Quantifying heterogeneous responses of fish community size structure using novel combined statistical techniques

Area of Science:

• Marine ecology
• Ecosystem dynamics
• Fisheries science

Background:

• Large Marine Ecosystems (LMEs) are useful for monitoring but may obscure local ecological dynamics.
• Understanding ecological change requires appropriate spatial scales of analysis.
• Previous assessments often treat large ecosystems homogeneously.

Purpose of the Study:

• To mathematically determine local and regional patterns of ecological change within an LME.
• To identify potential drivers of these changes using statistical models.
• To highlight spatial heterogeneity in ecological responses within the North Sea.

Main Methods:

• Empirical Orthogonal Functions (EOFs) were used to define regions with distinct ecological change patterns.
• Nonlinear AutoRegressive Moving Average with eXogenous input (NARMAX) models assessed drivers of change.
• Spatial datasets (fish abundance, temperature, oxygen, net primary production, fishing pressure) from 1980-2008 were analyzed.

Main Results:

• The central North Sea showed decreased community size structure, linked to fishing pressure.
• The Norwegian trench region exhibited increased community size structure, linked to sea-bottom temperature changes.
• An area off the Scottish coast showed no significant change, associated with net primary production.

Conclusions:

• Ecological changes in the North Sea are spatially heterogeneous, influenced by multiple drivers.
• Fishing pressure and temperature are key drivers in specific North Sea regions.
• Local spatial dynamics are crucial and often overlooked in broad-scale ecosystem assessments.