As farmed fish continues to emerge as a long-term alternative to traditional fisheries, there is a simultaneous shift occurring within the aquaculture industry itself. Because of the need to produce greater amounts of seafood through sustainable, consistent means, many of the most traditional farming practices – low intensity, poorly regulated, land-based systems – are being replaced by more advanced, high-volume technologies such as open-ocean cages.
With this change, new questions have arisen about the environmental impact that these cage farms may have on local environments. Indeed, in the past there have been many situations where excess nutrient loads from intensive cage culture have led to severe degradation of surrounding ecosystems. Despite assurances by industry representatives that cages located in areas of high-current such as the open ocean would likely have minimal impacts, many opponents of cage-farming insist that there is insufficient evidence to support this claim.
However, a new study published in the Journal of the World Aquaculture Society has provided long-term evidence that the offshore environment may widely negate the effects of nutrient spillover from high density cage-culture.
The study tracks a large offshore farming operation in the Western Caribbean from 2012-2018 and measures the key effluent parameters that may indicate negative effects from the farm’s presence. It found no significant difference in dissolved oxygen, chlorophyll‐a, particulate organic carbon, particulate organic nitrogen, nitrate + nitrite, or total dissolved nitrogen concentration in the water column at any location around the farm, whether up-current or down-current from the cages. Additionally, sediment samples were taken in the same locations and no significant difference was documented for any parameter that was analyzed.
These results may provide strengthened footing for advocates of expanding offshore aquaculture within the Western Hemisphere, provided that siting accounts for proper dispersal of nutrients by high-energy offshore waters.
The regulatory environment surrounding the creation of new offshore farms in the United States, and N. America broadly, is still highly complex and intentionally limiting. As more cage farms slowly become operational however, it is extremely important for owners to minimize environmental impacts and closely monitor the surrounding waters for any signs of degradation. Continued improvement in the sustainability of offshore farming will likely ease the regulatory burdens imposed on the industry and will also help combat negative stereotypes that still surround cage-culture.
You can find a link to the paper, by Welch et al., here: