Showing papers in "Aquaculture Research in 2003"
TL;DR: The "Atlas of Marine Invertebrate Larvae" is the most comprehensive guide to larval form and anatomy ever produced and provides key references to review articles and classic works.
Abstract: The "Atlas of Marine Invertebrate Larvae" is the most comprehensive guide to larval form and anatomy ever produced. Each chapter provides a referenced overview of life cycles, reproduction, embryology, larval life, larval form and metamorphosis in a particular group of invertebrates. More than 1200 drawings and photographs illustrate the gross anatomy of all known types of marine larvae and provide a visual survey of the range of larval diversity within each phylum. Most of the plates, which include some color photographs and numerous scanning electron micrographs, are original. However, the book also assembles into one place many of the best larval photographs previously published in the scientific literature. More than 50 recognized authorities on larval development from throughout the world contributed chapters and illustrative material. It provides glossy photographs of all known types of marine invertebrate larvae in a single reference. It includes juvenile forms, paralarvae, etc. of several groups with direct development. It illustrates metamorphosis from larval to juvenile form for most groups. It provides brief synopses of life history biology, larval development, embryology, and metamorphosis. It provides key references to review articles and classic works.
241 citations
TL;DR: It was established that a 10-20 kg batch of eels in fresh water could be rendered unconscious immediately and until death by applying electricity in combination with nitrogen gas, and clearly indicated that humane slaughter of eel is possible in practice.
Abstract: The objective was to evaluate industrial and research slaughter methods for Atlantic salmon (Salmo salar), gilt-head seabream (Sparus auratus) and eel (Anguilla anguilla) with respect to welfare and quality. As a general term of reference, an optimal slaughter method should render fish unconscious until death without avoidable excitement, pain or suffering prior to killing. For Atlantic salmon, commercial slaughter methods (carbon dioxide stunning followed by gill cutting, and gill cutting alone) are not in conformity with the general term of reference, as the fish are not rendered unconscious immediately and possibly experience stress. Evaluation of automated percussive stunning remained unconclusive. More research should enable us to ascertain whether loss of consciousness is instantaneous. Electrical stunning can be humane if applied properly. However, because flesh of electrostunned fish was characterized by occasional bloodspots, optimization of the electrical parameters is required. Prototypes for percussive and electrical stunning of salmon have been recently developed. This implies that humane slaughter of salmon is feasible for industry. For gilt-head seabream, neither aphyxia in air nor transfer of the fish to an ice slurry were considered to be humane: the methods did not induce immediate brain dysfunction and vigorous attempts to escape occurred. Percussive and electrical stunning can be in conformity with the general term of reference. However, conditions for stunning whole batches of seabream have not been established. Quality of the fish slaughtered by percussive stunning was similar to that obtained by the industrial method, i.e. immersion in an ice slurry. Further work is required to establish optimal stunning conditions and to develop prototypes. For eel, desliming in a salt-bath followed by evisceration, electrical stunning performed under the conditions prescribed by the German legislation, and live chilling and freezing were not considered to be humane. In contrast, it was established that a 10-20 kg batch of eels in fresh water could be rendered unconscious immediately and until death by applying electricity in combination with nitrogen gas. The conditions used were 0.64 A dm2 for 1 s, followed by 0.17 A dm2 combined with nitrogen flushing for 5 min. A preliminary assessment of flesh quality suggests that it may be improved by application of the latter method, compared with the salt bath. The results clearly indicated that humane slaughter of eels is possible in practice.
192 citations
TL;DR: The protein from PPM can completely replace the FM protein in the diets for Nile tilapia, based on the results of this study, and the PPM diets were economically superior to FM.
Abstract: A plant protein mixture (PPM) was tested to replace ¢sh meal (FM) in diets for juvenile Nile tilapia, Oreochromis niloticus. Fish averaging (7SD) 3.770.14 g were divided into 15 groups. Three groups were fed each of ¢ve isonitrogenous (33.6%) and isocaloric (4.7 kcal g � 1 ) diets replacing 0%, 25%, 50%, 75% and 100% of the FM protein with similar percentages of PPM (PPM0, PPM25, PPM50, PPM75 or PPM100 respectively). The PPM consisted of 25% soybean meal, 25% cottonseed meal, 25% sun£ower meal and 25% linseed meal, and 0.5% of both methionine and lysine were added to each diet except for the control. After 16 weeks of feeding, the ¢sh fed diets PPM75 and PPM100 exhibited growth performance not diiering signi¢cantly from the ¢sh fed control diet. PPM substitution of up to 75% of the FM protein did not result in diierences in the apparent protein digestibility compared with the control, whereas in the PPM100 group digestibility was signi¢cantly lower than in the other groups, except for ¢sh fed the PPM75 diet. The incorporation of PPM in diets did not signi¢cantly aiect whole-body dry matter, protein, fat or energy compared with the control. The cost^bene¢t analyses of the test diets indicated that the PPM diets were economically superior to FM. The protein from PPM can completely replace the FM protein in the diets for Nile tilapia, based on the results of this study.
176 citations
TL;DR: Generally, fish performed better when fed diets containing defatted maggot meals than full-fat maggot meal, and compared favourably with fish fed the fish meal-based diet.
