The Overshadowed Environmental Benefits of Aquaculture - Lab Manager Magazine

Aquaculture, the practice of raising aquatic organisms in controlled environments, is the root of several environmental concerns, including habitat destruction, pollution, and native ecosystems being disturbed should any organisms escape their environment. However, when applied properly, aquaculture can be conducive to the environment, as a new study in Conservation Biology shows.

Led by University of Melbourne researcher Kathy Overton, researchers identified 12 potential ecological benefits of aquaculture that have not received very much attention over the years. "Most people around the world live near freshwater or marine ecosystems, and we rely on them as sources of food, tourism, recreation, culture, and livelihood," Overton said in a news release. She explained that the negative impacts of aquaculture have been overshadowing its positive applications over the last century.

The 12 benefits identified by the researchers are:

1. Species recovery

Aquaculture can help restore fish species by repopulating natural habitats with farmed fish. "Species recovery programs for fish such as the white sturgeon in North America, the golden mahseer in India, and the Macquarie perch in Australia are trying to bring back wild populations and stop extinction," said Overton.

2. Habitat restoration

Habitat restoration is defined as the "use of cultivated aquatic species to substantially or fully restore function of a degraded, damaged, or destroyed habitat." An example would be The Nature Conservancy (TNC), which is the largest conversation organization in the world, leveraging aquaculture to restore shellfish reefs. Simon Branigan, PhD, marine restoration coordinator of the TNC, explained that aquaculture is vital to their method of rebuilding lost shellfish reefs "through creating healthy oyster and mussel juveniles to kickstart the reef restoration process."

3. Habitat rehabilitation

Similar to restoration, habitat rehabilitation uses cultured organisms to restore an ecosystem to a partially functional state, rather than attempting to revive it back to its prime state. For instance, rehabilitation may involve introducing cultured species onto artificial structures to provide partial recovery.

4. Habitat protection

Habitat protection seeks to protect existing natural ecosystems. An example would be mussel farms populated by Mediterranean long-snouted seahorses. The mussels serve as a substrate on which other organisms attach to, which are then preyed upon by the seahorse. The farms also protect the ecosystem from trawling, which protects the habitat and ensures that the seahorses will not be subjected to their source of food being harmed.

5. Bioremediation

Bioremediation is the process by which organisms break down pollutants by consuming them, thus cleaning their environment. In aquaculture, this can be deliberately introduced in degraded environments to remove metal contaminants, excess vitamins, or even hydrocarbon spills.

6. Assisted evolution

According to the study, "Current rates of evolution and adaptation for numerous organisms in aquatic ecosystems are being outpaced by anthropogenic stressors such as climate change." By selectively breeding species of conservation concern, the species itself can have better odds of survival as it will develop positive traits such as parasite resistance or tolerance to certain environmental conditions.

7. Biological control

Similar to bioremediation, cultured species can be introduced into a habitat to cut down on the pests infesting it either by consumption (such as using weevils to control the growth of water hyacinth), the spread of a pathogen from a cultured vector, or other methods.

8. Removal of overabundant species

Simply removing an overabundant species from a habitat can benefit the habitat while allowing the species to continue propagating in farms. The researchers cite overabundant sea urchins as contributing to the degradation of kelp and associated organisms. By relocating the urchins to aquaculture facilities, the natural habitat's biodiversity can flourish while the urchins are made more commercially viable with specialized diets to increase their roe count.

9. Ex situ conservation

Ex situ conservation, or off-site conservation, in the context of beneficial aquaculture involves culturing a species in a controlled environment while regulating its exposure to biotic and/or abiotic stressors. Doing so ensures the survival of a species of concern and can promote genetic diversity within it. Zoos, aquariums, and botanical gardens are all examples of positive ex situ conservation.

10. Coastal defense

Similar to ex situ conservation, coastal defense involves reducing a species' exposure to abiotic stressors such as coastal erosion or wave attenuation. Aquaculture activity that lowers these stressors or encourages coastal deposition can be considered coastal defense.

11. Climate change mitigation

Cultured aquatic creatures can be harnessed to help achieve climate change alleviation efforts. For instance, cultured algae will absorb large amounts of carbon dioxide that would otherwise contribute to the Earth's overcharged greenhouse effect (so long as these carbon sinks are moved into the deep sea or buried in coastal sediments).

12. Wild harvest replacement

Rather than catching organisms in the wild, culturing them may reduce the pressure on wild populations and enable them to thrive. However, the circumstances in which this is advisable have been debated. As a result, some have proposed that replacing wild harvest only be used when five criteria are met: (1) the cultured organisms can be sold instead of the wild version, (2) demand is met and does not increase, (3) it is more cost-efficient to culture organisms than harvest them from the wild, (4) it is also more cost-efficient to culture them than black-market prices for the same organism, and (5) wild populations are not relied on.

"Historically, there has been a disconnect between the fields of aquaculture and conservation and restoration with only partial attempts to identify where and how they might align," the study states. By delineating 12 ecological benefits of aquaculture with an emphasis on outcome, the authors hope their research aids others in identifying aquaculture activities with positive environmental impacts. Overton and her team believe that the next step is to develop an internationally-recognized accreditation model for beneficial aquaculture to incentivize commercial aquaculture industries to adopt environmentally-friendly practices.