Fate and effects of fish farm organic waste in marine systems: Advances in understanding using biochemical approaches with implications for environmental management

Abstract

AbstractParticulate waste from open‐cage fish farms in marine systems can cause organic enrichment of seabed habitats and enter the food web through consumption by wild organisms, with potential for broader ecosystem changes. Effects on biogeochemistry and benthic ecology are reasonably well understood in inshore, sheltered and soft sediment systems. However, food web effects and interactions with epifauna and larger consumers is less well understood, as is the fate of these discharges in more dynamic coastal areas with complex hydrodynamic regimes. Expected expansion of the aquaculture industry globally includes farming new areas that are more environmentally dynamic and biodiverse, with potentially sensitive habitats. Therefore, the aim of this review was to examine how biochemical tools can assist in identifying and managing impacts. Biochemical tools such as bulk stable isotopes and fatty acids can reliably trace the fate of fish waste in the environment and the food web, and have advanced our understanding of waste dispersal, as well as providing greater insights into biological interactions with fish wastes. This includes elucidating trophic subsidies to wild organisms, candidate species for co‐culture and waste assimilation mechanisms in native communities. Ultimately, biochemical tools can support improved environmental management, by helping to identify the zone of influence for spatial planning, providing additional ‘forensic’ evidence for farm‐related change, and by identifying potential risks to high‐value species and habitats. In this way, they can inform targeted research to link fish waste inputs meaningfully to potential ecosystem changes to better understand the consequences to support sustainable industry expansion.