Abstract: The nutritional implication of processed maggot meals, hydrolysed, defatted, full-fat, sun-dried and oven-dried, in the diets of Clarias gariepinus fingerlings were evaluated. The nutrient density, proximate composition, gross energy and mineral constituents of the maggot meals were determined. Five isonitrogenous and isocaloric diets were formulated to provide 40% crude protein in which fish meal in the reference diet was completely replaced by any of the following processed maggot meals: oven-dried full-fat (ODM), sun-dried full-fat (SDM), defatted oven-dried (DODM) and defatted sun-dried (DSDM) maggot meals respectively. Fish were fed ad libitum in triplicate treatments for 56 days in glass tanks. Biological evaluations of the fish were based on growth performance and nutrient utilization indices. The result of the nutrient composition analysis showed that processing methods of defattening and drying influenced the nutrient density of maggot meal, with crude protein content ranging between 43.30% and 46.70% for full-fat sun-dried and hydrolysed/defatted oven-dried maggot meals respectively. The result showed that growth performance and nutrient utilization of fish fed DODM and DSDM dietary inclusions were not significantly different and similar to fish fed the fish meal-based diet. However, fish fed the diet containing SDM exhibited lower daily weight gain, protein efficiency ratio and specific growth. Generally, fish performed better when fed diets containing defatted maggot meals than full-fat maggot meal, and compared favourably with fish fed the fish meal-based diet.
161 citations
TL;DR: Clove oil is more effective at reducing the short-term stress response induced by handling and blood sampling, and is recommended as an alternative fish anaesthetic.
Abstract: The effects of 60-mg L-1 clove oil and 60-mg L-1 tricaine methanesulphonate (MS-222) on the blood chemistry of rainbow trout were compared after exposure to handling stress via caudal puncture blood sampling. Fish sampled by caudal puncture and subsequently exposed to anaesthetics showed a typical handling stress response over a 48-h period. There were no significant differences between the responses of fish exposed to equal concentrations of clove oil and MS-222, with the following exceptions: the blood glucose at full anaesthesia, and lactate at full recovery increased significantly in the clove oil-exposed fish. In a subsequent experiment, the stress response observed in fish sampled by caudal puncture and exposed to clove oil and MS-222 was compared with a non-anaesthetized control group. The increases in plasma cortisol levels were significantly lower at recovery in fish treated with either anaesthetic compared with the control fish. Fish exposed to MS-222 had significantly higher cortisol levels at 1 h. These findings show that few differences exist between the anaesthetic effects of clove oil and MS-222 on the physiological response of fish to stress. However, clove oil is more effective at reducing the short-term stress response induced by handling and blood sampling, and is recommended as an alternative fish anaesthetic.
146 citations
TL;DR: It is indicated that corn gluten meal can replace up to 60% fish meal protein in diets for gilthead sea bream juveniles with no negative effects on fish performance.
Abstract: A 12-week growth trial was conducted to evaluate corn gluten meal as an alternative protein source to fish meal in diets for gilthead sea bream juveniles. The experimental diets were formulated to be isonitrogenous and isoenergetic and to have 20%, 40%, 60% and 80% of fish meal protein, the only protein source in the control diet, replaced by corn gluten meal.
At the end of the growth trial only the group fed the diet with 80% corn gluten protein exhibited significantly reduced growth and feed efficiency compared with the fish meal-based diet. This was most likely due to a dietary amino acid deficiency in that diet. A trend was noticed for feed efficiency to improve with the replacement of fish meal protein in the diets up to 60%. There were no significant differences among groups in protein and energy retention (as percentage of intake).
At the end of the trial whole body water content of the experimental groups was significantly lower and the lipid content of groups including 60% and 80% corn gluten protein was significantly higher than that in the control. No other differences were observed in whole body composition among groups.
Apparent digestibility coefficients (ADC) of the diets were evaluated in a separate trial. The ADC of dry matter of the experimental diets was significantly higher than in the control diet; there were no significant differences among diets in the ADC of energy and protein, except for the ADC of protein of diet with 80% corn gluten protein, which was significantly lower than the control.
The results of this study indicate that corn gluten meal can replace up to 60% fish meal protein in diets for gilthead sea bream juveniles with no negative effects on fish performance.
144 citations
142 citations
TL;DR: It was concluded that the solvent-extracted moringa leaf meal could replace about 30% of fishmeal from Nile tilapia diets.
Abstract: The suitability of raw and methanol-extracted moringa (Moringa oleifera Lam.) leaf meal to replace 10%, 20% and 30% of the total fishmeal-based dietary protein in tilapia feeds was tested. Ten isonitrogenous and isocalorific feeds (35% crude protein and 20 MJ kg−1 gross energy), denoted as diets 1 (fishmeal-based control), 2, 3, 4 (containing 13%, 27% and 40% raw moringa leaf meal), 5, 6, 7 (containing 11%, 22% and 33% methanol-extracted moringa leaf meal), and 8, 9, 10 (containing methanol-soluble extracts of the raw moringa leaf meal at the same level as would have been present in diets 2, 3, 4) were prepared. Forty tilapia (16.7±2.4 g), kept individually, were fed the experimental diets (four fish per treatment) at the rate of 15 g feed per kg metabolic body weight (kg0.8) per day. A reduction in the growth performance was observed with an increasing level of raw moringa leaf meal (diets 2–4), whereas inclusion of methanol-extracted leaf meal (diets 5–7) had no significant (P<0.05) effect on the growth performance compared with the control (diet 1). The growth performance of fish fed diets 8–10 containing methanol extracts of the moringa leaf meal were also similar to the control. The chemical composition values of the gained weight showed that lipid accretion decreased with increased inclusion of moringa leaves, and ash content increased. Dietary moringa methanol extracts reduced protein accretion, but had no effects on lipid and ash contents compared with the control. The inclusion of raw, methanol-extracted residues and methanol extracts of the moringa leaf meal (diets 3 and 4, 5, 6 and 7, and 8 respectively) reduced the plasma cholesterol content significantly. Similarly, a significant reduction in muscle cholesterol was observed in fish fed the diets 4, 8, 9 and 10. It was concluded that the solvent-extracted moringa leaf meal could replace about 30% of fishmeal from Nile tilapia diets.
130 citations
TL;DR: The industry should consider revising the basis of the current warranty system for their customers, from death on arrival to cumulative mortality at 7 days post shipment (or death after 7 days, DA7), in order to cut down ornamental ¢sh losses after shipment.
