Intentional release of wild-caught individuals has been widely used to establish new populations of the commercially valuable but threatened reef gastropod Trochus niloticus in oceanic islands. Is this also a viable strategy to enhance depleted populations of this species and other marine invertebrates? We monitored growth and survival of 765 translocated individuals and 486 in their original habitat for 5–9 months. Individuals translocated to a severely overexploited reef (mainland Palawan) grew 2–3 times faster than those at Tubbataha Reefs Natural Park, Phillipines. Despite variations in growth between the three sites, survival probabilities were consistently high, ranging between 0.77 and 0.92. So translocation is feasible, and sites at which a species has previously been found are likely to be suitable for their growth and survival. If site management can control over-fishing, this approach is likely to be a valuable tool for enhancing field populations of a large invertebrates like Trochus that have a short lived planktonic larva.
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.
The relative cost–benefit of alternative methods for rehabilitating blacklip abalone (Haliotis rubra) reefs depleted by viral ganglioneuritis was evaluated using quantitative population and bio-economic modeling. Fishery assessment models were adapted to describe population dynamics and economics of reseeding, translocation, and natural rebuilding. Past and current literature on reseeding, translocation, and mortality rates informed a stakeholders’ workshop that agreed on the parameters for the analysis. Comparative economic performance was quantified as the impaired value of the individual transferable quota from the area until the stock recovered to the level of maximum sustainable yield, as it was prior to the abalone viral ganglioneuritis impact. When the cost of capital is considered, none of the intervention scenarios produced any cost–benefit above that estimated to accrue from an unfished natural recovery. The translocation of adults and reseeding of juveniles were found to be similarly effective largely due to the productivity of the assumed stock–recruitment relationship at low stock densities. Across the scenarios, translocation was estimated to always at least pay for direct costs but rarely covered capital costs while reseeding only covered direct costs if the price of abalone was >$25/kg and seed was <$0.50 per individual. When a depensatory form of stock–recruitment relationship, related to adult biomass, was assumed, translocation was estimated to be an order of magnitude more effective due to the time required to augment the breeding biomass with reseeded juveniles.
This study presents a bioeconomic evaluation of the effect of stock enhancement on biomass, net present value, profitability, and gross value of product of the Australian greenlip abalone (Haliotis laevigata) fishery. Enhancement targets were defined as a function of natural recruitment (Nr) and compared with current harvest strategies. The model was conditioned on a Western Australian fishery, then applied to greenlip stocks throughout Australia. Two levels of releases (50% Nr and 100% Nr) at varying fishing mortality (F), size at harvest, and size at release were evaluated in detail. Model validation was also undertaken by comparing the model-derived spawning biomass (SSb) with an alternative estimate (SSbf) obtained using in-water surveys and a different growth model. Economic profitability and increased spawning biomass were achieved for most stock enhancement scenarios, and optimal profitability occurred with a 10–20% decrease in F from current levels, a 10% decrease in minimum legal length, and an annual enhancement of Nr juveniles to match natural recruitment. More radical scenarios, such as an annual release of 150% Nr combined with a 30% decrease in size at harvest resulted in greater profitability (+175%) but presented a higher risk of wild stocks being replaced with hatchery genotypes. Sensitivity analysis revealed that mortality, size at release, and harvest price were the critical parameters, while costs of production and fishing were less important. At the national scale, an enhancement scenario involving an annual release of 6.1 million 4-cm juveniles (∼age 2) resulted in a 60% increase in gross value of product ($25 to $40 million), a 120% increase in profitability ($12 to $26 million), and net present value ($190 to $420 million; 6% discount), and a 25% increase in SSb.
A genetic analysis was conducted of the critically endangered migratory catfish Pseudoplatystoma corruscans from the SAo Francisco River basin, the basin with the second highest hydropower capacity installed in Brazil. The analysis was conducted using five microsatellite markers previously described in the literature. Genetic diversity was analyzed and compared in three wild populations and a captive broodstock for a restocking program. Catfish populations of this river showed high genetic diversity in terms of heterozygosities; however, only half of the total number of alleles found in other basins were detected. Seven private alleles occurred in this basin and most of them at low frequencies, indicating they are under threat of extinction. Overall F-ST and assignment test suggested low differentiation among the three wild populations; however, a marked distinction between these populations and the captive broodstock was observed. The number of alleles and low average relatedness estimates found for the captive population suggest that it could be used for restocking in areas where the wild population has collapsed, but should not be used for stock enhancement in areas where the wild population is extant. These results are important as a reference for genetic aspects that should be considered in fish management activities.
