"I started a new business farming microscopic fish...
I call it a small-scale operation."
We even have a name for some microscopic fish... zooplankton! We can farm (culture) them, although not for large or commercial-scale purposes yet.
Global demands for food from aquatic environments are expected to increase in future decades because these foods will help to meet the needs and preferences of a growing human population. Many sources suggest global population growth of 2.4 billion, giving us a population of over 9.7 billion, by 2050. Food demand is set to rise even faster than population growth.
With the different types of aquatic food production that exist nowadays, from large-scale commercial operations to small-scale subsistence farms, it is vital that we give ourselves the time to learn more about their characteristics and what can make them more sustainable.
Aquatic Food Production (Definition)
Ordering seafood at a restaurant has never been easier - just navigate to the "seafood" menu and find lobsters, mussels... but wait, aren't these from the sea only? what if you wanted freshwater mussels?
Aquatic foods include anything that originated from a body of water and can be consumed.
Aquatic food production is the process of raising aquatic organisms for food. Aquaculture operations typically involve the raising and harvesting of fish, algae, aquatic plants, crustaceans, etc. in controlled environments such as ponds, tanks, or cages. These activities are carried out in salty, brackish and fresh water, meaning that they can be sourced from in-land wetlands, coastal areas like estuaries, or seas, oceans, etc.
Different organisms thrive in different environmental conditions. Farmed Atlantic cod prefer cold waters, whereas tilapia thrives in warm waters.
Have you ever had a green smoothie from a health shop? Some of them get their intense green colour from the spirulina. This cynobacteria, along with microalgae, such as chlorella, can be harvested from cultivation ponds in countries that benefit from high solar input, such as Spain or California.
Fishing communities, as well as massive industries, depend on this form of farming, and the activities of both can be sustainable and unsustainable, depending on a few factors which we will... dive into below!
Aquatic Food Production System
The aquatic food production system comprises different sectors. These are:
The commercial (industrial) sector, which intends to sell aquatic food resources, also called the seafood industry, for example, Atlantic Salmon farms in Scottish Lochs (lakes).
The recreational sector, where some fish farms are tourist attractions, offers services such as fish feeding and fishing, e.g. Kilnsey Park in Yorkshire Dales.
Moreover, the aquatic food production system is usually separated into freshwater and saltwater systems.
Saltwater food production systems are also called food mariculture, a word coming from the Latin mare, maris (“sea”) + culture. Mariculture occurs in open spaces that are enclosed, as opposed to tanks.
Freshwater includes mostly fish, crustaceans, molluscs and algae, and the primary environments are freshwater ponds, lakes, reservoirs and tanks.
The demand for aquatic food products increases with population growth. Seafood quality, however, remains highly dependent on two factors:
- food
- environmental quality
Both allow it to naturally reach desirable characteristics such as size, nutritional content and fat.
In 2018, fish harvested from aquaculture around the globe amounted to 114.5 million metric tons, with an estimated first-sale value of US$160.2 billion.1
Japan has specific aquaculture and storage laws in place to allow consumers to buy raw fish (sashimi) to be consumed as is, without heating or further processing. The lack of processing or burning fuels in preparing sashimi dishes makes the industry seem more sustainable from this point of view.
The highest aquaculture productivity rates correlate with the highest stress on biodiversity. This is because marine aquaculture is carried out in the upwelling and nutrient enrichment zones.
This coastal productivity is also related to the living preferences of humans and is one reason why the majority of the human population can be found living near the coast.
In 2003, it was reported that approximately 3 billion people — about half of the world's population — live within 200 kilometres of a coastline. By 2025, that figure is likely to double.2
Strategies to Improve Aquatic Food production
Some strategies are more impactful in improving aquatic food production and others are less impactful.
- beneficial strategies: improving the population health of certain ocean microorganisms
- harmful strategies: may harm the biota long-term, such as the removal of predators so that we can be the sole apex predator harvesting the food.
Improving primary producer population health
One of the most useful strategies to improve aquaculture is to promote the population health of phytoplankton (which uses photosynthesis) and of other natural food chains or processes (e.g. zooplankton). Phytoplankton supports most aquatic food chains and produces most of the Omega-3 fatty acids (healthy molecules) present there.
The dry food fish receive can range from vegetal pellets to dog food! Food is a vital part of aquacultural success, as it influences the taste, quality and nutritional benefits of fish that are consumed by both humans and other animals, or which end up as fertilizer.
Fish in the wild, known for their Omega-3s content, such as Atlantic salmon, present much fewer quantities of O-3s in captivity due to what they are fed. Salmon can't naturally synthesize O-3 and must obtain it from other sources.
