: Salmonid aquaculture has focused for many years on enhancing the quantity of fish produced. However, optimization of the quality of salmonids may lead to improved consumer acceptance and higher prices for the farmed product. The present review evaluates how the quality of salmonids is affected by parameters such as feed type, level of dietary intake (ration) and growth. Feed composition has a major influence on the proximate composition of salmonids. In particular, whole body lipid as well as the lipid content in the edible fillet is directly related to dietary fat content, while the fatty acid composition of the fish flesh is also strongly influenced by the dietary fatty acid profile. While fish body composition appears to be largely influenced by feed composition, an increase in other parameters such as feed ration and fish size also results in enhanced adipose deposition and decreased water content in the fish body. The protein content, however, remains more or less stable. An increase in fish body lipid content is not necessarily a negative factor, depending upon the processing procedure that follows. However, an increase in body fat content is generally accompanied by a reduction in slaughter yield, owing to an increase in the weight of viscera in relation to body weight. Although salmonid flesh quality with respect to levels of proximate constituents and yield appears to be under the strong influence of feed composition and feed amount, the sensory characteristics, such as odour, flavour, texture, etc., are only governed by these factors to a small degree. Tactics for the rearing of salmonids for specific purposes should therefore take into consideration the fact that the level of proximate constituents in the whole body as well as the fillet are readily manipulated by feed composition and feeding strategies, whereas the sensory parameters are less affected by these variables.
210 citations
TL;DR: High salmon lice infections may have profound negative effects upon wild populations of sea trout and anadromous Arctic char in northern Norway.
Abstract: The abundance of salmon lice and the physiological effects of infection were examined in two stocks of sympatric sea trout and anadromous Arctic char in northern Norway. One stock feed in a coastal area with extensive salmon farming (exposed locality), while the other feed in a region with little farming activity (unexposed locality). The results showed that the lice infection was significantly higher at the exposed locality, at which the mean intensity of infection peaked in June and July at over 100 and 200 lice larvae per fish respectively. At the exposed locality we also observed a premature return to freshwater of the most heavily infected fish. Such behaviour has previously been interpreted as a response by the fish to reduce the stress caused by the infection and/or to enhance survival. Blood samples taken from sea trout at sea at the exposed locality showed a positive correlation between intensity of parasite infection and an increase in the plasma cortisol, chloride and blood glucose concentrations, while the correlations from sea trout in freshwater were more casual. Several indices pointed towards an excessive mortality of the heaviest infected fish, and 47% of the fish caught in freshwater and 32% of those captured at sea carried lice at intensities above the level that has been shown to induce mortality in laboratory experiments. Furthermore, almost half of all fish from the exposed locality had lice intensities that would probably cause osmoregulatory imbalance. High salmon lice infections may therefore have profound negative effects upon wild populations of sea trout. At the unexposed location, the infection intensities were low, and few fish carried more than 10 lice. These are probably within the normal range of natural infection and such intensities are not expected to affect the stock negatively.
177 citations
TL;DR: In both experiments, mealworms, whether used as such or transformed into a dry meal, were found to be highly palatable to the African catfish and tend to have significantly higher lipids in their carcass.
Abstract: Two separate 7-week feeding trials were conducted to evaluate the use of mealworm, Tenebrio molitor, as an alternative protein source for African catfish, Clarias gariepinus. In Experiment 1, six isonitrogenous (40% crude protein) and isoenergetic (14.64 kJ g−1) practical diets were formulated. The fish meal component of the diets was progressively substituted at 0, 20, 40, 60, 80 and 100% with mealworm meal. The experimental diets were fed to triplicate groups of catfish fingerlings (mean initial weight of 5.1 ± 0.2 g) at 4% body weight day−1. Growth performance and feed utilization efficiency of catfish fed diets with up to 40% replacement of fish meal with worm meal were not significantly different (P > 0.05) compared to fish fed the control diet without any worm meal. Catfish fed diets with up to 80% replacement of fish meal with the worm meal still displayed good growth and feed utilization efficiency. In Experiment 2, the nutritive value of mealworms was compared with a commercial catfish pellet. Three dietary treatments consisting of fish fed catfish pellets only, catfish pellets and mealworms, and mealworms only were tested. Catfish fed solely on mealworms displayed a slight depression in growth performance but when fed in combination with the catfish pellets grew as well or better than fish fed the commercial catfish pellet only. In both experiments, mealworms, whether used as such or transformed into a dry meal, were found to be highly palatable to the African catfish. Catfish fed mealworm-based diets also tend to have significantly higher lipids in their carcass. Results indicate that mealworm was an acceptable alternative protein source for the African catfish.
174 citations
TL;DR: Among the carotenoids studied, β-carotene and astaxanthin elevated humoral factors such as serum complement and lysozyme activity, as well as cellular factorssuch as phagocytosis and nonspecific cytotoxicity, which exerted a greater influence on the bio-defense mechanisms of rainbow trout.
