Aquafeeds and the environment: policy implications

Abstract Aquaculture feeds and feeding regimes can play a major role in determining the quality and potential environmental impact or not of finfish and crustacean farm effluents. This is particularly true for those intensive farming operations employing open aquaculture production systems, the latter including net cages/pen enclosures placed in rivers, estuaries or open-water bodies, and land-based through-flow tank, raceway or pond production systems. This is perhaps not surprising since the bulk of the dissolved and/or suspended inorganic and/or organic matter contained within the effluents of intensively managed open aquaculture production systems are derived from feed inputs, either directly in the form of the end-products of feed digestion and metabolism or from uneaten/wasted feed, or indirectly through eutrophication and increased natural productivity. So, as to limit the potential negative environmental impacts of feeds on aquaculture effluents, the major approaches taken by government authorities within major aquaculture-producing countries have included (1) requiring the treatment of farm effluents prior to discharge, through the use of settlement basins, specific filtration devices, waste water treatment systems, etc., (2) limiting the concentration of specific dissolved/suspended inorganic/organic materials and/or nutrients contained within the effluent discharged from the farm, (3) establishing maximum permissible amounts of specific nutrients (such as total nitrogen or phosphorus) that the farm is able to discharge over a fixed time period, (4) limiting the total number of licenses that can be issued and/or size of farm, depending upon the vicinity of other farming operations and the assimilative environmental carrying capacity of the receiving aquatic ecosystem, (5) limiting or fixing the total quantity of feed the farm is able to use over a fixed time period, (6) fixing maximum permissible specific nutrient levels within the compound feeds to be used to rear the species in question, (7) banning the use of specific potentially high-risk feed items such as fresh/trash fish and invertebrates, (8) banning the use of certain chemicals on-farm, including specific chemical therapeutants/drugs and chemicals (i.e., potentially toxic herbicides and pesticides, etc., (9) prescribing minimum feed performance criteria, such as specific levels of allowable dust/fines, feed efficiency or nutrient digestibility, (10) requiring the use of specific Codes of Conduct, including appropriate Best/Good Management Practices for farm operations, including feed manufacture and use, and environmental management, (11) requiring the development of suitable farm/pond sediment management strategies for the storage and disposal of sediments, or (12) requiring the implementation of an environmental monitoring program. The paper describes the merits and demerits of each of the above initiatives, with specific country examples, and attempts to offer guidance for the development of government policies aimed at regulating off-farm effluents and outputs rather than regulating on-farm feed inputs and feeding practices.