Marine Aquaculture: Opportunities for Growth (1992)

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5 Engineering and Research ROLE OF SCIENCE AND TECHNOLOGY IN ADDRESSING MAJOR CONSTRAINTS A broad range of economic, institutional, environmental, and social con- cerns can, to some extent, be addressed through advances in the science and technology base supporting marine aquaculture. Problem areas that are susceptible to mitigation through technological approaches include economic feasibility, market structures and product form, the regulatory framework for leasing and permitting, land and water use, ecological impacts, aesthetic issues, use conflicts, and public attitudes. Summaries of the major issues follow, with examples of where science and technology can contribute to the resolution of related problems. Economic Feasibility Advances in technology can improve economic feasibility through (1) the creation of new capability, (2) the design of more productive (higher- yield) operations, and (3) the reduction of expenditures through more effective and efficient operations and the substitution of cost-effective capi- tal investment for labor. Specific opportunities for improving marine aqua- culture in these areas include: · new culture systems that make possible the production of marine spe- cies in environmentally sound ways; · improved technology for culture operations to utilize inputs more effi- ciently, increase productivity, and reduce costs of production and waste 116

ENGINEERING AND RESEARCH 117 disposal (e.g., water use and reuse, feeding technology, product inventory, product handling, waste disposal); · technology that improves the cost-effectiveness of operations through intensification of culture systems, reduced operating costs, and increased productivity; and · technology that reduces production uncertainty (e.g., through disease detection and treatment, inventory monitoring systems, and design of more seaworthy facilities), thereby reducing risk and the associated costs of capital, insurance, and other nonoperational factors. Marketing and Product Information Technology can enhance the quality and value of products in addition to increasing productivity and reducing costs. Examples are: · harvest, transportation, processing, and packaging technologies that will allow aquaculture to deliver high-quality products in good condition to appropriate markets; · technologies that can maintain high-quality standards and ensure wholesome and safe products; and · new product forms for new and traditional aquaculture species. Institutional and Regulatory Issues Technology can be used effectively to address many institutional issues. Opportunities include: · technology to diminish the amount of water or land necessary for cul- ture and auxiliary systems, thus minimizing land/water use conflicts; · information systems to improve communication with the public, pro- vide relevant facts, make information more accessible, and generally in- crease understanding of the benefits and constraints of aquaculture; · technology that will resolve issues associated with access to brood A.' _ ... .. . .. ~ a ~ ~ . - , 1 ~ _ _ 1_ · _ stock and seed/juvenile production from wild populations through achlev- ing controlled reproduction, an understanding of improved nutritional requirements, and better knowledge of species life cycles; · technology to better identify and control disease-related problems; and · technology for the identification of cultured fish in order to differenti- ate among stocks for marketing and management purposes. Environmental Issues Marine aquaculturists must be sensitive to issues of common resource use and must seek ways to reduce pollution and other environmental im- pacts. Science and technology can contribute significantly to this goal by

118 MARINE AQUACULTURE · achieving waste treatment and removal, and water and feed delivery, that alleviate pollution and discharge problems in culture and auxiliary systems; · providing means to minimize disease transmission in culture operations and thereby improve disease prevention and management; · providing improved culture and auxiliary systems (for open ocean pro- duction, closed systems, and ocean ranching) that mitigate the ecological impacts; · providing alternative, nearshore, culture systems that can mitigate con- flicts with recreational, commercial, and navigational use; · providing innovative culture systems that address the aesthetic issues associated with nearshore operations (i.e., by use of submerged cages, off- shore production, closed systems, and ocean ranching); · developing analytical techniques and computer models to simulate the environmental impact of aquaculture operations (Brune, 1990~; · improving stock sterilization capability that prevents reproduction in cultured animals and prevents genetic dilution of wild stocks from escaped fish; · improving harvest, packaging, and transportation systems to alleviate potential sanitation and public health concerns; and · providing the capability to identify genes that control growth (a capa- bility that has been achieved with nonfish food species). Socioeconomic Issues The development of technology for marine aquaculture not only can im- prove the economic situation for producers but can contribute to the year- round economic health of rural communities as well. Specific examples include (1) providing employment for laborers who work on aquaculture farms, and (2) creating or augmenting the need for suppliers and processors that, in turn, provide employment. INTERDISCIPLINARY SYSTEMS DESIGN Marine aquaculture systems require individual elements designed so that each can function effectively alone and can also function in concert with other elements to comprise an interactive system. For example, a simple home aquarium may be viewed as a system made up of a few common elements- a tank, air pump, air diffuser, water pump, and filter. Aquaculture systems, although conceptually similar, are much more complex in terms of design, operation, and management. The biological functions of the fish must be taken into account, including special requirements associated with intensive culture operations. Consequently, the design of a commercially viable system

ENGINEERING AND RESEARCH 119 involves considerations beyond purely engineering criteria for integrating the elements into a working physical system (Huguenin and Colt, 1989~. Design, operation, and management are further complicated by the need for profitability, the risks and challenges associated with the intensive pro- duction of animals, and the necessity of working in a frequently hostile environment—the ocean. The project team must select an adequate site; establish the physical, chemical, and biological requirements for the species in culture; and also design a system that is economically viable. An inter- disciplinary approach is needed to achieve all these objectives. The engineer, the biologist, and the entrepreneur must collaborate effectively in order to solve problems and develop improved technology for marine aquaculture, an arrangement not easily achieved in an era of increasing specialization. Although technology development is needed for the commercial success of marine aquaculture, research on the biology of potential cultivars is also essential. One of the principal constraints to economic viability is the lack of sufficient biological information necessary as design criteria for fish culture. Too little is known about life cycles, the means of controlling reproduction, the environmental and nutritional requirements of larvae, the causes and effects of stress, and biological and environmental requirements in general. Effective interdisciplinary systems design can be realized only if the biological criteria for design are well understood. Following are discussions of the major areas in which interdisciplinary research and developments can make significant contributions to the ad- vancement of marine aquaculture and to the resolution of many outstanding issues that presently constrain the industry. First, auxiliary systems that are an essential part of all types of culture systems are discussed. Then culture and confinement systems are discussed in the context of those that are adaptable to nearshore locations, those that can be used onshore, and sys- tems compatible with offshore production. Auxiliary Systems for Fish Culture Improvement and development of the various auxilliary systems that are required for culturing fish are essential to the establishment of commer- cially viable marine aquaculture. Aquaculture systems must ensure the con- finement or physical support necessary to hold the animal, as well as pro- vide the auxiliary elements required for healthy aquatic life (Fridley et al., 19881. Key needs are adequate water with adequate oxygen, effective feed and feeding systems for marine species, waste treatment, and sensors and monitoring capability. Expert systems, including computer monitoring and prediction capability, can be very helpful as well. Most of these needs are provided by auxiliary systems and are basic to the cultivation or husbandry of any animal, terrestrial or aquatic.

120 Hatchery Systems MARINE AQUACULTURE The culture of most species requires a hatchery in which to collect, incu- bate, and hatch eggs and/or rear larval fish and young juveniles. Hatcheries require rigorous controls and careful management. The young animals are intolerant of adverse water temperature and quality, and often are difficult to feed. A variety of jars, racks, sacks, and other containers have been developed to hatch eggs and to set the spat of shellfish. Special diets and Hatchery tank with a Macdonald jar an incubation container that provides an en- vironment conducive to egg development with minimum stress and minimum opportunity for disease.