The effects of release habitat on the effectiveness of stocking were evaluated in Miyako Bay, Iwate, Japan. Hatchery-reared black rockfish juveniles were released at four different stations characterized by different habitat conditions from 2002–2007, and a survey was conducted of landed fish at Miyako Fish Market. Growth rate and feeding condition of wild and released juveniles sampled from two known wild nursery areas (Stn. 1 and Stn. 2) were also examined to elucidate the conditions that form optimal habitat. Comparisons of growth and feeding condition of juveniles between Stn. 1 and Stn. 2 indicated that Stn. 1, with its brackish waters, seagrass beds, abundant mysids, and large gammarids, supported better growth and survival of released fish, which in turn led to a higher market return rate. The highest market return rate was estimated as 8.3% (for 45-mm total length juveniles released at Stn. 1 in 2007), corresponding to a maximum economic return rate (value of recaptured fish divided by hatchery and release costs) of 1.32.
Conditioning is the process of providing individuals reared for stock enhancement with some degree of natural experience prior to release. Conditioning flatfish in predator-free cages may help adjustment to the wild. From 2008-2010, the Obama Laboratory conducted pre-release, experimental cage conditioning for Japanese flounder in both the Takahama and Obama portions of Wakasa Bay, Japan. Recaptured fish were acquired through a cooperative effort between researchers and local fishermen. The objectives were to describe how characteristics of released flounder changed with cage exposure and to determine how recapture rates compared between conditioned and non-conditioned fish. Significantly more conditioned fish were recaptured than non-conditioned fish in Obama Bay in 2010 (p < 0.05). In 2008 and 2009, recapture rates of conditioned and non-conditioned flounder followed the same trend, although these were not significantly different. Laboratory experiments revealed that conditioned fish had significantly better burying abilities (p < 0.001) and enhanced feeding abilities compared to non-conditioned fish. This study is the first to examine flatfish conditioning strategies using market data and shows that cage conditioning can favorably alter the attributes and recapture rates of released fish.
Preliminary experiments that optimize release methods pave the way to larger-scale releases and proper evaluation methods. One evaluation method is before-after-control-impact, which requires that more animals remain at release areas (“site fidelity” to impact areas) than disperse to control areas. This study tested whether there are release methods that maximize fidelity to the release area and minimize dispersal to nearby areas, which might enable a before-after-control-impact experiment. Lingcod that were 17-months old at release showed greater fidelity to release areas (23% remaining one year after release) than lingcod that were 9- and 11-months old at release. None of the 17- and 21-month-old release groups were detected on more distant structured habitats 44 weeks after release, but 8% and 13% of lingcod from the 9- and 11-month-old release groups were detected at distant structured habitat. Thus, releasing 17-month-old lingcod maximized fidelity to the release area and minimized dispersal to other areas. Differences in fidelity and dispersal rates among release-age groups may reflect ontogenetic changes in dispersal and habitat use patterns that have also been reported for wild lingcod. These behavioral similarities with wild lingcod also suggest that hatchery lingcod have potential to interact and integrate with wild lingcod in nature.
The lucrative returns brought by abalone fisheries have caused overexploitation and decline of the wild population. In the Philippines, the Aquaculture Department of the Southeast Asian Fisheries Development Center has successfully produced Haliotis asinina seeds in the hatchery. Aside from utilizing these seeds in aquaculture, they are also being considered for future stock enhancement endeavors of the department. This study aimed to evaluate post release behavior, recapture and growth rates of hatchery-reared abalone juveniles released in the Sagay Marine Reserve. From the two release trials conducted, results showed that abalone of shell length >3.0cm had lower mortality during onsite acclimation and utilized transport modules as temporary shelter for a shorter period after release. Both wild and hatchery-reared abalone preferred dead branching corals with encrusting algae as their habitat. Recapture rates were comparable between the wild (7.97%) and hatchery-reared (HR2) abalone (6.47%). Monthly growth rates were almost the same between wild (0.25cm, 4.0g), hatchery-reared (HR1: 0.27cm, 4.6g; HR2: 0.35cm, 3.8g) abalone. Moreover, hatchery-reared abalone were recaptured up to 513days post-release, indicating viability of released stocks in the wild. Results of releases revealed that hatchery-reared abalone can grow and survive with their wild conspecifics.
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.
