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The Impact of Ocean Acidification on the Behavioral Lateralization of Fish

Paper Reviewed
Roche, D.G., Amcoff, M., Morgan, R., Sundin, J., Andreassen, A.H., Finnøen, M.H., Lawrence, M.J., Henderson, E., Norin, T., Speers-Roesch, B., Brown, C., Clark, T.D., Bshary, R., Leung, B., Jutfelt, F. and Binning, S.A. 2020. Behavioural lateralization in a detour test is not repeatable in fishes. Animal Behaviour 167: 55-64.

Introducing their work, Roche et al. (2020) write "various studies have evaluated how environmental and anthropogenic stressors such as pollutants and climate change affect [behavioral] lateralization in fishes, several of which have produced worrying results." And in this regard they say, "ocean acidification is reported to decrease lateralization across a range of marine fishes, including tropical and temperate species." However, they lament the fact that, to date, "no studies have systematically measured lateralization several times per individual, across multiple species, without a change in context, to establish the baseline repeatability of this behavior," adding "such a validation of the repeatability of lateralization assessed with a given test is crucial to establish the usefulness of a test for assessing this trait, particularly when differences between ecologically relevant treatments are used to infer effects on fitness."

Validation and repeatability are extremely important principles in formulating scientific hypotheses and theories, so it comes somewhat of a surprise to learn from Roche et al. that behavioral lateralization experiments, particularly those employing the T-maze (detour) test (a commonly utilized method in ecological, cognitive and behavioral sciences), have consistently failed to assess "the repeatability of individual lateralization scores" when "establishing the consistency of lateralization within individuals is essential for determining the relevance of this trait for evaluating fitness as well as the responses of animals to exogenous stressors," such as from so-called ocean acidification. Consequently the results and implications of such studies are remain in doubt.

In an effort to evaluate the short-term repeatability of behavioral lateralization in fishes, Roche et al. set out to conduct a "multispecies, international assessment of the repeatability of lateralization in four previously studied fish species using a detour test." They also reanalyzed the results of a fifth fish species using new statistical methods. The results of their analysis indicated that "behavioral lateralization as assessed by a detour test is not a repeatable trait in fishes over short timescales."

Given the above findings, the sixteen researchers ask the question why do some studies show significant positive relationships between lateralization and environmental stressors, such as ocean acidification? Answering their question, Roche et al. "carefully reviewed 31 published studies in which the detour test was employed to examine lateralization in fish and identified statistical issues in all of them," including low sampling size. They also say confirmation bias and poor research practices also contributed to "false positives, which are published more readily than negative results."

In light of all the above, Roche et al. conclude "the detour test as it has traditionally been implemented does not provide accurate, precise or repeatable estimates of behavioral lateralization in fishes." Consequently, they add, "drawing inferences from nonrepeatable measurements (or studies) not only obfuscates our understanding of a species' evolutionary ecology but also risks misleading policy and conservation efforts." Thus, the findings presented in all previous studies examining the relationship between ocean acidification and the behavioral lateralization of fishes using the detour test must be rejected until a more rigorous assessment is made.

Posted 15 January 2021