Behavioral responses of Atlantic cod to sea temperature changes

Area of Science:

• Marine Biology
• Climate Change Ecology
• Behavioral Oceanography

Background:

• Marine ectotherms are expected to exhibit behavioral plasticity in response to temperature variability.
• Understanding these responses is crucial for predicting the impacts of climate change on ocean ecosystems.
• Quantifying behavioral adjustments in wild marine species presents significant methodological challenges.

Purpose of the Study:

• To investigate the influence of sea temperature on the depth use and activity patterns of Atlantic cod (Gadus morhua).
• To assess how temperature variability affects diel vertical migration and movement patterns in different age classes of cod.
• To predict the potential consequences of rising sea surface temperatures on cod populations.

Main Methods:

• Combined four years of telemetry data on juvenile and adult Atlantic cod behavior with in situ ocean temperature measurements.
• Analyzed cod depth use, activity levels, and distances traveled in relation to ambient sea temperatures.
• Investigated variations in behavioral responses between smaller and larger cod specimens.

Main Results:

• Increased sea surface temperature correlated with cod occupying deeper waters, with a stronger effect observed in larger cod.
• Diel vertical migration patterns were more pronounced in smaller cod but were limited to deeper waters as temperatures exceeded approximately 15°C.
• Colder winter temperatures reduced diel vertical migration and activity levels in smaller cod.

Conclusions:

• Sea temperature significantly influences Atlantic cod behavior, including depth selection and activity.
• Rising sea surface temperatures may restrict access to critical shallow feeding habitats for cod during summer.
• These behavioral changes driven by warming oceans could negatively impact the viability of local Atlantic cod populations.