A meta-analysis of the straight fork lengths (herewith abbreviated as L) of 2,458,028 Atlantic bluefin tuna, Thunnus thynnus (L.), taken from 224 scientific publications and unpublished L data from scientific organizations and fishing companies spanning most of the known Atlantic and Mediterranean Atlantic bluefin tuna fisheries dating from 1605 to 2011, give L values ranging from L min = 20 cm and L max = 330 cm. The results indicate that the parameter L ∞ = 318.85 cm of the growth equation used by ICCAT's Standing Committee on Research and Statistics Atlantic bluefin tuna assessment group for the eastern stock (Lt = 318.85 [1 – e−0.093 (t + 0.97)]) lies within the confidence limits of the maximum Ls presented in the study: L max = 319.93 ± 11.3 cm, confirming that this equation perfectly fits the biology of the growth of this species. These conclusions are also valid for the equation for the western stock (Lt = 314.90 [1 – e−0.089 (t +1.13)]). The ICCAT Atlantic bluefin tuna database contains numerous records of Atlantic bluefin tuna L outside the biological feasibility, and solutions are provided to recognize and remove these outliers based on the application of fixed values of Fulton's condition factor (K) between 1.4 and 2.6 and appropriate L-W relationships to correct this situation in the future.
This article synthesizes information on marine and estuarine release programs in Australia and evaluates potential opportunities for stock enhancement. In Australia, the scale of restocking and stock enhancement programs in marine environments has been low compared with other countries, particularly Japan, China, and the United States. However, since the early 1990s, a number of government and industry organizations have made significant investments in research and development for the release of a variety of species to evaluate the potential of releases to increase the productivity of fisheries. The scale of these research programs has varied from releases of tens of thousands of individuals (abalone Haliotis laevigata, barramundi Lates calcarifer, and mulloway Argyrosomos japonicus), hundreds of thousands (tiger prawns Penaeus esculentus and black bream Acanthopagrus butcheri), and millions (eastern king prawn Penaeus plebejus). These programs, which have shown a strong commitment to the responsible approach to enhancement sensu (Blankenship and Leber, 1995; Lorenzen et al., 2010), have resulted in increased knowledge on the population dynamics and ecology of released species and the development of bio-economic and energetic models to better plan and evaluate releases. Currently, research is continuing in New South Wales (A. japonicus, P. plebejus), Queensland (L. calcarifer), and Western Australia (A. butcheri, H. laevigata). Furthermore, Victoria is developing a plan for releasing juveniles to enhance fisheries in estuarine and marine environments, and South Australia has developed a policy for marine and estuarine stock enhancement. Policies on stock enhancement are being considered for development in New South Wales and Western Australia. These developments in policy and the introduction of fishing license fees in some states have generated renewed interest in initiating release programs in Australia that follow the responsible approach to enhancement.
Scientific interest in deep-water marine resources has increased dramatically over the last 10-20 years as management bodies have sought advice on how to manage deep-water fisheries and protect deep-water ecosystems. The strengths and weaknesses of the management and monitoring of deep-water stocks, fisheries, and ecosystems in various areas of the world are described, with the objective of informing the EU FP7 DEEPFISHMAN project so that it can fulfill its primary aim, which is to develop strategic options for a short-and long-term management and monitoring ecosystem-based framework for the northeast Atlantic. To provide a baseline, the current monitoring and management regime in the northeast Atlantic is reviewed, followed by a brief description of the regimes applying to deep-water fisheries in the northwest Atlantic, the southeast Atlantic, off Brazil, in the Antarctic, off Australia and New Zealand, and in the Mediterranean. The strengths and weaknesses of these are discussed, taking into account additional information available from DEEPFISHMAN case study stocks, outcomes from consultations with stakeholders in the deep-water fishing industry in the northeast Atlantic, and the requirements of EU regulations and developing policy that will likely impact deep-water fisheries in the northeast Atlantic.
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.
The hatchery program for chum salmon in Hokkaido, northern Japan, constitutes one of the largest salmon hatchery programs in the world. The hatchery program has been conducted for over 120years, and returns of chum salmon rapidly increased during the last quarter of the 20th century. Since the 1990s, chum salmon returns to Hokkaido have remained at a historically high level, although different fluctuation trends have been observed among regions within Hokkaido. Although such intensive hatchery programs have been conducted for more than 25 generations, there has been no evidence indicating any decline of genetic diversity. The hatchery program for chum salmon in Hokkaido is successful in increasing commercial catches and will likely be the main management tool in future. However, information on naturally spawning chum salmon in Hokkaido remains scarce. Assessment of naturally spawning populations recently commenced, and it has been revealed that naturally spawning chum salmon populations remain in many rivers in Hokkaido. For future management, monitoring chum salmon of both hatchery and natural origin is important, and a novel strategy that accounts for the enhancement of commercial stocks and the coexistence of hatchery programs and wild populations should be established in Japan.
