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1.
Atlantic halibut (Hippoglossus hippoglossus) achieve a mature gastrointestinal tract approximately 2 months after first feeding (12 °C). The immature digestion may be the reason that compound diets fail to sustain growth and survival in first feeding halibut larvae and in larvae of other marine fish species. On the other hand, larvae fed with live feeds are capable of extraction of sufficient quantities of nutrients to sustain high growth rates. A lower availability of the protein in formulated diets compared with live prey is considered to be an important reason for the low performance of formulated diets. One approach to increase dietary protein availability is supplementation of pre‐digested proteins. Experiments using tube fed individual larvae show that halibut larvae are able to utilize hydrolysed protein more efficiently than intact protein. However, Atlantic halibut in culture did not respond well to dietary supplementation of hydrolysed protein, in contrast to some other species. One reason may be extensive leaching of pre‐hydrolysed proteins from the microparticulate feed. Atlantic halibut are slow feeders and may thus suffer more from nutrient leaching than species eating more rapidly. Feed formulation techniques affect dietary protein leaching, and in this paper, different techniques and their impact on feed properties are described. Microbound diets are most widely used in larval rearing, but show high rates of nutrient leaching. Lipid‐based capsules seem to have the best potential to prevent leaching, however, they are not able to deliver a complete diet. The high need for improvements in larval feed formulation techniques are clearly stated, and some suggestions are given. Among these are production of complex particles, where small lipid‐based capsules or liposomes containing the low molecular weight water‐soluble nutrients are embedded. In such feed particles the water‐soluble molecules are protected from leaching. Techniques for delivery of water‐soluble nutrients that are needed in large quantities, i.e. free amino acids or hydrolysed and water‐soluble protein, remain to be developed.  相似文献   

2.
Alternative marine resources from lower trophic levels could partly cover the rapidly increasing needs for marine proteins and oils in the future. The North Atlantic calanoid copepod, Calanus finmarchicus, has a high level of lipids rich in n‐3 fatty acids. However, these animals have wax esters as the main lipid storage component rather than triacylglycerol (TAG). Although these esters are considered difficult to digest by many fish, is it well known that juvenile Atlantic salmon (Salmo salar) feed on zooplankton species. It is therefore possible that the capacity to utilize these lipids should be well developed in salmonids. Nonetheless, salmon hydrolyse wax esters slower than TAG and absorb fatty alcohols slower than fatty acids. However, salmon have several adaptations to digest diets rich in wax esters. These includes increased feed conversion, higher production of bile and higher activity of lipolytic enzymes in the midgut. Atlantic salmon has been shown to feed and grow on diets with a medium amount of wax esters (30% of the lipid) with results comparable to fish maintained on fish oil diets. Ingestion of higher level of wax esters (50% of the lipid) cause, however, poorer lipid digestibility and growth, so that optimal utilization of wax esters in Atlantic salmon is closer to 30% than 50% of the dietary lipid.  相似文献   

3.
Abstract Compared to the extensive number of studies in nutritional immunology in humans as well as in livestock, the evaluation of nutritional impact on fish health is in its infancy. The mechanisms by which single nutrient modulate immunity are frequently not understood, even if experiments give some indication of the mode of action. With current knowledge in fish nutrition, the methods and criteria for optimal nutrient recommendations should be reevaluated to include health factors such as immunolgy and disease resistance. By increasing knowledge of the role of different nutrients in the general metabolism and in immunity, and by improving rearing conditions, it may be possible to reduce losses due to diseases by retarding the progress of diseases, improving recovery and improving protection through vaccines. This review covers research on dietary level of carbohydrate, n-3 polyunsaturated fatty acids, vitamin E and vitamin C in salmonids, of which the vitamins have been by far the most studied.  相似文献   