Abstract: This study examined the influence of different carotenoids on growth and some immune indices in rainbow trout. Six semipurified casein-based diets were formulated to contain one of three different carotenoids: astaxanthin, canthaxanthin and β-carotene, at 100 mg kg−1, each of them with vitamins A, C and E either added or omitted. The two control diets contained no carotenoids and were either with or without the vitamins. Rainbow trout weighing about 140 g were fed the diets for 9 weeks. Specific growth rate, feed:gain ratio and nonspecific immune parameters were determined. Growth and feed conversion were similar among the groups. Immune parameters like production of reactive oxygen species by head kidney leukocytes and plasma total immunoglobulin levels did not vary with the treatment. Serum complement activity in both β-carotene groups and the vitamin-containing astaxanthin group were significantly higher than both the control fish. Serum lysozyme activity in the vitamin-containing β-carotene and astaxanthin groups were significantly different from both control groups. Phagocytic activity was also high in the vitamin-containing β-carotene and astaxanthin groups compared with the controls. For phagocytic index, in addition to the foregoing groups, the vitamin-containing canthaxanthin group gave better results compared with the controls. The vitamin-containing astaxanthin and β-carotene groups also exhibited better nonspecific cytotoxicity for the peripheral blood lymphocytes at all effector-to-target ratios. Thus, among the carotenoids studied, β-carotene and astaxanthin elevated humoral factors such as serum complement and lysozyme activity, as well as cellular factors such as phagocytosis and nonspecific cytotoxicity. In the presence of the vitamins the carotenoids exerted a greater influence on the bio-defense mechanisms of rainbow trout.
162 citations
TL;DR: Control feeding trials on the tiger shrimp show that P. monodon has the metabolic ability to convert β-carotene into astaxanthin, in free and esterified form, showing that supplementing diets with β- carotene can achieve the same result as doing so with much more expensive astaxantha.
Abstract: We report the results of controlled feeding trials on the tiger shrimp, Penaeus monodon (Fabricius). The desired colour was obtained by feeding a diet supplemented with astaxanthin (50 p.p.m) for 7–8 weeks before harvest. Similar coloration was achieved, however, by including in the feed an algal material (Dunaliella salina) that contains β-carotene but no astaxanthin. Feed containing β-carotene at 125 p.p.m also gave the required coloration at 7–8 weeks, whereas the same results was obtained after only 5–6 weeks when feed containing 175 p.p.m β-carotene was used. Irrespective of whether the shrimp were fed astaxanthin or β-carotene, the main carotenoid accumulation was astaxanthin, in free and esterified form, showing that P. monodon has the metabolic ability to convert β-carotene into astaxanthin. The supplementation with β-carotene or astaxanthin had no significant effect on growth, average final weight, survival rate or feed conversion ratio, nor on the immune response of the shrimp in terms of production of haemocytes phenoloxidase in the cytoplasmic granules of the haemocytes, microbial clearance ability and resistance to infectious diseases. This is a highly significant development for commercial aquaculture, because it shows that supplementing diets with β-carotene can achieve the same result as doing so with much more expensive astaxanthin.
145 citations
TL;DR: Japanese flounder Paralichthys olivaceus (Temminck et Schlegel) showed half the activity of rainbow trout (Oncorhynchus mykiss Walbaum), suggesting that CSD does not seem to be responsible for low production of taurine in juvenile JapaneseFlounder, while bluefin tuna Thunnus thynus (Linnaeus) or skipjack (Katsuwonus pelamis) is suggested.
Abstract: In order to elucidate the participation of l-cysteinesulphinate decarboxylase (CSD) in taurine synthesis in Japanese flounder, and the synthetic ability of taurine in other fish species, hepatic (or hepatopancreatic) CSD activities of several fish species were compared. Enzyme activity was determined by measuring the production of hypotaurine during an incubation of crude enzyme preparation with l-cysteinesulphinate as a substrate. HPLC was used for the analysis of hypotaurine. The enzyme activities of fish were lower than those of mammals. Japanese flounder Paralichthys olivaceus (Temminck et Schlegel) showed half the activity of rainbow trout (Oncorhynchus mykiss Walbaum). As activity was almost constant throughout the fish growth cycle, CSD does not seem to be responsible for low production of taurine in juvenile Japanese flounder. On the other hand, CSD activity was not present in yellowtail (Seriola quinqueradiata Temminck et Schlegel), bluefin tuna Thunnus thynus (Linnaeus) or skipjack (Katsuwonus pelamis (Linnaeus)). The inability to synthesize taurine and the possible dietary requirement for taurine is suggested in these fish species.
143 citations
TL;DR: The present paper presents an overview of the role of fish nutrition on flesh quality, with both biological and nonbiological causes and parameters.
