Fish Groups Utilized by Humans

Updated: Jul 21, 2020

With roughly 33,600 species of fish worldwide, it comes as no surprise that humans have found numerous ways of utilizing them for easing their hunger, obtaining experimental results, and treating diseases.

This post will highlight the biggest groups of fish, give a short description of their respective group, and welfare issues they encounter.

As an organization, we focus on farmed fish because such interventions involving aquaculture are more tractable. Humans oversee the full life span of farmed fish as opposed to, for example, wild caught-fish (see Welfare Issues of Farmed and Wild-Caught Fish).

However, we want to have the highest possible impact on fish’s lives and are therefore open to widening our work in the future on other groups. We also strongly encourage other organizations to work on these groups because they are mostly neglected but have substantial welfare concerns.


June 1, 2020: Resource added with numbers for farmed food fish, feeder fish, and farmed cleaner fish. (19b. Šimčikas, S. (2020). Estimates of global captive vertebrate numbers.)

May 14, 2020: Resource added on skeletal deformities in cleaner fish (46. Gunnar Fjelldal, P. et al. (2020). Skeletal deformities in wild and farmed cleaner fish species used in Atlantic salmon Salmo salar aquaculture.)

May 4, 2020: Resource added on welfare problems for baitfish (37b. Riberolles, G. (2020). Pêche au vif: vivement la fin!)

Ornamental Fish

Fish used for aquariums and hence kept for visual appeal in aquaria rather than as a food source are described as ornamental fish or “pet fish” [1].

Hobby fish-keeping accounts for 99% of ornamental fish trade, for which individuals are either captured in the wild (which is the case for 98% of marine fish species) [2], or reared in captivity on fish farms (which is the case for 90% of freshwater fish species) [3]. While the Food and Agricultural Organization of the United Nations (FAO) tries to estimate numbers for the ornamental fish trade, there is little information about the sector’s actual scope. A study from 2007 suggests that over 1 billion ornamental fish are traded per year worldwide [4]. Numbers from 2010 suggest 2 billion individuals moved annually [5]. Asia is the biggest exporter with 51% of global exports [5]. In 2013, Singapore alone exported ornamental fish worth 56m USD to over 80 countries worldwide [5].

Welfare Concerns for Ornamental Fish

There are welfare issues present both before and after the fish are sold. Prior to purchase, inappropriate handling, and rearing conditions (e.g. poor water quality, malnutrition, and inter- & intra-specific aggression) often evoke stress and suffering [6]. This explains the 10-40% mortality rates prior to export of an ornamental fish farm in Bali, Indonesia [7]. During transport, ornamental fish are usually anesthetized and packed alive into small plastic bags with little water quality monitoring [8].

With 99% of ornamental fish kept by private persons, we can expect there to be little monitoring of their welfare after they are purchased. These conditions evoke great concern about their welfare.

Fighting Fish

Betta fish or “Siamese fighting fish” (Betta splendens) are an eye-catcher at every pet store. In Thailand, betta fish are the most exported aquatic animal with trades bringing in billions of bhats (THB) (1 THB = 30.4 USD) annually [9]. One betta fish farmer in Phnom Penh, Cambodia claims to sell up to 30 fish a day making roughly 90 USD [10].

When not kept for visual appeal, male betta fish (and sometimes females) are used for fish fights due to males’ aggressiveness against each other. Their territoriality and high aggressiveness lead them to start biting, pushing, and injuring each other when put into the same container or tank [11,12]. Research on the legal status of such fights is not fruitful, with little information about where these fish fights are allowed or not. It appears though that in Indonesia animal fighting can generally lead to imprisonment [13].

Betta fish usually expand their full tail to display a willingness to defend their territory (right). If stressed, male betta fish have also been observed biting their own tail (left, Source: Betta Care Fish Guide, Tankarium).

Welfare Concerns for Fighting Fish

Rearing conditions on farms are especially alarming with fish kept in small bottles with no water quality monitoring, no oxygenation, and high ammonia build-up from their own feces [14]. Wild betta fish live in dense vegetation with shelter opportunities [15], a habitat that their "pet"-counterparts rarely experience.

Before being exported, fish whose tails do not represent the norm are sorted out and dumped into canals or thrown away [16]. More than other pet fish, betta fish are largely bought from people with no aquarist experience and little knowledge about appropriate keeping & handling.

Fish fights themselves can cause severe injury and stress to these animals, usually leading to the death of one, if not both fish fighting [15].

Betta fish rearing conditions on a fish farm in Thailand where their export accounts for 10% of the annual total for fish. Source: PETA

Fish for Restocking

Recreational fishing is a popular sport worldwide, with 3.36 million individuals taking part in it in Australia in 2003, 49 million in the United States in 2017, and 4.2 million in Europe in 2005 [17]. In the U.S., the number of recreational fishers has increased by 56% between 2006 and 2017 [18].