4.
Analysis of nutrient flows in integrated intensive aquaculture systems   总被引：12，自引：0，他引：12  
This paper analyses nutrient conversions, which are taking place in integrated intensive aquaculture systems. In these systems fish is cultured next to other organisms, which are converting otherwise discharged nutrients into valuable products. These conversions are analyzed based on nitrogen and phosphorous balances using a mass balance approach. The analytical concept of this review comprises a hypothetical system design with five modules: (1) the conversion of feed nutrients into fish biomass, the “Fish-Biomass-Converter”; (2) the separation of solid and dissolved fish waste/nutrients; the “Fish-Waste-Processor”; (3) the conversion of dissolved fish waste/nutrients, the “Phototrophic-herbivore-Converter”; (4 and 5) the conversion of solid fish waste, the “Bacterial-Waste-Converter”, or the “Detrivorous-Converter”. In the reviewed examples, fish culture alone retains 20–50% feed nitrogen (N) and 15–65% feed phosphorous (P). The combination of fish culture with phototrophic conversion increases nutrient retention of feed N by 15–50% and feed P by up to 53%. If in addition herbivore consumption is included, nutrient retention decreases by 60–85% feed N and 50–90% feed P. This is according to the general observation of nutrient losses from one trophic level to the next. The conversion of nutrients into bacteria and detrivorous worm biomass contributes only in smaller margins (e.g. 7% feed N and 6% feed P and 0.06% feed N 0.03 × 10−3% feed P, respectively). All integrated modules have their specific limitations, which are related to uptake kinetics, nutrient preference, unwanted conversion processes and abiotic factors.  相似文献   

5.
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.  相似文献   

6.
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7.
The production of the Pacific white shrimp (Litopenaeus vannamei) has expanded to the point of being the most widely cultured species of shrimp. One of the advantages of this species is its acceptance of a wide variety of feed formulations including plant‐based feeds. Given the increases in ingredient costs, particularly fish meal, there is considerable interest in the use of alternative feed formulations for cultured species. Given that soybean meal is one of the most widely available protein sources for which production can be expanded, the move to soy‐based diets is inevitable. The successful use of alternative feed ingredients for shrimp production depends on a number of factors. This paper summarizes studies regarding the move towards high soy diets concerning manipulation of ingredients and nutrient profiles to maintain balanced feed formulations.  相似文献   

8.
The relative potential for soluble and transport losses of aquaculture waste was examined. The waste was collected at four junctures between introduction to the environment and the culmination of settlement, including samples of feed, faeces, particulate matter in the water column obtained from sediment traps, and the benthos. Organic matter was used as a model system to investigate the fate of these components because it was simple to analyse and previous research has found it to be correlated to carbon and nutrient levels in the samples. A narrow definition of each loss was considered. Soluble losses were examined by measuring change in organic matter content while the samples were in a stationary water field. The potential for transport losses was examined by determining if light and heavy fractions of a sample differed in their amount of organic matter. Faecal matter had a very high solubility potential, and lost approximately 50% of its organic matter in 12 days. No other sample had losses > 10%. The benthic samples gained organic matter while sitting in the stationary water field. There was no discernible trend to the samples' potential for transport losses. However, for all replicates combined, the smaller the proportion of the lighter fraction, the greater the difference (+) in the organic matter content between the light and heavy fractions. Thus, lighter material is the last to settle and thus more prone to be transported further afield. The implications of this study include the need for model studies to examine different types of loss and also elucidation of divergent degradation properties of each component. This study also points to a functional mechanism behind greater environmental impacts associated with poorly managed farms.  相似文献   

9.
Extinction vulnerability in marine populations   总被引：16，自引：0，他引：16  
Human impacts on the world's oceans have been substantial, leading to concerns about the extinction of marine taxa. We have compiled 133 local, regional and global extinctions of marine populations. There is typically a 53‐year lag between the last sighting of an organism and the reported date of the extinction at whatever scale this has occurred. Most disappearances (80%) were detected using indirect historical comparative methods, which suggests that marine extinctions may have been underestimated because of low‐detection power. Exploitation caused most marine losses at various scales (55%), followed closely by habitat loss (37%), while the remainder were linked to invasive species, climate change, pollution and disease. Several perceptions concerning the vulnerability of marine organisms appear to be too general and insufficiently conservative. Marine species cannot be considered less vulnerable on the basis of biological attributes such as high fecundity or large‐scale dispersal characteristics. For commercially exploited species, it is often argued that economic extinction of exploited populations will occur before biological extinction, but this is not the case for non‐target species caught in multispecies fisheries or species with high commercial value, especially if this value increases as species become rare. The perceived high potential for recovery, high variability and low extinction vulnerability of fish populations have been invoked to avoid listing commercial species of fishes under international threat criteria. However, we need to learn more about recovery, which may be hampered by negative population growth at small population sizes (Allee effect or depensation) or ecosystem shifts, as well as about spatial dynamics and connectivity of subpopulations before we can truly understand the nature of responses to severe depletions. The evidence suggests that fish populations do not fluctuate more than those of mammals, birds and butterflies, and that fishes may exhibit vulnerability similar to mammals, birds and butterflies. There is an urgent need for improved methods of detecting marine extinctions at various spatial scales, and for predicting the vulnerability of species.  相似文献   

