7.2 THE FUTURE

The increasing demand for seafood, including bivalves, will undoubtedly continue in the future and production will need to be increased to meet this demand. Supply is unlikely to increase significantly from traditional bivalve fisheries since most natural stocks are being harvested at or near maximum rates. Any significant increases in supply will likely come from aquaculture. Indeed, the present goal of many culture operations is to restore populations to levels that existed prior to over-harvesting. Future culture operations will need to be as efficient as possible, not only for reasons of economical viability, but to make optimum use of production areas that will come under ever increasing pressure from human activities and may even be reduced as human populations continue to increase.

Any future increases in bivalve production will require an increase in seed supply that must be reliable, plentiful and inexpensive. Collection of juveniles from natural sets will continue to be important but such areas are limited. Major increases in seed supply will be from hatcheries. There are added advantages in producing seed in hatcheries over the collection of natural sets including reliability, the capability to supply to meet demand and the ability to provide seed of selected strains, along with seed of exotic species.
Continuing research and development will improve hatchery technology and make them more efficient and hence more profitable. There are many areas where research is needed and some have already been mentioned in the text.

Improvements in nutrition are needed to produce healthy larvae that will metamorphose into healthy spat and can be grown quickly and economically to market size. Producing algae to feed the larvae and juveniles is a major cost in operating a hatchery. This expense could be greatly reduced if artificial diets of equal nutritional value to the best algal species could be formulated. Studies have been made but to date, although progress has been made, a satisfactory product is not available for sale. One of the obstacles is the size of market for such products which, at this time, is not large enough to attract investment in development by the major feed manufacturers.
For bivalve aquaculture to fully achieve its potential it must follow the methods of agriculture. This will require extensive research programmes for all phases of production. One of the most important fields for future research already discussed in section 7.1 is genetics where perhaps the greatest gain will be from the development of strains and varieties of bivalves that are suited to particular environments. This requires extensive research in the selection of brood-lines. Once stains are established they can only effectively be maintained by breeding them in hatcheries. A major goal for hatcheries will be to improve technology so that seed from such strains can be supplied to growers on demand and as inexpensively as possible.
Some developments in the field of genetics such as the production of triploid oysters have already been of major benefit to the industry, particularly the oyster industry on the west coast of North America. Continued improvements in polyploidy will ensure that a reliable supply of triploid seed of any desired bivalve species is available to industry.

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Figure 110: A – a device for exerting pressure on eggs to prevent chromosomal reduction through the suppression of meiosis. B – experiments in the cryopreservation of bivalve gametes and larvae.
Developments in cryopreservation technology for male and female gametes and even larvae will be of great benefit to hatcheries since gametes could be obtained when adults are in prime condition and stored for future use. Space and time needed to condition adults and the requirement to produce large quantities of food to keep adults in prime breeding condition could all be eliminated. Fertilization of thawed gametes could be effected in a short time period whenever desired. Progress has been made in this field but at present it is costly and beyond the scope of hatcheries to utilize the technology in-house (Figure 110B).
Siting of hatcheries will assume greater importance in the future. The advent and success of remote setting methods demonstrates that hatcheries do not need to be situated close to growout operations. With modern trade networks they can be located where ideal conditions exist to rear larvae and juveniles and then be transported over great distances to growout sites with virtually 100% survival. A case in point is provided by the practice of some hatcheries in the State of Washington in the USA. They have transferred part of their hatchery operations to Hawaii where a source of nutrient rich water requiring little if any heating is available year round. The abundant sunshine in Hawaii is used to culture algae. It is cheaper to transport mature larvae and juveniles from Hawaii to Washington State than it is to heat water and grow algae there.
Large hatcheries with highly trained staff can be operated efficiently and produce seed more economically than smaller ones. Economies of scale apply. If hatcheries are equipped with quarantine facilities they can produce seed of any commercially valuable species from any part of the world without major risk of introducing exotics to the local environment. Since larvae are generally cultured in water filtered to 1 ?m, which could be treated with UV-light or ozone, the danger of transferring pests, parasites and diseases from one area to another is greatly reduced. This applies to the shipping of eyed larvae compared to shipping juveniles that have been exposed to the open environment in the area of origin.
Large hatcheries could supply metamorphically competent larvae of any bivalve species anywhere it is needed in the world. This is the practice that agriculture has adopted. Seed required in many growing operations is often produced at great distances from where it is eventually planted. Similarly, many juvenile animals are often not produced where they are eventually raised.
It is necessary to get over a parochial attitude in bivalve culture and realize that the industry exists in a global economy. It is no longer essential for every area or even every country to have a bivalve hatchery to supply seed needed to meet local growout requirements. One well-placed, well equipped and well staffed hatchery can supply the seed requirements for many culture operations in many different parts of the world.
A possible major problem for hatcheries will be diseases as it is when any organism is mass cultured intensively. Future research needs to include the development of methods to control diseases in hatcheries so as to minimize instances of mass mortalities caused by either obligate or opportunistic pathogens. Results of genetic research are likely to be of value in selecting strains of bivalves that are more resistant to disease. Research is also required to develop inexpensive and effective treatments should diseases occur in a hatchery situation.
Future bivalve landings will undoubtedly continue to increase to meet the demands of an ever increasing human population. Most of this increase in production will be from culture operations and this will require the availability of large quantities of juveniles (seed) to meet culture demands. While collection of seed from natural sources will remain important, most of the seed needed for increased production will be from hatcheries. This is particularly true as the industry begins to demand strains or races of bivalves that are developed to grow in specific areas. Hatcheries will eventually become the mainstay of seed production for bivalve growout operations. In the future every effort must be made to improve hatchery technology to enable them to supply an abundant, reliable and inexpensive supply of juvenile bivalves for the culture industry.