Abalone farming occurs in many countries throughout the world, with the largest production being in China, South Korea, South Africa, Chile, and Australia. There is no single, universally acceptable, method to culture abalone, the method of choice depending on factors such as local sea conditions, availability of land or in-sea lease areas, labor and energy costs, and local environmental regulations. The farming process occurs in several distinct phases including broodstock collection and conditioning; induction of synchronous spawning; fertilization; larval culture and settlement; postlarval growth to the juvenile stage; and growth to market size. These phases are described with reference to the various ways in which they operate for different species, and in different countries. The advantages and disadvantages of the various methods are discussed. The future viability of abalone farms will depend, to a large extent, on the relative costs of production in each country.
Over the past 40 years, knowledge of infectious diseases in abalone has gone from nearly absent to prolific, largely as products of investigations of mass mortality events in both wild and cultured populations. Viruses, bacteria, protozoa, and metazoan pathogens and pests have all been shown to be important influencers of abalone health. The most significant viral pathogens are herpesviruses, an unusual “shriveling syndrome” virus, and a poorly described amyotrophia virus. Among bacteria, Candidatus Xenohaliotis californiensis (the agent of withering syndrome) and various species of Vibrio have caused the most harm. Protozoa of significance include Perkinsus olseni and two haplosporidians. Metazoan pests that harm abalone include the boring sponge Cliona, polydorid polychaetes, sabellid polychaetes, and a range of fungi that invade the shell or soft tissues. This chapter provides an overview of current knowledge on these and lesser-known causes and potential causes of disease.
With many of the world's abalone fisheries fully exploited or overexploited, together with loss of suitable abalone habitat in many countries, aquaculture-based enhancement is becoming more common. Juveniles, or larvae, produced in hatcheries, are used to restore or enhance depleted populations. Past experience, however, has suggested that relatively few enhancement programs have produced significant increases in yield or economic benefits. Many countries have initiated abalone enhancement attempts, some with more success than others. This chapter details enhancement operations in Japan, the USA, Canada, Australia, New Zealand, South Africa, and Mexico, and outlines the different protocols that have been used. Genetic considerations and economic viability are also considered.
Eastern Pacific abalone are part of the multitrillion dollar ocean economy. Abalone have a long history as food and are culturally significant for First Nations as well as the basis for economically valuable fisheries. Abalone are ecologically important grazers within rocky subtidal ecosystems that maintain crustose coralline algae pavements. Larval and newly settled abalone metamorphose on coralline algae; however, postsettlement mortality rates are extremely high. Predators and shell parasites further contribute to mortality. This combination of intensive exploitation and natural mortality can lead to low population densities and reproductive Allee effects. Abalone are highly susceptible to marine heatwaves and harmful algal blooms, which have triggered mass mortalities. Two species of abalone are now on the United States Federal Government endangered species list and three are species of concern. Therefore, drafting adaptive management and restoration strategies will require effective fishery controls and enhancement actions that incorporate climate change to support productive abalone resources in the region.
Knowledge and application of genetic variation is the foundation for the survival and exploitation of abalone, and its potential will be reached through greater communication and collaboration. Genetics encompasses a broad field of disciplines focused on the building blocks of life, the DNA molecules, which make up the genome of an organism. Whether working with individual genes or their protein products, random segments of DNA sequence or the entire genome, or the resulting phenotypes, variation is observed between individuals, populations, and species. It is utilized to assist in elucidating the phylogeny and relationships of the more than 50 extant species and subspecies of Haliotis. Genetic variation helps to determine connectivity between natural populations, which in turn helps managers determine fishery and conservation strategies to ensure sustainability and survival. Selective breeding programs—essential tools for the sustainable growth of the aquaculture sector—are founded upon and exploit the genetic variation of economically important traits. Genetic technologies are rapidly changing and to understand their potential requires ongoing communication with end users. This is particularly so as technologies become more cost-effective for application to the multiple needs of abalone, and within reach of research and commercial budgets. The recent sequencing of abalone species genomes is anticipated to have major flow-on in delivering greater knowledge and tools at a biological and molecular level not previously available. The application of genomic tools, as well as those of other disciplines such as metabolomic, proteomic, and epigenetic, has the potential to add significantly to the core areas of taxonomy, fishery management, conservation, and aquaculture. To exploit these fully for the benefit of all sectors requires improved international collaboration to maximize scientific knowledge. In addition to the new tools, opportunities need to be grasped to integrate other scientific disciplines with genetic studies, be that biogeographic and oceanographic to assist understanding natural populations, or nutritional and physiological to support aquaculture production. The culture of abalone globally will continue to expand, and to support such growth will require an increase in the application of selective breeding programs. These will take advantage of the inherent genetic variability present in abalone, as well as the opportunities presented by the ease of interspecies hybridization and the incorporation of genomic information to assist selection decisions.
