In this article, we respond to concerns raised by Brooks and Jones (2008) about recent advances in sea lice and salmon population dynamics in the Broughton Archipelago, British Columbia. We show that the assessment by Brooks and Jones (2008) is thoroughly mistaken and that their conclusions are based on a combination of obfuscation, misrepresentation, and fundamental misunderstandings. The extinction hypothesis is not actually a hypothesis at all, but rather an inevitable consequence of sustained population decline. Local extinction of Broughton Archipelago pink salmon can be prevented if population declines are turned around, and the data and models suggest this can be achieved if the infestations are stopped. We have organized our responses in an itemized manner according to the headings and subheadings in Brooks and Jones (2008).
Prior to the development of commercial whaling, several indigenous communities undertook hunts of whales to fulfill their subsistence needs. Fortunately, the two international conventions that implemented the regulation of commercial whaling did not lose sight of the needs of these aboriginal communities. How this was done, as well as the eventual evolution of the management of aboriginal whaling, is summarized in this review. The record shows that, whether in terms of exempting these aboriginal hunts from required management actions or of setting precautionary catch limits for otherwise protected stocks, an overriding management principle has emerged wherein international managers have been willing to accept conservation risks for aboriginal hunts that they otherwise would not assume for commercial operations. Although these risks were accepted, it was done at the cost to the aboriginal hunters of undertaking conservation measures often not applied to commercial hunts. While it is not clear from the record whether this guiding principle arose explicitly or implicitly, it is nevertheless explicitly clear that it has been and continues to be applied, and successfully so, when considering the conservation of the affected stocks.
Natural populations of global inshore fisheries are coming under heavy pressure, primarily due to overexploitation and habitat degradation. Stock enhancement of hatchery-reared seeds is perceived as an alternative strategy to enhance the regeneration process. The Aquaculture Department of the Southeast Asian Fisheries Development Center in the Philippines has been implementing activities related to stock enhancement of donkey's ear abalone (Haliotis asinina), mud crabs (Scylla spp.), giant clam (Tridacna gigas), and seahorses (Hippocampus spp.). Seed production techniques for abalone including a diet tagging method were established, and juvenile abalone were released and monitored in a marine protected area. Mud crabs conditioned before release had higher recapture rates compared to the non-conditioned crabs, which can be translated to higher survivorship. Giant clams stocked at 8-10 cm shell length have high survival 4 mo after stocking (90%), with initial mortalities occurring within the first few days due to transportation stress. Seed production trials for seahorse have begun.
Although a large portion of the world's farmed shrimp is produced in Asia, shrimp culture operations do not succeed over the entire area. There have been several problems and impediments that are yet to be resolved. One of these problems is disease. Several shrimp diseases have threatened shrimp production, but the most devastating ones are the viral diseases, namely, yellow-head virus (YHV), and White Spot Syndrome Virus (WSSV). At present, there is no curative procedure for the two viral diseases. As such, preventive measures are thought to be more practical. Several preventive measures have been studied and introduced, but the most acceptable one is the improvement of growout systems. Asian shrimp culture employs three shrimp culture techniques: the extensive, semiintensive, and intensive systems. Beginning with the extensive about 3 decades ago, parts of this system were modified into a semiintensive system in 1980, and later the intensive type was introduced. The extensive type evolved from the hunting and gathering of food by the nearshore communities. Mangrove environments were modified into trapping ponds for livestock during the stormy months. This system uses low technology and requires vast and low-lying areas, such as mangrove forested areas. The intensive system uses higher technology, requires a smaller area, and higher elevations. Thus, it does not require mangrove areas, but it is suitable for areas behind the mangroves. The production is quite high when compared with the two other systems. Because of the high stocking density and intensive feeding, however, this type of shrimp culture is faced with several problems, such as coastal pollution caused by the farm effluent and disease problems. The intensive system was later modified to a more biosecure system, that is, a closed recirculating water system, a reduced or zero water exchange system, and shrimp culture at inland locations away from coastal influences. These innovations have made shrimp culture more efficient in controlling diseases, more sustainable, and more environmentally friendly.