ENGINEERING AND RESEARCH 121 special ways of presenting the feed have been created. Each species tends to have some unique requirements that lead to continual innovation as advances are made with current species and as new species are cultured. Hatchery development can be a limiting factor in attempts to culture new species. Hatchery limitations generally tend to be more biological than technological. The intensive practices (high population density) of hatcher- ies and the relatively short time that animals are in the hatchery generally result in lower water requirements and smaller facilities than for the grow-out stage of development. This smaller scale of operations tends to limit the level of environmental and public concern. However, in the future, the pursuit of offshore systems may present technology problems related to the design of offshore hatcheries or to the transport of juveniles from an onshore. h~tc.herv to an offshore culture facility. In anv case. the biologi- cat information needed to produce high-quality stock consistently and eco- nomically is often a limiting factor in achieving cost-effective hatchery production. Feed and Feeding Systems The feeding habits and the morphology and composition of feed vary greatly by species. Consequently, different artificial diets and feeding sys- tems need to be developed in each kind of culture operation. A large body of information is available on feeds and feeding systems for salmonids and catfish (NRC, 1974a,b, 1977; Halver, 1988; Lovell, 1989~. Considerable in- formation is also available regarding the nutritional and feeding require- ments of oysters and lobsters (Conklin et al., 1983~. Future efforts should build on existing knowledge and focus on the special needs of different marine species. Of particular importance are nutritional requirements, ef- fective feeding systems, improved efficiency of feed utilization, and alter- native protein sources, especially in relation to protein quality and specific requirements during different periods of the life cycle. The larval and juvenile stages of many marine species are relatively small perhaps 2-3 millimeters (mm) at the time initial feeding is required. This factor presents unique problems with regard to the size of food of- fered, the acceptability of prepared food versus live food and the delivery system (Bromley and Sykes, 1985; Holt, 1990, 19921. Microencapsulated diets have been under development to replace live feeds for larval and juvenile stages, but they are not yet entirely sufficient (Kanazawa et al., 19891. Research on better attractants to promote feeding or on improved feed palatability should lead to lower feed conversion ratios (weight of feed consumed to weight of fish produced generally between 1 and 31. Nutritional requirements of a given species change with the transitions from larval to juvenile to adult stages. Nutritional requirements need to be

22 MARINE AQUACULTURE better defined for each species and for each life history stage so that rations can be tailored to meet the precise dietary requirements of the spe- cies and stage (Ratafia and Purinton, 1989~. In the future, rations will be tailored not only to the requirements of the species under culture but also to the characteristics of the culture systems (e.g., pond system, water reuse system). Protein is the single most expensive and essential component of fish feeds. Consequently, the substitution of less expensive sources of protein for fish and other animal meals in feed could substantially reduce produc- tion costs. Use of soybean meal to replace animal protein has been moder- ately successful with some species (Cowery et al., 1971; Cho et al., 19741. Other researchers have used poultry egg proteins (Davis et al., 1976; Conrad et al., 1988) or nematodes (Biedenback et al., 1989) to replace fish protein. Researchers have investigated a number of feed additives, including anti- biotics and other medications (Strasdine and McBride, 1979; Marking et al., 1988~; vaccines (McClean and Ash, 1990~; growth hormones (for review, see Donaldson et al., 1978), drugs to increase metabolic efficiency (Santulli et al., 19901; and synthetic reproductive hormones (Yamazaki, 1983~. Feed formulations are being developed to provide natural or synthetic pigments (Yamada et al., 1989) and to deliver stable and water-insoluble forms of necessary vitamins (Shigueno and Itoh, 1988; Grant et al., 19891. Because feed can release large amounts of nitrogen and phosphorus, and thus cause localized eutrophication in some areas, improved feeds could mitigate concerns about eutrophication. Ketola and his associates have investigated the problem of phosphorous enrichment of receiving waters via salmon feeds and the effects of feed improvements in reducing such re- leases (Ketola, 1975, 1982, 1985, 1988, 1990; Ketola et al., 1985, 1990~. Feeds that result in more efficient assimilation of nutrients are needed to reduce the waste treatment requirements and limit environmental impacts. Consideration should be given to the design of feeds that, if uneaten, can contribute to other links in the food chain. Waste products from feeds, for example, could serve as a primary source of nutrition in a serial polyculture system (i.e., in which water and nutrients pass from one containment vessel with one species to another vessel containing a different species) (Wang, 1988; 1990~. The feasibility of altering the nutritional value of aquaculture products for humans or of enhancing other components to improve the marketability or palatability of farmed aquatic products is also under investigation. As- sessments of the relative fatty acid profiles of farmed and wild fish are already under way, partly as a result of interest in nutritional information (Nettleton, 19901. This information will serve as a guide to the develop- ment of "finishing diets" that will provide consumer-ready products with the most nutritionally healthful compositions possible.

ENGINEERING AND RESEARCH 123 The diversity of feeds pellets, algae, seaweed, small and large- re- quired for different species in culture creates the need for a diversity of feeding systems. Feeding systems in need of development include systems for increasing the efficiency of utilization of the nutrient, decreasing waste production (in terms of feed that is not consumed and feces production of the culture species), delivering micronutrients and medications, and pro- moting by-product usage. The development of feeds and feeding systems that can provide feed at a rate consistent with the ability of the fish to consume it would enhance the cost-effectiveness of all feeding systems. Such systems would also provide environmental benefits from reduced waste and water pollution in both the rearing and the effluent receiving waters, including reduced release of additives such as antibiotics. Design parameters that need to be understood include presentation of the food, frequency and rate of feeding, physical properties of feed particles, and impact of feeds and feeding methodology on wastage, growth, feed utiliza- tion, and predator species. For example, broadcasting feed over the water surface for juvenile finfish can be advantageous in getting the feed to the fish, but the presence of the fish at the water surface may attract bird predators. Broadcast feeding of shrimp in lined seawater ponds.

124 Waste Treatment Systems MARINE AQUACULTURE Treatment of wastes must be an integrated part of water reuse systems (discussed later in this chapter) and also may be required in flow-through and cage systems (Alabaster, 19821. Water disinfection and removal of solid (excess feed and fecal material) and dissolved (ammonia and dis- solved organics) wastes are essential in any onshore water reuse system. In most cases, proper site selection for onshore or nearshore systems can minimize problems associated with waste. Dispersal or dilution of wastes for cage culture can be facilitated by proper site selection, but mech- anical means of dispersing or treating wastes and filtering effluents are needed for some situations. A fanlike pumping systems placed below cages reportedly can flush large quantities of water through the system (Aase, 1985~. In other cases, collection of wastes is required. Waste collec- tion systems vary greatly for different culture systems. For intensive cul- ture in ponds and tanks, solid waste collection sometimes can be accom- plished with the simple addition of a settling tank or pond. However, more cost-effective methods of waste collection and dispersal need to be developed. Reuse systems employ a wide variety of treatments to achieve the de- sired water quality changes. These may include the following components: filters, screens, clarifiers, oxygen injection, aeration, biofilters for dissolved organics and ammonia removal, chemical ammonia removal, heat exchang- ers, ultraviolet light disinfection, ozone disinfection, and chlorine disin- fection (Miller and Libey, 1985; Malone and Burden, 1988~. Biofilters are a critical component in the development of commercially viable recircu- lating systems, and research in this area continues to be very active (e.g., Brune and Piedrahita, 1983; Kruner and Rosenthal, 1983; Miller and Libey, 1985; Rogers and Klemetson, 1985; Malone and Burden, 1988; and Kaiser and Wheaton, 1991). Dead and diseased organisms present another waste disposal issue faced by marine aquaculturists. Management of this waste may be significantly different from that of fish processing plants because the risk of disease transmission to other cultured fish and to wild fish must be minimized in aquaculture operations. However, it is also essential that processing plants and other facilities take the steps necessary to ensure that diseases are not transferred to wild populations. Clearly, both commercial fish processing facilities and aquaculture processing facilities have to dispose of animal wastes. The technical issue of disposal can be accomplished by utilizing current land-based disposal methods including landfills or incineration. However, the continued use of landfills and incineration in the future may be problematic because of limits on their availability or environmental con- cerns. Alternative means of disposal need to be developed.

ENGINEERING AND RESEARCH Design for a larval fish-rearing tank with an internal biofilter. Sensors and Monitoring Systems 125 A sensor and monitoring system can provide valuable information and thereby improve the chances of success for marine aquaculture. For ex- ample, oxygen levels fluctuate in response to different internal or external factors, and these variations can stress or even kill the animals if adequate aeration is not provided. When fluctuations are not fatal, unsatisfactory fish health and growth, inefficient feed utilization, and poor reproduction can result (Wyban and Antill, 19891. Oxygen concentrations in ponds are particularly troublesome and difficult to measure and predict (Losordo et al., 1988; Piedrahita, 19914. Seemingly identical ponds within a single farm often have different oxygen conditions. Oxygen levels are changing constantly and can vary significantly even in the same pond.