Krill is a (sometimes microscopic) crustacean that feeds on phytoplankton with Omega-3 and represents the main food source of whales such as Blue Whales, polar seals, Adélie penguins, fish such as sardines and salmons, cephalopods such as squids, etc. Unfortunately, krill cannot be farmed at present, but only harvested from the wild. Nonetheless, it is possible for krill farming to be one of the sustainable farming methods of the future.
Using mechanical means
Mechanical food production techniques include cleaning the organisms by hand, or introducing cleaning species in penned fisheries. Specifically, cleaning species feed on external parasites which are extremely prevalent in fisheries.
Lumpfish Cyclopterus lumpus introduced among penned salmons ameliorates or decreases the chances of fish lice infestations. Infestations are detrimental to the fish's life quality and lifespan.
Using photochemical means
Photochemical food production enhancement techniques include:
the use of antibiotics to treat external and internal parasites, which can adversely affect human and animal health
the control of light and temperature levels to ensure maximum yield and comfort.
All fish species can be controlled to become either male or female, through artificial hormone injections and water treatments. Many aquaculture farms employ this technique to ensure maximum yield.
Consumer behaviour
Consumer behaviour can improve aquatic food production by mitigating harmful practices such as bottom trawling, and promoting sustainable aquaculture practices (e.g. farming and consuming seaweeds).
Bottom trawlers are heavy nets dragged across the seafloor which tend to destroy the habitats and shelters there present.
In the UK, ecologically sustainable farmed food options are Arctic chars and saltwater crabs, as opposed to wild Atlantic halibut for instance which is endangered.
Laws and Guidelines
Lastly, laws and regulations play an important role in managing aquatic food production. These are known as Food Industry Water Guidelines3, and they can differ from one country to another.
The Sustainability of Aquatic Food Production
Fish farming is considered more sustainable than hunting wild stocks!
Fish farming is considered more sustainable than hunting wild stocks!
The food conversion ratio (FCR) has the potential to show aquaculture gains and losses. It doesn't measure nutrient density but calculates the rate at which animal food gets converted into meat, milk, etc. It simply uses mass for mass values (usually calculated in kilograms).
Aquaculture salmon, carp and catfish have some of the best FCR ratios of farmed animals, at around 1.0. From this specific point of view, it is more sustainable than commercial breeds of beef (e.g. Angus), which hits a value of 7.0, sheep or poultry (such as broilers).
One of the most common problematic interactions with captive salmon is that migrating fish such as wild salmon come in contact with the captive ones, who tend to be infested with lice - thus also catching these external parasites. Captive fish infestations occur due to fish density inside pens and lack of abrasive surfaces or lack of interaction options with other marine organisms.
Bottom trawlers and other fishing techniques that destroy habitats are seen as unsustainable ways to obtain food for aquaculture fish.
Fish and seafood waste processing facilities in coastal communities are excellent options to avoid waste and turn it into fertilizer, pet food, fish lure, fuel, etc. However, the placement of aquaculture farms can be problematic, especially if it's an upwelling zone and/or blocks wildlife migration.
There are human ethical and legal issues around the "biorights" of indigenous communities and conservation laws preventing them from continuing traditions and/or fishing subsistence living.
Aquaculture Pros and Cons
Aquaculture farms can both contribute to pollution and be under threat from pollution, from sources such as:
The water table can be impacted by water used for aquaculture. Specifically, freshwater overuse may lead to drought and will lower the water table of a region. Both sea and freshwater can further be polluted with waste, nutrients, and medicine administered to fish. Antifouling agents, such as preservatives and dyes that prevent food from decaying, can also leak into the water.
Aquaculture can prevent diseases. Ciguatera food poisoning occurs especially in the sub-tropical and tropical waters of the world, and is caught by people fish that consume certain algae.
Bivalve mollusks feed by filtering large amounts of seawater, which can collect harmful pathogens that cause gastrointestinal problems in sensitive people.
Certain aquatic species can carry neurotoxic compounds originating from industrial processes, like PCBs (polychlorinated biphenyls), which are believed to affect brain development in children.
Recent advancements in farming techniques have led to us being able to cater to the nutritional needs of fish, mass-produce equipment and pellets and transport aquafoods from farms to consumers while keeping them refrigerated. This has meant that access to fresh produce became more widespread.
There are numerous health benefits associated with fish consumption, both wild and from aquaculture. Generally, they are a good source of Zinc, Iron, Magnesium, Copper, B vitamins, and others. In aquaculture however, the total nutritional content of fish depends on what they are fed with4.
