Behavioural Ecology of Large Tuna

Animal behaviour operates at the intersection of physiological capacity and ecological constraints, making it a sensitive biomarker for stressor impacts. However, understanding behavioural responses requires monitoring at temporal resolutions matching the biological processes of interest, from sub-second events to seasonal strategies. Accelerometers uniquely capture behaviour across this breadth: high-frequency sampling resolves acute, rare events, while lower-resolution deployments reveal long-term patterns. This thesis first synthesises six decades of accelerometry applications in animal research, reviewing 1,520 studies across 400+ species (Chapter 2). It then uses Atlantic bluefin tuna (Thunnus thynnus, ABT), large migratory apex predators with exceptional physiological capacity, as a model system to examine behavioural responses to stressors operating across contrasting temporal scales. Chapter 3 documents an opportunistic 19-minute predation event by an orca, revealing predator-prey dynamics and subsequent orca foraging behaviour over 11 days. Chapter 4 quantifies post-release behavioural recovery following recreational angling capture-and-release, revealing a biphasic response, an acute escape (5-9 hours) followed by prolonged activity disruption (mean: 11 days, range: 2-26 days). Multi-metric assessments revealed spatial displacement, diel activity patterns, and depth use recovered at different rates with high individual variation. Chapter 5 compares behavioural responses to temperature between ABT and yellowfin tuna (Thunnus albacares, YFT) across 2-12 month deployments, revealing how contrasting physiologies translate to divergent strategies. ABT demonstrated behavioural compensation maintaining activity across 22°C despite optimal performance at 10-16°C, while YFT showed thermal restriction with reduced burst activity above 22°C despite occupying predominantly warm habitats. Together, these findings demonstrate that stressor impacts operate at nested temporal scales requiring matched measurement approaches. Physiological capacity constrains performance, but behavioural plasticity determines what individuals actually achieve. Individual variation in this flexibility may confer resilience to environmental change, insights accessible only through multi-scale accelerometry spanning seconds to seasons.<p></p>

Author dc:creator

• Jessica Rudd (21058817)

• Accelerometry
• Biologging
• Atlantic bluefin tuna
• Behavioural ecology
• Post-release behaviour

Statement dc:rights

• All rights reserved

Identifier

10779/exe.32820842.v1

OAI identifier oai:identifier

oai:figshare.com:article/32820842