Paddlewheel aeration of an earthen aquaculture pond. MARINE AQUACULTURE Accurate and reliable sensors to monitor basic water quality parameters in seawater are not presently available. Existing automatic systems for continual in situ oxygen measurements are costly to install, require frequent and skilled maintenance, and typically have a short operating life. The marine environment causes rapid deterioration of equipment; metabolic by- products and other impurities in seawater interfere with the measurement process; and the cost for the multitude of measuring points needed is high. Oxygen is just one of many parameters that are currently difficult to monitor and control with available instrumentation (Kaiser and Wheaton, 1991~. Others parameters of special significance and technical challenge are ammonia, carbon dioxide, pH, salinity, light transmission, and biomass. Even when measurements are not especially complex technically- such as the determination of flow, water level, and temperature existing equip- ment is subject to biofouling and corrosion. Improved instrumentation and automatic monitoring systems are needed to solve these problems. Expert Systems The widespread availability of relatively inexpensive computers, together with the development of improved sensors and monitoring equipment, is

ENGINEERING AND RESEARCH 127 accelerating the evolution of more advanced monitoring, control, and pre- diction systems, collectively referred to as expert systems. A simple expert system for aquaculture would monitor biomass of fish, temperature, and concentration of oxygen. As the temperature or biomass changes, the com- puter would calculate the appropriate feed amounts and command the me- chanical feeder to release the desired amount, provided the oxygen concen- tration was adequate for good utilization of the feed. The expert system maintains the amount of food offered at a preprogrammed level, but avoids feeding in the event that the oxygen concentration has been lowered, and thereby reduces potential waste, increases food conversion efficiency, and maximizes growth, given the particular growing environment. With the addition of yet another computer routine, this expert system would deter- mine whether changes in the oxygen level after feeding match expected values. If not, the presumption would be that the feeders had not operated properly or that the fish are not consuming the feed as expected, and the operator would be signaled to take action. The characteristics of an expert system provide the ability to sense con- ditions, to take a variety of control actions in response to conditions that increase costs, to record events, to detect possible system failures, and to notify operators or set an alarm. The evolution of reliable expert systems specific to fish culture could have a major impact on the cost and risk of operations, and would benefit environmental studies and marketing control (Palmer, 1989; Weaver, 19901. Production Grow-out Systems Facilities for culturing marine species can be categorized as nearshore (located in coastal waters very close to the shore, i.e., within easy sight of other coastal users); onshore (located on land near the ocean or estuaries where seawater can be pumped to the facility); and offshore (located in the ocean at least somewhat away from the shore, i.e., in the vicinity of off- shore oil rigs or independently in deep water). A long-term objective for marine aquaculture that offers a variety of potential advantages is to locate projects inland or offshore, away from the socially and environmentally . . sensitive nearshore area. Nearshore Systems Until new technology makes relocation logistically and economically feas- ible, it will be necessary for most marine aquaculture operations to be lo- cated in nearshore shallow bays and estuaries. Therefore, high priority should be given to technological developments that will make nearshore aquaculture less objectionable and intrusive to other competing uses of the

28 MARINE AQUACULTURE coastal zone, aesthetically more acceptable, and environmentally benign if not beneficial. Mollusks are grown in the nearshore either on the shallow bottom (bot- tom cages) or on one of a variety of support systems (racks, bags, sus- pended lines, stakes). Bottom culture of mollusks is basically the culture of shellfish in their natural growing habitat. Seed are dispersed over a coastal or estuarine bottom area that is a productive environment for the species being sown. The animals are grown in a relatively natural and nonintensively managed setting; the culturist harvests mature animals much as one would gather animals from the wild. However, a variety of support systems have been created to intensify production and increase its efficiency. Support systems, if well conceived, can reduce labor requirements, increase produc- tivity, and increase the yield from seed. Commercial support systems in- clude structural racks and trays on which shellfish grow, supported bags that confine groups of shellfish, and suspended lines on which shellfish can grow. In each case, the support system provides a form of three- dimensional, off-bottom support, and the physical device used for support also facilitates harvest. Typical nearshore culture systems for finfish are cages or net pens men- tioned for salmon in Chapter 2. Cages or net pensi are usually supported by a floating structure. Each cage or pen is surrounded by netting or a similar mesh material with a bottom about 1 to 5 meters (m) below the water surface. Water flow and flushing are provided by natural currents and tidal flow. Biofouling is a common problem. At a minimum, cages must be ~^ "it ~~''~ ~~ 'it ~~ ~~ 'A ~~'~ ': aft'. I'd ~ ' ~~ '~:~''~'~'~ At' 'my. ' ',~' '''' at' '~; ~ ~~'~"~ ', ~~~ en'' ~ ;~ ~''~' ~ ~'#' '' i' ~ my'' O'er' .'"'';' ' '~ Cage facility for culturing Atlantic salmon in Hitra, Norway. Both circular and rectangular cages can be seen.

ENGINEERING AND RESEARCH 129 ~ ~~ ~ ~ ~ — j _, in, 1 ~ ~ _—~/ ,_ e ~ _ c ~ ,= ~~-~ __ _~ ~ ~~ . _ ~ Experimental stake culture of oysters (Crassostrea virginica) in a shrimp pond at the James M. Waddell, Jr., Mariculture Center in Bluffton, South Carolina. cleaned following harvest prior to starting a new cohort. Typically, walk- ways along the periphery of the cages provide worker access for feeding, inspecting, removal of any dead fish, maintenance, and harvest. Structures that support several cages usually provide space for feed storage and access to equipment as well. Limited technical studies have been published on cage systems (see Beveridge, 1987; Kerr et al., 1980; Linfoot and Hall, 19871. Although technical and economic feasibility has been established for the nearshore culture of some marine species, commercial viability is chal- lenged by numerous environmental, institutional, and social issues that in- crease costs. New technological advances are needed to permit aquaculture to flourish in the nearshore environment, which is often exploited for other uses or degraded and polluted from intensive development. Other users of the nearshore often oppose surface structures needed for marine aquaculture and thereby curtail efficient culturing of some species. For example, sus- pended off-bottom culture of mollusks is generally far more productive and successful than bottom culture and is widely practiced in most parts of the world; however, suspending such cultures from rafts or buoyed long lines is generally considered to be unacceptable in most U.S. coastal waters. Similarly, the culture of seaweed on rafts, of pelagic finfish in floating cages, and of mollusks in pens encounters opposition. Improved design and location of such surface structures or designs for their deployment beneath the sea surface would make them less objection-

130 MARINE AQUACULTURE able aesthetically and decrease the potential for interference with boaters by permitting passage of small boats through, around, or over the structures. An innovative approach to containment and harvesting of finfish is the use of sonar or electrical fencing as suggested by Balchen (1987) for use on salmon. Research is needed to determine the feasibility of such techniques. Opportunity for improvement exists also in the bottom culture of bivalve mollusks oysters, clams, scallops, mussels (Korringa, 1976; Imai, 1977)- which is one of the least objectionable forms of aquaculture with respect to visual impact and interference with other uses of the coastal zone. Im- proved methods of planting and harvesting stocks are needed to minimize impact on the benthic ecosystem and decrease the resuspension of bottom material. The carrying capacity of various environments for cultured mollusks needs to be determined. Pollution by waste from unused feed and feces is of particular concern with floating cage operations located nearshore (Weston, 1986~. Improved technology would aid ire site selection and in the operation of cages to avoid conditions under which accumulation of waste will occur. Once cages have been properly sited, technology can provide the capability to control the rates and intervals of feeding to avoid overfeeding. The ability to monitor accurately the biomass of fish in individual cages would enable feeding the amounts required for a reasonable growth rate with minimal waste and pollution. Human fecal contamination of coastal waters and the resulting risks and dangers to public health are major constraints to shellfish farming. The traditional methods of detecting contamination are inadequate and result in many areas of coastal waters being unnecessarily removed from production. New techniques are needed involving the use of better indicators of human pollution, preferably direct monitoring of the pathogens themselves. Shellfish do not become infected with human pathogens but accumulate the microorganisms in their intestinal tracts and become incidental tempo- rary carriers. With proper technology, shellfish can be quickly and effec- tively cleansed of harmful bacteria and made safe for human consumption through a process known as deputation (Richards, 1988~. Depuration is a natural self-cleansing of shellfish made possible by their biological need to ingest and discharge water to expel waste. Simply described, the shellfish are placed in clean water where they pump water through, and thereby purify, their bodies. Much more effective, dependable, and economical de- puration systems are required before the practice will be widely accepted and adopted. Also, the efficacy of deputation in purging animals of viruses on a commercial scale has not been evaluated. Shellfish may also become contaminated with dangerous poisons through ingestion of toxic microorganisms from the water. An increase in the inci- dence of phytoplankton blooms (i.e., red tides) of such toxic algae has been

