Aquaculture

Introduction

"Aquaculture, also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. lotus). Aquaculture involves cultivating freshwater, brackish water and saltwater populations under controlled or semi-natural conditions, and can be contrasted with commercial fishing, which is the harvesting of wild fish."

Disease

"Fish crammed in unsanitary conditions in aquaculture facilities are prone to infection and disease, such as infectious salmon anemia and sea lice.  Diseased fish can escape and spread such pathogens to wild stocks with potentially devastating effects."

Farmed Fish can Spread Infections, Pesticices, Antibiotics, Heavy Metals, and Parasites to Humans

"Fish are reservoirs of zoonotic pathogens that cannot only infect the animal host but can also infect humans who are in contact with the aquaculture facility and via foodborne infections [52]. Common infections in aquaculture facility fish handlers include Aeromonas hydrophilia, Mycobacterium marinum, Streptococcus iniae, Vibrio vulnificus, and Photobacterium damselae [53,54]. Although problematic as zoonotic pathogens, these microorganisms may also contain and spread AMR genes such as extended-spectrum beta-lactamases (ESBL) [5]. Faecal matter from Sparus aurata (Gilthead seabream) was found to contain ESBL-resistance genes, including blaTEM-52, blaSHV-12, as well as cmlA, tetA, aadA, sul1, sul2, and sul3 [55]. Furthermore, bacterial strains carrying resistance determinants in commercial seafood products [56] include disease-causing pathogenic bacteria in humans [57,58], thereby increasing the risk of spreading AMR from aquaculture to the consumer." - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5484108/

Slaughter and Processing Pollution Spreads Disease to Wild Fish

Habitat Destruction

"The exponential growth of aquaculture in recent decades has caused large swaths of mangrove forests to be cut down to make room for new farms. The loss of these important coastal habitats negatively affects the local people and ecosystems."

"Fish farms, or “aquafarms,” discharge waste, pesticides, and other chemicals directly into ecologically fragile coastal waters, destroying local ecosystems. And aquaculture farms that raise fish directly in fenced-in areas of natural waters kill off thriving natural habitats by overloading them far beyond their capacity. Waste from the excessive number of fish can cause huge blankets of green slime on the water’s surface, depleting oxygen and killing much of the life in the water. In Brazil, destruction caused by aquaculture changed the local climate so much that some aquaculture operations have been forced to shut down."

Deforestation

Soy is the second greatest cause of deforestation. The majority (76%) of which is fed to livestock in order from greatest to least: poultry (37% of all soy), pigs (20.2%), and aquaculture (5.6%), etc. compared to the 20% that is fed directly to humans: 13.2% oil, 2.6% as tofu, 2.1% as soy milk, and 2.2% as other products such as tempeh. - https://ourworldindata.org/soy#more-than-three-quarters-of-global-soy-is-fed-to-animals

Mangroves

"One of the biggest threats to mangrove forests is the expansion of aquaculture ponds. Roughly 30 percent of mangrove deforestation and coastal land-use change in Southeast Asia has been attributed to aquaculture, especially shrimp farming. And as the top aquaculture commodity, the marine shrimp industry is forecast to continue its expansion, according to a report launched by Planet Tracker." - https://forestsnews.cifor.org/66328/the-carbon-on-your-plate-mangrove-and-aquaculture?fnl=en 

Using Bycatch as Feed

1/3rd of the global fish catch is fed to livestock including aquaculture farms, even though scientists have determined that many of those same "junk" fish are actually highly nutritious and would be more efficiently used if fed straight to humans instead.

Unfortunately much of the planet's stock has already reached a tipping point with 61% of the ocean being "fully fished", and 29% being "overfished", leaving only 10% with a moderately healthy population left.

Wild stocks are crashing, and large adults who can produce the most eggs have been removed from the gene pool. More and more ships are being put out to see with bigger nets that can trawl deeper (despite declining catch rates), causing increasing degradation to the sea floor, even destroying coral in conservation areas before they have a chance to regrow. 

Click our Commercial Fishing button to learn more.

Pollution

"Industrial scale and congested aquaculture facilities often create pollution leading to severe habitat destruction, The pollution comes from faeces and food wastes flushed into the surrounding environment, The siting of culture facilities often does not take into consideration their interaction with the surrounding environment. They are often placed in inappropriate locations where environmental damage and/or aesthetic problems are maximized."

Rare Glass Reefs Smothered By Fish Farm Waste

"The live reef was at a depth of about 30 metres, which is unusually shallow for a glass sponge reef and Campbell did not drop a line into the water for fear of damaging the glass sponges.

“It was a little bit eerie doing the first dive, free-falling through the darkness and then my light illuminated this incredible sight — there were vibrant golden sponges, some standing two metres tall like giant vases. Schools of rockfish hovered over the top, there were king crab on top of the sponges and lingcod rested on the big egg masses with the males guarding the eggs. I was pretty gobsmacked,” Campbell said.

“I could hardly believe my eyes. It was like being on another planet. These sponges are ancient. These reefs have thrived there since the Jurassic [era] and were thought to have died off. It was like finding a herd of living dinosaurs.”