Abstract: Product quality includes a variety of aspects (Fig. 1), with both biological and nonbiological causes and parameters. Fish nutrition has an important impact on several parameters directly influencing the quality of the fish, such as colour and appearance, smell and taste, texture, nutritional quality, shelf life, and level of contaminants. Further, consumers (market) are becoming more concerned about how the fish are produced, which type of feed ingredients are used and other issues. Authorities in different countries have an increased focus on food safety and traceability of the production from egg to plate (for fish farming). The need for improved knowledge of fish nutrition is therefore of great importance. The present paper presents an overview of the role of fish nutrition on flesh quality.
Figure 1. Schematic overview of parameters important for flesh quality.
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141 citations
TL;DR: The results indicate that treatment with 0.6% NaCl reduces most of the physiological responses of matrinxa to the stress of transport.
Abstract: The present study evaluated the physiological responses of matrinxa, Brycon cephalus (Gunther) submitted to transport stress under the influence of sodium chloride. Different salt concentrations (0.0%, 0.1%, 0.3% and 0.6%) were added to four 200-L plastic tanks. Each tank was stocked with 30 fish (mean weight 1.0 ± 0.2 kg) and transported for 4 h. Blood was sampled prior to transport and immediately after and 24 and 96 h after transport. Plasma cortisol and glucose and serum sodium and potassium, plasma chloride and ammonia were analysed. Changes in plasma cortisol were observed immediately after transportation, except in fish transported in 0.3% and 0.6% salt. Twenty-four hours later, this hormone had returned to its initial level in all fish. Blood glucose was not changed in fish treated with 0.6% salt immediately after transport, and returned to the initial level within 96 h after the other treatments. All treatments resulted in lower levels of plasma chloride after transport, except for fish treated with 0.6% salt, with fish treated with 0.0% and 0.3% salt recovering 24 h later. Serum sodium decreased immediately after transport only in the control fish, returning to the initial level 24 h later. The results indicate that treatment with 0.6% NaCl reduces most of the physiological responses of matrinxa to the stress of transport.
TL;DR: It is concluded that substrate type has a strong effect on periphyton productivity and composition, and on fish productivity, and that good fish production was achieved without feed inputs.
Abstract: Two trials were conducted in mud-bottomed concrete tanks to assess the potential of using artificial substrates to enhance fish production in ponds. Three substrate types were tested: bamboo poles, PVC pipes and sugarcane bagasse bundles. In one trial, periphyton was grown on the substrates in the absence of fish. In the second trial, masheer (Tor khudree Sykes) fingerlings were stocked at three densities. Results showed a significant effect of substrate type on fish growth (P 0.001) and on net fish production (P 0.05), with best growth in the tanks using the bamboo substrate. In the bagasse treatment, 100 percent fish mortality occurred. Highest extrapolated periphyton-based gross fish yield (i.e. without feed inputs) was 450 kg ha1 90 d1 with PVC and 491 kg ha1 90 d1 with bamboo substrate. The best periphyton growth occurred on bamboo, followed by bagasse and PVC. Without fish, mean periphyton biomass during the culture period was 0.56-1.20 mg cm2 on bamboo [ash-free dry matter (DM)], against 0.09-0.36 mg cm2 on PVC and 0.20-0.59 mg cm2 on bagasse. No clear effect of fish density or water depth on periphyton biomass could be seen. Only on bamboo, fish density seemed to have a negative effect on periphyton ash-free dry matter and a positive effect on pigment content (chlorophyll-a and phaeophytin). Periphyton from bamboo had a lower ash content (38-47 percent of DM) than from PVC (54-55 percent of DM) or bagasse (51-58 percent of DM). It is concluded that substrate type has a strong effect on periphyton productivity and composition, and on fish productivity. Good fish production was achieved without feed inputs. More research is needed to study the economic viability of periphyton-based systems in the context of Indian aquaculture.
TL;DR: It is shown that dehulled lupin can be included at up to 40% of a rainbow trout diet without a significant effect on growth performance or nutrient utilization, but rainbow trout have a lower ability to utilize the energy content of deh Hulled l upin at higher inclusion levels.
Abstract: The utilization of dehulled lupin as a partial replacement for fish meal was studied in diets of rainbow trout. Fish were fed diets with 0%, 10%, 20%, 30%, 40% and 50% of dehulled lupin, at a daily feeding rate of 2% body weight for 8 weeks at 15 ± 0.5 °C. Growth performance generally decreased with increasing dehulled lupin in the diet (R2 = 0.81, P < 0.0001). However, there was no significant difference between 0%, 10%, 20%, 30% and 40% dehulled lupin fed groups. Feed conversion ratio generally increased at higher inclusion levels of dehulled lupin (R2 = 0.74, P < 0.002). The protein efficiency ratio, protein productive value, lipid efficiency ratio and lipid productive value were similar in all groups but the energy efficiency ratio was significantly lower (P < 0.01) in the 50% dehulled lupin fed group. Different treatments showed similar digestive enzyme activity, villus height, pyloric caeca and hepato somatic indexes. None of the nonspecific immune responses, with the exception of total plasma protein and neutrophils, was affected by different inclusion level of lupin. Results show that dehulled lupin can be included at up to 40% of a rainbow trout diet without a significant effect on growth performance or nutrient utilization. Rainbow trout utilize dehulled lupin protein as efficiently as fish meal protein but have a lower ability to utilize the energy content of dehulled lupin at higher inclusion levels.