10.
Yersinia ruckeri (Y. ruckeri) can cause mortalities that are contributing to substantial economic losses in the rainbow trout (Oncorhynchus mykiss) aquaculture sector. Because of its most characteristic clinical signs, the disease in rainbow trout caused by this pathogen is called enteric redmouth disease. Although it is considered to affect mainly salmonids, there are reports in the available literature of isolating this bacterium from other fish species, both clinically healthy and diseased. The aim of this study was to analyse the available data concerning yersiniosis in non‐salmonid fish. The analysed data indicate that Y. ruckeri is a threat not only to rainbow trout. Some of the affected species have high commercial importance and mortalities may contribute to high economic losses. The disease symptoms may not be specific and can be different from those characteristic for enteric redmouth in trout, which may lead to misdiagnosis. Collected information indicates that infection with Y. ruckeri should be taken into account in the diagnostic procedures not only in salmonids.  相似文献   

11.
用免疫蛋白质组学的研究方法鉴定了哈氏弧菌的免疫反应蛋白。将哈氏弧菌接种于TSB培养基28℃培养18h,利用裂解液裂解细菌,提取全菌可溶性蛋白,一向电泳采用7cmpH4～7的胶条进行等电聚焦,二向用12.5%的SDS-PAGE胶分离蛋白质,考马斯亮蓝染色,获得双向电泳图谱,再结合免疫转印技术检测免疫反应的蛋白质,利用ImageMaster 2D Platinum进行配对分析得到15个非特异性的免疫反应性蛋白点,30个特异性的免疫反应性蛋白点。经过鉴定得到13种非特异性的免疫反应性蛋白质,这其中有2对蛋白在胶上的位置不同,但鉴定为同一种蛋白;同时得到28种特异性的免疫反应性蛋白质,有一个蛋白点没有在数据库中查找到相对应的蛋白质,还有1对蛋白在胶上的位置不同,但鉴定为同一种蛋白。将特异性免疫反应蛋白鉴定结果与非特异性比较发现有1对蛋白鉴定为同一种蛋白;另外,No.17和No.19是F0F1 ATP synthase的两个亚基。特异性免疫反应蛋白鉴定结果中有6个蛋白质是已知的其他细菌的具有免疫反应的蛋白,分别为OmpN,OmpW,OmpU,alanine dehydrogenase,Elongation factor...  相似文献   

12.
China is the world's largest capture fisheries and aquaculture producer. Over recent decades, China's domestic marine catch composition has changed markedly, from large volumes of a few high‐valued food species to multiple, small, low‐valued, species, a significant proportion of which is primarily used as animal, especially fish, feed. Despite the growing volume and economic importance of the feed catches, their species composition, catch volumes and socio‐environmental impacts are all poorly understood. Based on a nationwide survey of >800 fishing vessels, and the identification and measurement of >12,000 fish and invertebrate individuals, the present study provides an overview of the feed component of China's domestic marine catch, by volumes, species and sizes, and found it to be substantial and biologically unsustainable. Half of the trawler catch (3 million metric tons, mmt), or 35% of the total catch (4.6 mmt) in China's exclusive economic zone, are now comprised of low‐valued “feed‐grade fish”. The present study identified 218 fish species, 50 crustaceans and five cephalopods, and of these, 102 fish species were food species with 89% individuals in their juvenile size ranges. Feed‐grade fish were mainly used as aquaculture feed directly, or indirectly, through the feed industry after reduction to fishmeal and fish oil. The unparalleled scale and poor fisheries resource condition of China's domestic marine fisheries, in parallel with severe overfishing of juveniles, creates a demand for fundamental changes to fishery management practices, including a significant reduction of fishing effort to ensure productivity and ecosystem resilience.  相似文献   

