World Aquaculture Magazine - June 2021

WWW.WA S .ORG • WORLD AQUACULTURE • JUNE 2021 17 Culturing scallops is somewhat problematic given the relatively mobile nature of most pectinids, highlighting the importance and need for gear that fully confines scallops as they grow. The chapter on scallop culture also includes a section on transportation of seed, juveniles and adults. Although the specifics are given as applied to scallops, the methods could easily be adapted to the transport of other molluscs. Relatively speaking, the chapter on scallops does not include as much detailed practical information, figures and tables as some of the other species chapters. Although the book includes a specific chapter on site selection, the chapter on mussel aquaculture includes a detailed section on considerations used for selecting sites for mussel aquaculture in North America and Europe. Interestingly, unlike many other mollusc species, most mussel seed continues to be collected from natural sources using spat collectors, with hatchery production playing a negligible role. The mussel chapter includes detailed descriptions of grow-out methods used in North America (Maine, PEI), China, New Zealand and Europe. The mussel chapter concludes with a detailed description of harvesting methods, processing and marketing. The prized abalone are rather different than other molluscan shellfish insofar as they are often fed seaweeds or formulated feeds in grow-out systems or provided with plates onto which algal biofilms are allowed to develop. Specialized feeds that include red seaweeds are valuable in broodstock conditioning diets. Most of the world’s abalone (like many other molluscan shellfish) are grown in China, where they are grown in nearshore cages. Unfortunately not much information is provided regarding the specifications of this culture system, as well as others used to grow abalone, with the exception of onshore tanks. The chapter on conch, another marine gastropod, focuses on the Gulf and Caribbean species queen conch and fighting conch. Relative to the culture of other molluscan shellfish, conch culture is relatively new, with the bulk of the chapter based on experiences obtained by investigators at the Caicos Conch Farm in the Turks and Cacos Islands, starting in the 1980s. One of the breakthroughs in conch culture was the identification and administration of suitable cues to induce metamorphosis from a swimming veliger to a benthic snail. Feeding flocculated diatoms after metamorphosis is also a key practice. As juveniles, conch are fed a gel-based or pelleted diet. Grow-out takes place in pens placed in nearshore seagrass pastures. The chapter also includes a discussion of cultured pearls produced in queen conch. Conch can be marketed for meat, as escargot and for the aquarium trade. A relatively short chapter on the carnivorous marine snail Concholepas concholepas , well known in Chile and Peru, summarizes the state of knowledge of hatchery and grow-out culture practices of this species and completes a trio of chapters on marine gastropod mollusc aquaculture. The culture of this species faces numerous bottlenecks and culture methods have not yet been fully elaborated. An excellent chapter on pearl oyster culture rounds out the species chapters, focusing on oysters of the genera Pinctada and Pteria . The first part of the chapter describes spat collection and hatchery production methods, nursery culture and grow-out. The second part describes pearl production, with good information about nucleation options. The lack of more specific information about nucleation techniques is not surprising because many commercial pearl operations consider their technology and practices to be proprietary, with the ultimate outcome dependent on the skill and experience level of nucleation technicians. Site selection is important in every form of aquaculture but, given that molluscan shellfish are mostly filter-feeding species dependent on natural productivity for growth, site selection assumes outsized importance. Nearly all species chapters address the issue of site selection, both for hatchery operations and grow-out areas, but the book also includes a specific chapter that addresses this topic comprehensively. The chapter discusses each consideration that enters into the site selection process. The chapter also addresses the related concept of carrying capacity, differentiating among physical, production, ecological and social categories. Decision support tools that can assist in the site selection process, licensing and regulation, marine spatial planning and climate change are other topics discussed in this chapter. A few case studies of the application of the site selection process would have provided useful practical illustrations of the occasionally generalized discussion of the topics presented in this chapter. The next chapter addresses the critically important area of water and shellfish quality, otherwise known as shellfish sanitation. Given that nearly all molluscan shellfish are grown in production systems embedded in natural waters and that they are extractive species, the risk of contamination is potentially high and attention is needed to assure the food safety of farmed shellfish. This long and detailed chapter focuses on the regulatory programs of mainly the US and less so of the EU. The chapter provides introductory information on microbiological contaminants, microbial indicator organisms, marine biotoxins and chemical contaminants. The systems used to classify waters in the US and EU are then described. The elements of surveys and sampling programs for water and shellfish are provided. The chapter also includes a deeply detailed discussion of the analysis and interpretation of fecal coliform data. The chapter concludes with seven pages of appendices consisting of useful and relevant website links, a glossary and a sampling protocol for shellfish growing waters. This chapter certainly gives potential producers an appreciation of the regulatory compliance requirements associated with a shellfish sanitation program but most of the information is perhaps more useful to regulatory authorities in countries with weak governance systems and nascent molluscan shellfish aquaculture sectors. Throughout, the book rightly emphasizes the role of hatcheries, and each of the major species chapters includes sections on sourcing, conditioning and spawning induction of broodstock, egg incubation and larval culture to metamorphosis and settling in hatcheries, and nursery culture in land-based or nearshore facilities. The potential complications of spawning hermaphroditic species are noted. The long chapter on hatchery design is comprehensive and is perhaps the most practically oriented chapter in the book. It includes sections on hatchery sizing criteria, seawater system layout, intake and pumping stations and general layout. There are major sections on larval production, algal production, broodstock facilities, post-set rearing systems and intermediate nurseries. The relatively short chapter on algal culture could probably have been included in the hatchery chapter, but this does not detract from the quality of either. Despite the key role of hatcheries, molluscan shellfish seed of some species ( C O N T I N U E D O N P A G E 1 8 )