Energy use in Recirculating Aquaculture Systems (RAS): A review

Recirculating aquaculture systems (RASs) are intensive fish production systems, with reduced use of water and land. However, their high energy requirement is a drawback, which increases both operational costs and the potential impacts created by the use of fossil fuels. Energy use in RAS has been studied indirectly and/or mentioned in several publications. Nevertheless, its importance and impacts have not been studied. In aiming to achieve economic and environmentally sustainable production a compromise has to be found between water use, waste discharge, energy consumption and productivity. The current review discusses published studies about energy use and RAS designs efficiencies. Moreover, with the aim of making an industry baseline study a survey about the energy use in commercial scale RAS was conducted. The design of more efficient and less energy dependent RAS is presented, including optimized unit processes, system integration and equipment selection. The main conclusions are: fossil based fuels are less cost-effective than renewable energies; energy is of little concern for the majority of the industry, and renewable energies are of potential use in RAS.     

The integrated development and application of controlled reproduction techniques in Pacific salmonid aquaculture

During the last several years there has been rapid progress in the development and application of controlled reproduction and associated biotechnologies to the culture of salmonids. This review focuses on the development of those techniques for Pacific salmon (Oncorhynchus species) and rainbow trout (Salmo gairdneri). These include methodologies for the induction of ovulation, storage of gametes, chromosome set manipulation, i.e., induced gynogenesis and triploidy, hormonal feminization, hormonal sterilization and hormonal masculinization of genotypic females to produce milt containing only female spermatozoa.The current and future applications of these methodologies to the commercial mariculture of salmonids and to the enhancement and management of ocean and fresh water stocks are described. The implementation of each individual methodology for the control of reproduction can in itself have a significant impact on the efficiency of culture systems. It is, however, from the combination of specific complementary methods in production systems that the greatest gains will ultimately be made.It is concluded that the utilization of single or paired controlled reproduction techniques by themselves or in combination with other biotechnologies (e.g. sterilization plus growth acceleration) offer significant advantages for both the commercial mariculture of salmonids and the rearing of salmonids by government agencies for release into the oceanic or lacustrine environment.     

A review of methods for Centropomus spp. (snooks) aquaculture and recommendations for the establishment of their culture in Latin America

The positive features of Centropomids and Latids for cultivation are analysed and highlighted. The main life cycle characteristics as well as market prices and demands are presented. Good growth, highly efficient food conversion ratios and energy utilization allow very high biomass yields per unit volume in nursery and grow‐out systems. They have shown notable tolerances to main environmental conditions, as well as considerable versatility in adapting to culture systems (cages, ponds and tanks), and culture intensity (extensive, semi‐intensive, intensive and superintensive), especially in estuarine and coastal sites and ponds. These positive features provide them with a high culture potential. A general summary of their culture is presented, based on the commercial cultivation of the Asian sea bass or barramundi Lates calcarifer as well as the experimental and pilot‐scale results from the main American species. The importance of hatchery fry production as an essential culture pre‐requisite is emphasized, in addition to an analysis of the main difficulties and constraints for future development.     

The use of immunostimulating herbs in fish. An overview of research

The use of immunostimulants as an alternative to the drugs, chemicals and antibiotics currently being used to control fish diseases in fish culture is attracting the attention of many researchers. In this context, many have focused on the use of medicinal plant products as potential therapeutic measures for modulating the immune response and, specifically, on the use of herbs to prevent and control fish diseases. Medicinal plants (plant remedies) are a deeply rooted component of the cultural heritage of many people from diverse cultures and countries and are, as such, closely linked to the maintenance of good health. The aim of this paper is to review research currently being carried out on the herbs and herbal extracts that have been shown to modulate the immune system of fish. Special attention is given to the use of Chinese and Indian herbs.     