The coastal zone in the United States and in other areas worldwide is under increasing stress from human population growth and associated development, and that stress extends to the animal populations that occupy coastal habitats. Considerable effort is being expended to restore the habitats and animals that characterize this biome. I herein describe historic and recent developments regarding the application of the larval release approach to marine animal population restocking efforts. Beginning with cod (Gadus morhua) larvae in the late 1800s, the larval form has been exploited for restocking of various fish and invertebrate species with mixed results. Success has been elusive when working with cod and hard clams (Mercenaria spp.), but efforts using striped bass (Morone saxatilis), abalone (Haliotis spp.), and most recently bay scallops (Argopecten irradians) have been at least partially successful. In the case of bay scallops, competent (ready-to-settle) larvae released into containment enclosures were tracked through the post-settlement, juvenile, and adult life stages. That sampling scheme provided evidence that the released larvae ultimately contributed to a substantial increase in the subsequent year-class. However, those results are equivocal, and rigorous genetic sampling will be required to fully document the linkage between larval release and subsequent year-class strength. It is concluded that larval release, while not suitable for all species in all situations, may be an effective strategy for rebuilding marine animal populations.
Escapes of farmed fish from aquaculture installations, as well as large scale stock enhancement and sea ranching activities, are regarded as risk factors for negative genetic impacts on native gene pools. These aspects have been discussed for several decades, and a number of recent experiments on Atlantic salmon have clearly demonstrated dramatically reduced overall fitness of farmed offspring compared with offspring of wild origin. The Atlantic cod (Gadus morhua L.) is now the most promising new marine species for large scale farming in Norway, and more than 500 commercial farming licenses have been issued, corresponding to a maximum annual production capacity of about 300,000 tonnes. In comparison with the environmental problems caused by escapes from the salmon farming industry, cod farming presents new challenges. As a marine species, cod are able to spawn in the net pens during the ongrowing period and thus release genetic material into the environment. Coastal cod stocks in Norwegian waters are depleted and therefore may be particularly vulnerable to genetic interaction with farmed cod. Thus, there is an urgent need for more detailed knowledge of potential hazards. A pilot experiment performed in Heimarkspollen in Austevoll (a practically landlocked fjord) demonstrated for the first time that farmed cod are capable of producing viable cod larvae that mix with larvae from wild cod. The farmed cod used in the pilot experiment were homozygotic for a rare allele (GPI-1*30), and mature fish were placed in a net pen to allow spawning and egg drift into the surrounding water to take place. Surveys of eggs found the highest densities in the vicinity of the net pen. Later larval surveys found that 20% to 25% of the larvae sampled in the area possessed the unique genetic marker and could therefore be traced to the spawning cod in the net cage. Numerous genetically marked larvae were also found outside Heimarkspollen, indicating a high degree of dispersal of eggs and larvae by tidal advection.
The nutritional requirements of the freshwater shrimp Macrobrachium rosenbergii are reviewed and compared with those reported for several species of marine shrimp genus Penaeus. Most of the information has been derived from experiments with juveniles. A comparison of essential amino acid proportions [A/E ratios] between M. rosenbergii and penaeid species suggests only minor, if any, differences in requirements of essential amino acids exist. Qualitative and quantitative fatty acid requirements of the freshwater shrimp are reflective of the lower n-3/n-6 polyunsaturated fatty acid (PUFA) ratio found in the body tissue. In contrast to marine shrimp, both classes of n-6 and n-3 PUFAs with more than 20 carbon atoms [>20C] are equally effective in producing maximum weight gain responses. The dietary requirement for PUFAs appears to be lower than that of penaeid shrimp. Absence of dietary 18°C n-3 or n-6 PUFAs does not affect growth but is associated with a reduction in the weight of the midgut gland expressed as a percent of whole body weight. There is still a level of uncertainty about whether M. rosenbergii requires dietary phospholipid, particularly phosphatidylcholine. A requirement may be age dependent, as suggested for larval and juvenile forms of penaeid species. A combination of dietary phytosterols is equally effective as cholesterol in satisfying a dietary sterol requirement of 0.6% for juvenile M. rosenbergii . Penaeid species require sterols, but dietary phytosterols are not as effective as cholesterol in promoting growth. M. rosenbergii and penaeid shrimp appear to use the same biosynthetic pathway for the production of the carotenoid astaxanthin from dietary (-carotene and canthaxanthin. The freshwater prawn obtains most, if not all, of its dietary energy requirement from carbohydrates and lipids, thus sparing protein. Protein sparing is maximized when the dietary lipid: carbohydrate ratio is 1:4. Using water-stable sources of dietary vitamin C, a vitamin C requirement for M. rosenbergii has been identified and estimated to be 100 mg/kg. The levels of different ingredients used in the manufacture of diets will ultimately depend on relative digestibilities and nutrient requirements as influenced by the age of the animal and the system used for culture.