Abstract: Current ornamental ¢sh packaging systems are characterized by very high ¢sh loading densities and high metabolic wastes in the transport water after shipment. They focus mainly on management of the quality of transport water. Recent studies using the guppy as a model ¢sh showed that post-shipment mortality could be reduced through enhancement of the stress resistance of the ¢sh, and hence emphases should also be placed on the preparation of the ¢sh for transport and recovery of the ¢sh after shipment. Farmers can contribute signi¢cantly by applying nutritional prophylaxis before harvesting. Exporters may use the salinity stress test to identify ¢sh lots of good quality for transport, apply health prophylaxis to eradicate parasites and optimize other techniques such as starvation of the ¢sh or addition of salt to the transport water to enhance the stress resistance of the ¢sh. Importers may adopt proper acclimation procedure and allow ¢sh to recover in low salinity water to reduce post-shipment mortality. As the main bulk of post-shipment mortality is stressmediated and occurs during the 1-week recovery period, the industry should consider revising the basis of the current warranty system for their customers, from death on arrival to cumulative mortality at 7 days post shipment (or death after 7 days, DA7), in order to cut down ¢sh losses after shipment.
112 citations
102 citations
TL;DR: A captive population of Pacific white shrimp replicated in two environments was evaluated for genetic variability and covariability of size traits and the females were significantly larger than the males for all traits, except for abdominal (tail) length and weight.
Abstract: A captive population of Pacific white shrimp (Penaeus vannamei) replicated in two environments was evaluated for genetic variability and covariability of size traits. A total of 37 full-sib families, each with an average of 16–20 individuals within family, were used for the analysis. There was no family by environment interaction for any of the traits. However, both fixed effects, sex and environment, were significant. The shrimp grown in environment ‘B’ (Sinaloa) grew larger and heavier than those grown in environment ‘A’ (La Paz), possibly because of the higher temperatures and lower densities in the first one during grow-out. The females were significantly larger than the males for all traits, except for abdominal (tail) length and weight. The heritabilities, estimated through MTDFREML (multiple-trait derivative-free restricted maximum likelihood) after introducing environment and sex as fixed effects, were total length 0.22±0.07, abdominal length 0.23±0.07, cephalothorax length 0.17±0.06, total weight 0.17±0.06, abdominal weight 0.18±0.06, cephalothorax weight 0.15±0.06, and width of the first abdominal segment (0.14±0.05). Genetic correlations (rg) were high between the length and weight (total and abdominal), but lower for cephalothorax weight or length with the other traits. The width of the first abdominal segment correlations with other traits was intermediate.
TL;DR: The results of this series of experiments indicate that altering the environment or diet has little effect on the ability of Nile tilapia to survive low temperatures.
Abstract: This study was conducted (1) to evaluate the effects of photoperiod (fixed vs. decreasing light), fish size (136 vs. 220 mm), dissolved ions (hardness and salinity) and diet (menhaden oil vs. coconut oil-based) on the tolerance (survival) of Nile tilapia, Oreochromis niloticus, to low temperatures (decreased by approximately 0.5 °C per day) and (2) to evaluate the effect of dietary fatty acid composition on selected physiological characteristics of Nile tilapia exposed to decreasing temperatures. Size significantly affected mortality, with smaller fish being less tolerant to low temperatures than larger fish. Results were equivocal in the photoperiod, dissolved ion and dietary lipid experiments, and were dependent on the method of data analysis employed. Diet significantly affected plasma osmolarity, with higher values in fish fed the menhaden-based diet. Haematocrit, serum glucose, sodium and cortisol concentrations, serum and splenic lysozyme activities, lymphocyte count and hepatosomatic index were not affected by diet. Haematocrit, white cell count and serum glucose and sodium concentrations were significantly affected by temperature, but serum and splenic lysozyme content, hepatosomatic index, and serum cortisol concentrations were not. The results of this series of experiments indicate that altering the environment or diet has little effect on the ability of Nile tilapia to survive low temperatures.
TL;DR: Weight gain of silver perch fed diets containing wheat meal or carbohydrates at 45% inclusion content had significantly reduced weight gain when compared with fish fed the basal diet, and protein retention and energy retention efficiency were similar or better.
Abstract: The ability of juvenile silver perch (Bidyanus bidyanus) to utilize dietary raw wheat meal, raw wheat starch, gelatinized wheat starch and dextrin as energy sources to spare protein for growth was quantified. Energy utilization and protein sparing were assessed by comparing the weight gain, energy retention efficiency, protein retention and body composition of silver perch that had been fed a series of diets in which the basal diet (low carbohydrate) was systematically replaced with graded levels of each carbohydrate ingredient or an inert diluent, diatomaceous earth. The protein content decreased as the carbohydrate content increased, giving four different protein to energy ratios for each of the four carbohydrate sources (except for the 60% inclusion level, at which only three carbohydrate sources were tested). Silver perch were efficient at utilizing carbohydrate for energy to spare protein. Silver perch fed diets containing up to 30% wheat meal, raw wheat starch, gelatinized wheat starch or dextrin exhibited similar growth, protein retention and energy retention efficiency to the fish fed the basal diet. Weight gain of silver perch fed diets containing wheat meal or carbohydrates at 45% inclusion content had significantly reduced weight gain when compared with fish fed the basal diet. However, protein retention and energy retention efficiency were similar or better. Whole-body protein levels of silver perch remained constant regardless of carbohydrate sources, and there was no evidence of increasing whole-body lipid concentrations for fish fed diets with up to 60% dietary carbohydrate. Silver perch were more efficient at utilizing processed starch (either gelatinized starch or dextrin) than wheat meal or raw wheat starch.
TL;DR: Changes in the enzyme activity after the shrimp reach 6 g in body weight are evidenced by a decrease in total protease and an increase in lipase and amylase activities, suggesting an adaptation of the enzymatic activity to diets with lower protein content as body weight increases.