Is a better strategy necessary for development of native species for aquaculture? A Mexican case study

Native species development is often based upon the interests of individuals, the specialities of particular institutions or even the simplicity of the technology required. The methodology of developing native species for aquaculture is discussed with particular reference to current concerns over loss of biodiversity. The biological and technical issues are outlined and prioritized, and the question of socio-economic targeting of the activity, the needs for marketing and promotion, and the requirements for farming systems studies are described. Time-scales and costs for research and development programmes are illustrated using the example of Cichlasoma urophthalmus (Günther) culture in Mexico. Finally, the increasing use of geographical information systems large-scale strategic planning and in facility location is also discussed.     

Culture methods of live algal feeds for European aquaculture: optimising culture conditions for Ulvella lens

The Japanese development of mass culture techniques for Ulvella lens during the 1980s for aquaculture has stimulated the development of rearing techniques for abalone and sea urchins in producing countries. However, since the late 1980s, there has not been any in-depth evaluation of culture methods for U. lens, nor the development of a new robust method for aquaculture operators. The use of this known inducer for settlement of veliger larvae has not been employed on a commercial scale in Ireland or in European aquaculture systems. The new methodology described here has produced a threefold increase in the settlement of sea urchins (Paracentrotus lividus) and is recommended for adoption by the European aquaculture industry.     

Gonadotropins and their paracrine signaling network in the zebrafish ovary

Pituitary gonadotropins, follicle-stimulating hormone (FSH) and luteinizing hormone (LH), play fundamental roles in vertebrate ovarian development and function. However, there has been an increasing body of evidence that the actions of FSH and LH are mediated or modulated by a variety of locally produced peptide or protein factors, which form an intimate regulatory network within and between the ovarian follicles. In the past few years, a variety of growth factors have been identified and characterized in the zebrafish ovary including activin and epidermal growth factor (EGF), which are important components of the intraovarian communication network. To understand how this local network interacts with the gonadotropins from the pituitary, we have recently cloned and characterized all the subunits of zebrafish FSH and LH from the pituitary as well as their receptors (FSHR and LHR) from the ovary. Using the Chinese hamster ovary (CHO) cells as the bioreactor, we have produced recombinant zebrafish FSH and LH with biological activities. With the recombinant hormones available, the functions of zebrafish FSH and LH in the ovary and their interactions with the local factors will be an important issue to address in the future. This review briefly summarizes some recent work from our laboratory and others on both gonadotropins and their potential intraovarian signaling factors in the zebrafish.     

A survey of aquaculture production economics and management

Abstract

The literature on production economics and management of fish culture has grown as aquaculture has matured as a commercial industry. Salmon, catfish, shrimp and trout are the focus of this literature survey as a reflection of the volume of research that has been completed on these species and their importance in US production and world trade. In addition, a discussion of low resource production systems is included that is dominated by tilapia and carp culture systems. A brief overview of the principles of aquaculture production economics and management is presented followed by a review of economic studies.     

The use of information technology in aquaculture management

Abstract

The recent advances in information technology (IT) have had profound impacts on all walks of life and aquaculture is no exception. The growing importance of aquaculture as an alternative source of protein has further emphasized the need to adapt and develop advanced IT for the better management of aquaculture facilities as well as the regional planning for aquaculture development.

It is the objective of this paper to review the use and potential prospects of IT in aquaculture management. The information technologies considered are instrumentation and process control, data management, computerized models, decision support systems, artificial intelligence and expert systems, image processing and pattern recognition, geographical information systems, and information centres and networks. The review includes a brief introduction of each of the aforementioned technologies, followed by a survey of their current application as well as their potential use in aquaculture management.     

Economic production of estuary grouper, Epinephelus salmoides Maxwell,reared in floating net cages

