Marine Mammal Impacts

Intensive types of aquaculture, such as industrial finfish farming, increasingly conflicts with marine mammal conservation, posing threats through both direct and indirect interactions. 

Most aquaculture operations are located in sheltered coastal and estuarine environments – critical habitats for many marine mammals. Aquaculture shares territory with pinnipeds (seals and sea lions) and cetaceans (dolphins and whales), resulting in gear damage, predation on fish stocks, and frequent entanglement incidents. Pinnipeds, particularly fur seals and sea lions, are the most frequent farm intruders, often tearing nets, reducing feeding rates of farmed fish due to stress, and entering cages to access dead or live fish. Anti-predator nets, intended to prevent predator access, have become a significant cause of entanglement and death, especially for seals and dolphins. 

Cetaceans, including bottlenose dolphins and baleen whales, are especially vulnerable to entanglement due to poor net visibility and acoustic disturbances from fish farm operations. Many entangled dolphins have been pregnant or lactating, which has negatively impacted population recovery. Open ocean aquaculture also disrupts natural predator behavior, leading to shifts in foraging patterns, aggression among species, and habitat abandonment. Entangled marine mammals often suffer fatal consequences as they cannot reach the surface to breathe.

Furthermore, aquaculture’s contribution to nutrient pollution, antibiotic use, and microplastic contamination impacts marine mammal health through trophic transfer and habitat degradation. Plastic debris from aquaculture infrastructure – such as ropes, netting, and packaging – can be ingested or cause entanglements, compounding the threats to marine mammals. Heavy vessel traffic and acoustic deterrent devices cause chronic noise pollution, disrupting marine mammals’ echolocation and social structures. Despite efforts to deter them, marine mammals continue to be attracted to aquaculture sites by concentrated prey and feeding opportunities, placing the industry and these protected species in an ongoing conflict.