Abstract: A study was conducted to evaluate variations of digestive enzyme activities in Litopenaeus vannamei (Boone) reared in commercial ponds under semi-intensive conditions. Shrimp were collected at each body weight increase of 2 g. As the shrimp grew (2^12 g), signi¢cant increases in the activities of lipase and chymotrypsin were observed. The total protease activity decreased from 6 g onwards. Trypsin activity showed a peak at 6 g and amylase activity increased two-fold after 2 g. Additionally, the stomach contents were analysed microscopically for shrimp between 2 and 10 g. Plant matter contributed above 30% of the total stomach content in 6-, 8- and 10-g shrimp. Detritus represented 58% and 62% of the total stomach content in 2- and 4-g shrimp, respectively, decreasing to 33^43% at greater shrimp weights. Arti¢cial feed showed a maximum contribution of 20% in 6-g shrimp. The present results show changes in the enzyme activity after the shrimp reach 6 g in body weight, evidenced by a decrease in total protease and an increase in lipase and amylase activities. The amylase/protease ratio was 2.6 in 2-g shrimp and increased steadily to 9.6 in 12-g shrimp. These ¢ndings suggest an adaptation of the enzymatic activity to diets with lower protein content as body weight increases, and may be related to the variation of the diierent items found in the stomach.
TL;DR: It was evident that use of vegetable oils in freshwater feed did not interfere with low temperature acclimation or parr-smolt transformation of juvenile salmon, and subsequent on-growing in seawater was better when vegetable oil had been used in the feed.
Abstract: The aim of this study was to investigate the effects of water temperature and salinity on lipid nutrition of farmed Atlantic salmon (Salmo salar L.) parr and smolt. Salmon parr were held at low water temperature (2°C) for six months while being fed feeds that differed in oil source (i.e. marine fish oil or vegetable oil blend) and concentration (low, 21% and high, 34%). The responses at low temperature were compared with those of fish held at 8°C using full-factorial design.Feeding and growth were maintained at 2°C, although at lower rates than at 8°C. Growth and feed utilisation improved over time, suggestive for a long-term acclimation response in fish held at low temperature. Overall feed efficiency was better at the lower temperature. A gradual decrease in growth rate and feed utilisation was seen at the higher temperature as the fish grew larger.The fish compensated for reduced energy density by increasing feed intake. At the higher temperature, better growth was found for fish fed the low-fat feeds, and there was also a tendency for improved growth when vegetable oil was used. Thus, there were no signs that vegetable oils are inferior to marine fish oil in promoting growth of Atlantic salmon parr in fresh water.Fish fed high fat feed were fatter than fish fed low fat feed, suggestive of lipostatic regulation of feed intake. Fat and protein digestibility were high at both 2°C and 8°C, although both fat and protein digestibility were lower at 2°C. At the lower temperature, increased dietary fat level increased the fat digestibility, and improved protein digestibility were seen when vegetable oil was included in the feed. Protein retention was higher at the higher temperature irrespective of feed treatment, indicating that proteins were both readily digested and converted into new tissues.The effects of feed treatment on low temperature acclimation responses were assessed from deposition of dietary fatty acids in fish tissues and from n-3 and n-6 essential fatty acid (EFA) budgets. Fatty acid composition of polar (membrane) and non-polar (storage) lipids in muscle, viscera and carcass were markedly influenced by the dietary oil, and non-polar lipids were more influenced than polar lipids. The retention n-6 EFAs was lower than for n- 3 EFAs, and was independent of temperature. The retention of n-3 EFAs retention was higher at the 2°C, especially amongst fish given the fish oil based diets. This may be a reflection of the importance of n-3 HUFAs during low temperature acclimation. However, the unsaturation (UFA:SFA ratio) of polar lipids was higher in fish fed the vegetable oils than for fish fed fish oil based feed. This may imply that vegetable oils produced fish that were better able to withstand exposure to low temperature, while having membrane lipids less susceptible to oxidative damage, due to the lower contents of n-3 HUFAs (mainly EPA and DHA).The six months feeding period in freshwater was followed by parr-smolt transformation, and a subsequent 42-days on-growing in seawater. Feed history during freshwater rearing influenced on-growth of smolts. A positive effect of using a vegetable oil was indicated, but this effect was only seen when there was a shift to a high-lipid fish oil based feed at the time of transfer to seawater.As such, it was evident that use of vegetable oils in freshwater feed did not interfere with low temperature acclimation or parr-smolt transformation of juvenile salmon, and subsequent on-growing in seawater was better when vegetable oil had been used in the feed. This indicates that fatty acid (lipid) requirement of Atlantic salmon are probably different in fresh water and seawater, and that these changes are linked to parr-smolt transformation. It could be speculated that that salinity may be more important than temperature as an environmental influence on the fatty acid requirements of Atlantic salmon.
TL;DR: Modelling applications require information about the proportionate increase in fillet fat over time, but the relative changes in body mass can be used as a surrogate provided that both fillet yield (as a % of body mass) and filletfat percentage change little over time.