13.
Viral haemorrhagic septicaemia (VHS) is a well-characterized disease of rainbow trout, Oncorhynchus mykiss, which has also caused economic losses in marine turbot farms in the British Isles. We have previously demonstrated that turbot, Scophthalmus maximus, are susceptible to isolates of viral haemorrhagic septicaemia virus (VHSV) that are endemic in the marine environment, highlighting a potential risk to marine aquaculture. Given the increasing interest in the intensive rearing of additional aquaculture species such as Atlantic cod, Gadus morhua, and Atlantic halibut, Hippoglossus hippoglossus, this study aimed at investigating the susceptibility of these species to VHSV. Both species were found to be largely resistant to VHS following immersion challenge with a selection of 18 isolates, representing the known marine VHSV genotypes. Only one and two VHSV-associated mortalities occurred out of a total of 1710 and 1254 halibut and cod, respectively. These findings suggest that there is a low direct risk to the development of commercial cod and halibut aquaculture from the existing endemic reservoir of VHSV. This study, coupled to field observations has, however, highlighted the fact that both species can become infected with VHSV. The known adaptability of RNA viruses, together with the selection pressures associated with intensive aquaculture would thus advocate a cautious approach to VHSV surveillance within these emerging industries.  相似文献   

14.
Nitrogen removal techniques in aquaculture for a sustainable production   总被引：1，自引：0，他引：1  
As the aquaculture industry intensively develops, its environmental impact increases. Discharges from aquaculture deteriorate the receiving environment and the need for fishmeal and fish oil for fish feed production increases. Rotating biological contactors, trickling filters, bead filters and fluidized sand biofilters are conventionally used in intensive aquaculture systems to remove nitrogen from culture water. Besides these conventional water treatment systems, there are other possible modi operandi to recycle aquaculture water and simultaneously produce fish feed. These double-purpose techniques are the periphyton treatment technique, which is applicable to extensive systems, and the proteinaceous bio-flocs technology, which can be used in extensive as well as in intensive systems. In addition to maintenance of good water quality, both techniques provide an inexpensive feed source and a higher efficiency of nutrient conversion of feed. The bio-flocs technology has the advantage over the other techniques that it is relatively inexpensive; this makes it an economically viable approach for sustainable aquaculture.  相似文献   

15.
Diadromous fishes are known biotransport vectors that can move nutrients, energy and contaminants in an upstream direction in lotic ecosystems. This function has been demonstrated repeatedly in anadromous salmonids, but the role of other diadromous species, especially tropical taxa, as biotransport vectors is less studied. Amphidromous fish species exhibit potential to act as upstream vectors of nutrients and contaminants in their postlarval and juvenile stages, but this role is largely unknown because of limited understanding of larval growth habitats. Moreover, because some species are harvested in artisanal fisheries as postlarvae, and postlarvae are consumed by riverine and estuarine predators, heavy contaminant loads may present a human or wildlife health concern. This research incorporates stable isotope and contaminant analyses to infer larval habitats and contaminant accumulation of amphidromous fishes on the Caribbean island of Puerto Rico. The isotopic signatures of postlarval amphidromous fishes indicated marine basal sources and food web components, rather than those from riverine habitats. Additionally, postlarvae did not contain concentrations of anthropogenic pollutants that would be of ecological or human health concern. These findings are the first and strongest evidence that amphidromous fish postlarvae function as biotransport vectors of marine nutrients into and up river ecosystems without posing a health threat to the receiving food web or human consumers.  相似文献   

16.
Detailed observations of the behaviour of harbour seals, Phoca vitulina L., at sites within the estuaries of the Rivers Dee and Don, in north-eastern Scotland, were made over two full years between 1993 and 1996. Small numbers of grey seals, Halichoerus grypus Fab., were also present. The presence of seals within the estuaries was strongly related to season, with maximum numbers observed in winter and early spring; seals were virtually absent in June and July. The River Don was used largely as a haul-out site, while the River Dee was used predominantly as a foraging site, although it was not possible to determine whether the same seals were using the two estuaries. More seals were hauled-out on the River Don during twilight and dark than in daylight. The seals were observed to eat mostly salmonids, Salmo salar L. and S. trutta L., unidentified roundfish and flounder, Pleuronectes flesus L. The otoliths identified in scats collected at the mouth of the River Don belonged to marine species indicating that the seals were also feeding outside the estuaries. A minimum estimate is given of the numbers of large salmonids eaten in each river during the course of the year. Although no information was available on the numbers of salmonids using the rivers or the reproductive status of the fish eaten by the seals, as a cause of mortality, seal predation on large salmonids in estuaries is apparently an order of magnitude less important than mortality caused by angling within the river.  相似文献   