Increased fishing activities, both recreational and commercial, reduce fish populations in rivers and lakes. On top of that, climatic warming alters reproductive cycles and induces further stress on wild fish stocks. To combat declining fish populations, fish farms rear restocking fish which are then released in large numbers to increase stock numbers, improve stocks for commercial and recreational fishing, and add highly desirable individuals (game species) [19]. At any given point 0.8 to 65 billion fish are reared of which 35 to 150 billion are released annually [19b].

Welfare Concerns for Restocking Fish

For general welfare concerns for fish on fish farms, see our report and the report by Animal Charity Evaluators. Also see the report by Rethink Priorities on welfare issues specific to restocking fish.

A major welfare concern of restocking fish is stress upon release into an unknown environment [20]. Farm-raised fish are less suited for survival than their wild counterparts which are generally well adapted to their environment [21]. In addition to that, released fish might become subject to recreational fishing. This raises welfare concerns with respect to the capture methods, in particular tissue damage from hooks and inappropriate slaughter from potentially letting fish suffocate upon capture.

Laboratory Fish

Fish in laboratories are used for scientific exploration and drug testing. Generally, experiments with fish are conducted to infer implications for other groups of vertebrates [22], and to test new medication for farmed fish [23].

Exact numbers on how many fish are used for laboratory experiments annually are difficult to determine. For example in the U.S. fish do not fall under the Animal Welfare Act [24] and statistics are unavailable.

Public data from the UK suggests that in 2011 15% (=1,350,000 individuals) of laboratory animals were fish [24]. A commonly used species is zebrafish (Danio rerio). Many scientists appreciate the species for their transparent larval stage, during which scientists can watch organ development without any surgical intervention [25].

The transparent body of a zebrafish larvae

The transparent body of a zebrafish larvae. Source: University of Queensland, 2018

Welfare Concerns for Laboratory Fish

Animal experiments can intentionally cause intense suffering. Fish toxicity tests are very popular [26], with the LD50 test still allowed on fish while it has been outlawed as a worldwide standard for all mammals [27].

There are no international welfare guidelines for specific fish species used in laboratory experiments, and suggested guidelines are more liberal than for mammals [28]. Such guideline suggestions comprise experiment set-up parameters (for example water quality) which are not kept constant and lead to the need for more experiments (involving more fish) to achieve acceptable results [28].

Health monitoring appears to be sparse and is mainly done for whole populations rather than individuals [28]. This Increases the risk of overlooking individual health issues and thus allowing for increased suffering of individuals.

Fish Used for Medicine

Fish used for medicine either originate from fish farms or are wild-caught. A common form of medical fish therapy is Ichthyotherapy. It describes the use of “doctor fish of Kangal” (Garra rufa) for the treatment of skin diseases such as psoriasis and eczema.

Garra rufa, native to Turkish mountain regions [29] is now found in “foot spas” across the world [30]. Other fish groups such as tilapia are used to treat second- and third-degree burns [31]. Their non-infectious and highly moist skin contains collagen proteins that prevent scarring and promote healing [32]. So far, most fish skin demand for burn treatment seems to come from Brazil. Brazilian pig and human tissue supply is significantly lower than in Western countries and can thus not be used for burn treatment as frequently [33].

Footspa fish garra ruffa

Garra rufa at work. A common scene at “foot spas”. Source: Wesley, 2018 (Picture from Kevinrevell)

Welfare Concerns for Fish Used for Medicine

In “foot spas,” Garra rufa fish are generally held in confined spaces and are unable to display their natural behavior such as hiding underneath rocks and vegetation [34]. Fish are starved to make them search for food on human skin and thereby remove dead skin parts. Human skin is largely composed of keratin, which is barely digestible and does not provide sufficient nutritional value for the fish [30].

Without proper monitoring, water quality in small tanks can quickly decrease due to ammonia build-up and insufficient aeration. Another cruel operation is heating tank water to 36-40°C to verify Garra rufa's “authenticity” [30]. This causes severe suffering and even death of “non-authentic” individuals (only the Turkish mountain species will survive these temperature extremes).

Welfare monitoring for fish used in medicine is limited in the UK and non-existent in other countries [30].


The primary purpose of baitfish is not direct consumption but the attraction of larger predatory species [35]. According to a publication by the U.S. Southern Regional Aquaculture Center, roughly 50% of baitfish are farm-raised while the other half are caught from the wild. Numbers of baitfish produced per year are hard to track and there are conflicting estimates even within countries.

For example, in the U.S., baitfish production per year ranges from 1.17 to 6 billion [36, 19b]. Common freshwater baitfish families include carp, minnow, sucker, and shad. For saltwater, popular baitfish include anchovies, herring, gudgeon, and halfbeaks [37].

