Fish health management in aquaculture
Epizootic Ulcerative Syndrome (EUS) affected snakehead (Channasp.) fish
Aquaculture is the fastest growing food production sector in the world and provides a significant supplement to, and substitute for, wild fish and plants. However, disease has become a primary constraint to aquaculture growth and is now responsible for the severe impact on both the economic and socio-economic development in many countries of the world. Addressing health questions with both pro-active and reactive programmes has therefore become an urgent requirement for sustaining the growth of aquatic animal food production.
A multitude of factors has contributed to the health problems currently faced by aquaculture. Over the past three decades, aquaculture has expanded, intensified, and diversified, based heavily on movements of animals and animal products such as broodstock, seed, and feed. Such movements are now clearly recognized as having played a pivotal role in the introduction and spread of pathogens and disease into aquaculture systems.
Impacts of diseases
The impacts of many such transboundary disease movements extend beyond direct mortalities and production losses - they are particularly hard-felt by small-scale farmers, who represent the backbone of many rural communities in developed as well as developing countries. Aquaculture losses in these situations directly threaten the livelihoods of whole communities through reduction in food availability, loss of income and employment, with all the associated social consequences.
In addition to the emergence of new diseases, and their potential establishment in new areas and wild populations, the irresponsible use of chemical disinfectants and antibiotics is also increasingly recognized as having potential environmental impacts. Furthermore, intensive culture practices with poorly controlled feed use and waste production have adversely affected local environments. Since good water quality is paramount to optimum health and production in aquaculture, such adverse effects are beginning to provoke increased scrutiny, and there is now a growing appreciation of the need to develop, sustain and publicize better husbandry practices. A good example is the reduction of antibiotic use in Norwegian salmon production, as vaccine production became the favoured practice for control of bacterial and viral diseases.
Effective health management
An effective health management programme must cover all levels of aquaculture activity, from the production unit (pond, tank, cage, etc.), farm, district/local or zone levels, to the national and regional/international level. The success of such a broad-ranging programme relies on the constant open communication and information exchange flowing in all directions.
Mass mortality of freshwater fish due to water pollution
Formulators of an effective health management programme will always be confronted with a wide range of problems concerning:
Other challenges to effective health management programmes lie in the demonstration of its benefits to the farmer and other 'fish links' involved in production, trade and use of aquatic resources (such as anglers and ornamental hobbyists). In order to secure cooperation and support of programmes aimed at prevention and control of aquatic diseases, all parties must be convinced that benefits (in terms of socio-economics, environmental health, etc.) will result from compliance with such programmes and achieve clean health status.
Diseases will continue to emerge, efforts to control them will be pursued and there will always be a range of problems to be tackled along the way. The varying levels of political, economic and social development among countries, the transboundary nature and commonality of many major disease problems, and the need to harmonize approaches, all strongly argue for effective cooperation at all levels of management in order to make the most effective use of limited resources. Building on sub-regional, regional and international cooperation through joint strategies and approaches that avoid duplication of effort and competition are essential for this process.
However, all such efforts will be ineffective without national commitment from responsible authorities. The current situation offers big challenges to all concerned and, if maintained at the present level, risks of major epidemics will continue to threaten and emerge with costs that extend far beyond economics.