The anatomy of abalone is complicated. The effects of torsion and other developmental constraints, the dramatic flattening and open spiral of the shell, and the central location of the highly enlarged right columellar muscle impact the placement and morphology of the major organs as well as the circulatory and nervous systems. The details of how many of the major organs function are still being investigated. The anterior head has a pair of sensory tentacles and stalked eyes. The ventral mouth leads to a buccal region with an elaborate odontophoral apparatus to take in food. The large dorsal mantle cavity is filled by two bipectinate gills, or ctenidia. All other exchanges with the environment, including gas exchange, collection of sensory information about the incurrent water, elimination of wastes, and the release of gametes, occur in the mantle cavity via the movement of water through incurrent and excurrent openings, or tremata, in the shell. The enlarged foot consists of complex networks of collagen-wrapped muscle fibers. The mantle lines the mantle cavity, covers the organs, and secretes the layers of the shell. The digestive system has complex regional specialization and loops posteriorly and anteriorly within the body. The heart consists of two auricles and a ventricle. The heart receives hemolymph from the gills, and pumps it via arteries through unlined capillary-sized spaces in the organs to veins that carry most of it to the gills for gas exchange. The coelom of adults is restricted to the pericardial and renal cavities. The left and right kidneys are distinctly different in structure and function. Sexes are separate. The large gonad is divided into chambers by trabeculae and gametes move to the right kidney, where they are released into the mantle cavity. The streptoneurous nervous system consists of a series of ganglia from which extend nerves to all the tissues of the body. Specialized sensory structures include the chemosensory osphradium located in the mantle cavity; sensory bursicles on the ctenidial leaflets; cephalic, epipodial, and mantle tentacles; statocysts; and eyes.
Over the past three decades, several major haliotid fisheries have closed and the remainder are in decline or substantially depleted compared to peak periods in the fishery. The challenge of assessing stock status and implementing timely management decisions to maintain abalone harvests at sustainable levels continues to be problematic for those remaining wild fisheries. Wild haliotid fisheries are distributed within a thin coastal margin over large geographic distances involving hundreds, or in some cases thousands, of kilometers. Fundamental differences between the biology and ecology of haliotids and of much larger industrial target species preclude the rich suite of tools available to many other significant fisheries. Almost all dynamic pool assumptions that are central to the more advanced modeling tools available are broken for wild haliotid fisheries. In addition to restricting the potential tools available to abalone assessment scientists, many of the key biological attributes have major implications for how we use research surveys and our implicit assumptions in the ways we use the data obtained. Matching assessment frameworks to the recognized biological features is key to ongoing sustainable management of the remaining wild fisheries. New techniques such as passive GPS datalogging technology and a range of other technological advancements will assist greatly with the challenge of determining the stock status of our wild haliotid fisheries.
Abalone present an unrivalled opportunity to investigate metabolic function and gas exchange in a gastropod that retains ancestral features, including paired organs and secondary shell openings. If Haliotis is regarded as a functionally homogenous genus, it is concluded that the gills are responsible for almost all gas exchange, rather than exploiting modified mantle or epipodium surfaces, as favored by many other gastropods. Gill ventilation is facilitated by external water currents, supporting a two- to three-fold increase in resting metabolic rate above levels in static water. Further increases in metabolic rate are achieved by recruiting the otherwise under-perfused left gill. As aerobic scope is exceeded, energy demand is initially supported by phosphoarginine and then anaerobic glycolysis and the tauropine and, to a lesser extent, alanopine, lysopine, and strombine pathways. Even modest muscular exertion may induce a localized anaerobic response as hemolymph circulation preferentially targets the central vasculature rather than muscles. Muscle blocks must also retain resident hemolymph to provide hydrostatic antagonism for muscle fiber extension. In the foot this is achieved using a valve structure. The valve also guards the main vasculature from damaging pressure surges and may be combined with transient cardiac arrest. Circulating hemocyanin protein tightly binds oxygen, with unloading further discouraged by a reverse Bohr shift which appears consistent with an oxygen storage function, only unloading when tissue oxygen tension is very low. Metabolic performance in resting, active, and feeding abalone is considered in the context of a changing ocean climate. As Haliotis is, in fact, far from structurally or functionally homogenous, some guidance is offered for on-going research to develop a more representative synthesis of the physiological mechanisms of this extraordinary snail.
