Ocean warming and acidification degrade shoaling performance and lateralization of novel tropical–temperate fish shoals. (17th December 2021)

• Record Type: Journal Article
• Authors: Mitchell, Angus; Booth, David J.; Nagelkerken, Ivan
• Is Part Of: Global change biology. Volume 28:Number 4(2022)
• Page Start: 1388
• Page End: 1401
• Publication Date: 2021-12-17
• Subjects: climate change -- lateralization -- ocean acidification -- ocean warming -- range extension -- shoaling -- species interactions -- tropicalization; Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.16022
• Languages: English
• ISSNs: 1354-1013

Abstract

Abstract: Gregarious behaviours are common in animals and provide various benefits such as food acquisition and protection against predators. Many gregarious tropical species are shifting poleward under current ocean warming, creating novel species and social interactions with local temperate taxa. However, how the dynamics of these novel shoals might be altered by future ocean warming and acidification remains untested. Here we evaluate how novel species interactions, ocean acidification and warming affect shoaling dynamics, motor lateralization and boldness of range‐extending tropical and co‐shoaling temperate fishes under controlled laboratory conditions. Fishes were exposed to 1 of 12 treatments (combinations of three temperature levels, two p CO2 levels and two shoal type levels: mixed species or temperate only) for 38 days. Lateralization (a measure of asymmetric expression of cognitive function in group coordination and predator escape) of tropical and temperate species was right‐side biased under present‐day conditions, but side bias significantly diminished in tropical and temperate fishes under ocean acidification. Ocean acidification also decreased shoal cohesion irrespective of shoaling type, with mixed‐species shoals showing significantly lower cohesion than temperate‐only shoals irrespective of climate stressors. Tropical fish became bolder under ocean acidification (after 4 weeks), and temperate fish became bolder with increasing temperature, while ocean acidification dampened temperate fish boldness. Our findings highlight the direct effect of climate stressors on fish behaviour and the interplay with the indirect effects of novel species interactions. Because strong shoal cohesion and lateralization are key determinants of species fitness, their degradation under ocean warming and acidification could adversely affect species performance in novel assemblages in a future ocean, and might slow down tropical species range extensions. Abstract : Conceptual diagram showing how the future combined effect of temperature and CO2 increases can reduce the inter‐individual distance (IID), relative lateralization (LR) and startle escape distance (SED) of novel shoal types of local temperate and vagrant tropical fishes. Integration of tropical vagrants into residing temperate shoals slows down shoal oscillation frequency, increases shoal cohesion amplitude and decreases shoal cohesion compared to temperate‐only shoals who exhibit higher shoal cohesion and lower amplitude faster oscillation frequency.