Anguillid eels are high-value aquaculture species. Eel aquaculture techniques were developed in Japan and subsequently transferred to Taiwan and South Korea. When glass eel and elver supplies became a constraint in Japan, Taiwan used this opportunity to establish its own eel aquaculture industry. Later on, China and Malaysia also started to develop eel aquaculture. In Europe, many countries also adopted the Japanese eel aquaculture techniques, although Italy and France already had a long history of very extensive eel aquaculture. Driving forces for the development of eel culture techniques have been the need to overcome temperature limitations, enhance productivity, and comply with increasingly stringent environmental regulations while reducing production costs. Culture techniques have evolved from primitive methods to the highly sophisticated intensive systems. In this article, the current major growout culture systems are grouped into three categories: the outdoor culture system, the greenhouse culture system, and the intensive recirculating culture system. Innovations in Taiwan that apply Danish intensive recirculating culture technology are described separately. The eel aquaculture industry is facing constraints, such as unstable glass eel and elver supplies, lack of knowledge on larval rearing, disease occurrences, inconsistent product quality, limited markets, and a lack of culture techniques for other eel species. The challenge is to overcome these constraints in a sustainable manner with the technical, environmental, and economic considerations.
Lipids are the predominant source of energy for fish. The mechanisms by which fish allocate energy from lipids, for metabolism, development, growth and reproduction are critical for understanding key life history strategies and transitions. Currently, the major lipid component in aquaculture diets is fish oil (FO), derived from wild capture fisheries that are exploited at their maximum sustainable limit. The increasing demand from aquaculture for FO will soon exceed supply and threaten the viability of aquaculture. Thus, it is essential to minimize FO use in aquaculture diets. This might be achieved by a greater understanding of lipid storage and muscle growth, or the identification of alternatives to FO in feeds. This review focuses on recent research applying molecular and genomic techniques to the study of fin-fish lipid metabolism from an aquaculture perspective. Accordingly, particular emphasis will be given to fatty acid metabolism and to highly unsaturated fatty acid (HUFA) biosynthesis, and to the transcriptional mechanisms and endocrine factors that regulate these processes in fish. Comparative studies of gene function and distribution are described which, when integrated with recent fish genome sequence information, provide insights into lipid homeostasis and the outcomes associated with the replacement of FO in fish diets.
This article was downloaded by: [Bellis, Diane]On: 24 November 2008Access details: Access Details: [subscription number 905736162]Publisher Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,37-41 Mortimer Street, London W1T 3JH, UK
Because of convenience in production and their suitable biochemical composition, brine shrimp Artemia spp. nauplii have been adopted as a standard diet in the commercial larviculture of several crustacean species. The nutritional value of Artemia , however, is not constant, but varies both geographically and temporally. During the past decade both the causes of Artemia nutritional variability and methods to improve poor-quality Artemia have been identified. Enriching Artemia spp. with emulsified lipophilic products is a technique that has allowed delivery of extra doses of essential nutrients, for example, highly unsaturated fatty acids (HUFA) and vitamins, to crustacean larvae. The enrichment technique has limitations, however, because the Artemia spp. currently available selectively catabolize some of the nutrients such as docosahexaenoic acid and phospholipids. Decapsulated Artemia cysts, juveniles, and adult brine shrimp are also used increasingly as suitable diets for different crustacean species.
