Habitat use and behaviour of lemon sharks (Negaprion brevirostris) at a sub-tropical nursery site in the Bahamas

Bullock, Robert William

Abstract

Understanding how animals behave in their natural environment provides important insights into their ecology and is valuable for species conservation. For many aquatic species, observation of behaviour is difficult and research has in the past largely focused on understanding space use and movement patters. However, a more comprehensive ecological understanding requires knowing not just where animals are within their habitat but what they do whilst there and why. With the emergence of new technologies capable of obtaining more accurate temporal behavioural data, pathways to a more complete understanding can be forged. This research used a series of semi-captive experimental trials, tagging and tracking of wild animals, environmental sampling and prey species mapping to observe the spatio- temporal behavioural routine of young lemon sharks using a nursery habitat in the Bahamas. Capture and handling practices were found to minimally impact the behaviour of young lemon sharks and individuals recovered quickly, upon release. Periods of refuging behaviour were exhibited by sharks, post-release, but in all instances this behavioural response was over a short timeframe (< 1 h). Wild lemon sharks were found to display repeatable patterns in space use, activity and specific behaviours within the nursery habitat. Supporting existing research, movement within the habitat was shown to be, in part, driven by tidally mediated predation threat, forcing most sharks to move closer to shore at times of increased threat. Furthering existing research, findings here uncover a behavioural strategy in these sharks to trade-off predation risk with foraging and bioenergetic management. Accelerometer-derived measurements of activity and specific behaviour, alongside prey abundance mapping, show that sharks increase swimming activity and foraging behaviour at times of lower predation risk in areas further from shore, coinciding with increased abundances of preferred prey and potentially favourable environmental conditions. At times of higher predation threat, sharks use nearshore areas, decrease swimming activity and exhibit resting behaviour. Findings also demonstrate changes in space use, activity and specific behaviour of sharks as they grow and predation risk decreases. This research elucidates the complete spatio-temporal behavioural routine of young sharks using a nursery site and furthers understanding of the critical components these habitats provide to support the survival of sharks to adulthood.

Citation

Bullock, R. W. Habitat use and behaviour of lemon sharks (Negaprion brevirostris) at a sub-tropical nursery site in the Bahamas. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/4222655

• Thesis Type: Thesis
• Deposit Date: Sep 8, 2020
• Publicly Available Date: Feb 23, 2023
• Keywords: Environmental sciences
• Public URL: https://hull-repository.worktribe.com/output/4222655
• Additional Information: School of Environmental Sciences, The University of Hull
• Award Date: May 1, 2018