Johann D Bell

A New Era for Restocking, Stock Enhancement and Sea Ranching of Coastal Fisheries Resources

The growing number of countries investigating the potential for releasing cultured juveniles to augment coastal fisheries resulted in the First International Symposium on Stock Enhancement and Sea Ranching (ISSESR) in Norway in 1997. The 1st and 2nd ISSESR, in Japan in 2002, were instrumental in developing methods for mass production of environmentally fit juveniles and for releasing them in responsible ways. The 3rd ISSESR, held in the U.S.A. in 2006 (www.SeaRanching.org), ushered the discipline into a new era. The major advances included: (1) definitions of the various objectives for releasing cultured juveniles (restocking, stock enhancement, and sea ranching); (2) a framework for integrating releases within their fisheries management context, including tools for quantitative assessment; (3) a systematic, transparent, and stakeholder-participatory planning process to determine whether releases have a cost-effective role to play in managing a fishery; (4) a comprehensive case study (blue crabs in Chesapeake Bay) describing the multi-disciplinary approach needed to evaluate the potential benefits of releases; and (5) a suite of other lessons to guide stakeholders in evaluating the potential for and implementation of releases. The papers in this Special Issue of Reviews in Fisheries Science elaborate how restocking, stock enhancement and sea ranching programs can create synergies between aquaculture and some coastal fisheries to help meet the future demand for seafood and aid in restoring depleted stocks.

Restocking and stock enhancement of marine invertebrate fisheries

1. Introduction 2. Restocking Initiatives 2.1 Giant Clams 2.2 Topshell 2.3 Sea Cucumbers 3. Stock Enhancement Initiatives 3.1 Scallops 3.2 Other Bivalves 3.3 Abalone 3.4 Queen Conch 3.5 Shrimps 3.6 Spiny Lobsters 3.7 Lobsters 3.8 Sea Urchins 4. Overview and Progress Towards a Responsible Approach 4.1 Restocking Initiatives 4.2 Stock Enhancement Initiatives 5. Lessons Learned 5.1 Lessons for Restocking 5.2 Lessons for Stock Enhancement 5.3 Lessons for both Restocking and Stock Enhancement 6. Management of Restocking and Stock Enhancement 6.1 Information to Evaluate the Need for Restocking 6.2 Management of Restocking 6.3 Information to Evaluate the Need for Stock Enhancement 6.4 Management of Stock Enhancement 6.5 Measures to Optimize Social and Financial Benefits of Restocking and Stock Enhancement 6.6 Independent Assessments 7. Other Important Considerations for all Initiatives 7.1 Measuring Success 7.2 Genetic Considerations 7.3 Disease risks 7.4 Other Environmental Impacts Conclusions 8.1 Achievements 8.2 The Responsible Approach 8.3 The Way Forward 8.4 Future Research 8.5 Summary Remarks Acknowledgements References Appendix

Population Structure and Genetic Variability of Six Bar Wrasse ( Thallasoma hardwicki ) in Northern South China Sea Revealed by Mitochondrial Control Region Sequences

The genetic relationships among northern South China Sea populations of the six bar wrasse (Thallasoma hardwicki) were investigated. Fish collected from the Solomon Islands were used for geographic comparison. In 1998 and 1999, a total of 100 fish were sampled from 6 localities of the northern South China Sea and 3 localities of the Solomon Islands. Genetic variations in DNA sequences were examined from the first hypervariable region (HVR-1) of the mitochondrial control region, as amplified by polymerase chain reaction. High levels of haplotypic diversity (h = 0.944 ± 0.0016, π = 0.0224 ± 0.01171) in the HVR-1 region of the mitochondrial control region of T. hardwicki were detected. This yielded 94 haplotypes that exhibited a minimum spanning tree with a starburst structure, suggestive of a very recent origin for most haplotypes. Neutrality tests indicated that the pattern of genetic variability in T. hardwicki is consistent either with genetic hitchhiking by an advantageous mutation or with population expansion. Partitioning populations into coherent geographic groups divided the northern South China Sea samples (ΦCT = 0.0313, P < 0.001) into 3 major groups: a north-central group composed of northwestern Taiwan and northern Vietnam; a southwestern group containing southern Vietnam; and a southern group including the central Philippines. These results are in concordance with mesoscale boundaries proposed by allozyme markers, thus highlighting the importance of identifying transboundary units for the conservation and management of fisheries in the South China Sea.

