Choice of Species and Diversification

Each (European) country or region is unique in a biogeographic sense and taking into account the naturally occurring species, the available aquatic resources and local topography, it is possible to cultivate only certain species using the existing farming technologies.

For example, Atlantic salmon occur in temperate to arctic regions, with optimum temperatures for growth at sea in the range 15-18 ºC, and have both a freshwater and marine phase in their life history. In contrast, sea bass and sea bream are entirely marine but require temperatures in excess of 20 ºC for growth. Consequently, salmon aquaculture is largely confined to northern Europe (Norway, Scotland and Ireland) while sea bass and sea bream aquaculture is focussed on the Mediterranean.

Thus, there is a limitation on the range of species that can normally be reared in any given location. Nevertheless, many countries attempt to diversify their aquaculture production to new species and to extend aquaculture activities to all available aquatic resources. Many people believe that such diversification confers greater stability and security to the aquaculture industry. In reality, however, the diversification options open may be naturally restricted by a series of factors:

- Inadequate scientific knowledge of the species - Biological requirements compared to ambient conditions/technologies
- Regulatory control on the introduction of exotic species
- Markets and financial viability

Inadequate scientific knowledge of the species: In several cases, the biology (in the wild) of highly valued species is virtually unknown, therefore, considerable scientific research must be undertaken before the culture of the animal can be undertaken. In many instances, researchers have short-circuited this process by rearing wild caught juveniles. As a long-term activity, this is not recommended, as it may be detrimental to natural stocks and thus no longer occurs in the major European farmed species.

Biological requirements compared to ambient conditions/technologies: Do the necessary aquatic conditions exist and are the relevant rearing technologies available that will recreate the conditions that are required by the stock for growth and completing their life history? For example, with many marine fish species, there are significant difficulties in nurturing the larvae through early life (post-hatching) to give adequate numbers of viable juveniles.

Regulatory control on the introduction of exotic species: This issue is of growing importance in Europe. It is now recommended that only native (local) species should be cultured in a region. This is an effort to prevent the translocation of exotic species and associated pathogens that may give rise to specific ecological problems in the future. In practical terms, this would imply that the (existing) culture of Pacific oyster and Japanese abalone would now not be permitted. Currently, the importation of species from other continents that could be cultured in Europe e.g. hybrid striped bass, is actively prohibited. Even within Europe, the movements of stocks from one region to another is strictly governed by EU regulations.

Markets and financial viability: This, in many respects, is probably the most important consideration as it is on this basis that entrepreneurs make their decision to invest funds. It is apparent that the harvested produce must attract an adequate price to justify undertaking the business and yield positive financial returns. Examining the range of cultured species, it should be noted that, in general, extensive culture methods are most often used for lower valued species (e.g. mussels) while higher valued species merit a higher level of investment since it is presumed that the margin (and profits) will be greater. The market price of wild supplies and the cost of production are extremely important in the business decision. For many years, the technologies to rear cod were well known, but until recently, the cost of production exceeded the market price for wild caught cod. With falling wild cod stocks, this situation has altered in the past 5 years and cod farming is now emerging as a viable proposition. Similarly, the cost structures of competitors in various locations is important as the market will favour those with lowest cost of production.

It is the interaction of these four elements that dictate the composition, size and status of the aquaculture industry in any country. In conclusion, the pace of technological innovation is a critical factor for the development of European aquaculture. The 1990's have seen a considerable increase in the use of technology on farms, and an increased mechanisation of farm operations. Among these trends has been the emergence and development of recirculation systems, where water is treated and re-used. These systems are unique in that they are virtually closed systems, lacking direct contact with the ambient environment, and rearing conditions can be controlled and monitored to desired levels. In effect, recirculation systems can circumvent many of the limiting factors outlined above - with the exception of financial viability.