Funding for this research was provided by:
Association for the Study of Animal Behaviour
Received: 7 November 2020
Accepted: 7 March 2021
First Online: 20 March 2021
: This study was carried out in accordance with the relevant animal-welfare guidelines [CitationRef removed]. Our set-up prevented direct physical contact between fish, removing any risk of injury, and our protocol kept staged contests brief, reducing contest-related stress levels (as recommended by Huntingford [CitationRef removed]). By minimising the number of transfers, the duration that fish needed to be out of the water and by always transporting fish in water, we limited stress from handling and disturbance. Veterinary inspections by DHSSPS, Northern Ireland, deemed no need for licensing and an institutional ethical approval was acquired (No.: QUB-BS-AREC-17-004). Following the study’s conclusion, animals were kept for separate non-invasive tests.
: Not applicable.
: The authors declare that they have no competing interests.