The aquaculture industry exploits wrasses and lumpfishes to “clean” the captive salmon farming individuals of parasites, but this causes even more deaths.
Salmon farming is an industrialised aquaculture practice where thousands of captive salmons (Salmo salar) are confined in massive ocean cages or land-based tanks to be slaughtered for human consumption. In these highly congested, polluting, artificial environments, parasitic infestations flourish, particularly sea lice (Lepeophtheirus salmonis), who attach themselves to the salmons and feed on their skin and blood. To combat this issue without relying entirely on chemical treatments, the aquaculture industry exploits “cleaner fishes” (we use the plural of fish as “fishes”, or of salmon as “salmons”, as we write in veganised language).
The primary species forced into this role are wrasses, such as the ballan wrasse (Labrus bergylta) and corkwing wrasse (Symphodus melops), as well as lumpfishes (Cyclopterus lumpus), who naturally eat exo-parasites of other fishes in the wild. These individuals are introduced directly into the crowded salmon pens to pick the parasites off the captive salmons.
The industry presents the use of these fishes as a natural, eco-friendly solution, but in reality, it simply replaces one form of suffering with another, causing even more deaths. Instead of addressing the underlying causes of parasite outbreaks (namely the unnatural overcrowding and filthy conditions of industrial fish farms), the industry has chosen to enslave additional species, drawing them into a cycle of captivity, suffering, and premature death.
How cleaner fishes are used in aquaculture
The use of cleaner fishes in commercial aquaculture began in the late 1980s and early 1990s, gaining widespread traction in major salmon-producing nations such as Norway, Scotland, and Chile (where it is less common). Ocean net cages provide ideal conditions for sea lice to multiply rapidly, causing severe open wounds and stress to the salmons. As sea lice developed resistance to chemical baths and parasiticides, the industry turned to cleaner fishes as a biological control mechanism.
Before 2011, all cleaner fish used in sea cages were wild-caught wrasses of several species, including ballan (Labrus bergylta), corkwing (Symphodus melops), goldsinny (Ctenolabrus ruptestris), and cuckoo (Labrus mixtus). Later, the use of farmed lumpfish and farmed ballan wrasse increased, with wild wrasse populations still used and kept in sea cages.
When used, thousands of wrasses or lumpfishes are deployed into salmon net pens alongside tens of thousands of salmons. Lumpfishes are often preferred in colder waters during winter months because they remain active at lower temperatures than wrasses. The cleaner fishes are expected to swim among the salmons and pick off the parasites. To keep them alive long enough to perform this task, farmers place artificial kelp ropes within the net cages to offer hiding spots, along with supplementary feed pellets, as sea lice alone do not meet their full nutritional requirements. Cleaner fishes are typically kept at ratios of 2–8% of the salmon population (higher ratios often used for farmed ballan wrasses).
The scale of this operation grew exponentially during the first two decades of the 21st century. Millions of these small marine beings are now routinely transferred into intensive farming operations each year. However, the use of these cleaner fishes in aquaculture peaked around 2019 and has declined since due to welfare concerns, inconsistent results, alternative technologies, and regulation.
The rapid expansion was driven by the progressive loss of efficacy of chemical parasiticides against sea lice, combined with the availability of former cod hatcheries that were converted to produce lumpfishes and ballan wrasses after the collapse of Norway’s cod-farming industry.
In Norway alone, more than 510 million wild-caught and farmed cleaner fishes were deployed into salmon pens between 1998 and 2024. Numbers rose sharply after 2008, reaching a peak of over 61 million individuals stocked in a single year in 2019 (of which roughly 70 per cent were farmed lumpfishes). By 2024, the figure had fallen to approximately 22.5 million, and the number of farms using cleaner fishes dropped from 473 to 214 over the same period. Parallel large-scale use has occurred in Scotland, where estimates indicate more than 22 million cleaner fishes (around 16 million lumpfishes and 6 million wrasses) were introduced on monitored farms between 2020 and 2024. Chile has also employed the practice, although on a smaller scale and with more limited published data.
More species trapped in aquaculture
Forcing cleaner fishes into aquaculture is a severe ethical issue that expands systemic animal exploitation by trapping additional species in captivity and servitude. Millions of wrasses are captured directly from the wild using pot traps, disrupting local wild coastal ecosystems, while lumpfishes are mass-bred in intensive hatcheries solely to serve as disposable biological tools.
Once inside the salmon pens, these fishes face horrific conditions. Wrasses and lumpfishes are naturally territorial and accustomed to complex, sheltered marine environments. In ocean cages, they are exposed to high currents, extreme overcrowding, and aggression from the much larger salmons. Mortality rates amongst cleaner fishes in farms are catastrophic, sometimes reaching 40% to 100% over a single production cycle.
Research has shown how intelligent wrasses are, being one of the few species who can recognise themselves in a reflection (having passed the “mirror test”), so their confinement is bound to cause them great distress.
Because they are treated merely as expendable commodities rather than sentient individuals, when the surviving salmons are sent to be killed, the remaining cleaner fishes are routinely killed or discarded as waste (adding additional deaths to the macabre tally of the aquaculture industry). They are given no protection, no “retirement” after their forced labour, and no consideration for their fundamental right to live free from human exploitation.
Mortality among cleaner fishes remains extremely high. In Norway, the cumulative mortality risk across a full production cycle reached 82.1% in 2024 (including individuals killed at the end of the cycle). Commercial-scale studies have recorded losses of 27% for lumpfishes and 57% for ballan wrasses over periods of a few months, while broader industry surveys report minimum registered mortalities of 33–47%, with actual losses frequently higher once unregistered escapes, predation and handling deaths are included. In Scotland, analysis of official reports from larger farms estimates that at least 7 million cleaner fishes (5.8 million lumpfishes and 1.2 million wrasses) died between 2020 and the end of 2024; the true figure is likely higher because smaller incidents and smaller farms were excluded.
The principal causes of death are bacterial disease (especially atypical furunculosis), emaciation and starvation, stress from high currents and overcrowding, aggression from the much larger salmons, and physical injury during routine mechanical or thermal delousing operations aimed at the salmons. When the surviving salmons are sent to be killed, any remaining cleaner fishes are almost invariably killed or discarded because reuse is rare due to disease-transfer risk. Therefore, millions of sentient beings are exploited and killed each year solely to attempt to solve an animal welfare problem created by the aquaculture industry, making the overall record of this industry even worse.