Abstract: The fatty acid compositions of fish tissue lipids usually reflect those of the feed lipids, but few attempts have been made to predict the way in which the profiles change or assess the time required for the fatty acid profile to stabilize following a dietary change. The present focus on the influences of vegetable oils and fish oils on the fatty acid compositions and sensory attributes of fish fillets increases the interest in the ability to make such predictions. A dilution model was tested using data for the influences of feed oils (rape/linseed (V) vs. sand-eel (F)) and dietary fat concentrations (ca. 30% (H) vs. ca. 20% (L)) on the body growth and fatty acid compositions of the fillets of Atlantic salmon, Salmo salar L., parr and post smolt. Fish given HV or LV feeds during freshwater rearing (mass increase from ca. 19 g to ca. 130 g) were switched to HF and LF feeds following parr-smolt transformation. The changes in fillet percentages of 18:1, 18:2 (n-6) and 18:3 (n-3) during 98 days of on-growing in seawater (mass increase from ca. 130 g to ca. 380 g) conformed closely to predictions made on the basis of the dilution model. Model applications require information about the proportionate increase in fillet fat over time, but the relative changes in body mass can be used as a surrogate provided that both fillet yield (as a % of body mass) and fillet fat percentage change little over time. This is not the case for small salmon, but does seem to apply to larger salmon as they approach harvest size. This means that, for large salmon, ratios of changes in body mass can be substituted for ratios in the quantitative change in fillet fat without the introduction of a large error in the prediction of the change in fillet fatty acid profile following the introduction of a novel feed.
TL;DR: The results indicated that both carcass proximate composition and liver lipid class of juvenile Spinibarbus hollandi were affected by dietary treatments.
Abstract: A feeding trial was conducted to investigate the influence of dietary protein levels on growth performance, carcass proximate composition and liver lipid classes of juvenile Spinibarbus hollandi (Oshima), a cyprinid fish. White fish meal was the primary protein source in the study. Eight experimental diets containing 13–55% crude protein were fed to three replicate groups of six fish weighing nearly 8.5 g each for 10 weeks. Both percentage weight gain and feed efficiency ratio increased significantly with increasing dietary protein levels up to 31%, but there was no further increase for protein levels from 31% to 55%. Application of broken-line regression analysis to the percentage weight gain provided an estimate of 32.7±1.5% dietary protein for maximum growth. The protein efficiency ratio and productive lipid value were inversely correlated with dietary protein level. The hepatosomatic index and the viscerosomatic index were also inversely related to dietary protein level. The carcass protein of fish fed lower protein diets was significantly lower than that of the fish fed higher protein diets. Carcass lipid content decreased with increasing dietary protein levels, whereas moisture was inversely related to lipid content. Both liver glycogen and liver lipid contents decreased with increasing dietary protein levels. Triglyceride was the major component in the liver lipid, and the amount of triglyceride deposited in the liver also decreased with dietary protein levels. The results indicated that both carcass proximate composition and liver lipid class of juvenile Spinibarbus hollandi were affected by dietary treatments.
TL;DR: Overall, it is concluded that slaughter by electricity and gas improved the quality of raw and smoked eels compared with the commercial method.
Abstract: Eels (Anguilla anguilla L.) were slaughtered using two procedures. The commercial method consisted of desliming the fish in dry salt followed by evisceration. The alternative method consisted of stunning and killing in water with a combination of electricity and oxygen removal. Eels slaughtered as commercially exhibited aversive reactions and consequently a higher level of muscular activity before death. In raw fillets, differences appeared clearly between the two batches. The alternative slaughter by electricity and gas led to redder, firmer flesh with a higher pH. Myofibrillar proteolysis, lipid oxidation and loss of freshness (as evaluated by K-value) were reduced. After hot-smoking, which is a process that greatly modifies the fish flesh properties, differences between batches were less pronounced. However, eels slaughtered by the alternative method were characterized by a higher pH and a redder colour of the dark muscle, a desirable property form a commercial point of view. When assessed by sensory difference tests, appearance seemed to be the only attribute that allowed panellists to discriminate the two batches. Overall, it is concluded that slaughter by electricity and gas improved the quality of raw and smoked eels compared with the commercial method
TL;DR: It is clear that faecal coliforms from pigeon faeces significantly contaminated the ponds and tilapia intestines, and Escherichia coli was the only coliform organism found in pond water, sediment, intestine oftilapia and pigeon faes.
Abstract: Total bacterial load, total coliforms faecal coliforms in pond water, sediment, intestine of hybrid tilapia Oreochromis niloticus×Oreochromis aureus and pigeon Columba livia faeces were investigated monthly over a period of 1 year from July 1999 to June 2000. Fish were collected randomly by a cast net. Samples were analysed for coliforms using the multiple-tube fermentation technique. Results showed total viable bacterial counts in the pond water, sediment, intestine of tilapia and pigeon faeces ranging from 1.8±0.9×102 to 6.0±1.2×104 cfu mL−1, 3.2±1.2×105 to 2.8±1.5×107 cfu g−1, 8.2±1.6×105 to 9.9±1.5×107 cfu g−11.0±0.4×107to9.7±0.2×109 cfu g−1respectively. The most probable number (MPN) of coliforms and faecal coliforms ranged from 287±12 to ≥1600±0 100 mL−1 in pond water; the MPN ranges for sediment, tilapia intestine and pigeon faeces were 257±29 to ≥1100±0 g−1, 237±46 to ≥1100±0 g−1 and 403±98 to ≥1100±0 g−1 respectively. The abundance of normal bacteria coliforms was greater in the warm months than in the cold months. Ground water was free from any sort of coliform organisms, and there were no sources of human faecal matter in the pond. So, it is clear that faecal coliforms from pigeon faeces significantly contaminated (P<0.05) the ponds and tilapia intestines. Escherichia coli was the only coliform organism found in pond water, sediment, intestine of tilapia and pigeon faeces.
TL;DR: It is indicated that the inclusion of mucuna seed meal (replacement of 25% of total dietary protein of feed) after soaking in any one of the tested solutions followed by autoclaving significantly improved the growth performance and feed utilization of tilapia compared with that of the raw seeds.