TL;DR: The results of the present study demonstrate a link between the magnitude of lipid stores, feed intake and weight gain, and provide some evidence for lipostatic appetite regulation in fish.
Abstract: Feed-restricted fish gain less body mass and storage reserves than well-fed fish, and reduced rates of gain often trigger compensatory responses, characterized by increased appetite (hyperphagia) and growth rate. The results of previous investigations have introduced a hypothesis in which adipose tissue (fat stores) had a regulatory role in governing appetite. An extension of this suggests that hyperphagia may relate to the severity of the feed restriction, and that the compensatory responses will cease once fat reserves are restored relative to body size. This was tested in two trials in which feed-restricted or -deprived postsmolt Atlantic salmon, Salmo salar, became hyperphagic after transfer to excess feeding. At the end of the first trial, previously feed-restricted fish had fully compensated for their lost weight gain compared to continuously fed control fish, but had a leaner body composition (i.e. reduced energy stores) and were still showing signs of compensatory growth. In the second trial, feed deprivation drained body lipids and caused a stronger hyperphagic response than restrictive feeding, although it took longer to develop. Feed intake became coincident when fish had a similar body composition for size, but this occurred at different times. Hence, the fish that had been deprived of feed were smaller than the restricted fish at the end of the trial. The results of the present study demonstrate a link between the magnitude of lipid stores, feed intake and weight gain, and provide some evidence for lipostatic appetite regulation in fish.
TL;DR: Neither the microbial product nor the frequent water exchange was effective in overcoming the problems caused by the poor pond bottom, and the average counts of different bacteria were not significantly higher in treated ponds than control.
Abstract: The efficacy of a commercial microbial product was tested in commercial tiger shrimp, Penaeus monodon (Fabricius), ponds for one culture period in Kuala Selangor, Malaysia. Four ponds with replicates for treatment and control were used. The pond bottom was dried but the organic sludge was not removed as normally practised in pond preparation. The ponds were stocked with 15 post-larvae at the rate of 31 m-2. Physical, chemical and biological parameters of the pond were analysed every 2 weeks during the culture period. Water quality parameters remained within the optimum range for shrimp culture except for ammonia-nitrogen being significantly higher in control ponds and silica in treated ponds. Benthic organisms were not found in any of the ponds. The average counts of different bacteria were not significantly higher in treated ponds than control. Because of poor health, the shrimp were harvested earlier (72 days) than the usual 120 days. An average of 875.60 ± 67.00 kg shrimp ha-1 was obtained in treated ponds with a feed conversion ratio (FCR) of 1.57 ± 0.10 and survival rate of 42.35 ± 5.37% compared with 719.50 ± 130.94 kg shrimp ha-1, 2.99 ± 0.70 and 21.25 ± 3.26%, respectively, in control ponds. Neither the microbial product nor the frequent water exchange was effective in overcoming the problems caused by the poor pond bottom.
TL;DR: Higher specific activity of most digestive enzymes in PW shrimp was probably due to natural productivity in the pond water that served as a source of organic substrates, and this increased activity may contribute to the growth-enhancing effect of shrimp pond water.
Abstract: Crude enzyme extracts were obtained from the digestive glands of Pacific white shrimp, Litopenaeus vannamei (Boone), reared in oligotrophic well water and eutrophic shrimp pond water to compare digestive enzyme activity between the two groups. Specific activities of serine protease, collagenase, amylase, cellulase, lipase and acid phosphatase were significantly higher (P < 0.01) in pond water-reared shrimp (PW shrimp) than in well water reared-shrimp (WW shrimp). For most enzymes assayed, specific activity was more than two times higher in PW shrimp, and cellulase activity was over six times higher. In contrast, chitinase activity was significantly higher (P < 0.001) in WW shrimp. Higher specific activity of most digestive enzymes in PW shrimp was probably due to natural productivity in the pond water that served as a source of organic substrates, and this increased activity may contribute to the growth-enhancing effect of shrimp pond water.
TL;DR: Although fish meal has been found to be the most suitable protein source for inclusion in formulated diets, plant proteins such as soy bean meal, cottonseed meal and sunflower meal presented good growth and apparent protein digestibility.