Aquaculture is providing an ever-increasing proportion of fish in the human food basket prompting a search for new species to expand the range available to consumers. Large tunids/scombrids have long-since been a very valuable resource providing not only high quality protein, but also a rich source of the highly beneficial omega-3 (or n-3) long-chain polyunsaturated fatty acids including eicosapentaenoic and, especially docosahexaenoic acids in the human diet. Consequently, there is considerable interest worldwide in developing the culture of large tunids, including Atlantic northern bluefin tuna (Thunnus thynnus), Pacific bluefin tuna (Thunnus orientalis), southern bluefin tuna (Thunnus maccoyii) and yellowfin tuna (Thunnus albacares). Nutrition is vital to this development, playing key roles in reproductive success, including the establishment of successful broodstock producing high quality eggs and larvae, and ultimately the cost-effective production of nutritious seafood. This review summarises the rather fragmentary data that compromise the current state-of-the-art in relation to tuna nutrition and the development of artificial, formulated feeds for these species. In highlighting the various considerable challenges that feed development will pose, we discuss the future perspectives for tuna culture in terms of both fish and human nutrition and welfare, against the background of diminishing global marine resources.
Sea cucumbers are highly marketable as a food and medicinal product. Many species are being cultured in addition to being fished to meet the high demand for these products. This review explores the potential use of the Northern sea cucumber, Cucumaria frondosa, as a viable aquaculture species in the North Atlantic. Utilizing the literature available on this species, the marketability, biology, production cost, hatchery potential, grow-out technology, and alternate uses within integrated multi-trophic aquaculture sites were examined. C. frondosa is well suited for culture in that it has an established market, it is abundant, its reproductive biology is well understood, and it has potential as an extractive co-culture species. Its slow growth rate and low value could limit its production.
A series of stock enhancement experiments were carried out on Haliotis laevigata populations. Methodologies included a large-scale BACI (before, after, control, impact) experiment (42 sites); a carrying capacity experiment, which involved a high-density release at two sites; and a detailed survey of abalone populations and ecological parameters. Increased densities were detected for most age classes, although fishing mortality began obscuring the effect by age 5+. Age-4+ animals showed the clearest result, with no difference between enhanced and control sites at 6, 12, and 18 months post-release, and then a 300% increase at enhanced sites at 30 months post-release. Overall, a single release of age-1+ animals in May 2006 had doubled the total density by November 2008. In the carrying capacity experiment, densities initially increased rapidly (by up to 800%) but had stabilized at a 400% increase after 2.5 years, at around 8 per m2. This was the predicted carrying capacity, with the enhanced cohort representing 50% of the population. A PERMANOVA (permutational multivariate analysis of variance) analysis of ecological similarity detected no effect of enhancement, although changes in algal percent of coverage were detected at both control and enhanced sites. Overall, this study suggests that as long as release densities are controlled within natural limits, successful stock enhancement can be attained for this species with minimal ecological impacts.
A cohort of Haliotis laevigata, spawned from wild broodstock, was monitored from settlement at a hatchery until age 8. Animals were released into the wild at 31 mm (± 4 SD), targeting an enhancement size-class of 135–145-mm shell length. Release densities were tailored to match wild-stock densities using a size-dependent mortality model. A total of 7,500 animals were released into 24 sites, and each site was precisely mapped to control release densities. Environmental and husbandry factors were also quantified. Initial survival rates (six months post-release) differed significantly among sites (range: 11–67%) but not beyond this time period. Legal minimum length (140 mm) was achieved, on average, at 5 years of age or 3.5 years post-release, and the cohort entered the fishery over 3 years (age 5–8). Cumulative survival at age 5 varied between 20% at the better sites and 6% at the worst sites, with an average of 13%. Water depth was significantly positively correlated with growth (r = 0.47; p F) of 0.27, but site differences in F were significant and highly correlated with growth.
