Escapes

Aquaculture escapes pose serious ecological, genetic, and pathogenic threats to marine ecosystems. 

Fish escapes from open net-pen aquaculture significantly challenge environmental sustainability and marine ecosystem health. The structural and operational vulnerabilities of containment systems make both large-scale events and chronic low-level leakage inevitable. Prominent causes include net wear and tear, biting by caged fish, storms, predators, vessel collisions, and human error.

The ecological risks of farmed fish escapes are substantial. Escaped fish compete with wild populations for food, habitats, and mates – effectively altering ecosystem dynamics. Non-native species can become invasive, disrupting local biodiversity and threatening the survival of native species. When farmed species are native, escapes result in genetic introgression — interbreeding between genetically uniform, selectively bred farmed fish and the more diverse wild stocks. This leads to reduced genetic diversity, diminished adaptability, and a long-term decline in fitness and resilience of wild populations. 

Escaped fish also act as vectors for disease and parasites. The crowded conditions of net-pens foster the development of pathogens and mites, which spread to wild populations through direct contact, waterborne exposure, or infected escapees. This pathogen transfer has been linked to population declines in wild fish, particularly in regions with high aquaculture intensity, and raises socio-economic concerns in communities dependent upon a healthy aquatic ecosystem.