Abstract: Although abalone fisheries in South Africa have existed since 1949, cultivation started by successful spawning of captured specimens in 1981 to produce spat and juveniles. Twelve abalone farms, with an estimated investment of US$12 million, have since been established on the coast of South Africa, with a projected production of 500‐800 tons. While Haliotis midae could reach a maximum size of about 200 mm shell length at an age of over 30 years in the wild, farm production is concentrating on an average size of 100 mm after 5 years. Growth rates of 0.08‐4.5% body weight day ‐1 for abalone of 10‐17 mm shell length have been found under stimulated farming conditions on formulated diets, while the corresponding feed conversion ratio (FCR) was 0.9‐2.4. Growth rate, FCR and protein efficiency ratio decline at water temperatures above 20 ∞C. Anaesthetics, for example magnesium sulphate, are used to prevent injury during removal from tanks. Prostrate diatoms, such as Cocconeis sublittoralis (Hendey), Amphora proteoides (Hustedt) and Achnanthes brevipes (Agardh) are preferred after the larval stage (5‐7 days, depending on temperature) are finished. South Africa abalone growers prefer formulated feeds in pellet form, which is convenience and cost favourable to farm operations and management. Although fish meal has been found to be the most suitable protein source for inclusion in formulated diets, plant proteins such as soy bean meal, cottonseed meal and sunflower meal presented good growth and apparent protein digestibility. The parasite sabellid polychaete, Terebrasabella heterouncinata, recently named by Australian and American researchers, is indigenous to a variety of South African intertidal molluscs and impedes growth by causing irritation beneath the mantle in abalone. Prevention to some degree is possible by high standards of hygiene and husbandry of abalone in the tanks, but new techniques to control large infestations now include ultrasound. In spite of a reputation for toughness, abalone meat frozen immediately after shucking is tender relative to red meat. The success of abalone farming in South Africa has been as a result of a high degree of cooperation between the private sector and government-backed research institutions, and it is anticipated that this collaboration will continue.
TL;DR: The cross-sectional area of muscle fibres from triploid fish was found to be larger than from diploidFish, both in fresh and smoked fillets, and the sarcomere length did not change.
Abstract: This study was carried out to examine differences in microstructure and texture of fresh and smoked farmed Atlantic salmon Salmo salar L. fillets with different biological characteristics. The left fillet was analysed fresh and compared with the salted and smoked right fillet from each individual fish. Light microscopy and image analysing techniques were used to study both transversal and longitudinal sections of the muscle. The fish muscle fibres shrank during the salting and smoking process, but sarcomere length did not change. After smoking, a considerable number of fat globules were dispersed among the muscle fibres. The biological characteristics studied were based upon diploid and triploid fish held in both sea cages and land-based tanks. Different starvation times were used and one group was stressed during slaughter. The cross-sectional area of muscle fibres from triploid fish was found to be larger than from diploid fish, both in fresh and smoked fillets.
TL;DR: Males and females of Rhamdia quelen were subjected to capture and tank transference in order to evaluate the stress response, with cortisol values reaching a peak in one hour after stress.
Abstract: Males and females of Rhamdia quelen (Quoy & Gaimard) were subjected to capture and tank transference in order to evaluate the stress response. This process provoked a characteristic stress response in both sexes, with cortisol values reaching a peak in one hour after stress. High levels of cortisol found in females were explained by the increase of energy demand and the mobilization in the vitellogenic phase. Several previous studies have shown that cortisol is strongly correlated to these periods in another catfish.
TL;DR: Rohu seems to be a more suitable candidate for periphyton-based aquaculture systems than gonia, and grew faster, resulting in a 77␑igher net production between the substrate and control ponds.
Abstract: The effects of periphyton, grown on bamboo substrates, on growth and production of two Indian major carps, rohu, Labeo rohita (Hamilton) and gonia, Labeo gonius (Linnaeus), were studied at the Bangladesh Agricultural University, Mymensingh. For each species, five ponds were provided with bamboo substrates and five ponds without substrate (control). Ponds were stocked at a rate of 10 000 ha1 in both treatments. There was no discernible difference in water quality parameters between treatments. A large number of plankton (39 genera) showed periphytic nature and colonized the bamboo substrates. Rohu grew faster, resulting in a 77␑igher net production (P 0.05) between the substrate and control ponds. Rohu seems to be a more suitable candidate for periphyton-based aquaculture systems than gonia.
TL;DR: Results contrast with those obtained by other authors with rainbow trout, Oncorynchus mykiss, and imply that the absorption or utilization of the pigments differs between species.
