Atmospheric carbon dioxide (CO2) is expected to more than double by the end of the century. The resulting changes in ocean chemistry (ocean acidification) will affect the behaviour, sensory systems and physiology of a range of fish species. Although a number of past studies have examined effects of CO2 in social fish species, 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. In a new study, Lauren Nadler, Shaun Killen, and colleagues at the Lizard Island Research Station and James Cook University find that exposure to increased dissolved CO2 causes a reduction in the tendency of green chromis damselfish to prefer to shoal with familiar fish. Even under elevated CO2, however, the presence of shoal-mates causes an apparent “calming effect” for individual fish, detectable via a reduction in metabolic rate. These results provide insight into some of the effects of rising CO2 levels and ocean acidification on shoaling behaviours in fish which are crucial for their ability to find food and avoid predators. Read more in the OPEN ACCESS paper here:

http://conphys.oxfordjournals.org/…/4/1/cow052.full.pdf+html

Nadler LE, Killen SS, McCormick MI, Watson S-A, Munday PL (2016) Effect of elevated carbon dioxide on shoal familiarity and metabolism in a coral reef fish. Conserv Physiol 4(1): cow052; doi:10.1093/conphys/cow052

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