Abstract: A fish feeding trial was conducted in a warm-water recirculating system for 8 weeks to assess the nutritive value of processed mucuna seeds as a dietary protein replacement for fish meal in practical diets of tilapia. Diets 2–6 contained mucuna seeds processed as follows: raw, soaked in water, soaked in sodium bicarbonate solution (0.07%), soaked in ascorbic acid solution (0.1%) or soaked in water containing 3% of freeze-dried moringa leaf powder, followed by autoclaving. The mucuna seed meals were then used to replace 25% of the total dietary protein in each diet. The performance of fish fed these diets was compared with fish fed a fish meal-based control diet (diet 1), which contained 35% protein. All diets were prepared to be isonitrogenous and isoenergetic. Each treatment had three replicates, using seven fish per aquarium, with a mean initial body weight of 3.9 ± 0.06 g. Fish were fed five times about their maintenance level (3.0 g feed × body weight (kg)−0.8 day−1), and no mortality was observed during the experiment. The growth rate, feed conversion ratio and protein productive value of fish fed diets 1, 3, 4, 5 and 6 were similar. However, with regard to energy retention and apparent net lipid utilization, the values observed in fish fed diet 1 were similar to those of fish fed diets 5 and 6, and diet 6, and significantly higher than other dietary groups. Fish fed diet 2 showed a significantly (P < 0.05) reduced growth performance, higher carcass moisture and ash contents, and lower levels of lipid and energy compared with all other dietary groups. Fish fed diet 2 had a significantly lower plasma cholesterol level compared with other diets. However, no significant variation of muscle cholesterol was found between the dietary groups. Even though the hepato-somatic index of the fish fed diets 3, 4, 5 and 6 was significantly lower than diet 1, these values appeared to be significantly higher compared with fish fed diet 2. The present study indicates that the inclusion of mucuna seed meal (replacement of 25% of total dietary protein of feed) after soaking in any one of the tested solutions followed by autoclaving significantly improved the growth performance and feed utilization of tilapia compared with that of the raw seeds. Moreover, these values were similar to the performance obtained with the fish meal-based control diet 1. This might be due to the relative reduction of anti-nutrients, particularly the non-protein amino acid 3, 4-dihydroxyphenylalanine, and increased palatability and nutrient availability of processed beans.
TL;DR: P pond water and sediment bacteria reflected the bacterial composition in the gills and intestine of tilapia, and in contrast to gill bacteria, more diversification was observed in intestinal bacteria.
Abstract: The bacterial flora of the rearing pond water and sediment as well as the gills and intestine of healthy hybrid tilapia cultured in Saudi Arabia was estimated quantitatively and qualitatively, the isolates being identified at genus or species level. Total viable counts of bacteria (measured as colony-forming units, cfu) were in the range 5.6 ± 0.8 × 103 to 2.4 ± 1.2 × 104 cfu mL−1 in pond water; 9.3 ± 1.1 × 106 to 1.9 ± 1.5 × 108 cfu g−1 in sediment; 7.1 ± 0.7 × 105 to 8.7 ± 1.1 × 106 cfu g−1 in the gills of tilapia; and 3.4 ± 1.8 × 106 to 5.8 ± 0.4 × 107 cfu g−1 in the intestine of tilapia. In total, 15 bacterial genera and 18 species were identified. Pond water and sediment bacteria reflected the bacterial composition in the gills and intestine of tilapia. In contrast to gill bacteria, more diversification was observed in intestinal bacteria. Corynebacterium urealyticum, Shewanella putrefaciens and Aeromonas hydrophila predominated in all samples. In pond water, C. urealyticurn, S. putrefaciens, A. hydrophila, Flavobacterium sp. and Pseudomonas sp. were the most predominant bacterial species (prevalence > 10%), whereas A. hydrophila, C. urealyticum, S. putrefaciens and Escherichia coli were predominant in pond sediment, and C. urealyticum, S. putrefaciens and A. hydrophila were predominant in both the gills and intestine of tilapia.
TL;DR: Brown trout reared in freshwater for 8 months at water velocities of <0.1, leading to a higher condition factor, greater body height and width, and muscle fibre hypertrophy, while flesh quality was affected, with greater dry matter content and lower post-mortem pH.
Abstract: Brown trout (Salmo trutta) (2.7 g initial mean weight) were reared in freshwater for 8 months at water velocities of <0.1 (control group), 1 or 2 body lengths per second (BL s−1) (exercise groups). Growth (body weight, body length and body width), muscle structure (muscle fibre diameter and width of myosepta) and flesh quality parameters (dry matter, muscle pH, collagen content and solubility, instrumental evaluation of texture) were measured at the end of the experiment. The body weight of fish at 1 BL s−1 was 22% higher than the control group. Muscle development was stimulated at 1 and 2 BL s−1, leading to a higher condition factor, greater body height and width, and muscle fibre hypertrophy (55 vs. 59.5 μm fibre diameter in the control and 2 BL s−1 groups respectively). Connective tissue and collagen were only slightly affected by exercise (no difference in collagen solubility, but a greater proportion of γ trimer and fewer α chains in the control compared with the exercised group). Flesh quality was affected, with greater dry matter content and lower post-mortem pH in the 1 BL s−1 group compared with the control and 2 BL s−1 groups. The mechanical resistance of the raw fillets was slightly but significantly increased by exercise. The exercise-related changes in muscle structure and texture are discussed.
TL;DR: The ability of silver perch (Bidyanus bidyanus) to digest and utilize dietary starch or starch breakdown products was investigated in this paper, where a 41-day period was used to investigate the ability of Silver perch to digest wheat starch at two dietary inclusion levels (30% or 60%).