Abstract: The characteristic pink colour of salmonid flesh is a result of deposition of naturally occurring carotenoid pigments. Achieving successful pigmentation in farmed salmonids is a vital aspect of fish farming and commercial feed production. Currently commercial diets for farmed salmonids contain either or both of the synthetic pigments commercially available, astaxanthin and canthaxanthin. Atlantic salmon, Salmo salar L. ( = 220 g initial weight) were given feeds where the pigment source was astaxanthin only, canthaxanthin only or a astaxanthin/canthaxanthin mix. The rearing environment was 12 × 3 m tanks supplied with sea water at the EWOS research farm Lonningdal, near Bergen, Norway. As the proportion of dietary canthaxanthin increased, flesh pigment levels also showed an increase; the pigment content in the muscle of canthaxanthin-only fed fish was 0.4 mg kg−1 (or 14%) higher than that of the astaxanthin-only fed fish, with the mixed pigment fed fish being intermediate between the two extremes. Results of cross-section assessment for Minolta colorimeter redness (a*) values and Roche SalmofanTM scores also showed an increase in colour with increasing proportions of canthaxanthin in the feed. The data reported clearly indicates that S. salar ( = 810 g final weight) of this size deposit canthaxanthin more efficiently than they do astaxanthin. These results contrast with those obtained by other authors with rainbow trout, Oncorynchus mykiss (Walbaum), and imply that the absorption or utilization of the pigments differs between species.
TL;DR: Ability to control membrane fluidity according to temperature appears in early ontogenesis and is first evident in swim-up fry of carp.
Abstract: The effect of temperature on fluidity, fatty acid and molecular species composition of liver and brain phospholipids in fish adapted or exposed to extreme temperatures was investigated. Membranes from cold-adapted fish were more fluid than those from warm-adapted fish. Ability to control membrane fluidity according to temperature appears in early ontogenesis and is first evident in swim-up fry of carp. Red blood cells as well as neurons of adult carp can continuously adjust the fluidity of their external membranes to changing temperatures. Segregation of choline and ethanolamine phosphoglycerides from livers of fish adapted to a cold/warm environment showed an accumulation of molecular species containing a monoenic fatty acid in position sn-1 and a polyenic fatty acid in position sn-2 of the molecule in cold conditions. Model experiments using mixtures of synthetic 18:1/22:6 phoshatidylethanolamines and 16:0/18:1 phosphatidylcholines demonstrated the involvement of these molecular species in rendering the membranes less packed (more fluid) during adaptation to reduced temperatures.
TL;DR: The levels of protein, glucose, cholesterol, LDH,LDH, GPT and GOT in the serum of rockfish were significantly affected by dietary n-3HUFA levels, and abnormal and necrotic hepatic cells were found in rockfish fed the n- 3HU FA-deficient diets.
Abstract: In order to investigate the effects of dietary lipid and essential fatty acids (EFA) on growth and biochemical change of rockfish (Sebastes schlegeli), a series of studies was conducted. Juvenile rockfish required 0.9% n-3 highly unsaturated fatty acids (n-3HUFA) in the diet. The requirements of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were both 1%, and DHA was superior to EPA as an EFA. Fatty acid compositions in polar lipid of fish were directly reflected from those of dietary fatty acids. The levels of protein, glucose, cholesterol, LDH, GPT and GOT in the serum of rockfish were significantly affected by dietary n-3HUFA levels. Abnormal and necrotic hepatic cells were found in rockfish fed the n-3HUFA-deficient diets. Ca2+-ATPase activities in the liver microsomal membrane were lower in fish fed the n-3HUFA-deficient diets than in those fed the n-3HUFA-sufficient diets. Apparent digestibilities of lipid and saturated fatty acids of rockfish fed the diet were affected by water temperature and fish size, especially in the diet containing beef tallow. These results may be used in developing feed formulation and improving the health of rockfish.
TL;DR: The greater prevalence of goblet cells supports the suggestion that sloughing off mucus is a protective response against bacterial infections and makes an important contribution to the understanding of how nutrition can affect the disease resistance of fish.
Abstract: Arctic charr (Salvelinus alpinus L.) were fed diets based on a commercial recipe supplemented with either linseed, soybean or marine oil prior to cohabitant challenge with Aeromonas salmonicida ssp. salmonicida. Mortality varied significantly between the three dietary groups. Highest mortality (48%) was observed in fish fed the marine oil and the lowest mortality (20%) was in the group fed soybean oil. Transmission electron microscopy (TEM) examination of the digestive tract of uninfected fish demonstrated substantial numbers of bacterial cells between microvilli. However, only a few bacteria were recovered that were associated with the microvilli of infected fish. Immunocytochemical staining/labelling investigations using TEM and an immunogold method were performed on mid-gut segments of fish fed the marine oil diet and showed augmentation of goblet cells and the presence of A. salmonicida ssp. salmonicida in the gastrointestinal tract of diseased fish after challenge with the pathogen. It is suggested that the gastrointestinal tract could be an infection route of A. salmonicida ssp. salmonicida. The greater prevalence of goblet cells supports the suggestion that sloughing off mucus is a protective response against bacterial infections. These results make an important contribution to our understanding of how nutrition can affect the disease resistance of fish.
