Long-term cleaner fish presence affects growth of a coral reef fish

Abstract

Cleaning behaviour is considered to be a classical example of mutualism. However, no studies, to our knowledge, have measured the benefits to clients in terms of growth. In the longest experimental study of its kind, over an 8 year period, cleaner fish Labroides dimidiatus were consistently removed from seven patch reefs (61 -285 m 2 ) and left undisturbed on nine control reefs, and the growth and parasite load of the damselfish Pomacentrus moluccensis determined. After 8 years, growth was reduced and parasitic copepod abundance was higher on fish from removal reefs compared with controls, but only in larger individuals. Behavioural observations revealed that P. moluccensis cleaned by L. dimidiatus were 27 per cent larger than nearby conspecifics. The selective cleaning by L. dimidiatus probably explains why only larger P. moluccensis individuals benefited from cleaning. This is the first demonstration, to our knowledge, that cleaners affect the growth rate of client individuals; a greater size for a given age should result in increased fecundity at a given time. The effect of the removal of so few small fish on the size of another fish species is unprecedented on coral reefs.

Power and temptation cause shifts between exploitation and cooperation in a cleaner wrasse mutualism

“…The cleaning mutualism involving the cleaner wrasse Labroides dimidiatus provides a model system to study cooperation in asymmetric games such as this: cleaners may cooperate with client fish by consuming their ectoparasites, leading to net benefits for clients [39,40] but preferentially exploit them by eating mucus [41], while non-predatory clients lack the option to cheat in return (they cannot eat a cleaner). Lacking the option to reciprocate, clients face the challenge of inducing cleaners to feed against their preference, in order to obtain a good cleaning service.…”

Parasites and cleaning behaviour in damselfishes

“…This relationship suggested that mobile reef fish actively seek cleaner wrasses in order to have gnathiids and other parasites removed. Clague et al (2011) showed that on reefs with cleaner fish, older P. moluccensis were larger at a certain age than those from reefs with no cleaner fish. They also found that copepod abundance was higher on fish from reefs with no cleaner fish, but only for larger host fish.…”

“…Clague et al (2011) showed that, on reefs with cleaner fish, older Pomacentrus moluccensis were larger at a certain age than those from reefs without cleaner fish. Gnathiids have been demonstrated to be important during settlement, in that a single gnathiid can decrease the success of settlement of P. amboinensis larvae significantly .…”

“…Typically cleaners have defined territories, 'cleaning stations', which are visited by organisms, the 'clients' (Côté 2000). There is strong evidence to show that clients do obtain net benefits from the interaction (Bshary et al 2007;Clague et al 2011;Ros et al 2011;Soares et al 2011). Several studies have shown that the presence of cleaner fish affects the size and abundance of crustacean parasites on fish (Gorlick et al 1987;Grutter 1999a;Cheney and Côté 2001;Grutter and Lester 2002;Clague et al 2011), increases the size distribution of fish (Clague et al 2011;Waldie et al 2011), and affects the composition of client fish communities (Bshary 2003;Grutter et al 2003;Waldie et al 2011).…”

“…Cleaner presence could also affect larval fish growth or survival through modification of the behaviour of predatory fish and thus the risk of predation, as there is evidence that predators reduce aggression towards bystanders in the presence of a cleaner wrasse (Cheney et al 2008). I examined the effects of cleaner fish presence on juvenile density using patch reefs that have been experimentally manipulated for 12 years by being kept free of cleaner wrasses (Clague et al 2011;Waldie et al 2011). …”