Fish Predation in Bivalve Aquaculture: Impacts and Potential Mitigation Strategies

Fish predation poses a significant challenge to bivalve aquaculture throughout the global range of production. However, the issue remains poorly understood, preventing the advance of effective interventions. Fish predation, especially on mussels in longline culture, can be severe and, in some instances, lead to crop losses of up to 100%, which has resulted in the closure of farming operations in several major European production regions. Although the predation of oysters, clams, and scallops by fish is generally less severe in bottom culture, they are more vulnerable to predation when cultivated in off-bottom culture systems. The fish species responsible for crop losses on shellfish farms typically vary both spatially and temporally, making it crucial to identify the species responsible and also the stages of bivalve aquaculture production most affected for developing practical and long-term solutions to the problem. Many approaches used for controlling fish behaviour in other situations (e.g., for limiting fish access into water intake pipes of industrial powerplants) appear to show promise for use in aquaculture environments. Potential mitigation strategies for fish predation fall into four broad categories: physical exclusion, deterrence, removal, and changes to husbandry practices. However, further research is required to determine their effectiveness in aquaculture situations, among different fish species, and their potential effects on non-target species. This review highlights the importance of a comprehensive approach to addressing fish predation in shellfish aquaculture by balancing economic interests with ecological considerations within aquaculture operations.