Demand for seafood, including abalone, has been increasing over the past few years and is likely to continue to increase into the foreseeable future. China is one of the largest producers and consumers of seafood, including abalone. While, over the past few years, legal abalone fisheries have been decreasing, illegal exploitation has been increasing in several countries. At the same time, farm production of abalone has seen massive increases, especially in China and South Korea. In 2018/2019, total worldwide production of farmed abalone was estimated at more than 188,000 metric tonnes. By 2020, the total supply of abalone available worldwide from all sources (fished, farmed, and illegal) had increased to more than 200,000 mt. Currently estimated at about 7000 mt annually, illegally sourced abalone has a significant effect on the world market. Surprisingly, however, prices for high-quality abalone are still very high, and demand in China still outstrips supply. It is currently unknown what effect increasing world inflation levels will have on the international abalone market.
In China, abalone has been regarded as the "jewel in the crown" of seafood for thousands of years. More recently, abalone has become a popular item in celebratory banquet menus for family gatherings and festivals. Research into abalone biology and aquaculture began in the late 1960s in China, with artificial seed production technologies of two local species—Haliotis diversicolor in subtropical southern China and Haliotis discus hannai in temperate northern China—being developed. Following the development of hybrids between Japanese and Chinese species, farming developed significantly during the late 1990s and subsequently expanded rapidly. Over the past 15 years, abalone farming in China has developed very quickly, production in 2018 being 14.5 times greater than in 2003. In 2018, 163,000 metric tons of abalone was produced in China, valued at US$2.8 billion, and accounting for 93% of global farmed production. Seed production has also increased sharply, from 1.04 billion in 2003 to 8.23 billion in 2018.
In the past, abalone farming has been perceived as high risk, often inhibiting investment. Potential investors may be reluctant to become involved because they may have little understanding of the farming process, or of the financial implications and potential risks. Provision of a comprehensive business plan may help to increase confidence in the venture. Such a plan would need to cover all aspects of the operation, from initial construction right through to marketing the product. This chapter outlines the main categories of costs that might be expected, and suggests possible timelines for financial inputs. It includes a hypothetical cash flow model for the first 3 years of operation, expressed in a series of spreadsheets. It suggests that, for an abalone farm, a business plan would need to extend for considerably longer than 3 years, at least until the first crop is available to harvest.
Abalone are marine snails that belong to a group of invertebrates called molluscs, that also include common bivalves such as scallops, oysters, mussels, pippies, and cockles, as well as octopus, squid, and cuttlefish. Abalone have a moderate to heavily calcified snail-like, flattened shell. They belong to the exclusively marine family, Haliotidae and to the single genus-level taxon, Haliotis. There are 56 valid species, with 18 additional subspecies. Abalone shells are flattened, similar to limpets, and have little external signs of coiling. The shell has a wide opening for the body and a single row of respiratory pores along one side that are used in respiration, excretion, and reproduction. The flat body shape of abalone is important in reducing drag forces that are generated by waves that are typical of their shallow, exposed coastal reef habitat. Viewed from the ventral side, the internal anatomy is dominated by a large, flat, muscular foot, surrounded by a pigmented epipodium, which is a flat circle of tissue with sensory tentacles. On temperate and tropical shores, abalone occur from the low intertidal to a depth of about 30 m, especially in areas supporting seaweed beds, where adults are macroalgal herbivores. In most areas where abalone are common, they have formed the basis of important fisheries.
Wild abalone graze on a range of micro and macroalgal species. Macroalgae are also used to feed farmed abalone in a number of countries, including China, Korea, South Africa, and Chile. Abalone cultured in intensive systems are predominantly reliant on formulated feeds. These diets are formulated using current knowledge of the nutritional requirements of a range of cultured abalone and fish species, and use a range of terrestrial ingredients (cereal, oilseed, and pulse meals) and low levels of marine ingredients (sustainable levels of fish meal and fish oil). Any number of ingredient and inclusion level combinations can be used to arrive at the nutrient specifications. Abalone, like fish and other animals, have a requirement for protein (essential amino acids), lipids (omega-3 highly unsaturated fatty acids), and a range of vitamins and minerals. Although research into abalone dietary development has been extensive, knowledge gaps remain regarding nutrient requirements and their role in growth, health, and product quality. Unlike for some commonly cultured freshwater and marine fish, such as rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar), knowledge of the key nutrient requirements for essential amino acids, fatty acids, vitamins, and minerals for commonly cultured species of abalone are incomplete or nonexistent. This places some constraints on formulating commercial production diets for optimum growth and health. To improve abalone production further, it is recommended that research be conducted to establish more detailed nutrient requirement information for abalone on a species-by-species basis. Research needs to occur in relation to age, water temperature, and the use of traditional and new ingredients for formulated feeds to optimize commercial abalone production.
