title: Effect of elevated carbon dioxide on shoal familiarity and metabolism in a coral reef fish.
abstract: Atmospheric CO2is expected to more than double by the end of the century. The resulting changes in ocean chemistry will affect the behaviour, sensory systems and physiology of a range of fish species. Although a number of past studies have examined effects of CO2in gregarious fishes, most have assessed individuals in social isolation, which can alter individual behaviour and metabolism in social species. Within social groups, a learned familiarity can develop following a prolonged period of interaction between individuals, with fishes preferentially associating with familiar conspecifics because of benefits such as improved social learning and greater foraging opportunities. However, social recognition occurs through detection of shoal-mate cues; hence, it may be disrupted by near-future CO2conditions. In the present study, we examined the influence of elevated CO2on shoal familiarity and the metabolic benefits of group living in the gregarious damselfish species the blue-green puller (Chromis viridis). Shoals were acclimated to one of three nominal CO2treatments: control (450 µatm), mid-CO2(750 µatm) or high-CO2(1000 µatm). After a 4-7 day acclimation period, familiarity was examined using a choice test, in which individuals were given the choice to associate with familiar shoal-mates or unfamiliar conspecifics. In control conditions, individuals preferentially associated with familiar shoal-mates. However, this association was lost in both elevated-CO2treatments. Elevated CO2did not impact the calming effect of shoaling on metabolism, as measured using an intermittent-flow respirometry methodology for social species following a 17-20 day acclimation period to CO2treatment. In all CO2treatments, individuals exhibited a significantly lower metabolic rate when measured in a shoal vs. alone, highlighting the complexity of shoal dynamics and the processes that influence the benefits of shoaling.
authors.affiliation: College of Science and Engineering, James Cook University, Townsville, Queensland 4811, Australia; ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland 4811, Australia.
authors.forename: Lauren E
authors.initials: LE
authors.lastname: Nadler
authors.affiliation: Institute of Biodiversity, Animal Health and Comparative Medicine , University of Glasgow , Glasgow G12 8QQ, UK.
authors.forename: Shaun S
authors.initials: SS
authors.lastname: Killen
authors.affiliation: College of Science and Engineering, James Cook University, Townsville, Queensland 4811, Australia; ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland 4811, Australia.
authors.forename: Mark I
authors.initials: MI
authors.lastname: McCormick
authors.affiliation: ARC Centre of Excellence for Coral Reef Studies , James Cook University , Townsville, Queensland 4811 , Australia.
authors.forename: Sue-Ann
authors.initials: SA
authors.lastname: Watson
authors.affiliation: ARC Centre of Excellence for Coral Reef Studies , James Cook University , Townsville, Queensland 4811 , Australia.
authors.forename: Philip L
authors.initials: PL
authors.lastname: Munday
keywords: Calming effect; carbon dioxide; familiarity; respiratory physiology; shoaling; social recognition