ENGINEERING AND RESEARCH 131 observed around the world. These events are sometimes correlated with outbreaks of paralytic shellfish poisoning (PSP) and diarrhetic shellfish poisoning (DSP) in humans, when people ingest shellfish contaminated with such toxins. Current methods for toxicant detection are often based on bioassays that are slow and expensive to conduct. As a result, harvest closures frequently are implemented on a seasonal basis rather than as a response to the actual detection of toxic conditions. Simpler, quicker, and more dependable methods are needed for detecting the presence of such toxins, along with methods for detoxifying or otherwise depurating the contaminated mollusks. Toxic algal blooms may prove dangerous or lethal to the cultivated ani- mals, particularly to cage- or pen-cultivated finfish. Mobile culture systems could be developed that can be raised or lowered within the water col- umn (i.e., below a toxic algal bloom that might be concentrated at or near the surface) or towed away from a local concentration of pollutants as a crop-saving measure. Onshore Systems The development of onshore systems would enable the movement of culture operations inland from the nearshore coastal waters where many other competing activities tend to take place such as recreational boating and fishing. The major factors limiting further expansion of the industry would then become technical and economic rather than political and institutional. Onshore culture systems are based on fixed rearing units of various types, such as ponds, tanks, and raceways. Ponds are shallow (typically 1 to 1.5 m deep) reservoirs of water. Historically, large earthen or lined ponds are most common (Lannan et al., 1985~. The water supply to the ponds is often intermittent, although continuous supplies are also used. Water supply over- turn rates (time to replace pond water) typically are measured in days or weeks, and aeration is often required intermittently. Tanks are shallow (typically 1 to 1.5 m deep), aboveground, circular structures. Raceways are elongated concrete or fiberglass channels. Tanks and raceways most often are constructed of concrete or fiberglass. The water overturn rates typically are measured in minutes or hours. Thus the biomass loading (in kilograms per cubic meter or kilograms per square meter) in tanks or raceways is generally much higher than in ponds; biomass loadings may reach 20 per- cent or more of the water volume. Aeration or oxygenation is usually required. Use of pond systems for marine aquaculture is limited primarily by the availability of suitable sites (including the large amount of space required) and environmental concerns. Tanks and raceways are suggested as inten-

132 ~~ is,, ~ ~ ~~ ~~ I __ - MARINE AQUACULTURE Intensive tank facility that incorporates water recirculation and the use of liquid oxygen (AquaFuture, Paso Robles, California). Water is introduced into the tanks by a radial pipe that directs water tangentially into the tank to provide circulation. sive alternatives to pond culture to reduce space requirements and provide controlled environmental conditions, especially temperature (Arnold et al., 19901. Environmental issues of water use and effluent discharge that are associated with pond systems also exist with tanks and raceways. The preferred system depends largely on land cost, the cost and availability of labor, and the cost of capital. Ponds are best under conditions of low land and labor costs. Tanks and raceways require less land and labor but more capital facilities and equipment. Tanks, and to a lesser degree raceways, also can be employed with water reuse systems (to be discussed later) and therefore are preferred where water is expensive or in short supply, and where environmental concerns about water supply or discharge can be ad- dressed by their use. Site selection is a key component for the success of any aquaculture operation, including land-based systems. The further development of on- shore systems awaits the determination of particular marine species that can be cultured in enclosed and crowded conditions. High-density recirculating systems have been tested for animals such as red drum, freshwater prawns, tilapia, and penaeid shrimp (Reed, 19891. At the present time, red drum, shrimp, striped bass, sturgeon, salmon, and abalone are being cultured on- shore, at least on a limited scale. As production levels intensify, oxygen- ation and aeration systems become components of the culture system. All species require sufficient quantities of oxygen for survival and growth. Cost-

ENGINEERING AND RESEARCH 133 Construction of a greenhouse for the intensive closed-system culture of shrimp in a raceway. effective aeration systems for both daily and emergency use are available for transfer from other fields. Water Supply Systems Marine animals typically require large quantities of high-quality seawater. The water supply systems of marine aquaculture projects, therefore, are critical to the success of the operation and are an important component of the capital and operating costs. Several approaches are possible: · open flow-through systems; · systems that recirculate and thereby reuse some of the water; and · closed systems (only makeup water is added to compensate for evapo- ration and leakage). Flow-through systems use the largest water quantities for a given produc- tion level. They require a high level of reliability for the pumping system and a discharge capacity equal to the flow rate. Concomitant economic implica- tions of flow-through systems for marine aquaculture include the following: · the cost of water is high because the entire flow must be pumped and, if needed, must be heated, cooled, or treated; · the total cost is related to the volume of water required and the height of lift; and

34 MARINE AQUACULTURE · flow-through systems require continuous flow, and system reliability is more critical than for intermittently operating systems that pump at high tide only. Water cost is an important factor in either freshwater rearing (e.g., anad- romous fish nurseries and rearing) or systems using pumped seawater. Most onshore systems, therefore, can benefit from some form of water reuse that either reduces energy and facility requirements for pumping and tempera- ture control or reduces freshwater consumption where it must be purchased or pumped. Although a broad definition of reuse systems can apply to pond, raceway, or tank systems, reuse systems most typically refer to tanks. For the purposes of this discussion, the term "reuse system" is defined as a Harvesting shrimp in a greenhouse with raceway-recirculating system.

ENGINEERING AND RESEARCH 135 system that recirculates all or part of the water passing through it using one or more processes to improve its quality. Aquaculture water reuse encom- passes a variety of system designs ranging from relatively simple aeration systems with limited recirculation to 100 percent water recirculation for complete environmental control (Losordo, 19911. The need for develop- mental research in reuse systems is well accepted, but the technology is presently in operation in a number of noncommercial systems in the United States. Two examples are the Dworshak steelhead hatchery (Idaho) and the Living Seas Aquarium exhibit at Epcot Center (Florida). The Dworshak hatchery was constructed in 1966-1967 in an attempt to mitigate damage to natural runs of the anadromous rainbow trout (the steel- head) from the construction of dams on their breeding rivers. Initially, 25 rearing tanks were connected to a 15,000-gallon-per-minute (GPM) reuse system that provided treatment of water as it left the tanks and partial reuse in these same tanks (Carey and Kramer, 19661. The primary justification for employing a reuse system at Dworshak was to reduce the energy and capital costs associated with cooling, heating, and disinfecting the water supply. The original filter system has long since been replaced by other systems, which, in turn, have also been replaced. Today, three systems are in place with a total flow of 45,000 GPM, and although research continues, technology development is mature for this application. The Dworshak hatchery has served as a center of reuse research and development for the federal government. Most of the major marine aquariums of the world are based on closed reuse systems little water is added to the process, even though the biomass of fish and marine mammals may be significant. For example, the major tank in the Living Seas Aquarium exhibit at Epcot Center in Florida holds 6 million gallons of water. The contents of the tank are recirculated every four hours at a rate of 25,000 GPM, and the daily inflow is 1,500 gallons. In many ways, this type of closed system is technically feasible for marine aquaculture operations. However, a combination of technical and economic factors constrains the development of these reuse systems for marine aqua- culture applications. The economic situations of a food producer, a recre- ational aquarium, and a fish hatchery are very different. Although techni- cally successful reuse systems are in service, cost-effective technologies applicable to commercial aquaculture still need to be developed (Mayo, 1989). Offshore Systems Use of offshore or "open-ocean" production systems could alleviate many of the institutional, regulatory, and environmental problems associated with coastal marine aquaculture activities by moving them out of the sensitive