The factors affecting production of estuary grouper, Epinephelus salmoides, in floating net cages are discussed. The concept of economic production in cage culture is outlined. Economic production of estuary grouper could be achieved by providing a suitable culture site with good water quality; ensuring proper farm management and regular maintenance of cages; preventing disease and ensuring efficient treatment; providing optimum stocking density, a balanced diet, optimal feeding frequency; manipulating fish behaviour by providing artificial hides; and manipulating physiological characteristics, e.g. by the use of growth promoters.The paper futher describes environmental parameters, such as dissolved oxygen content, water temperature, salinity, water current, bacteria count, pH, and bottom sediments, as important factors in site selection. Their effects on the growth and production of fish are discussed and their optimal levels determined. The problems involving management and maintenance of the farm are also outlined. The main problem in cage culture is fouling which demands considerable labour and money for cage maintenance. Other problems such as predators, poaching, and cannibalism are discussed at length. It is suggested that by manipulation of stocking density, production could be increased. The optimal stocking rate was found to be 60 fish/m³ which gives a high yield of marketable fish. Stocking could be further intensified by providing artificial hides using used car tyres. The net production could be increased by 230% if hiding space of 251 cm³ per fish was provided and the stocking density increased to 156 fish/m³. Although formulated feeds enhanced growth by 27.1% over that of groupers fed on trash fish, the production cost was much higher, rendering the use of formulated feeds alone uneconomical for commercial fish culture. Growth promoters such as 17α-methyltestosterone and nitrovin have been found to promote growth of young estuary grouper by 43.4 and 62.8%, respectively.Using various combinations of culture techniques, it was shown that net production could be increased from 23.76 kg/m³ using conventional culture methods to 136.75 kg/m³ with a combination of hiding space, heavy stocking, appropriate feeding frequency and formulated feeds incorporating growth promoters. The production time was also shortened considerably from 6 months to 2.7 months.Cost-benefit analysis of the eight culture techniques tested indicated that the production cost could be reduced from US$2.00/kg with conventional methods to as low as US$1.28/kg using a sophisticated method. However, based on current market proces, the conventional culture technique was still economically feasible, as the net income over total capital costs was 33.3%. Improvements of the conventional culture technique will increase the ratio of net income over total capital costs by 1–3 times.     

Gar biology and culture: status and prospects

Many lepisosteid populations in North America have declined and many are now threatened as a consequence of habitat loss and alteration and commercial and sport overfishing. Over the last two decades, morphological, histological and molecular studies allowed distinguishing between different phases of development and the nutritional condition of larvae. Ontogeny of the digestive enzymes of gar larvae indicated the possibility to feed them artificial feeds since early developmental stages. An in vitro digestibility system to test different feed ingredients has been used. Important characteristics of artificial diets were identified through different feeding experiments. Endocrinological studies showed the feasibility of altering larval development and the digestive capacity of larvae. Cloning of gar growth hormone opened new avenues to enhance growth in the gars. Plasmatic vitellogenin was isolated and purified, to develop a competitive enzyme‐linked immunosorbent assay, which allowed the straightforward separation of males from females to establish appropriate proportions for reproduction and also was used to evaluate hormonal protocols to induce gonad recrudescence and spawning. This review analyzes the biology, ecology and physiology of different gar species as a basis for their domestication, mass production of larvae for repopulation experiments and for the culture of commercial‐size gar.     

海水养殖鱼类仔、稚鱼骨骼发育与畸形发生

骨骼畸形可导致鱼类运动困难、摄食能力降低、生长缓慢、成活率低,因此,畸形鱼苗的出现将增加生产成本、影响养殖的经济效益。在海水鱼类人工育苗阶段,骨骼畸形现象普遍存在,严重制约了海水鱼类养殖产业的可持续发展。本文首先系统总结了卵形鲳鲹、黄尾鰤、尖吻鲈等经济海水鱼类颌骨、脊柱、尾骨的早期发育时序及特点,比较了仔、稚鱼骨骼畸形发生的部位、时间及发生规律。之后针对仔、稚鱼阶段影响骨骼发育的主要因素,从遗传、环境、营养等方面进行了剖析,以期为寻找降低人工养殖条件下海水鱼类仔、稚鱼的骨骼畸形提供启示。     