The potential for restocking with hatchery organisms as a tool to rebuild depleted populations of blacklip abalone (Haliotis rubra) was investigated through replicated, control-impact studies in New South Wales, Australia. Long-term survival (>2 years) of hatchery-reared and released abalone, their impact on wild abalone abundance, and the effect of diffuse versus concentrated release was investigated on natural reefs. Long-term survival of released hatchery abalone varied between releases but averaged about that expected for wild abalone. There was no significant effect of released juveniles on the persistence or recruitment of wild abalone. Significantly greater numbers of all (released and wild) abalone persisted at release locations through time, while the total number of wild abalone increased significantly through time at release and control locations. There was no significant difference in long-term survival of abalone released in clusters of high density (2–4%) or in a diffuse or concentrated array (0–9%). These results show that restocking can supplement natural rebuilding processes of depleted wild abalone populations in New South Wales, Australia.
Acanthopagrus butcheri was restocked in an estuary in which it had become depleted. The restocked fish were cultured in 2001 and 2002 using broodstock from that estuary. These fish, whose otoliths had been stained with alizarin complexone, were released into the estuary and their biological performance tracked for seven to eight years. The 2002 cohort, introduced at circa four months old in autumn, survived far better than the 2001 cohort, introduced at circa seven months old in winter, when freshwater discharge peaks and temperatures are low. While restocked fish matured and grew nearly as fast as wild fish, the increase in density was accompanied by a reduced growth of wild fish. Genetic comparisons, using seven microsatellite loci, demonstrated that the expected heterozygosity and relatedness of restocked and wild A. butcheri, which is naturally characterized by low levels of genetic polymorphism, were similar. Although culturing did not demonstrably increase the level of inbreeding, it did result in the loss of some rare alleles. The biological and genetic results, together with the contribution of restocked A. butcheri to the commercial catch for this species in the estuary rising to 62–74% by 2007–2010, demonstrates the efficacy of using restocking to replenish depleted A. butcheri stocks.
The dynamics of fish behavior, migration, and habitat use following stock enhancement will influence the outcome of recovery programs and indicate the ecological limits of the system. This study tested the effect of release density on emigration, activity patterns, and space utilization by releasing juvenile mulloway (Sciaenidae: Argyrosomus japonicus) at low and high densities and monitoring movement intensively for 336 h post release. Mulloway released at high densities had faster emigration and greater overall emigration rates than low density releases. Also, mulloway released at high densities used sub-optimal habitats at a greater frequency. Released fish dispersed into habitat patches at densities proportional to the quality of the habitat patch, consistent with density-dependent habitat selection. Targeting releases of small numbers of fish to the carrying capacity of individual patches of habitat will contribute to the success and economic viability of release programs in open systems. Releases of high densities of individuals or repeated releases at the same site may lead to increased emigration and losses from the stocked system. The capacity of a target habitat to support released fish can be rapidly assessed using pilot releases and intensive monitoring of acoustically tagged fish, prior to the implementation of large-scale release programs.
Large river ecology has evolved through time, from perceiving rivers as big streams to accepting rivers as spatiotemporally diverse and complex ecosystems spanning terrestrial, aquatic, and socio-political realms. This review summarizes past and present concepts in large river ecology and highlights uncertainties facing the science and management of large rivers, and provides examples of tools (river restoration and adaptive management) that may be used to continue the advancement of large river ecology into the future. We need to ask, “Where do we go from here?” and, “How do we get there?” The science, management, and policy of large rivers are inseparable and decisions formulated by river stakeholders today will inevitably shape how rivers are studied and managed into the future.