Variation in short-term survival of cultured sandfish (Holothuria scabra) released in mangrove-seagrass and coral reef flat habitats in Solomon Islands

Abstract Juvenile cultured sandfish ( Holothuria scabra ) with a mean size of 35.6 mm±11.4 S.D. were released on soft substrata near mangrove–seagrass and lagoonal coral reef flat habitats in the Western Province of Solomon Islands. Mean survival of H. scabra at the mangrove–seagrass sites was 95–100% 1 h after release and approximated 70% 3 days later. At the coral reef flat sites, however, mean survival was as low as 37.5% 1 h after release and total mortality occurred in two of the three releases within 48 h. Mortality of the juvenile H. scabra was due mainly to predation by fish in the families Balistidae, Labridae, Lethrinidae and Nemipteridae. Survival of juvenile H. scabra was improved significantly by releasing them within a cage of 8-mm mesh. This procedure resulted in 100% survival of juveniles in the coral reef flat habitat during the course of the experiment. Our data indicate that mangrove–seagrass areas should be suitable habitats for release of cultured juvenile sandfish in restocking and stock enhancement programs. Release of sandfish at night, to coincide with the time they emerge during their inherent diel burrowing cycle, and the short-term use of protective cages, should be investigated to improve survival of individuals released in mangrove–seagrass habitats.

Restocking, Stock Enhancement, and Sea Ranching: Arenas of Progress

There are concerns about the sustainability of the worlds capture fisheries at the current total level of ∼ 96 million tons per year. The warning signals are an increase in the proportion of depleted or recovering stocks, from about 10% in 1974 to 28% in 2004, and a corresponding decrease of under-to moderately exploited stocks from about 40% to 24%. It is widely acknowledged that reductions in fishing effort and restoration of fish habitats are needed to improve resilience of capture fisheries. Nevertheless, for some coastal fisheries, application of aquaculture technology through restocking, stock enhancement, and sea ranching also promises to help restore lost production and possibly increase harvests beyond historical levels. However, application of this technology still has a long way to go before integrated management systems are in place that successfully address all the biological, ecological, social, cultural, and economic issues. The main challenges include identifying when and where to use the interventions to add value to other forms of management; integrating these initiatives with institutional and fisheries management regimes; monitoring success of the interventions; producing cultured juveniles cost-effectively; and releasing them in the wild so that they survive in high proportions. We summarize progress to date by describing the main lessons learned from 30 years of research into the potential for releasing cultured juveniles into coastal fisheries, and from application of this technology at various scales. We also describe other lessons to be learned from stocking freshwater habitats and other emerging issues for enhanced coastal fisheries, such as market opportunities and the need to develop widely accepted definitions for “restocking,” “stock enhancement,” and “sea ranching.” These definitions are needed so that nations can report and monitor different strategies used to improve productivity of capture fisheries.

Combined culture of Trochus niloticus and giant clams (Tridacnidae): benefits for restocking and farming

Abstract The potential benefits of using giant clam farming systems to rear trochus for restocking were investigated in Solomon Islands. Trochus with a mean size of 5.61 mm±0.06 SE maximum basal diameter (MBD) reared in concrete tanks used to produce juvenile giant clams attained a mean size of 28.28 mm MBD±0.25 SE after 22 weeks and grew approximately twice as fast as trochus raised in fibre-glass tanks fitted with poly-carbonate plates. Trochus from the concrete tanks were then transferred to the small (0.36 m −2 ) sea cages used to grow-out Tridacna derasa for the marine aquarium trade. Mortality in the sea cages was negligible and the trochus grew from a mean size of 30.52 mm MBD±0.04 to 46.33 mm±0.39 SE in 18 weeks. Stocking density and husbandry (to remove algae and sediment) had a significant effect on the growth of trochus in sea cages: animals stocked at a density of five individuals per cage grew significantly faster than those stocked at 10 per cage and growth was significantly greater in cages where the larger species of algae were removed regularly. Trochus did not appear to have any deleterious effects on the growth and survival of T. derasa . On the contrary, there was some evidence that growth and survival of the giant clams were improved at the highest stocking density of trochus. Trochus grazed on a range of filamentous and turfing algae within the sea cages but were ineffective at removing larger species of algae compared to husbandry procedures. Trochus harvested from sea cages were released at seven coral reef flat sites, with two levels of shelter. Mean survival at all sites after 4 weeks was at least 76%±4.6% SE and was not affected significantly by the amount of shelter. There were no apparent morphological weaknesses, or behavioural deficits, in the cultured trochus compared to wild individuals. In fact, the shells of cultured animals were significantly heavier than those of wild trochus. Rearing trochus in combination with giant clams produces individuals that are fit for survival in the wild at reduced cost, and paves the way for giant clam farmers to restock trochus by releasing them on reefs under their customary marine tenure, or in marine protected areas.