Experimental Studies of Feeding in Larval Red Drum

The red drum ( Sciaenops ocellatus ) is the only marine fish species in commercial culture in the US. Red drum can be induced to spawn on demand at any time of the year and the young grown to marketable size in indoor raceways or in ponds. Although many eggs are produced (up to 1 million per spawning pair), grow-out through the larval stage remains a bottleneck in commercial production. Most larvae for commercial use are grown in outdoor ponds where natural blooms of phytoplankton and zooplankton are induced, but pond production is limited seasonally and geographically since red drum larvae require sea water and are intolerant of temperatures below 20 C.
It is possible to raise larvae indoors in tanks year-round by controlling temperature and salinity and by culturing live food, but not in sufficient number to supply commercial fish growers. Experimental studies are being carried out to modify the feeding and rearing systems to improve production of post-larvae. Of utmost importance is the development of a complete diet independent of live foods. Results of studies of highly unsaturated fatty acid requirements, digestive system development and activity levels of digestive enzymes are being incorporated into the development of an improved diet for red drum larvae.     

水产品副产物蛋白回收和高值化利用研究进展

水产品由于其丰富的营养价值,在世界范围内的需求量持续增加。然而,水产品消费与加工过程中产生的大量副产物,带来了严重的资源浪费和环境污染等问题。鉴于此,水产品加工副产物依据其不同特性已经被开发应用到诸多领域。其中,水产品副产物蛋白因其独特的功能特性与较高的经济附加值,在实际生产中得到了广泛的回收和利用。因此,本文综述了现阶段广泛用于回收水产品副产物蛋白的物理学、化学和生物学方法,同时,介绍了鱼类、甲壳类和贝类副产物蛋白高值化利用的研究进展,并对水产品副产物蛋白未来的发展趋势进行展望,旨在进一步提升水产品副产物资源的综合利用潜力,促进我国水产品加工业高质量发展。     

The influence of hydrology and hydraulics on salmonids between spawning and emergence: implications for the management of flows in regulated rivers

Abstract Flow regulation is a major constraint on fish populations in many river systems. Current scientific understanding of the direct and indirect influence of hydrology on salmonids between spawning and emergence is reviewed and used to identify key knowledge gaps. The review emphasises difficulties in linking ecological response to physical process understanding and, conversely, the difficulties in applying detailed process understanding to large‐scale management. It is suggested that the lack of process understanding in the development of current environmental standards reflects differences in perspective, language and scale consideration between researchers and river managers. This presents considerable difficulties for the development of new and more defensible environmental standards. Although upscaling of process understanding should remain a focus for researchers, it is also necessary to acknowledge the ‘uniqueness of place’ and consequently that local data collection may frequently be required.     

Advance in the Culture Research of Small-Eye Flounder,Paralichthys microps,and Chilean Flounder,P. adspersus,in Chile

ABSTRACT

Over 71% of the aquaculture production of Chile is based on salmonids, and given the recents problems in the world salmon industry, it is necessary to investigate the culture of new species as a vital priority to maintain an industry of great social and economic impact for Chile. Small-eye flounder, Paralichthys microps, and chilean flounder P. adspersus, are native, high-value flatfish present off the coasts of Perú and Chile, that are commonly exploted by artisanal fishermen. Since 1986 both species have been objects of research studies for culture based on techniques developed for Japanese flounder. This paper is a review of current knowledge of this species and to identify research needs for the near future. Natural spawning of small-eye flounder and chilean flounder broodstock in captivity is already possible, but the manipulation of spawning using photoperiod and hormonal inducement, as well as the role of broodstock nutrition in egg and larval quality, needs to be explored. Successful incubation and larval culture protocol for both species have been developed, with larval survival over 24% from certain egg batches. Nutritional characterization and requirements for chilean flounder eggs and larvae during the culture period, optimal temperature, density, light intensity and green-water culture, are all subjects of ongoing research. Efforts to improve early culture protocol continues with emphasis on causes of larval mortality, early use of dry feed, microbial ecology of culture tanks and water quality. Weaning from live to formulated diets has been investigated, demonstrating survival of 30-50%. Presently only about 1-5% of hatchery raised flounder show a pigment disorder. Research on formulated diets and the weaning process are under way to ameliorate these results. Juveniles are being grown experimental in tanks and net pens systems and their performance (growth, survival, health) in both systems is being evaluated. Chilean flounder require approximately 2.8 years to reach 1 kg. Effort is also focusing on improving juvenile growing protocol, including recirculation systems, culture environment and diet formulation. Much future research will be required to attain optimal production of the species, such as species-specific nutritional requirements, optimum stocking density, disease and health management and growing protocols with new systems (shallow raceway). At present there is enough known about chilean flounder to begin a pilot-stage that will be the key for future development of its culture.     