TL;DR: There were marked histological changes in the hepatopancreas of shrimp fed diet containing aflatoxin B1 at a concentration of 100‐2500 p.p.b. for 8 weeks, as noted by atrophic changes, followed by necrosis of the tubular epithelial cells, as well as encapsulation of necrotic tissue/cells.
Abstract: Aflatoxin B1 was studied in juvenile black tiger shrimp (Penaeus monodon Fabricius) (1‐2 g) to see the effects on growth performance and histopathology, and in adult shrimp (10‐12 g) to study the effects on immuno-physiological function, histopathology and aflatoxin residue. Feeds supplemented with 0, 50, 100, 500, 1000 and 2500 p.p.b. aflatoxin B1 were given to test groups for an 8-week period. Aflatoxin B1 in the diet showed highly negative correlation to average weight, weight gain and survival (r = ‐ 0.99, ‐0.96 and ‐0.95 at P < 0.05, respectively). Aflatoxin B1 at 50‐ 100 p.p.b. produced no effect on growth in juvenile shrimps; however, growth was reduced when aflatoxin B1 concentrations were elevated to 500‐ 2500 p.p.b. Survival dropped to 26.32% when 2500 p.p.b. aflatoxin B1 was given, whereas concentrations of 50‐1000 p.p.b. had no effect on survival. Total haemocyte count and phenoloxidase activity increased by the fourth week in shrimp receiving the highest concentration of aflatoxin B1 and gradually declined from the sixth to eighth week. Alkaline phosphatase and cholesterol in serum have no correlation to aflatoxin in the diet after 4 weeks of the feeding but have a high correlation after 6 weeks of feeding. Calcium and phosphorus levels in the blood have no correlation with the aflatoxin concentration in diet. There were marked histological changes in the hepatopancreas of shrimp fed diet containing aflatoxin B1 at a concentration of 100‐2500 p.p.b. for 8 weeks, as noted by atrophic changes, followed by necrosis of the tubular epithelial cells. Severe degeneration of hepatopancreatic tubules was common in shrimp fed high concentrations of aflatoxin B1. Infiltration of connective tissue into interstitial tissue of the hepatopancreas, as well as encapsulation of necrotic tissue/cells, was also observed. The residue detected in muscle was higher than in the head and shell after 4 weeks of feeding. After 6 weeks, the residue found in muscle was very low and the residue found in the mixture of head and shell decreased compared to the 4-week sample.
TL;DR: Using algae meal as an inexpensive and locally available feed ingredient in the supplementary diet of striped mullet resulted in improved muscle quality and firmness, as shown from the examination of fish muscle ultrastructure by electron microscopy at the end of feeding trial.
Abstract: This study was conducted to evaluate algae meal as an inexpensive and locally available feed ingredient in the supplementary diet of striped mullet, Mugil cephalus L. Four 40%-protein diets (D1–D4) containing 10, 15, 20 and 25% Ulva meal were tested to determine the proper incorporation level for best growth and utilization. A fifth test diet (E) containing 40% dietary yeast enriched with vitamin E was further investigated.
Mullet fingerlings (6.4 ± 0.5 g) were stocked into 12 1 m3 net cages fixed in an earth lined pond, at a rate of 15 fish per cage, and were fed the test diets twice a day at 4% of biomass for 15 weeks. Two cages were used for each dietary treatment, except for the control group, which did not receive any feed. Performance of fish fed the five test diets was evaluated for final mean weight, percent weight gain, specific growth rate, survival, feed conversion ratio, protein efficiency ratio and proximate composition. Results indicated that the best weight gain and feed efficiency were obtained from fish fed the 20% dietary Ulva meal (diet D3), as well as the yeast-based diet enriched with vitamin E (diet E). In addition to growth enhancement, using these feeds (D3 and E) resulted in improved muscle quality and firmness, as shown from the examination of fish muscle ultrastructure by electron microscopy at the end of feeding trial.
TL;DR: The effects of dietary lipid levels on growth, feed utilization, hepatosomatic index (HSI), liver lipid deposition and tissue fatty acid composition in haddock were investigated and histological analyses did not reveal any overt pathology.
Abstract: The effects of dietary lipid levels on growth, feed utilization, hepatosomatic index (HSI), liver lipid deposition and tissue fatty acid composition in haddock were investigated. Triplicate tanks of juvenile haddock (6.9 g) were fed graded levels of herring oil to supply 14, 16, 19 and 22% lipid (DM, dry matter) in fish meal-based, isonitrogenous diets. Growth and feed conversion ratio of juvenile haddock was not significantly (P < 0.05) affected by increasing the lipid content of the diet. A significant increase in HSI (9.8–12.1%), total liver lipid (63.2–69.0%) and whole body gross energy content (6.03–6.39 kcal g−1 DM) were observed in haddock fed 14% vs. 22% lipid. Although the HSI of these cultured haddock was high in comparison to wild gadoids, histological analyses of these haddock livers did not reveal any overt pathology. Muscle lipid levels (1.0%) did not increase significantly with dietary lipid. Liver fatty acid levels mirrored dietary fatty acid (FA) composition. The muscle consisted mainly of polar lipid (84.3 ± 2.5% of total lipid) and a large proportion (52.6 ± 0.8%) of polyunsaturated FA. A dietary lipid level of 14% DM or less is recommended for juvenile haddock.
