MEPS 571:183-191 (2017)  -  DOI: https://doi.org/10.3354/meps12130

ABSTRACT: Ocean acidification induces strong behavioural alterations in marine fish as a consequence of acid-base regulatory processes in response to increasing environmental CO₂ partial pressure. While these changes have been investigated in tropical and temperate fish species, nothing is known about behavioural effects on polar species. In particular, fishes of the Arctic Ocean will experience much greater acidification and warming than temperate or tropical species. Also, possible interactions of ocean warming and acidification are still understudied. Here we analysed the combined effects of warming and acidification on behavioural patterns of 2 fish species co-occurring around Svalbard, viz. polar cod Boreogadus saida and Atlantic cod Gadus morhua. We found a significant temperature effect on the spontaneous activity of B. saida, but not of G. morhua. Environmental CO₂ did not significantly influence activity of either species. In contrast, behavioural laterality of B. saida was affected by CO₂ but not by temperature. Behavioural laterality of G. morhua was not affected by temperature or CO₂; however, in this species, a possible temperature dependency of CO₂ effects on relative laterality may have been missed due to sample size restrictions. This study indicates that fish in polar ecosystems may undergo some, albeit less intense, behavioural disturbances under ocean acidification and in combination with ocean warming than observed in tropical species. It further accentuates species-specific differences in vulnerability.

KEY WORDS: Ocean acidification · Climate change · Fish behaviour · Laterality · Activity · Polar habitat · Atlantic cod · Polar cod