A novel apparatus for studying fish cognition in the wild

Summary

Fish show a huge variation of ecological, anatomical and behavioural traits, which makes them prime subjects for studying behaviour, cognition and their evolution. Lab-based studies allow a controlled examination of some of the mechanisms underpinning cognition and have yielded many insights into fish cognitive abilities. However, they may skew our understanding of fish cognition, as the artificial captive environment might affect cognitive and behavioural performance. Few fish cognition studies have been conducted in the field or with wild fish populations. To address this, we introduce a novel cognitive apparatus designed for fish in their natural habitats. To demonstrate its efficacy, we conducted two tests using a social foraging task: one focused on learning and social foraging decisions in guppies (Poecilia reticulata) in tropical Trinidad, and another on learning in nine-spined sticklebacks (Pungitius pungitius) in the temperate Netherlands. We obtained learning curves over sessions for both species, consistent with established laboratory assays. We also succeeded in analysing producer–scrounger dynamics; we found stable proportions of producer and scrounger individuals across populations, but low consistency of individual strategies over time. Our results show that this low-cost, easy-to-adapt apparatus is effective for assessing a variety of cognitive abilities across different fish species. This study provides a starting point to test different aspects of fish cognition under natural conditions and can pave the way for examining in situ cognitive variation between species and populations exposed to different ecological conditions.