Habitat occupation and destruction remain a risk, especially with the aquacultural practices and applications of shrimp farming in South-East Asian and South-American mangrove forests.
Mangroves are tropical tree species forming ecosystems, especially through their intricate system of roots. They are incredibly valuable as carbon sinks and host high levels of biodiversity.
Non-native escaped species can cause ecological problems. For example, the Eurasian and Asian carp are included in the world's topmost invasive species due to their resilience, being able to live in highly degraded and oxygen-deprived aquatic environments. As a result, they are considered invasive in countries like the United States and Australia. Although they are used as food, they reproduce faster than they are being caught, by wild predators and humans alike. Some invasive species can also interbreed with their wild "relatives", thus altering the gene pool.
The problem of escaped individuals becomes more acute when genetically modified organisms escape and breed in the wild, with unknown ripple effects throughout the ecosystem.
If a fish that is genetically modified to grow fast escapes into the wild, it may outcompete native fish during food abundance seasons in body size and aggressiveness, which may lead to increased mating rates among genetically modified individuals. However, when food stocks eventually get low, genetically modified fish and their offspring that are unable to essentially pause their growth start to exhibit strong cannibalistic tendencies to survive. This can lead to a population collapse.
Examples of Aquatic Food Production Systems
Food production systems can focus on one single species (monoculture) or on multiple species being bred in the same place or ponds (polyculture). They can also be employed for vegetables, where the soil is replaced with water enriched with essential nutrients (aquaponics).
Trout fisheries
Trout is a popular fish, which has both edible meat and roes (female fish eggs). Clear Springs in Idaho has the largest rainbow trout fishery in the world, with a constant number of around 10 million fish.
Sturgeon fish farming
The Sturgeon fish roes, known as caviar, are highly appreciated for their taste and nutritional content, but habitat destruction due to water body diversions and hydropower dams have plummeted their numbers in the wild. The only (relatively more) sustainable method of harvesting sturgeon fish, such as beluga, is farming, although the roe extraction methods are sometimes questioned.
Oyster farming
Molluscs that filter water for phytoplankton are eaten both cooked and raw, and produced by extensive farms.
Algaculture
A branch of aquaculture that focuses on growing seaweed or microalgae. Certain cultures are more interested in harvesting and consuming seaweed than others, for example, Japan and South Korea.
Aquatic vs Terrestrial Food Production Systems
Agricultural production systems can be broadly classified as aquatic or terrestrial, with distinct pros and cons. Aquatic production systems are defined as those that use water bodies to grow crops, which we described in this lesson. In contrast, terrestrial production systems are based on land (wheat, fruit trees, berries, mushrooms, guinea fowl, etc.).
Factors that must be considered when choosing between an aquatic or terrestrial system for food production include climate, land and water availability, and the species being grown.
Climate: Aquatic production systems are more efficient in tropical and subtropical climates, with a plentiful supply of warm water. On the other hand, terrestrial production systems are better suited to temperate and arid climates.
Availability of land and water: aquatic production requires less land than terrestrial production, but it also demands a reliable source of water which disperses pollutants more easily.
Types of crops being grown. Some crops, such as rice, are better suited to semiaquatic production systems, while others, such as wheat, do better in terrestrial systems.
Aquatic Food Production - Key takeaways
- The sustainable management of aquatic food production is paramount to avoiding over exploitation of necessary biotic and abiotic factors.
- Enhancement techniques are used to boost aquaculture production, and they include hormonal treatments, cleaner fish, light and temperature control, etc.
- Aquaculture can still negatively impact marine stocks by transmitting diseases or parasites, colonizing non-native environments, blocking migration paths, or being fed threatened organisms used as food pellets.
- Aquaculture positively impacts fishing stocks by giving them respite from industrial hunting.
- Aquatic food production can be done in saltwater, brackish water or freshwater, and it can benefit commercial, tourism and cultural sectors.
References
- Global Aquaculture, NOAA, 2021, https://www.fisheries.noaa.gov/national/aquaculture/global-aquaculture. Accessed 10.09.22
- Ripple Effects: Population and Coastal Regions, PRB, 2003, https://www.prb.org/resources/ripple-effects-population-and-coastal-regions/. Accessed 10.09.22
- Food Industry Water Guidelines, die pat, 2022, https://www.die-pat.co.uk/food-industry-water-guidelines-risks-use-regulations. Accessed 10.09.22
- Can we eat fish sustainably and maintain health benefits?, medical news today, 2021, https://www.medicalnewstoday.com/articles/can-we-eat-fish-sustainably-and-maintain-health-benefits. Accessed 10.09.22
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