136 MARINE AQUACULTURE region of the coastal zone. Achieving such a transformation, however, is dependent on innovations in technology and design that will create econom- ical offshore systems. Furthermore, the issue of the appropriate private use of public waters would not be circumvented by going offshore. Also, it must be kept in mind that a regulatory framework for such operations has yet to be established (see discussion in Chapter 3~. The most crucial factors constraining further development of marine aqua- culture offshore are the capital and operating costs, the safety and efficacy of workers in the offshore environment, and the reliability of systems in the absence of continuous monitoring by personnel. Currently, capital costs would appear to prohibit profitability under most offshore conditions. The systems and materials available are expensive and have limited life in the harsh offshore marine environment. Efforts focused on the design of inno- vative culture systems and the development of low-cost durable materials are essential prerequisites to the economic feasibility of offshore opera- tions. For example, cost-effective materials for marine use are critical to long-term maintenance, increased operating life, and reduced risk. Also essential are the design of either rigid or flexible structural systems, means of confinement, and anchoring systems that can withstand the physical forces of the offshore environment while still protecting the animals. Other criti- cal engineering considerations are animal behavior characteristics related to containment and the effects of wave action (Gowen, 19881. Interest in offshore marine aquaculture has been increasing recently. This interest is evident from two international meetings that have addressed en- gineering for offshore systems. The first meeting was held in October 1990 in Glasgow, Scotland (Institute of Civil Engineers, 1990~. That meeting focused on the engineering problems associated with moving aquaculture operations (predominantly cage culture) from highly protected locations in fjords and estuaries to more exposed sites in the near coastal zone. The second meeting, a workshop held in September 1991 at the East-West Center in Hawaii (NSF, 1991), brought together biologists, engineers, researchers, and practitioners to explore the opportunities of offshore aqua- culture, with particular attention to moving aquaculture operations even further away from protected coastal waters. Although technical problems and economic feasibility present major challenges to offshore operations, there is increasing optimism, based on experience, that aquaculture can be successful in the offshore environment (NSF, 1991~. Recently, interest has been expressed in the possibility of stabilizing atmospheric carbon dioxide (a major contributing factor to projected changes in global climate) through huge open ocean farming of macroalgae (the area needed to absorb significant amounts of atmospheric CO2 is postulated to be slightly more than half the size of the contiguous 48 states) (EPRI, 19901.

ENGINEERING AND RESEARCH 137 Considerable research and technology development will be needed be- fore offshore aquaculture can be commercially successful. The systems dynamics of cages need to be understood so that designs can provide (1) the functional requirements of the species being reared, (2) adequate equipment life and reliability, and (3) economical performance. Innovative confine- ment systems including nonmechanical means such as electrical, sound, and light behavior conditioning need to be developed for finfish along with new approaches to providing support media for shellfish. A broader knowledge base is necessary to facilitate better site selection, determined by considerations of water currents, environmental impacts, and anchoring or mooring requirements. Model and field testing is needed to evaluate com- ponent and systems design. New and improved construction materials and anchoring/mooring systems need to be developed. The potential for artifi- cial upwelling to provide enhanced nutrition in select locations must be evaluated. Underlying these technical and engineering advances, an ex- panded base of biological research is necessary to provide the requisite knowledge of the life history of candidate species, nutrition requirements, fish behavior, controlled reproduction, and ecological impacts. Existing Offshore Structures The use of existing offshore structures could alleviate some of the excessive cost of offshore operations. For example, structures that are built for other purposes, such as offshore oil platforms, can be utilized for shellfish production. Shellfish, clams, and mussels grow in large numbers when attached to such structures. An additional advantage is that these structures are privately owned, and therefore harvest rights can be controlled. One such example is a private firm using oil platforms off the coast of California. Meek (1990) reported that although the Food and Drug Administration (FDA) was concerned about potential sanitation problems from culture in conjunction with oil and gas platforms, studies of the levels of numerous contaminants yielded no evidence of a problem. Finfish cage culture also can be moored on existing offshore structures. In the Gulf of Mexico, experimental production of red drum in cages is based on an offshore oil platform. Existing structures that are available for this kind of multiple use or reuse are limited, of course. Offshore Cage Systems Use of net pens for offshore production could relieve some of the siting concerns associated with net pens in coastal waters but raises a number of technology-related questions. Functionally, offshore cage systems are very similar to nearshore net pens, but they are much more costly with presently available technology. The concept also introduces a whole new range of technical and engineering problems that have to be addressed if offshore cages are to become commercially feasible. An offshore cage must be wave transparent, be designed to withstand the

138 MARINE AQUACULTURE significant energy of the unprotected environment offshore or to be moved from place to place to avoid heavy seas, or be under water. Forster (1990) noted that current models are mostly of the transparent type and cost more than two times the amount of traditional nearshore cages. Innovative research has been under way in California to develop a flexible cage system that enhances water exchange through what has been called "hydrodynamic mariculture" for offshore, in-the-sea cultivation of abalone and macroalgae. By following examples of the successes of agronomic researchers and agricultural engineers, this bioengineering approach to agri- culture could also be applied to U.S. marine aquaculture (Neushal, 1990~. Several cages have been developed internationally for offshore use. No less than 18 trademarked systems for confined rearing of finfish were men- tioned in a recent workshop (NSF, 1991), some of which were reported to be under development for offshore applications and others in commercial operation. A variety of sizes, shapes, and constructions have been used. For example, one type, known as the Japanese "Bridgestone" cage, uses 10- to 16-m-long, 0.4-m-diameter pressurized rubber cylinders to form a flex- ible collar from which a net is suspended (Beveridge, 1987~. The collars may contain 6 to 10 sections, resulting in cages that are up to 50 m in diameter. A French company reported on a vessel-based operation an- chored 3 kilometers (km) from the shore of Monaco (NSF, 19911. Hatchery and juvenile rearing were reported to be conducted on board the vessel, and grow-out was completed in cages in a semiexposed location near Malta. Surplus oil equipment was used in the system to keep capital costs to an affordable minimum. An Irish firm operated a system described as being It consisted of 12 canes, 14 m2 and 15 m deep, for open-ocean use. ~ l suspended in a rigid framework that provided workways and flotation. The unit featured a computerized feeding system. This system was moored by two anchors in the shelter of an island and has not yet been tried in a truly open-ocean environment (Flynn, 19901. The costs of building and operat- ing the structure were high. Designs for fixed structures that move with the waves (i.e., up and down on a system of poles) or are submerged beneath the waves (Clarke and Beveridge, 1989) have been tested. A Canadian firm has tested a German spherical cage design (the Kiel cage) and is developing a design that can be fabricated in sizes from 12 to 30 m in diameter (NSF, 1991~. The cage can be submerged to avoid heavy seas, and thereby reduce both mechanical stress and stress to fish, and to reduce interference with others. The spheri- cal shape allows easy rotation for repair, maintenance, and harvesting by use of a set of internal nets. Experimental cylindrical submerged cages have been used in the Caribbean, and other mechanical means of raising and lowering various cage designs have been tried in Canada and Spain (Fish Farming International, 19901.

ENGINEERING AND RESEARCH 139 Artificial Reefs Artificial reefs can provide a good environment for both finfish and shellfish. Reefs have been designed and used to enhance natural production, to provide a focal point for stock enhancement, and to provide an attachment point for aquaculture operations. Reefs that have been de- signed for purposes not directly related to fisheries also attract fish. Other primary uses of reefs include control of beach erosion; provision of recre- ational diving sites; and disposal of municipal wastes, scrap, and solid waste. Reef systems, therefore, can be classified either as structures constructed specifically for the purpose of fisheries enhancement or as structures built for other purposes that also attract fish. Reefs constructed for fisheries enhancement efforts are usually located in public waters. Because they are publicly owned waters, assigning harvest rights is difficult; as a result, public reefs offer little to the aquaculture entrepreneur in the United States. Artificial reefs are being explored outside the United States both as a medium for increasing commercial fisheries and for their potential use in aquaculture activities (Fabi et al., 1989; Grove et al., 19891. Fabi et al. (1989) demonstrated potential for rope culture of bivalve shellfish in asso- ciation with artificial reefs in areas outside those normally used for shellfish culture. On a larger scale, Grove et al. (1989) describe a "marine ranch" in Japan consisting of artificial reefs, feeding and support stations, and on- shore hatchery and nursery rearing of fish that are then released into the area after they have been trained or conditioned to respond to acoustic signals for feeding. Use of Deep Ocean Water One futuristic system that could operate either onshore or offshore involves the coupling of marine aquaculture operations with ocean thermal energy conversion (OTEC) projects that are currently being engineered and tested (ECOR, 1989~. Cold nutrient- rich deep ocean water is pumped up from below an OTEC facility for energy conversion and then passed through an onshore culture system, allowing the growth of various plant species, finfish, crustaceans, or mollusks. In addition, the use of cold water from the deep ocean offers the potential for cultivation of cold water species in tropical climates. Thermal power plants sited in the marine environment often use sea- water for thermal cooling, thus producing and discharging large quantities of heated water. Use of this water for marine aquaculture is being practiced in Europe and the United States for certain site-specific applications. This arrangement has limitations, however. The water may be too warm, or the "plumbing" may not be suitable. Moreover, power plants are subject to shutdowns, which cause fluctuations in temperature a condition that gen- erally precludes aquaculture. A system in operation in Hawaii does not use the cold water for energy conversion, but instead provides the water directly for cultivation of cold