The potential of sea ranching sandfish (Holothuria scabra) for production and stock restoration was investigated in the Philippines. A total of 14,300 fluorochrome-stained juvenile sandfish (>3g) were released in 8 batches over a 15-month period in a 5-hectare pilot communal sea ranch. Abundance of sandfish increased from 416 to 5,562 individuals, with a corresponding increase in biomass from 7 to 221kg ha(-1) over the 19-month period. Apparent survival over the study period was estimated at 20-30%. Incidences of in situ spawning were observed in the sea ranch within a year, and estimated densities of reproductively mature sandfish increased from 37 ind ha(-1) 7 months after initial release to 249 ind ha(-1) after 19 months. Average weight at onset of sexual maturity (approximate to 185g) is estimated to be attained 7-9 months after release. Juveniles without fluorochorome stained ossicles were found during most monitoring periods, indicating presence of wild recruits. A well-managed communal sea ranch has the potential to contribute to fisheries production and stock restoration objectives.
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.
In the last decade, the trade of marine ornamental species has experienced a significant expansion worldwide; however, this industry still relies on a large number of unsustainable practices (e. g., cyanide fishing, overexploitation of target species) and needs to shift its operations urgently to avoid collapsing. Under this scenario, traceability and certification emerge as important management tools that may help this industry to shift toward sustainability. This industry relies on the trade of thousands of small-sized species that are traded live on a unitary basis with high market value. These features, along with a fragmented and complex supply chain, make the traceability of marine ornamental species a challenging task. This study presents the most commonly used methods to trace aquatic organisms and discusses their suitability to trace marine ornamental species. The use of bacterial fingerprints appears to be the most promising method to successfully trace marine ornamentals, but it is most likely that a combination of two or more traceability methods need to be implemented to cover all the unique features displayed by the live trade of marine ornamental species.
The kuruma prawn, Penaeus japonicus is widely distributed in the Indo-West Pacific. The Japanese stock enhancement program, which produces and releases juvenile kuruma prawns into their natural habitat, started in 1964 and has expanded throughout Japan. The annual number of juveniles released ranged from approximately 240 to 300 million until the mid-1990s but then decreased steadily to approximately 105 million in 2008. National annual landings of kuruma prawns recovered to a record of 3,741 t in 1985 from 1,263 t in 1970 but then declined steadily to the historical minimum of 726t in 2008. Thus, kuruma prawn catches have decreased dramatically despite the release of juveniles. The aim of this study is to analyze the catch fluctuation of kuruma prawns relative to ocean climate variability and the stock enhancement program. The effects of ocean climate on kuruma prawn stock sizes were evaluated by generalised additive models (GAMs). In the GAMs, catch-per-unit effort and catch data transformed to reduce the dependence of the amplitude of the catch fluctuation on the level of the catch were used as response variables, and three indices for ocean current conditions were used as explanatory variables: the Oyashio (cold current), the Kuroshio (warm current), and the Tsushima Warm Current. The GAM analysis suggested that kuruma prawn stock sizes declined during the period with a strong warm current intensity, and 42 mark-recapture surveys indicated an estimated average yield per release of 0.9g. Our analysis highlights the fluctuation of kuruma prawn stocks with ocean climate variability and indicates that the stock enhancement program could have an impact on kuruma prawn catches depending on the magnitude of the releases. Ocean climate change, decreased fishing effort, and reduced hatchery releases could be responsible for the recent decline in kuruma prawn catches in Japanese waters.
The high demand for shells of the large reef-associated gastropod Trochus niloticus in the manufacture of mother-of-pearl buttons has resulted in a widespread decline of its population. As a consequence, juvenile mass production and restocking has been practiced as one of the many conservation measures. Trochus has long been successfully bred in captivity, but culturing of juveniles until ready for release is faced with many problems, including the shortage of natural food. Terrestrial plants have traditionally been used by fishermen as food in keeping wild trochus juveniles, but their potential use in intermediate culture of trochus has not been evaluated. We conducted four growth trials for 60-120days, rearing hatchery-produced juveniles (10-28-mm shell diameter) at different stocking densities in indoor tanks and sea cages, with coconut leaves as the main or an additional substrate. An average growth rate of 4.4mm mo(-1) (95% CL 4.0-4.7mm mo(-1)) for all stocking densities was achieved in growth trials using small cages deployed at 5-6m on the reef slope, which was comparable to growth rates in the wild. This growth rate was three times higher than in trials using large metal cages on the reef slope, and 2 to 23times higher than indoor trials using wooden tanks or small cages in concrete tanks. Survival rates were as high as 99%. Incidence of escape in sub-tidal cages was low except when some cages were damaged by strong waves. The results indicate that trochus juveniles can be successfully cultured at high density in sub-tidal cages with coconut leaves as substrate.