TL;DR: The results of the present study confirmed that sensory modality and associative learning appear to be critical factors in determining food discrimination of Chinese perch, indicating that both minced trash fish and Oregon-type moist diet can be substituted for live prey fish in intensive commercial production.
Abstract: Chinese perch are one of the most valuable food fish in China, but the sole source of feed for intensive Culture is live prey fish. Our previous studies on systematic sensory physiology revealed that this species have a mechanism for this peculiar feeding habit. In the present study, a specific training procedure was designed, and both experimental (initial body weight 171,0 g: 120 days) and commercial (initial body weight 52.4 g: 240 days) net-cage cultures were conducted to investigate the training success, growth performance and survival of the trained yearlings fed with nonlive or Oregon-type moist diet. The training successes of minced prey fish and the Oregon moist diet were 100 and 89.9%, respectively, in experimental culture, and 92.2 and 83.5% in commercial culture, In an experimental trial, the fish fed minced prey fish or the Oregon moist diet attained final body weights of 472.7 g or 344.7 g, although the specific growth rates of these groups were significantly lower than that of the fish fed live prey fish (final body weight 560.0 g). Mortality was not significantly related to dietary treatment. In commercial culture, the final body weights were as follows: 750 g on live prey fish, 705 g on minced prey fish and 651 g on the Oregon moist diet. Feed costs to produce 1 kg Fish were estimated to be US$6.59 for live prey fish, US$1.76 for minced prey fish and US$2.07 for the Oregon moist diet. The results of the present study confirmed that sensory modality and associative learning appear to be critical factors in determining food discrimination of Chinese perch, indicating that both minced trash fish and Oregon-type moist diet can be substituted for live prey fish in intensive commercial production.
TL;DR: White shrimp Litopenaeus vannamei is a most tolerant shrimp species with a high capacity to use a wide range of dietary P/E ratios for growth, which may be due to its lower energy requirements.
Abstract: The influence of protein and energy levels on growth rate, survival, pre- and post-prandial oxygen consumption, ammonia excretion, haemolymph glucose (HG), glycogen in digestive gland and osmotic pressure (OP) in white shrimp Litopenaeus vannamei (Boone) and L. setiferus (Linne) juveniles was studied. Diets containing a high-quality protein at a protein/energy (P/E) ratio of 16, 26, 31 and 36 mg kJ−1 were fed at 20% of shrimp body weight of two sizes: 1 g. Both species showed a optimum P/E ratio of 36 mg kJ−1 (33–44% protein and 6–23% carbohydrate) in juveniles 1 g, L. setiferus showed a higher growth rate in the diet with 16 mg kJ−1 (27% protein; 32% carbohydrate) and L. vannamei between 26 and 36 mg kJ−1 (33–44% protein and 6–23% carbohydrate). In both experiments, the growth rate of L. vannamei was 2–3 times that observed in L. setiferus. Routine oxygen consumption and apparent heat increment (AHI) of L. setiferus juveniles was two times higher than that observed in L. vannamei juveniles, which could indicate that L. setiferus has a higher metabolic rate. The O/N ratio varied according to protein level, with higher values (O/N = 180) with a 16-mg kJ−1 diet and lower values (O/N = 73) with a 36-mg kJ−1 diet in L. setiferus juveniles. A similar variation in O/N ratio was obtained in L. vannamei fed with all diets with an interval between 22 and 50. An inverse relation between ammonia excretion and HG, and digestive gland glycogen (DGG) in relation to an increase in the P/E ratio indicate that both shrimp species are well adapted to use carbohydrates and/or proteins from their diet. The higher values of hyper-osmotic capacity (hyper-OC) were observed in L. setiferus 1 g. All results showed that juveniles > 1 g of both species are less dependent of P/E ratio than juveniles < 1 g. Litopenaeus vannamei is a most tolerant shrimp species with a high capacity to use a wide range of dietary P/E ratios for growth, which may be due to its lower energy requirements. Litopenaeus setiferus showed a lower capacity to accept different P/E ratios but the optimum P/E ratio obtained with this species shows that L. setiferus accept diets with a high carbohydrate level as well. These results demonstrate that there are nutritional and physiological differences that explain the differences that have been observed when both species were cultured in commercial ponds.