140 MARINE AQUACULTURE Microalgae production facility (Cyanotec) located on the OTEC facility in Kona, Hawaii. water species. The system was funded by the state and is used for develop- ment of new technologies and culture systems. This aquaculture park, as it is called, has umbrella permits for effluents, land use, and other require- ments, and thus allows for a streamlined approach to efforts to develop new species, technologies, and culture systems. Another system designed for use in Japan similarly utilizes the nutrient-rich deep ocean waters (ECOR, 1989). Harvest and Postharvest Technology Advances in harvest and postharvest technology can have significant positive impact on the commercial success of marine aquaculture through associated benefits such as: . increased shelf life of fish products; · diversification or increase in range of marketable products; control and monitoring of the quality and safety of products; and reduction in labor costs. Technological approaches can help marine aquaculture to provide high- quality, safe products, as well as enable more efficient, economical, and adaptable marketing strategies. Most of the needs discussed below require the modification or improvement of an existing technology or the transfer of a technology successfully used in another industry. It should be noted

ENGINEERING AND RESEARCH 141 that most aspects of preprocessing, processing, packaging, and transport to market apply not only to marine aquaculture but to freshwater aquaculture and wild-caught fish as well. Harvest Innovative harvest technology can contribute to improved product qual- ity, increased yield, and reduced labor costs. In some situations, environ- mental benefits also can be realized, such as the elimination of escapement. The development of methods to distinguish male from female salmon in order to harvest each at the most appropriate time is an example of using technology to increase yield. The male salmon ideally would be harvested earlier than the female, but no technology exists for distinguishing between them nondestructively, quickly, and economically. Such technology would be advantageous for other species as well. Product quality can be enhanced by the development of rapid and accu- rate quality testing methods (e.g., disease identification and detection of - 1\ ~ 1 ~ Power reel and seine used to harvest fish from earthen ponds. 1 ~

42 MARINE AQUACULTURE heavy metals or human pathogens). In Alaska, development of the shellfish industry has been hampered by the lack of such quality testing technology for naturally occurring toxins. Once developed, the technology would serve other shellfish producers as well. The cost of shrimp harvest could be reduced by improved seining (har- vesting by net) equipment that would decrease labor requirements and po- tentially provide for size selection as well. Similarly, improved technology to harvest shellfish mechanically could reduce labor costs and also reduce environmental impacts. Mechanization of the harvest of finfish can benefit producers also. In addition to reducing cost, technology can help minimize the stress to fish during harvest and thereby maintain the quality of the product. Preprocessing A fundamental objective of aquaculture is to provide nutritious, high- quality seafood. To meet this objective, postharvest technologies and meth- odologies are needed that will ensure the preservation of quality. Higher product quality could be realized if economical means that are available for rapid precooling and for cooling and holding other food products were applied to the fish and shellfish industry. For example, during warm weather, up to two days can be required to properly cool oysters in a truck. This slow cooling results in significant quality loss. Better methods exist for cooling and holding or bagging oysters, but the cost of these systems typi- cally is too high for commercial application. A significant loss of product is common when finfish are eviscerated. For example, the recovery rate for gutted salmon with the head is 87-88 percent, and without the head 71 percent, leaving potential by-products that could be used as new products such as fish or livestock feed. The opportunity already exists for efficient and economical use of by-products to minimize waste and increase product yield. The shelf life of fish products could be improved by surface sterilization methods (e.g., disinfectant dip or irradiation) that reduce microbial load on the surface of seafood. The surfaces of fish that have been cut, such as product made into fillets, or of peeled shrimp, can have a large microbial load due to exposure and handling. Some foreign companies allow low- dosage irradiation in order to kill microorganisms on the surface. The use of irradiation for this application has not been approved in the United States, but it is approved for other products such as spices and potatoes (to prevent sprouting). Current technologies for peeling and deveining shrimp are detrimental to both the quality and the yield of shrimp. Improved mechanical methods of shucking shellfish and of peeling and deveining shrimp can reduce labor

ENGINEERING AND RESEARCH 143 costs and possibly increase yield. The mechanical peeling method uses a great deal of water. Consequently, quality is reduced as soluble proteins and flavor are leached from the flesh; yield (meat) is lost; and significant levels of water effluent are discharged to the environment. Mechanical methods for shucking shellfish are used, but only on those that are to be cooked. Other methods have been used experimentally for shucking (e.g., high-pressure steam), but they are not very effective. Methods also are needed for sizing and grading to ensure uniform fish tailored for specific markets (e.g., white tablecloth restaurants want specific sizes and shapes). Processing and Packaging The primary objectives of processing and packaging are the preservation of quality and the extension of shelf life. Many traditional methods of preservation could be improved through technical advancement. Salt, sugar, and pH could be lowered, for example. Shelf life can be increased by controlling the gas content in the package using modified atmosphere and controlled atmosphere packaging (MAP/CAP). In addition to ensuring longer shelf life, technology can contribute to increased yield and improved market appeal; product losses or deterioration due to dehydration and drip- ping can be minimized with the right combination of materials, gases, and temperature control. Packaging and labeling of fish as an aquaculture product can enable consumers to identify the product. Aquaculture producers have a greater ability to control the environment and inputs for their product than do wild fish producers, so they have the capacity to ensure consistency in product quality and safety through differentiation in packaging and labeling. The opportunity also exists for development of new products, new product forms (i.e., salmon sold as pan-size fish), and value-added products (e.g., smoked fish). Transport to Market Proper transport of fish and fish products is critical to achieving high- quality product. More precise temperature and time controls are needed to maintain quality and improve shelf life of seafood. To maximize the shelf life, refrigeration at low temperatures is necessary because temperature rise can cause significant loss of quality. Refrigerated trucks and temperature monitoring and control devices are available but are not used consistently in many segments of the aquaculture industry because of their costs. Enforced standards for transport may encourage better use of this technology. Many consumers in the United States prefer to buy live fish and crusta- ceans and are willing to pay a premium if the fish arrive at the market in

144 MARINE AQUACULTURE good condition. Technologies for feeding, aeration, and maintaining water quality would facilitate live transport to domestic and international markets. The Chinese have developed methods of transport that allow them to ship live fish to Japan by boat, taking three weeks, with a survival rate compa- rable to an overnight air shipment from the United States. Japanese re- searchers have also developed technology to ship live animals to Japan from other countries: live shrimp are shipped in wet sawdust, and acu- punctured fish are reported to be shipped live from New Zealand and Australia (Thompson, 19921. Live transport by ship could help the U.S. producer compete with foreign producers. OTHER RESEARCH AND ENGINEERING OPPORTUNITIES Marine Fisheries Enhancement Advances in a number of technological areas would benefit both public stock enhancement and private ocean ranching. For example, improved hatchery techniques for production of red drum, striped bass, oysters, scal- lops, and other species would contribute to the success of marine fisheries enhancement of endangered and threatened species for recreational and commercial fisheries in the Gulf of Mexico, the central and south Atlantic, San Francisco Bay, and along the Atlantic and Gulf coasts. A number of other species could benefit from the development of new hatchery produc- tion techniques. Candidate species include haddock, halibut, codfish, red snapper, flounder, snook, and tarpon. Water reuse systems have particular significance for private ocean ranching of salmon, where the production of smelts requires large quantities of fresh water of appropriate quality and temperature. Such water supplies are limited and generally already committed to other uses. Where adequate water supplies are available, they often are not well located for effective management of the return and harvest of adults. An ideal release site would be one where no other salmon runs exist nearby and where harvest in the ocean can be managed in an appropriate manner (Bevin, 19881. An effec- tive water reuse technology system would make it possible to rear and release salmon with small, isolated water supplies or, possibly, on the margin of the normal range of salmon streams. Improved understanding is necessary to establish the biological design criteria and the biological behavior of species for which ocean ranching and stock enhancement are viable. Improvements in hatchery design and development must be based on an understanding of reproduction physiology and juvenile nutrition that is presently lacking for many candidate species. Research is needed, too, on the straying of released juveniles and returning adults. The relationship between hatchery and release strategies and the

