Nonlinearity in interspecific interactions in response to climate change: Cod and haddock as an example

Area of Science:

• Marine Ecology
• Climate Change Biology
• Population Dynamics

Background:

• Trophic interactions are crucial for ecosystem stability.
• Climate change, particularly sea temperature (ST) increases, significantly impacts marine species distribution and interactions.
• The coexistence of Atlantic cod and haddock in the North Atlantic is influenced by their predator-prey relationship and competition.

Purpose of the Study:

• To analyze the dynamic effect of climate on the coexistence of sympatric cod and haddock in the Barents Sea.
• To investigate how long-term climate variation, specifically sea temperature, influences species demography and interactions.
• To understand shifts in the cod-haddock interaction over the last two decades due to rising sea temperatures.

Main Methods:

• Utilized 33-year time series data of haddock and cod abundance estimates from acoustic and trawl surveys.
• Employed a Bayesian state-space threshold model to analyze climate-driven demographic effects.
• Examined the influence of sea temperature on density-independent processes and interspecific interactions.

Main Results:

• Long-term climate variation, indicated by sea temperature changes, significantly affected species demography.
• The interaction between cod and haddock shifted over the past two decades, correlating with increased sea temperature.
• During warmer years (ST > 4°C), increased cod abundance negatively impacted haddock abundance, altering equilibrium population sizes.

Conclusions:

• Long-term climate change can alter the equilibrium conditions of species assemblages in Arcto-Boreal systems.
• Shifting predator-prey dynamics between cod and haddock due to rising sea temperatures can lead to higher overall population sizes in warmer periods.
• Understanding climate-driven shifts in trophic interactions is vital for predicting future marine ecosystem dynamics.