For an assessment of how effective lobbying for stricter baitfish regulations in the U.S. can be, see this article by Saulius Šimčikas from Rethink Priorities.

Welfare Concerns for Baitfish

Baitfish are often crowded, frequently handled, and stored in small containers with bad water quality and, at times, even outside of water [37b]. When being used as bait, fish can experience pain from tissue damage if a hook is forced through them. Upon release into a new environment, they can experience stress and anxiety from sensing predators nearby while being immobile.

In cases where baitfish are thrown out without being hooked, they might be alive, dead or immobile from injuries and/or exhaustion. More welfare issues arise at the point of death, which often culminates in the fish being eaten alive or having parts of their body bitten off. The welfare of baitfish is challenging to monitor due to the missing supervision of recreational and commercial fishing practices.


Raised at fish farms or caught from the wild, feeders are not directly consumed. Instead, they are fed to predatory species in private households, zoos, lakes, and the ocean. A large portion of feeder fish is further processed into fishmeal and fish oil by drying and grinding them. Fishmeal was used as fertilizer until 1917 when, due to its high nutritional value, farmers used it to feed livestock [38]. As such, there is a far higher demand for fishmeal than single countries could produce and it is exported around the world. Worldwide 460 to 1,100 billion fish are “reduced” to fishmeal and fish oil every year [39].

Fishmeal trade network based on import and export data from the International Fishmeal and Oil Organization

Fishmeal trade network based on import and export data from the International Fishmeal and Oil Organization (2006-2010). Source: Ganias, K. (2014)

Welfare Concerns for Feeders

For fish that are live-fed, the potential for suffering is similar to baitfish with a high amount of stress and anxiety caused by the release into an unknown environment in close proximity to predators. Fish used for fishmeal are often caught and reared inhumanely, with high demand pushing for rapidly producing and capturing billions of individuals.

Due to the international market of fishmeal, there is little concern for monitoring the welfare of fish used for fishmeal, particularly in countries where fish welfare regulations do not exist.

Cleaner Fish

Farmed salmonids greatly suffer from sea lice infestations, which reduce growth, feed conversion ratios (FCR), and market prices (due to skin damage). Additionally, lice infestations facilitate secondary infections and generally increases mortality rates [40].

As an alternative method to stressful delousing [41], cleaner fish are added to such stocks to remove dead skin, ectoparasites, and/or infected skin and gill parts. This symbiotic relationship is a natural phenomenon and has been suggested to effectively manage parasites (Lepeophtheirus salmonis) in the “client fish” [42]. However, various scientists doubt its effectiveness [43]. Species from the family wrasse (Labridae) [44] as well as Cyclopteridae (lumpfish) are commonly used as cleaner fish.

Cleaner fish were mainly caught from the wild until around 2011 when demand for healthy individuals forced the industry to start farming them under controlled conditions [45]. By 2018 close to 90 million cleaner fish were kept on farms worldwide [19b].

Welfare Concerns for Cleaner Fish

Fish Welfare Initiative talked to an employee from North-European fish farm who pointed out that most polyculture systems focus on the welfare of their selling species (e.g. salmon) as opposed to the cleaner fish (e.g. wrasse) which leaves a great potential for the cleaner fish to suffer from inadequate water quality, rearing and feeding methods, and no medical treatment during disease outbreaks.

Welfare is ensured to the extent of keeping their natural behavior of cleaning intact in order to execute their primary and sole function on farms: delousing. This creates a high-stress environment. A recent study found that poor bone health and skeletal deformities due to this mechanical stress are common in wrasse [46]. Stressful rearing conditions also make for high mortality rates among cleaner fish [47]. Wild wrasse and lumpfish are diurnally active and prefer to hide under rocks and seaweed during the day [45]. Display of this natural behavior is impossible on most farms unless shelter obstacles are purposely introduced into the tanks/cages.

After their delousing lifetime (which can be as short as one season for lumpfish), cleaner fish are usually processed with the unused parts of salmon. There appears to be no information about how humane this death is and whether fish are desensitized first (it seems likely they are not).

Mercy Releases

An old Buddhist practice commonly referred to as “fang sheng”, “live release”, “mercy release”, and “prayer animal release”, suggests the release of captive animals to create good karma [48]. It is practiced in countries around the world including Taiwan, China, Thailand, Singapore, Nepal, India, Australia, France, England, and the United States. In Taiwan alone, 200 million animals are released annually, with releases several times a month [49].

While traditionally an act of compassion, this practice is increasingly criticized for releasing previously captured animals, often into foreign environments.