"The euphoria of seeing the first reef, teeming with life, contrasted violently with the second site where the sponges were clearly dead and appeared to be smothered by waste and salmon feces from the farm, said Campbell, spokesman for Wild First, a coalition of organizations working to have salmon farms move from ocean pens to land-based operations by 2025." - https://thetyee.ca/News/2018/04/30/Glass-Sponge-Reef/

“It was incredibly disheartening... one of my first thoughts was, with more than 130 salmon farms on the B.C. coast, what else is being smothered that we have yet to discover,” Campbell said.

“These sponges rely on clean water, free from excessive sedimentation, but unfortunately this is the exact opposite of the conditions under a salmon farm. With close to a million farmed salmon swimming overhead, the steady rain of feces and feed waste is a death sentence for life underneath.”

The fragile sponges, made of silica, were thought to have gone extinct 40 million years ago until living glass sponge reefs, estimated to be 9,000 years old, were discovered in Hecate Strait and Queen Charlotte Sound in 1987. Reefs were then found in Chatham Sound, Howe Sound and the Strait of Georgia." - https://thetyee.ca/News/2018/04/30/Glass-Sponge-Reef/

The War Against Sea Lice = Pesticides, Heavy Metals, & Antibiotics

"Aquaculture systems and farms have been designated as “genetic reactors” or “hotspots for AMR genes” where significant genetic exchange and recombination can occur, which can shape the evolution of future resistance profiles [38,39]. It has been estimated that 90% of bacteria originating in seawater are resistant to one or more antibiotics and up to 20% of the bacteria are resistant to at least five [40]. Once bacteria have acquired AMR genes, they may exist in the environment for a long time, even after the selection pressure ceases [41].

The prolonged use of antibiotics in aquaculture increases the selective pressure on bacterial populations, even at concentrations of antibiotics well below the minimum inhibitory concentration of the susceptible wild type population [42], and also increases HGT rates, including human and fish pathogens. Due to antibiotics being relatively stable and non-biodegradable, residual antibiotics can remain in commercialised fish and shellfish for consumption [7,8]. Done and Halden (2015) [43] measured low but significant levels of tetracycline (oxy- and 4-epioxytetracycline), macrolide (virginiamycin), and sulfonamide (sulfadimethoxine/ormetoprim) antibiotics in samples of farmed trout (Oncorhynchus spp.), tilapia (Oreochromis spp.), and salmon from 11 countries including the US, China, Mexico, Thailand, Scotland, and Canada. While the concentrations were in compliance with US FDA regulations, it was suggested that the presence of these antibiotics might provide a selection and enrichment mechanism for resistant bacteria [43]. Similarly, Wang et al. (2017) [44] screened finfish and shrimp samples collected from across Shanghai City for 20 common antibiotics (tetracyclines, fluoroquinolones, macrolides, β-lactams, sulfonamides, and phenicols). Antibiotic residues were found in 52% of the samples (40–91% of the finfish sampled and 17% of shrimp), with residues and their consumption accounting for 75% and 70% of the overall variance of estimated antibiotic exposure for men and women, respectively [44]. ..." - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5484108/

"Antimicrobial agents are usually administered to fish, mixed with food, and doses can be proportionally higher than those in livestock [13]. Not only can residues of antimicrobials remain in fish products, but undigested food and fish faeces containing unabsorbed antimicrobials and secreted antimicrobial metabolites can remain in the water and sediment around fish farms for an extensive period of time, depending on their concentrations and biodegradability [19,59]. Indeed, some studies suggest that 70–80% of antibiotics given to fish are excreted into the water [17,20,60] and can further alter the microbial communities present [61]. Such material can persist and select for AMR bacteria, even at low concentrations [42], leading to major alterations in the biodiversity of the sediment and water in the near proximity of open aquaculture systems, by replacing susceptible communities of bacteria (and other microorganisms) with resistant ones ([13] and references therein). Not only is the biodiversity altered in the surrounding sediments, but the resistome also increases in complexity, with larger numbers of antibiotic resistance genes and increases in mobile genetic elements [40,62,63,64,65] " - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5484108/

Phosphorous Emissions

Escapes

"Farmed fish and shrimp are often genetically different from fish inhabiting the adjacent environment and ecologists have expressed concern that farmed escapes are diluting wild populations’ genetics. This is particularly worrisome in salmon aquaculture where millions of fish escape every year from netcages suspended in the open ocean. Tilapia too, which are grown in freshwater ponds have a great proclivity to take over watersheds should they escape."

Further Reading

Click the Commercial Fishing button for an understanding of how fishing effects the environment and people. The Fishing Industry button to focuses on pollution caused by the industry ranging from gas emissions and bilge waste, to bycatch ghost gear.

Ways to Help

Click the Seafood Alternatives button for ideas on how to enjoy seafood flavors without the ecological or humanitarian impact of the fishing industry.

If you want to help clean up harm done by fishing and other human activities, consider the following resources:

Mangroves

Grants

International