Site selection and regulation issues for trout and carp farming in Germany

Abstract

In most industrialized countries very few natural freshwater habitats are available for the establishment of new fish farms. These limits require regulatory measures, largely depending on local conditions. Regulations on volume and type of water to be extracted from groundwater and/or surface resources exist in Germany on the «Lander» federal level (contained in the «Water Acts» («Wasserhaushaltsgesetz»). These regulations also set water quality criteria for effluent discharge into receiving waters. Site selection criteria are largely determined by the type of aquaculture considered: in extensive, conventional pond farming systems, criteria on natural factors include water resource availability, space and geomorphological (e.g. slope) and geochemical factors (e.g. soils). The appropriate positioning and levelling of ponds will decide on whether excessive energy costs can be avoided. Different site selection criteria will have to be employed for trout and carp culture. For carp, availability of large areas with suitable soil characteristics is essential. Comparably low yields per unit area will be achievable (productivity of the water determines stocking density and yield). Construction costs need to be kept at a minimium, otherwise the operation will never become economically feasible. Exceptions are special ponds for overwintering, or spawning or other special purposes. Trout culture in earthern ponds require different site selection criteria, depending on the volume of water supply, because yield does not depend on area specific productivity of the water body. Water quality management criteria become an overriding issue for this type of culture system. Stocking density will be determined by the permit for extractable water volumes per unit time. (set by the water authorities). Intensification methods for trout farming exist within the range of regulated effluent standards by using specifically designed system components such as concrete ponds, raceways, circular tanks, aeration, oxygenation, etc. The effluents, however, are considered an industrial waste and their release into receiving waters will be under the water management law (7). If standards are not met within the set limits effluents will be charged as the release of any other industrial wastewater