Scientists have observed that some aggressive pulpy fish can hinder the cleaning work of other fish species, a finding reported by Cambridge University.
The Caribbean favorite for cleaner fish, the goby Elacatinus evelynae, feeds on parasites, dead tissue, scales, and mucus scraped from other fish. By removing these parts, gobies provide their “cleaning services” to marine life, illustrating a mutually beneficial relationship between species. These fish may operate alone or group with relatives to establish a coral reef cleaning station where other fish species willingly swim for service. This behavior demonstrates a key ecological exchange between cleaners and clients, showing how interspecies cooperation supports reef health, as noted by Cambridge University.
New research published in Behavioral Ecology shows that an abundance of pomacentric fish at a site can disrupt cleaning activity by displaying aggression toward other fish. This finding highlights how social dynamics among cleaners can influence the delivery of cleaning services to clients, with potential consequences for reef balance.
The study tracked cleaning stations on a shallow Tobago reef over six weeks, totaling more than 34 hours of observation. Observers found that client fish were less likely to approach stations that were frequently patrolled by pomacentres, who drive away intruders through displays of aggression and chasing behavior, a pattern attributed to territorial defense. These patrols appear to shape where clients choose to receive grooming, impacting the distribution of cleaning services across the reef.
Researchers describe the cleaners as ecosystem farmers, effectively removing algae and other unwanted growth to encourage the development of preferred algal communities on the reef. Pomotherines spend significant time guarding and patrolling algal zones, repelling intruders with bites and chases, according to the authors. These activities help maintain local algal balance and influence the overall health of the benthic community, illustrating a dynamic interaction between cleaning behavior and habitat management. The spatial reach of pomacentres can cover large portions of some reefs, even up to about 70 percent of certain areas, underscoring how intense patrolling can shape cleaner–client encounters and reef dynamics.
A healthy coral reef relies on a balance between algae and corals. When reef conditions deteriorate and fishing pressure increases, algae can flourish, leading to higher concentrations of pomacentric fish. This shift can interfere with the cleansing process and health of client fish, potentially threatening sensitive coral ecosystems as a whole. The study emphasizes the link between cleaner behavior, habitat health, and reef resilience, a chain of effects that researchers say warrants closer attention for conservation planning.
Looking ahead, the team aims to uncover the purpose behind pomacentres. Are they primarily protecting their own feeding grounds, or are they trying to monopolize treatment stations that they rarely use themselves? Answering these questions could reveal the strategic motives behind cleaner fish behavior and help elucidate how reef communities balance cooperation and competition in crowded habitats, as reported by Cambridge University.