Abstract: The ability of silver perch (Bidyanus bidyanus) to digest and utilize dietary starch or starch breakdown products was investigated. For experiment 1 the ability of silver perch (2.7 ± 0.01 g) to digest wheat starch at two dietary inclusion levels (30% or 60%), each at four levels of gelatinization (0%, 25%, 50% or 80%), was investigated over a 31-day period. For experiment 2, the ability of silver perch (15.9± 0.25 g) to digest wheat starch, dextrin (at three levels of dextrinization), maltose, glucose and pea starch, all at the 30% inclusion level, was investigated over a 41-day period. Water temperature for both experiments was 25 ± 1 °C. Apparent digestibility coefficients (ADCs) for starch, dry matter (DM) and energy were affected by both degree of gelatinization (80% > 50% > 25% = 0%) and inclusion level (30% > 60%). Specific growth rate (SGR) was unaffected by the inclusion of 30% starch; however, it was reduced at the 60% starch content level. Degree of gelatinization had no effect on SGR. For experiment 2, there were significant differences between carbohydrate and DM ADCs for the test ingredients. The carbohydrate, DM and energy ADCs were ranked as follows: dextrin (Fieldose 9) = dextrin (Fieldose 17) = dextrin (Fieldose 30) = gelatinized wheat starch = maltose = glucose > raw wheat starch > raw pea starch. The protein ADC of the diets, postprandial plasma glucose concentration and SGR were all unaffected by ingredient type. For both experiments, HSI tended to increase with carbohydrate inclusion. Liver glycogen concentrations were also elevated, but muscle glycogen and liver and muscle triacylglycerol concentrations were unaffected. Digestibility of starch by silver perch is clearly affected by inclusion content and processing.
TL;DR: In a sensory test, the test panel found that saithe from the fjord without ¢sh farms tasted better than saithe collected near the cages, and the results suggest that there were individual diierences in the time spent near cages for saithe Collected near the farm.
Abstract: There is an ongoing controversy on whether ¢sh farming aiects the quality of wild ¢sh in fjords. In northern Norway, local people prefer not to eat saithe, Pollachius virens L., from areas in the vicinity of ¢sh farms because they say the taste is inferior to saithe from other areas. To address this issue, saithe were collected in the vicinity of a salmon ¢sh farm in a fjord in northern Norway and in two reference areas: one site 6 km away from the nearest ¢sh farm in the same fjord, and the other in a fjord nearby with no ¢sh farms. The objective of this study was to clarify whether the physiology or taste of saithe near ¢sh farms diiers from saithe in areas with no or limited in£uence from ¢sh farms. The ¢sh collected near farms were larger than those from control sites of the same age and had been eating pellets. Analysis of fatty acid composition of the ¢llet indicated that ¢sh collected near the farms had fatty acid pro¢les that resembled that of pellets more than ¢sh from reference sites. The results suggest that there were individual diierences in the time spent near cages for saithe collected near the farm, and that saithe collected at the reference area in the same fjord had also been eating pellets, i.e. had visited at least one of the ¢sh farms in the fjord. In a sensory test, the test panel found that saithe from the fjord without ¢sh farms tasted better than saithe collected near the cages. The test panel found no clear diierences in taste between saithe collected near the ¢sh farm and saithe from the same fjord, but 6 km from the nearest ¢sh farm.
TL;DR: Investigation of the impact of various salinity levels on qualitative and quantitative characteristics of the natural community and, more particularly, ciliated protozoa in shrimp growth and survival found no significant difference between survival rates and decreasing salinity led to a significant decrease in final shrimp body weight.
Abstract: Recent efforts have been made to culture marine shrimp in systems operating under low or zero-water exchange and with decreased water salinity. The aim of this study was to investigate the impact of various salinity levels on qualitative and quantitative characteristics of the natural community and, more particularly, ciliated protozoa, and compare this information with shrimp growth and survival. Tanks with 9‰ salinity were characterized by a higher pH, but also by a significantly higher concentration of chlorophyll a (Chl a) per weight of suspended matter (1.93 ± 0.72 µg Chl a/mg TSS) than tanks with 18‰ (1.29 ± 0.68 µg Chl a/mg TSS) or 36‰ (1.37 ± 0.61 µg Chl a/mg TSS) salinity. Concentrations of ciliates (max 6000 cells mL−1) showed considerable fluctuations over the sampling period, reflecting the impact of water salinity, dynamic interactions between ciliates and their diverse roles within the shrimp production system. There was no significant difference between survival rates of shrimp reared at 9‰, 18‰ or 36‰, but decreasing salinity from 36‰ to 9‰ led to a significant decrease in final shrimp body weight (from 13.40 ± 0.26 g to 10.23 ± 2.72 g). Future work should address the potential of ciliates as an indicator of aquaculture water quality, as is currently being done in the wastewater industry, and the contribution of ciliates as food sources.
TL;DR: The results suggest that salmon position themselves in relation to the artificial light gradient to maintain schooling behaviour and that the use of submersible lights may be a precaution to secure the welfare of caged salmon.
Abstract: Artificial photoperiods that postpone sexual maturation and increase growth are now widely used in the Atlantic salmon Salmo salar L. farming industry. Few studies have been carried out to examine the effect of this treatment on fish behaviour and welfare in production cages. In this study, echo-integration was used to observe the swimming depth and fish density of salmon in 20-m-deep production cages illuminated by lamps mounted above the water surface (SURF) or submerged in the cage (SUBS). From January to May, SUBS swam at a greater depth (5–11 m) than SURF (1–3 m) at night. SURF descended and SUBS ascended at dawn, but SUBS were still swimming at greater depth than SURF during the day from January to March. The difference in swimming depth resulted in SURF swimming at a median fish density about twice as high as SUBS at night and up to five times the calculated fish density. SURF increased the utilization of the cage volume as the biomass increased, but fish swimming at the highest density did so at up to 20 times the calculated fish density. The results suggest that salmon position themselves in relation to the artificial light gradient to maintain schooling behaviour and that the use of submersible lights may be a precaution to secure the welfare of caged salmon.
TL;DR: WG, FCR, and apparent retention of crude protein and phosphorus were signi¢cantly improved in rainbow trout fed the diet containing 1.65 g MHA kg � 1 diet compared with an equivalent diet without MHA.