A global model is used to calculate feed and nutrient budgets for freshwater and marine omnivorous and carnivorous aquacultural finfish production. The model uses national production data for the period 1970–2010 and the Millennium Ecosystem Assessment scenarios for production and management for 2010–2050. Results indicate that annual nutrient release to the freshwater (1.2 million tonnes of N and 0.1 million tonnes of P in 2010) and marine aquatic environments (0.3 million tonnes of N and 0.05 million tonnes of P) increased less rapidly than fish production, mainly due to improving feed conversion. In the coming five decades, annual nutrient release to freshwater environments may increase to 1.5–2.1 million tonnes of N and 0.1–0.2 million tonnes of P, depending on the production scenario and assumptions on feed conversion and the share of integrated aquacultural production. At present, the global contribution of freshwater aquaculture to nutrient loading of rivers is small. This is the same conclusion reached for the assessment of nutrient export from shellfish aquaculture (Bouwman et al., 2011). However, particularly in Asia, nutrient loading from freshwater fish production and from seaweed and shellfish production is an important factor that should be accounted for when developing models for estimating river nutrient export. Compared to chicken meat and egg production, freshwater aquaculture is a rapidly growing and important cause of the anthropogenic acceleration of the N and P cycles in many parts of the world, and this is especially pronounced in Asia.
In a world where nearly 30% of humanity is suffering from malnutrition and over 70% of the planet is covered with water, aquatic foods represent an essential component of the global food basket to improve the nutrition, health, and well being of all peoples.It is not by chance that Japan, the country with one of the world's highest reported life expectancies and lowest incidences of obesity and deaths from heart related illnesses, is also one of the world's top consumers of captured and farmed aquatic animal food products and aquatic plants. According to the FAO, in 2009, total captured and farmed aquatic animal food products accounted for 16.6% of the global population's intake of animal protein, providing more than three billion people with almost 20% of their average per capita intake of animal protein, and 4.3 billion people with at least 15% of such protein.This article reviews the nutritional composition of different farmed and captured aquatic food products and compares these with conventional terrestrial meat products. In addition to the superior nutritional profile and benefits of aquatic animal food products, small-sized marine pelagic fish play an important role in the nutrition of the poor as an affordable and much needed source of high quality animal protein and essential amino acids, omega-3 fatty acids, vitamins, minerals, and trace elements. As one of the best aquatic animal foods from a nutritional perspective, the direct consumption of small pelagic fish should be encouraged and promoted, as apposed to the continued targeted use of these species for reduction into fishmeal and fish oil for use in animal feeds.
Although fish health may influence key population-level processes, particularly those dealing with natural mortality, reproduction, and growth, which, in turn, affect stock productivity, little emphasis has been placed on the links between fish health and the management of marine fisheries. This article addresses this gap and illustrates how knowledge of fish health could provide insight for marine fisheries biologists, stock assessment modelers, and managers. The study proposes ways in which the consideration of condition indicators (energy reserves) and parasitism improves stock assessment and fisheries management, especially in situations of data shortage when standard methods cannot be applied, as is the case in many Mediterranean fish stocks. This article focuses on seven case studies of different fish species from the Mediterranean and Black Seas. Overall, and although the relationship between fish health and productivity cannot always be found or quantified, the article emphasizes the importance of the physical health of exploited stocks, particularly during critical life periods of the fish (e.g., prior to spawning, migration, or in the early life stages), as an essential element of sustainable and profitable fisheries. On the basis of these results, stock assessment and fisheries management implications are discussed.
![Figure 3 Comparison between density of Haliotis laevigata per m 2 of available habitat and density per total m 2 surveyed using a logistic regression. Parameter estimates are a = 12.9, b = –3.73, c = –4.75, and x 0 = 0.20. Maximum theoretical density is 8.2 per m 2 of habitat (6.7–11.3 confidence limits [CL]). Data from n = 42 sites (84 × 30 m 2 transects). Gray shading represents 95% CL, obtained from bootstrapping (n = 10,000).](https://www.researchgate.net/profile/Anthony-Hart-6/publication/263344179/figure/fig2/AS:392480752193554@1470586111754/Comparison-between-density-of-Haliotis-laevigata-per-m-2-of-available-habitat-and-density_Q320.jpg)
