Cognitive Abilities in Fish: Biological Predictors and Impact on Reproductive Success

Abstract

Cognitive Abilities in Fish: Biological Predictors and Impact on Reproductive Success

Thesis Abstract

Cognitive abilities underpin almost every animal behaviour and allow them to gather, store, process, and use information essential for survival and reproduction. Great variation in cognitive abilities exists not only between different species, but even across individuals from the same population. This variation suggests that the evolution of cognition involves multiple factors. Cognitive abilities, their adaptive value, and their biological predictors remain poorly understood in wild animals, and are particularly overlooked in fish. In this thesis, I present five experimental studies exploring how various animal traits and environmental factors impact cognition, and how cognition can enhance fitness in wild animals.

In Chapter 1, I explore the ability of mosquitofish (Gambusia holbrooki) to express inhibitory control, an essential cognitive trait that inhibits impulsive actions in favour of delayed rewards. I show how sex, age, and personality can impact their inhibitory control.

Chapter 2 investigates the effect of a widespread environmental pollutant, fluoxetine, on inhibitory control of guppies (Poecilia reticulata). I discuss how sex, dosage and body size influence the effects of fluoxetine, and the potential transgenerational impact of pollution on fish behaviour.

In Chapter 3, I look at how the negative effect of inbreeding on cognition can be amplified in stressful environments in guppies. I discuss how the magnitude of inbreeding depression can change depending on sex and sex-specific tolerance to environmental stress in the form of elevated temperature.

Chapter 4 explores sexual selection on cognitive abilities in mosquitofish. I design a battery of five cognitive assays to measure different cognitive traits. First, I investigate whether individual scores are correlated across tasks, which is suggestive of the presence of "general intelligence". Second, I test whether performance in these tasks correlates with male paternity, which is consistent with sexual selection on cognition.

Finally, Chapter 5 tests for the existence of cognitive senescence, the anticipated decline of cognitive abilities with age. Using the battery of five cognitive assays, I investigate how age impacts performance across different cognitive domains. I discuss the biological relevance of sexually selected cognitive abilities and the observed scale of senescence. Show more