Abstract: Two experiments were conducted to evaluate the effects of supplementing methionine hydroxy analogue (MHA) on the performance, body composition, and nutrition retention of rainbow trout. In experiment 1, a 2 � 4 factorial arrangement with two MHA supplemental levels (with and without) and four ¢sh meal replacement levels (25%, 50%, 75%, and 100%, replaced with soybean meal (SBM) and wheat gluten) was used. A ¢sh meal diet was included as a control. Results showed that ¢sh meal replacement levels had signi¢cant eiects on ¢sh weight gain (WG), feed conversion ratio (FCR), body moisture, crude protein, crude fat, and ash (Po0.05). In experiment 2, a ¢sh meal reference diet and seven other diets were made using SBM and distiller’s dried grain with solubles supplemented with 0, 0, 0.55, 1.1, 1.65, 2.2, and 2.75 g MHA kg � 1 diet to replace 50% of ¢sh meal. WG, FCR, and apparent retention of crude protein and phosphorus were signi¢cantly improved in rainbow trout fed the diet containing 1.65 g MHA kg � 1 diet compared with ¢sh fed an equivalent diet without MHA.
TL;DR: Gene technology opens new opportunities to comprehend the nature of the genetic variation underlying production traits, enabling improvement in economically important traits, in particular traits difficult to breed for, such as food conversion efficiency and disease resistance.
Abstract: Selective breeding has been very successful in increasing production in Atlantic salmon. Gene technology opens new opportunities to comprehend the nature of the genetic variation underlying production traits. Two major areas in which gene technology may play an important role are (1) production of genetically modified fish and (2) development and utilization of genetic markers. Several studies of transgenic salmonids have shown substantially increased growth rates. However, many different issues are related to whether genetically modified fish should be used or not. Genetic markers can be used for aquaculture purposes and for monitoring wild populations. Construction of genetic maps based on markers enables the identification of quantitative trait loci (QTL) and/or markers linked to them. This will facilitate marker-assisted selection, enabling improvement in economically important traits, in particular traits difficult to breed for, such as food conversion efficiency and disease resistance. Several experiments aimed at mapping QTL in salmonids using genetic markers are ongoing. DNA marker technologies can also be used for identification and monitoring of lines, families and individuals, and for genetic improvement through selection for favourable genes and gene combinations.
TL;DR: The objectives of this study were to determine how periphyton and phytoplankton biomass vary with grazing pressure by tilapia Oreochromis niloticus, to evaluate the growth performance of fish when substrate is introduced and to calculate the efficiency of nitrogen utilization in substrate and non-substrate systems.
Abstract: The objectives of this study were to determine how periphyton and phytoplankton biomass vary with grazing pressure by tilapia Oreochromis niloticus, to evaluate the growth performance of fish when substrate is introduced and to calculate the efficiency of nitrogen utilization in substrate and non-substrate systems. Ten circular 1000-L plastic tanks were filled with 15 cm of loamy soil bottom and water. Five different treatments were applied: eight tilapias with substrate (treatment 8T/S), eight tilapias without substrate (treatment 8T), four tilapias with substrate (treatment 4T/S), four tilapias without substrate (treatment 4T) and no tilapia with substrate (treatment OT/S). Each week, 2 g of NaNO3 and 3.5 g of single superphosphate (SSP) were applied to each tank. Sixteen glass slides (1 m x 4 cm x 4 mm) were installed vertically in the tank bottom, one portion extending above the water surface and equally spaced within the water column in all substrate tanks. Periphyton and phytoplankton quantity and quality, water quality, fish growth and proximate fish composition were measured. Because of grazing, phytoplankton and periphyton biomass decreased after the introduction of fish to the tanks. The periphyton biomass was higher in non-fish tanks (treatment OT/S) throughout the experiment than that in tanks with fish (treatments 8T/S and 4T/S). The periphyton biomass was similar in the 4T/S and 8T/S treatments, suggesting that the grazing pressure on periphyton biomass reached threshold levels. Fish ate 25-36% of the total standing biomass every day. Tilapia growth was significantly higher in treatments with substrate. Nitrogen retention was double in substrate ponds compared with in control ponds. There were no significant effects of periphyton substrate or fish density on body composition of fish.
TL;DR: The study was carried out to quantify the periphyton biomass developed on glass substrates over time, to investigate the effects of peripHYton quantity and fish size on the ingestion rate by fish, and to determine the feed conversion ratio (FCR) of perIPhyton by tilapia Oreochromis niloticus.
Abstract: The study was carried out to quantify the periphyton biomass developed on glass substrates over time, to investigate the effects of periphyton quantity and fish size on the ingestion rate by fish, and to determine the feed conversion ratio (FCR) of periphyton by tilapia Oreochromis niloticus. Periphyton was grown in two fertilised 1000-l tanks on glass slides and monitored as dry matter (g), ash-free dry matter (g) and chlorophyll a concentrations (mg) per unit surface area (m2) over a six week period. Ingestion rate was determined for two sizes of tilapia (7 and 24 g) which were provided with four different periphyton densities. Determination of FCR was made after feeding three individual fish ad libitum with periphyton for two weeks. Periphyton ash-free dry matter increased sharply during the first half of the trial with a peak being recorded at week 3 (75.5 g m-2). Productivity was 2.4 g ash-free dry matter m-2 d-1 during the first three weeks. Mean chlorophyll a concentration showed a cyclic pattern throughout the study with the lowest value being measured during the last week. Ingestion rates were 0.90 and 0.18 mg dry matter g fish body weight-1 h-1 for small and medium fish respectively. Ingestion rate among small fish increased significantly (P <0.05) with periphyton density, but not for medium size fish. Although periphyton ash content was high (55% dry matter), fish growth was sustained. Fish harvested 70% of total periphyton dry matter that was offered to them. The FCR for periphyton was 2.81 on a dry matter basis and 1.34 on an ash-free dry matter basis.