Disruption of behavioural lateralization and shoaling cohesion on sand smelt (Atherina presbyter) larvae under ocean acidification

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Projected future CO2 levels influence the behaviour and development of early life coral reef fishes; it is uncertain to what extent this effect occurs in temperate species. The effect that elevated CO2 levels, expected to occur in coastal upwelling regions in the future, have on lateralization and shoaling behaviours of fish were tested in temperate sand smelt Atherina presbyter larvae. Routine swimming speed did not differ between control and high CO2, but exposure to high pCO2 for 7 days affected group cohesion. Lateralization was affected in fish reared at high CO2. To test if behavioural changes were caused by interference of high CO2 with GABA-A receptor function, larvae were treated with a receptor antagonist (gabazine). Gabazine reversed the loss of lateralization on larvae exposed to high CO2. These results suggest that pCO2 levels probable to occur in coastal temperate ecosystems in the near-future will have an adverse effect on larval behaviour, which can potential compromise survival of fish early life stages.