Predicting feeding success in a migratory predator: integrating telemetry, environment, and modeling techniques

Area of Science:

• Marine Ecology
• Fisheries Science
• Animal Behavior

Background:

• Foraging theory suggests mobile predators frequent resource-rich "hotspots."
• Research often focuses on identifying these hotspots and their environmental drivers for migratory species.
• Southern bluefin tuna (Thunnus maccoyii) are a key target species in fisheries.

Purpose of the Study:

• To investigate factors predicting foraging success in southern bluefin tuna during their annual oceanic migrations.
• To test if southern bluefin tuna adhere to traditional "hotspot" foraging models.
• To understand the relationship between movement, feeding, and environmental variables in a large pelagic predator.

Main Methods:

• Integrated telemetry-based feeding and movement data from 19 southern bluefin tuna (99 +/- 3 cm LCF) with environmental data (1998-2000).
• Employed generalized linear models and generalized linear mixed models, formulating feeding as a Markov process.
• Analyzed foraging patterns across the scale of annual oceanic migrations.

Main Results:

• Coastal waters of southern Australia showed increased feeding predictability, suggesting a potential foraging hotspot for juvenile tuna in austral summer.
• In oceanic waters, southern bluefin tuna displayed high foraging success throughout their range, particularly during continuous travel, deviating from typical hotspot models.
• Both foraging hotspots and coldspots were observed, strongly predicted by warm ocean temperatures.

Conclusions:

• Southern bluefin tuna foraging ecology is more complex than a simple "hotspot" model, especially in oceanic environments.
• Opportunistic and continuous feeding may be prevalent in large pelagic predators across heterogeneous ocean conditions.
• Environmental factors, notably temperature, significantly influence the distribution of foraging success and failure during migrations.