Daily estuary tides orchestrate clients seeking service from facultative cleaners

Abstract

Mutualism essentially encompasses the ecological and evolutionary aspects of net cooperative gain for multiple taxa and genes. Despite many aquatic assemblages and communities being investigated for trophic and competitive interactions; mutualism is not always as closely scrutinised. Notable exceptions are provided by studies of cleaner fish and invertebrate cleaning behaviour in clear-water, tropical coral reef ecosystems and nearshore subtropical marine contexts. Recently, estuarine fish cleaning of parasites has been reported from detailed above-water observations made in eastern Australia and the current study provides additional records of subtropical estuarine fish cleaning relationships based on underwater observation. Specifically, the ubiquitous subtropical estuarine fish, yellowfin bream, Acanthopagrus australis (Sparidae) was observed regularly presenting for parasite cleaning by the common stripey, Microcanthus joyceae (Microcanthidae) in the lower Maroochy River (Queensland, Australia), most notably around morning high tides. Additionally, M. joyceae was occasionally observed cleaning Moses Perch, Lutjanus russelli (Lutjanidae) and Racoon Butterfly fish, Chaetodon lunula (Chaetodontidae) and pomacentrids (Abudefduf vaigiensis and A. bengalensis) were infrequently cleaning juvenile yellowfin bream. These interactions provide examples of small-bodied fishes with comparable body demarcation (black and yellow bands or stripes) to that of a previously identified fish cleaner (juvenile silver batfish, Monodactylus argenteus (Monodactylidae)) in estuaries, typically servicing clients larger in body size than the cleaners. Interestingly, juveniles of M. argenteus were present but not seen performing cleaning behaviour in the current study. Facultative cleaning species warrant further attention with water clarity and benthic structure representing promising factors to consider in planning future work.