Stock Enhancement Initiatives

Publisher Summary This chapter reviews stock enhancement initiatives for a wide variety of marine invertebrates such as, Scallops, Other Bivalves, Abalone, Queen Conch, Shrimp, Spiny Lobsters, Lobsters, and Sea Urchins. Stock enhancement of scallops stands out among marine invertebrates for the nature and scale of the operations. A major advantage of using wild spat for stock enhancement of scallops is that the seed has no inherent morphological, behavioral or genetic deficits. Another major problem limiting the potential for stock enhancement of queen conch is the limited availability of nursery habitats. A limiting factor for restocking and stock enhancement programs for Abalone may be the inability of hatcheries to produce the required number of juveniles. The potential for extensive mariculture of Queen Conch was considered to be low because of high hatchery costs, lack of mass-rearing techniques, and high predation on juveniles. The great economic value of Shrimp fisheries has led to very high exploitation and prompted several countries to assess the potential for stock enhancement programs. Two main types of interventions are underway to increase production of Spiny Lobsters further. Major problem limiting the potential for stock enhancement of Queen Conch is the limited availability of nursery habitats. Much of the basic technical and ecological knowledge required to mass produce juvenile Sea Urchins and release them with a relatively high probability of survival is now in place.

Other Important Considerations for All Initiatives

Publisher Summary This chapter presents the differences between restocking and stock enhancement, several considerations apply equally to both types of interventions, where they are deemed to be beneficial to the management of invertebrate fisheries. These considerations are the need to measure whether the intervention has been as successful as expected, minimize the potential negative impacts of releasing cultured juveniles on the genetic integrity of the wild populations, reduce the risk of introducing diseases to the target species and broader animal community, and avoid undesirable changes to the relative abundances of other valuable species in the ecosystem. The changes to the genetic diversity of target stocks, and the risks of introducing diseases to conspecifics and other species in the ecosystem, are not the only potential impacts of restocking and stock enhancement. There is concern that the changes in relative abundance of target species, brought about by successful large-scale releases or associated manipulations, may be at the expense of other valuable components in the ecosystem. Another feature of the stock enhancement of marine invertebrates to be considered when assessing potential impacts of releases is that many of the target species feed low in the food chain.

Overview and Progress Towards a Responsible Approach

Publisher Summary This chapter presents the approaches and outcomes across species and outlines general progress toward the components of a responsible approach done separately for the species/groups used in restocking and those used for stock enhancement initiatives. A key feature of the restocking initiatives for marine invertebrates described in the chapter is that the cultured juveniles have always been produced in hatcheries. Two striking features of the restocking initiatives, compared with stock enhancement programs, are that they are all at an early stage and that they are underway mainly in developing countries and Small Island Developing States (SIDS) with the assistance of international partners. In contrast to restocking initiatives, several different methods have been used to supply juveniles for marine invertebrate stock enhancement programs, these include collection and nursing of wild spat, translocation of excess juveniles that have settled naturally, hatchery-reared juveniles, and provision of suitable habitat to enable spat to settle in greater numbers or in areas where settlement would not otherwise be possible. The chapter discusses the stock enhancement initiatives for the eight species/groups that provide more opportunities to assess progress toward a responsible approach than the work done so far on restocking. It is evident that capture and culture of wild spat is one of the simplest and most attractive options for stock enhancement; it reduces the cost of supplying large numbers of environmentally fit juveniles and can avoid effects of releases on the genetic structure of stocks.

Management of Restocking and Stock Enhancement Programmes

Publisher Summary This chapter outlines the basic information required to determine whether restocking is likely to help rebuild severely depleted stocks or whether stock enhancement could help overcome recruitment limitation in operational fisheries and return a profit on investment. The chapter demonstrates that either restocking or stock enhancement is likely to be beneficial and identifies various ways in which the released animals should be managed to obtain optimum benefits from these two types of interventions. It explains whether release of cultured juveniles will add value to other measures normally used to rebuild spawning biomass to more productive levels. Managers need sound information on stock delineation, that is, the biological and genetic structure of the population(s) comprising the fishery, the projected time frames for recovery with and without various levels of restocking, and the capacity of hatcheries to produce juveniles. The managers of restocking programs are aiming for long-term benefits, and the managers of stock enhancement programs need to demonstrate, often over a short term, that the value of the additional harvest exceeds the cost of producing and releasing the juveniles. The chapter focuses on development of regulations to optimize the biological, social, and financial sustainability of the interventions made to increase the productivity of the fishery and need to pay particular attention to the number of juveniles released and to identifying and implementing measures that maximize the benefits from the process.