Nutritional regulation of hepatocyte fatty acid desaturation and polyunsaturated fatty acid composition in zebrafish (Danio rerio) and tilapia (Oreochromis niloticus)

The desaturation and elongation of [1-¹⁴C]18:3n-3 was investigated in hepatocytes of the tropical warm freshwater species, zebrafish (Danio rerio) and Nile tilapia (Oreochromis niloticus). The hepatocyte fatty acid desaturation/elongation pathway was assayed before and after the fish were fed two experimental diets, a control diet containing fish oil (FO) and a diet containing vegetable oil (VO; a blend of olive, linseed and high oleic acid sunflower oils) for 10 weeks. The VO diet was formulated to provide 1% each of 18:2n-6 and 18:3n-3, and so satisfy the possible EFA requirements of zebrafish and tilapia. At the end of the dietary trial, the lipid and fatty acid composition was determined in whole zebrafish, and liver, white muscle and brain of tilapia. Both zebrafish and tilapia expressed a hepatocyte fatty acid desaturation/elongation pattern consistent with them being freshwater and planktonivorous fish. The data also showed that hepatic fatty acid desaturation/elongation was nutritionally regulated with the activities being higher in fish fed the VO diet compared to fish fed the FO diet. In zebrafish, the main effect of the VO diet was increased fatty acid Δ6 desaturase activity resulting in the production of significantly more 18:4n-3 compared to fish fed the FO diet. In tilapia, all activities in the pathway were greater in fish fed the VO diet resulting in increased amounts of all fatty acids in the pathway, but primarily eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3). However, the fatty acid compositional data indicated that despite increased activity, desaturation of 18:3n-3 was insufficient to maintain tissue proportions of EPA and DHA in fish fed the VO diet at the same level as in fish fed the FO diet. Practically, these results indicate that manipulation of tilapia diets in commercial culture in response to the declining global fish oil market would have important consequences for fish fatty acid composition and the health of consumers. Scientifically, zebrafish and tilapia, both the subject of active genome mapping projects, could be useful models for studies of lipid and fatty acid metabolism at a molecular biological and genetic level. This revised version was published online in August 2006 with corrections to the Cover Date.     

Fathead minnow reproduction: Implications for commercial culture

The fathead minnow, Pimephales promelas, is widely used as a bait, forage, and research fish in the United States. A hardy and fecund fish, this species has many attributes that are excellent for culture. Unfortunately, despite the widespread use of fathead minnows in toxicity testing and thousands of resulting publications, relatively little aquaculture‐related research has been conducted in support of commercial production. On the surface, current commercial fathead minnow production practices appear much the same as those of a decade ago. However, producers continue to refine culture methods, balancing broodfish stocking rates, spawning substrate quantity, and feeding rates in an attempt to meet both losses to predators and market demand. This review examines relevant reproduction‐related studies in the fields of ecology, behavior, toxicology, and aquaculture with the goal of advancing fathead minnow culture. In fathead minnow production, relative to the culture of food fish species, reproduction is vital, more so than rapid growth or a low feed conversion ratio. Fish numbers may exceed 1 million fish/ha, while feeding rates are relatively low and in feeder fish production, growth is deliberately restrained in order to maintain fish within market sizes year‐round. Underappreciated factors identified as affecting reproduction and with implications for commercial culture include: (a) poor egg adhesion to commonly used spawning substrates, (b) egg and fry cannibalism at high fish densities, and (c) the relatively short breeding period of individual males. Results highlight the importance of selecting an appropriate broodfish stocking rate based on fish size, anticipated pond fertility, and feeding program. New methods to improve reproductive performance will likely increase costs and will need to be accompanied by thorough economic analyses.