Open-ocean fish farming: ecological issues
The seafood industry remains booming. It comprises 16% of the protein we eat globally, the majority of which is farmed. Aquaculture is surpassing global beef production, and by 2030, it is predicted that over 60% of the world’s seafood will be farmed. However, most of our seafood resources are depleting, as there have been many reported cases of overfishing, resulting in decreased wild-caught seafood production. As a way to curb this problem, open ocean aquaculture, primarily open ocean fish farming has been considered as an alternative to commercial fisheries.
Open ocean fish farming is simply defined as the rearing of fish in exposed areas beyond significant coastal zone. It is the mass breeding, rearing, and harvesting of fish in areas of the ocean in underwater nets, ponds, and cages. Its operation would be located at a substantial distance from shore with the influence of environmental conditions such as wind and wave action. These facilities are an underwater factory, with little pollution controls. The net pens, pods, and cages are used to farm massive populations of fish with no real barrier between the underwater farm and the ocean. This results in a free exchange between the nets and open water, which can include direct deposits of untreated fish wastes, diseases, parasites, excess feeds, and agricultural chemicals, drugs, and antibiotics residues from the farm’s infrastructure.
The implementation of open-ocean fish culture has often become a topic of debate, with raising concerns by aquaculturists, environmentalists, recreational fishermen, and commercial fishermen. This farming technique is extremely risky and fraught with ecological factors.
Pollutions and eutrophication
The location of industrial fish farms increases the risk of direct discharge of harmful pollutants such as agricultural chemicals, untreated fish waste, pathogens, and excess nutrients into our oceans. Studies show that an industrial ocean fish farm operation of 200,000 salmon will release nitrogen equivalent to the untreated sewage of approximately 20,000 people, phosphorus equivalent to approximately 27,000 people, and fecal matter equivalent to approximately 63,000 people. When these excess nutrients are added to a water body, eutrophication occurs. This is the process where water becomes too enriched, causing environmental degradation such as low dissolved oxygen levels, murky water, death of seagrasses and corals, fish kills, and harmful algal blooms. The stimulating effects of vitamins and fish wastes on the growth of red tide species have also been demonstrated in several laboratory studies.
The infrastructure of industrial ocean fish farms contains a combination of various chemicals and heavy metals to prevent corrosion and other damage from abrasive ocean conditions. These anti-foulant substances often leech off the farm over time, contaminating the water and the farmed fish. Typical chemicals involved are copper and zinc. A high amount of these chemicals is highly toxic to marine life, causing mortality and adverse effect on fish growth, reproduction, blood chemistry, and metabolism. Unlike their terrestrial counterparts, underwater fish farms do not utilize any type of waste treatment or ventilation to mitigate waste, pollution, and discharge.
Disease, pests, and agricultural drugs
It is no secret that a massive population of animals in closed space will breed pests and diseases. Farmed fish in net pens are host to various diseases and pests such as infectious salmon anemia and sea lice. Some industrial open ocean fish farms have introduced pesticides to ward off sea lice and other parasites. It was recently uncovered that the Scottish government likely colluded with pharmaceutical company Merck to cover up the widespread damage to wildlife due to sea lice pesticides. The chemical, known as emamectin, was found to have contaminated 45 Scotland lochs causing a substantial reduction in crabs, lobsters, and other crustaceans.
Industrially farmed animals are sometimes given antibiotics to treat and prevent disease but are often misused for growth acceleration. Bacteria found in the environment will develop antimicrobial resistance through contact with already resistant bacteria, antibiotics, and disinfectant agents released by human activity. It was reported that more antibiotics are used by industrial ocean fish farms than any other player in the meat industry in Chile alone. Furthermore, around 75% of antibiotics used by the industrial fish farming industry are directly absorbed into the surrounding environment.
Massive farmed fish spills
These farms are usually anchored to the ocean floor, held up by buoys and other floatation equipment, connected by walkways, ropes, or any other surface-level infrastructure. The farmed fish enclosures are typically fully submerged and workers must dive to access and tend them directly. Due to the high influence of surrounding ocean conditions, the farm infrastructure is highly fallible and easily floats away from their positions. Nets can become disconnected due to tides, winds, and other elements. Over time this will weaken the infrastructure, which creates an increased risk of damage to the farm that often leads to massive fish spills.
The introduction of farmed fishes that are typically nonnative species, might affect the genetic makeup of marine wildlife species. Even the smallest rupture of nets may allow fishes to escape and oftentimes due to harsh weather conditions, the workers may not be able to repair the damage up until a high number of farmed fishes escaped. These farmed animals have been described by the industry as sluggish and unable to compete in the wild. These claims proved to be otherwise. On August 19, 2017, over 263,000 farmed Atlantic salmon escaped from an industrial net pen facility in Puget Sound owned by Cooke Aquaculture, due to poor maintenance. 110 days after the fish pen collapse, many of the farmed fish are still thriving and swimming free – some have even been documented as far as 100 miles away from the farm. Farmed fish are usually genetically bred to grow bigger and faster, which caused threats of genetic degradation and reproduction issues to wild species in the event of cross-breeding. When a farmed fish escapes, it immediately increases competition for the limited space and resources that native marine life requires to feed, live, and reproduce.
Notably, industrial open ocean fish farming raised a handful of environmental concerns. Open ocean fish farming can be a sustainable development, provided pollution loadings generated by fish farms are kept well below the carrying capacity of the water body. Effects can be significantly reduced by careful site selection, control of stock density, improved feed formulation, and integrated culture (with macroalgae, filter-feeders, and deposit-feeders). Environmental impact assessment and monitoring should also be carried out regularly to ensure culture activities are environmentally sustainable.