ENGINEERING AND RESEARCH 145 rate of straying is not well understood. Furthermore, the impact of straying on the genetic diversity of wild stocks has not been adequately quantified. An improved system of marking hatchery fish that are released for en- hancement and ocean ranching (akin to branding cattle) also would benefit marine fisheries management. Although technology is available to mark (or tag) small fish released into the ocean, current techniques are labor inten- sive and costly. In addition, the procedure for recognizing and reading the mark (i.e., coded wire or nose tag) when the adult fish are harvested, is costly and subject to uncertainty. Most current marking systems, whether tags attached to the shell of a mollusk or a wire implant for a fish, are used on only a small proportion or sample of the animals released. The labor requirements for obtaining and processing the data from returns result in a long time lag after harvesting before the information is available. Conse- quently, this information can be used only to evaluate what happened last week or last year and does not provide data in "real time" to assist in distinguishing between natural and hatchery-produced stocks for the purposes of fishery management. Passive integrated transponder tags have the potential to be miniaturized and produced at a reasonable cost. In situations where fish from public hatcheries, private ocean ranching, and natural spawns are being harvested in the same waters (e.g., coastal Oregon), harvest managers often have to decide whether to manage for the natural fishery (i.e., allow very low harvest) or to allow a higher harvest and risk unacceptable losses without knowing what fish are being caught. Because the time frame in which the harvest takes place is often 24 hours or less, a manager cannot postpone decisions until small, hard-to-extract wire tags are located and read. Ideally, a mark should be easy to impose, easy to recognize on the harvested fish, easy to read without expensive special equipment or major effort, and it should not diminish the chances of the individual fish's survival (Sedgwick, 1982~. Cost allocation and recovery are also of special concern to those engaged in private marine fisheries enhancement. These concerns raise one of the most fundamental issues of ocean harvest—who owns the fish (Keen, 1988~. A number of schemes have been suggested, including the idea of charging private "enhancers" for the use of ocean ranges while charging fishermen a tax on any privately produced fish or shellfish harvested. In addition, some suggest a need for compensation based on the straying of certain finfish such as salmon. All fishery stocks that are released can be expected to have some straying of individuals from their acclimatization sites, whether they have been produced naturally or in a hatchery (Mayo, 1989~. Quantifica- tion of the degree of straying would be useful in defining damages, but sufficient and reliable data are not available at this time. The availability of a system for providing visible marks, as defined above, could alleviate

146 MARINE AQUACULTURE some of the concerns surrounding harvest management, cost allocation, and straying. Stock enhancement in a variety of forms appears to have been helpful in sustaining and rebuilding populations of salmonids, striped bass, red drum, oysters, clams, scallops, and perhaps other species in the marine environ- ment. Nevertheless, the fact is that not all enhancement efforts are success- ful; historically, most have not been. Lack of success generally has been due either to poorly conceived and executed programs that target species whose biology makes them unsuitable candidates or to the lack of fully developed culture technology. Broodstock Domestication The utilization of wild broodstock is necessary at the initiation of a marine aquaculture operation. Consequently, continued access to public stocks of fish for brood animals is essential at the present time for several species. The use of wild broodstock to support commercial operations will probably not be acceptable for the long term because of the shortage of such stock and opposition from sports or commercial fishermen. Advantages from breeding domesticated stocks and making genetic improvements in- clude increased disease resistance and accelerated growth, maturation, and reproduction. The availability and predictability of access to wild broodstock are seri- ous concerns that should decrease in importance as domesticated stocks are established. Marine aquaculture cannot develop into a truly commercial industry until it is free of dependence on wild stocks for its supply of brood animals. This has occurred to date for very few, if any, marine animals (Pacific oysters, hard clams, and Atlantic salmon, to some degree), and true domestication may take decades or more to achieve. The domestication of agricultural crops and animals has taken place over hundreds of years; at- tempts to domesticate marine aquatic organisms have been under way for only about 20 years at most. In California, producers of striped bass and white sturgeon depend on access to wild fish for spawning. Although the California broodstock col- lection program was intended to last only 5 years, it now appears that 10 years or more may be necesary before the industry can rely on its own spawning stock (California Department of Fish and Game, 19891. Produc- ers are anxious to develop domestic broodstock to end their dependency on public agencies for permits and to be able to implement genetic improve- ments. Recent spawning success with some domestically reared sturgeon . ~ . . gives reason for optimism. The process of establishing founder populations for broodstock and initiating the domestication of a species requires careful attention to the

ENGINEERING AND RESEARCH 147 fundamentals of breeding and a long-term commitment of people, facilities, and funding (Doyle, 1983; Gjerdem, 1983; Kinghorn, 1983; Lester, 1983; Refstie, 1990~. Systems have to be developed for the long-term husbandry, selection, and special requirements of each broodstock, with precaution to include escape-proof features to allay concerns over genetic impacts of escapees on wild stocks. Broodstock domestication for the future is likely to include a wide range of species. Finfish species for which broodstock domestication is im- perative include striped bass and its hybrids, Pacific salmon, sturgeon, red drum, dolphin, snapper, grouper, and flounder for food fish, as well as ornamentals. The shellfish species include penaeid shrimp, clams, and oys- ters (particularly for disease resistance). Biotechnology and Genetic Engineering Production of Improved Strains The United States has been the leader in the development of transgenic species (species carrying introduced genes) for culture purposes. Transgenic organisms may possess a variety of potential advantages including increased growth rates, disease resistance, decreased aggression, sterile progeny, in- creased tolerance of temperature, or other environmental conditions, and improved market characteristics. According to Kapuscinski and Hallerman (199Oa), a total of 14 species of transgenic fish had been produced as of July 1989. Other countries are already making use of the (largely American) tech- niques of transgenic production. In the United States, advances in this area await the establishment and implementation of a regulatory system that provides for the use of transgenic organisms in aquaculture (Hallerman and Kapuscinski, 1990; Kapuscinski and Hallerman, l990b). Kapuscinski and Hallerman (199Ob) point out that the introduction of nonnative genes into fish is likely to affect nontarget traits as well and that the phenotypic performance of transgenic fish is virtually unknown. This is in large part due to regulatory constraints on the release of transgenic fish into outdoor production systems for cultural trials. Further, Tiedje et al. (1989) note that uncontrolled introduction of transgenic fish into natural aquatic communities should not be allowed because their ecological impacts are entirely unknown. Thus, Kapuscinski and Hallerman (199Ob) recom- mend that the American Fisheries Society take the following positions with regard to transgenic fish: 1. Support research in such areas as "phenotypic characterization of trans- genic lines, evaluation of the performance of transgenic lines, improvement

148 — —1 ~ _ _, MARINE AQUACULTURE of sterilization techniques, and development of ecological risk assessment models and protocols" to provide data for rational policy decisions. 2. Advocate caution in the use of transgenic fish. No introductions of transgenic fish into production-scale aquaculture facilities should be al- lowed until risk assessments and demonstrations of little possibility of envi- ronmental impact have been completed. Further, "stockings of transgenic fishes into natural waters should be barred unless and until a body of re- search strongly indicates the merits of and ensures the ecological safety of stocking a particular transgenic fish into a particular receiving natural system." 3. Advocate regulations improving the comprehensiveness of the Coor- dinated Framework (National Institutes of Health (NIH) and U.S. Depart- ment of Agriculture (USDA) guidelines) in the United States. This recom- mendation would require that all production of transgenic species to take place under NIH guidelines and would establish mandatory federal regulatory review and authority over proposed releases and transport of transgenic fish. The application of selected or directed breeding to aquatic organisms has been reviewed by a variety of authors (e.g., Doyle, 1983; Gjerdem, 1983; Lannan and Kapuscinski, 1986; Shultz, 1986; Gall, 19901. Breeding pro- grams in aquaculture are generally in their infancy, but efforts have been initiated in a number of groups, especially finfish: Atlantic salmon (Friars et al., 1990; Refstie, 19901; and coho salmon (Hershberger et al., 19904. Selective breeding of mollusks has been limited principally to bivalves (Purdom, 1987; Wada, 19871. Hybridization and polyploidy may produce culture-adapted strains. Hy- bridization has been documented among salmonids (for review, see Chevassus, 1979, 1983) and several groups of algae (Sanbonsuga and Neuschal, 1977, 1978; Cain, 1979; Guiry, 1984~. Another biotechnical op- tion with potential for aquaculture is the production of monosex populations (Purdom, 1983; Yamazaki, 1983; Billard, 19871. Gynogenetic or androge- netic (all female or all male) offspring can be produced, resulting in non- reproducing populations. A drawback is that the population may lack vigor due to inbreeding (Thorgaard, 1986~. Clearly, the United States has sufficient capabilties to make substantial progress in the areas of biotechnology and genetic engineering for aquacul- ture. Discussions among leading researchers suggest that application and adaptation of such technologies in the culture of marine species could be expected to result in numerous advances in marine aquaculture, including the following: · accelerated growth and maturation of brood animals via ploidy manipu- lation, gene insertion, hormonal treatment, or other methods;

ENGINEERING AND RESEARCH 149 · improved culture characteristics (growth, food conversion efficiency, body composition, disease resistance, fecundity, hardiness, etc.) via selec- tive breeding, hybridization, ploidy or sex manipulations, or transgenic techniques; · production of 100 percent sterile organisms for commercial grow-out on farms or in pens, while reproductively competent organisms serve as brood stock; · use of mitochondrial DNA methods or other analyses to detect low- level genetic change in cultured stocks to permit assessments of potential impacts of released hatchery animals on wild populations; and · insertion of genes coding for particularly desirable traits (e.g., homing in salmon) into other species of cultured or "sea-ranched" animals. Hedgecock and Malecha (1990) conclude that "it is very unlikely that genetic engineering by direct genomic intervention and modification will contribute to shrimp and prawn aquaculture in the next decade," due to the lack of basic knowledge of genes that affect production characteristics and of methods for inserting these genes into crustaceans. Biotechnology is more likely to be employed as a tool in more traditional programs, espe- cially for establishing genetic markers, manipulating gametes via cryopre- servation and chromosome number, and controlling sex. Disease Assessment and Treatment Disease Diagnosis The development of diagnostic tests has been identified as one of the principal means of improving aquaculture productivity (Ratafia and Purinton, 1989~. Rapid, accurate, and inexpensive techniques for disease assessment and certification for marine organisms in culture are essential prerequisites to screening large numbers of fry, fingerlings, postlarvae, or spat rapidly for certain critical diseases. Biotechnical methods, when applied to marine aquaculture, should allow the establishment of meaningful, effective state and national disease certification programs, which are critical for advance- ment of the industry. Some types of diagnostic tools have improved markedly in recent years, and further advances are likely. Isoelectric focusing (Shaklee and Keenan, 1986) and mitochondrial DNA analyses (Brown and Wolfinbarger, 1989; Palva et al., 1989; Reeb and Avise, 1990) permit detailed analyses of fish and shellfish stocks and detection of minute genetic differences, sometimes even within a limited geographic area. Fatty acid composition analysis provides another way by which wild aquatic organisms can be differentiated from cultured individuals of the same species. This effectively eliminates

150 MARINE AQUACULTURE the possibility of poaching protected wild stocks for sale as aquaculture products. Therapeutics Disease treatment represents another as yet underdeveloped research area. Currently, only six chemotherapeutics are approved for aquaculture use by the Environmental Protection Agency (EPA) and the FDA. Seven other chemicals, either EPA approved for aquaculture uses and exempt from FDA registration or exempt from EPA registration entirely, are also being used as chemotherapeutics (for review, see Williams and Lightner, 1988~. The most comon approach to the administration of antibiotics and other therapeutic agents is immersion (osmotic), injection, or oral intake with feed (DeCrew, 1972; Strasdine and McBride, 1979; Austin et al., 1981; Marking et al., 19881. Few vaccines have been developed for aquaculture use. Immunization against Vibrio spp. and related bacteria genera has been practiced among finfish culturists for several years, with treatment by immersion or intraperitoneal injection (Cipriano et al., 1983; Schiewe et al., 1988~. Similar methods of immunization are now being explored for shrimp (Itami et al., 19891. Experimental work also has been conducted on the use of gelatin capsule implants for some antibiotics (Strasdine and McBride, 1979) and on various types of water treatment, including ozonation (Wedemeyer et al., 1978; Tipping, 1 987), ultraviolet irradiation, and chlorination (Bedell, 1 97 1; Sanders et al., 19721. Formal actions by the U.S. Fish and Wildlife Service and the USDA have ensured that federal and state animal scientists, the pharmaceutical industry, and the USDA collaborate on determining needs and developing research protocols for aquaculture-related drugs, which fall under the category of minor-use animal drugs (Schmick, 1988~. As the above discussion suggests, the need and potential for improve- ments in disease treatment are substantial. The development of medications and immunizations is badly needed, as are improved delivery systems for antibiotics that will not result in the release of antibiotics to the rearing waters. The cost of obtaining FDA approval is a major barrier, however. SUMMARY Advances in technology and an improved understanding of the biology of relevant species are essential for marine aquaculture to overcome many of the major constraints on future development. Some new and improved technologies would solve specific technical problems directly and thereby improve economic feasibility; other technologies would alleviate environ- mental concerns and diminish conflicts with other coastal zone activities.

ENGINEERING AND RESEARCH 151 Many of the technical constraints on marine aquaculture can be reduced or eliminated by developing new and improved onshore and nearshore sys- tems; developing new and improved auxiliary systems; and establishing the biological, ecological, and engineering knowledge base required for making sound decisions. NOTE 1. The term cages and pens have been defined by Beveridge, 1987 as follows: cages are enclosed on the bottom as well as the sides, typically by mesh or net screens, whereas the bottom of pens is formed by the seabed. REFERENCES Aase, H. 1985. Effect of the use of flow developers in fish-rearing cages for salmon, Fisherdirektoratets, Havforskningsinstitutt, Bergen, Norway. Alabaster, John S. 1982. Report of the EIFAC Workshop on Fish-Farm Effluents. EIFAC Technical Paper No. 41. European Inland Fisheries Advisory Commis- sion, FAG. 186 pp. Arnold, C.R., B. Reid, and B. Brawner. 1990. High density recirculating grow out systems. Pp. 182-184 in Red Drum Aquaculture. University of Texas, Austin, TAMU-SG-90-603. Austin, B., D.A. Morgan, and D.J. Alderman. 1981. Comparison of antimicrobial agents for control of vibriosis in marine fish. Aquaculture 26:1-12. Balchen, J.G. 1987. Bridging the gap between aquaculture and the information sciences. In Automation and Data Processing in Aquaculture, J.G. Balchen and A. Tysso, eds. IFAC Proceedings 1987. No. 9. Pergamon Press. Bedell, G.W. 1971. Eradicating Cerotomyxa Shasta from infected water by chlori- nation and ultraviolet irradiation. Prog. Fish-Culturist 33:51-54. Beveridge, M.C.M. 1987. Cage Aquaculture. Farnham, England: Fishing News Books, Ltd. 332 pp. Bevin, D. 1988. Problems of managing mixed-stock salmon fisheries. In Salmon Production, Management, and Allocation Biological, Economic and Policy Is- sues, William J. McNeil, ed. Oregon State University Press. Biedenback, J.M., L.L. Smith, T.K. Thomsen, and A.L. Lawrence. 1989. Use of the nematode Panagrellus redivivus as an Artemia replacement in a larval penaeid diet. Journal of the World Aquaculture Society 20~21:61-71. Billard, R. 1987. The control of fish reproduction in aquaculture. Pp. 309-305 in Realism in Aquaculture: Achievements, Constraints, Perspectives, M. Bilio, H. Rosenthal, and C. Sindermann, eds. Breden, Belgium: European Aquaculture Society. Bromley, P.J., and P.A. Sykes. 1985. Weaning diets for turbot (Scophthalmus maximus L.), sole (Solea solea) and cod (Gadus morhua L.) Pp. 191-211 in Nutrition and Feeding in Fish, C.B. Cowery, A.M. Mackie, and J.G. Bell, eds. New York: Academic Press. Brown, B.L., and L. Wolfinbarger. 1989. Mitochondrial restriction enzyme screen-

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