Welfare Concerns for Mercy Releases

While waiting for their release, fish are often kept in small buckets with questionable water quality and many individuals crowded together. The resulting stress and anxiety continue when entering a new environment. Having grown up on farms, these fish are often not capable of surviving in the wild. When released into the wrong environment (e.g. saltwater fish into freshwater), fish might suffer for a prolonged period before dying. Introducing non-native species also has the potential of challenging local species, and increasing their mortality rates [48]. During our field research, we have heard accounts of fish released while still in plastic bags, as well as sellers catching the released fish again to re-sell them after.

Farmed Fish

Fish raised in hatcheries and reared under human care until their processing stage are commonly referred to as farmed fish. Farming systems are generally distinguished as being extensive, intensive, or semi-intensive (see here) and can either be situated inland (e.g. in the form of Recirculating Aquaculture Systems and ponds) or in the ocean (mariculture).

Fish farms are often the first life stage of various fish groups represented above (baitfish, feeders, fish for medicine, restocking fish, ornamental fish, cleaner fish, mercy releases). Other groups include fish farmed for human consumption and for fertilizer, as well as those farmed for glue & medicine production. At any given point, 73 to 180 billion fish are reared exclusively for human consumption [50]. 90 billion fish are slaughtered each year [51]. Interestingly an estimated 15 to 1,000 billion fish die on farms before they even get slaughtered [51].

Welfare Concerns for Farmed Fish

See our report (p.4-8) and the report by Animal Charity Evaluators.

Wild fish

From 2007 to 2016 between 0.97 and 2.3 trillion fish have been caught from the wild worldwide [52]. While fishing practices date back 500,000 years, they experienced a major boost in technological advancement during the 19th century [53]. In a past report, we listed the most common capture methods for open-ocean fishing practices including trawling, purse seine, longline, and gill nets. Individual numbers of recreational fishers fluctuate between 220 and 700 million annually, the higher border being twice the number of commercial fishermen [54].

While recreational fishing sees more people involved, the advanced equipment of commercial fisheries allows for much higher yields. Wild-caught fish are generally used for the same purposes as farmed fish, including those purposes represented above (baitfish, feeders, fish for medicine, restocking fish, ornamental fish, cleaner fish, mercy releases). They are also caught for human consumption, and to produce fertilizer, glue, and medicine products.

Welfare Concerns for Wild Fish

See our report (p. 9-12) and the report by Fishcount.


1. Sneddon, L., & Wolfenden, D. (2018). Ornamental Fish (Actinopterygii). Companion Animal Care and Welfare: The UFAW Companion Animal Handbook, 440-466.

2. Dey, V. K. (2016). The Global Trade in Ornamental Fish. Infofish International.

3. Miller, S. M., & Mitchell, M. A. (2009). Ornamental fish. In Manual of exotic pet practice (pp. 39-72). WB Saunders.

4. Whittington, R. J., & Chong, R. (2007). Global trade in ornamental fish from an Australian perspective: the case for revised import risk analysis and management strategies. Preventive Veterinary Medicine, 81(1-3), 92-116.

5. Monticini, P. (2010). The ornamental fish trade. GLOBEFISH Research Programme, Vol. 102. Rome, FAO 2010

6. Sharpe, S. (2019, December 9). Nitrite poisoning in aquarium fish.

7. Schmidt, C., & Kunzmann, A. (2005). Post-harvest mortality in the marine aquarium trade: A case study of an Indonesian export facility. SPC Live Reef Fish Information Bulletin, 13, 3-12.

8. Gates, S. (2013). Shipping Live Fish: Striking Images Reveal How Betta Fish Are Packaged And Delivered. Huffpost.

9. Mahavongtrakul, M. (2019, March 4). Something in the water. Bangkok Post.

10. Chakrya, K. S. (2008, September 18). Betting on fighting fish big business in Pnomh Penh. Phnom Penh Post.

11. Elcoro, M., Silva, S. P. D., & Lattal, K. A. (2008). Visual reinforcement in the female Siamese fighting fish, Betta splendens. Journal of the experimental analysis of behavior, 90(1), 53-60.

12. Elwood, R. W., & Rainey, C. J. (1983). Social organization and aggression within small groups of female Siamese fighting fish, Betta splendens. Aggressive Behavior, 9(4), 303-308.

13. Blog post on Punishment for Fighting Betta Fish.

14. Peta Asia as cited in Hugo, K. (2018, October 30). Betta fish often mistreated in pet industry, evidence suggests.

15. Pleeging, C. C. F., & Moons, C. (2017). Potential welfare issues of the Siamese fighting fish (Betta splendens) at the retailer and in the hobbyist aquarium. Vlaams Diergeneeskundig Tijdschrift, 86(4), 213-223.

16. Peta Asia as cited in Hugo, K. (2018, October 30). Betta fish often mistreated in pet industry, evidence suggests.