17.
Abstract –  The native and non-native freshwater fish species richness as well as the proportion of native fish species to overall fish species were examined to test a hypothesis of a spatial linkage between the distributions of dams and non-native fishes based on survey data collected in rivers and streams in Hokkaido, Japan. Non-native fish species have steadily increased in Hokkaido since the mid 1970s, as indicated by the decreasing proportion of native fish species per fish survey. Non-native species richness was significantly higher in areas above dams (i.e., reservoirs and their inlet streams) compared to areas without dams. As a result, the proportion of native fish species was lower above dams. This proportion was lower in developed and agricultural areas compared with forest areas, although both native and non-native species richness were higher in areas with development and agriculture. Non-native cyprinids, catfish and snakehead occurred primarily in a particular river basin with the largest drainage area, the longest history of reclamation and highest human population in the island. Non-native salmonids on the other hand, occurred in forest areas at higher elevations and their occurrence was associated with the existence of dams. There was a spatial linkage between the distribution of dams and non-native species, although it was applicable only to salmonids. The management of dams and reservoirs needs a strategy to prevent further expansion of exotic salmonids such as rainbow and brown trout. These species can be a significant threat to native Japanese salmonids as a result of various biological mechanisms.  相似文献   

18.
Important operational changes that have gradually been assimilated and new approaches that are developing as part of the movement toward sustainable intensive aquaculture production systems are presented via historical, current, and future perspectives. Improved environmental and economic sustainability based on increased efficiency of production continues to be realized. As a result, aquaculture continues to reduce its carbon footprint through reduced greenhouse gas emissions. Reduced use of freshwater and land resources per unit of production, improved feed management practices as well as increased knowledge of nutrient requirements, effective feed ingredients and additives, domestication of species, and new farming practices are now being applied or evaluated. Successful expansion into culture of marine species, both off and on shore, offers the potential of substantial increases in sustainable intensive aquaculture production combined with integrative efforts to increase efficiency will principally contribute to satisfying the increasing global demand for protein and food security needs.  相似文献   

19.
The growth and feed utilization of Atlantic cod (Gadus morhua) (437 g), Atlantic salmon (Salmo salar) (485 g) and rainbow trout (Oncorhynchus mykiss) (413 g) fed a diet (170 g kg−1 fat, 600 g kg−1 crude protein; LE) similar to that used in commercial cod production or one that was top dressed with additional fat (280 g kg−1 fat, 530 g kg−1 crude protein; HE), were compared in an 11‐week trial. In the cod, relative feed intake was 41–58% and thermal growth coefficient 63% of that in the salmonids, but the feed efficiency ratio (FER) was 38% better (P ≤ 0.05). In contrast to the cod where there was no effect of diet on feed intake, growth or FER, both the salmon and trout fed the HE diet had greater feed intake than those fed the LE diet, but the effect of this was only positive for growth in the salmon. The cod retained more of the digested nitrogen (44.9 ± 2.7%) than the salmon (39.4 ± 0.8%), and both of these species retained more than the trout (33.6 ± 1.1%) (P ≤ 0.05). The retention of digested energy was significantly higher in the salmon (52.2 ± 0.9%) than in the trout (44.8 ± 1.1%), with the cod (44.9 ± 4.9%) not different from either of the other species. There were no differences between the species in the retention of absorbed phosphorus (65.9 ± 3.6%). There were very few dietary effects on nutrient utilization in this trial and, for the cod, this indicates that higher energy diets may be feasible for use in production.  相似文献   

20.
To support the expected increase in aquaculture production during the next years, a wider range of alternative ingredients to fishmeal is needed, towards contributing to an increase in production sustainability. This study aimed to test diets formulated with non‐conventional feed ingredients on gilthead seabream (Sparus aurata) growth performance, feed utilization, apparent digestibility of nutrients and nutrient outputs to the environment. Four isonitrogenous and isoenergetic diets were formulated: a control diet (CTRL) similar to a commercial feed and three experimental diets containing, as main protein sources, plant by‐products, glutens and concentrates (PLANT); processed animal proteins (PAP); or micro/macroalgae, insect meals and yeast (EMERG). Diets were tested in triplicate during 80 days. The EMERG treatment resulted in lower fish growth performance, higher FCR and lower nutrient and energy retentions than the other treatments. The lowest protein digestibility was found for the EMERG diet, which caused increased nitrogen losses. The PLANT and PAP treatments resulted in better fish growth performance, higher nutrient and energy retentions, and lower FCR than the CTRL treatment. The significant improvement in FCR found for fish fed PLANT and PAP diets and the high protein digestibility of these diets contribute towards minimizing the environmental impacts of seabream production.  相似文献   

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