Assessing Granger-Causality in the Southern Humboldt Current Ecosystem Using Cross-Spectral Methods.

Area of Science:

• Marine Ecology
• Fisheries Science
• Oceanography

Background:

• The southern Humboldt Current ecosystem is crucial for pelagic species.
• Sea surface temperature is traditionally considered a primary driver of anchovy (Engraulis ringens) biological indicators.
• Understanding regional drivers is essential for ecosystem management.

Purpose of the Study:

• To investigate the influence of regional drivers, specifically Pacific decadal oscillation anomalies, on anchovy reproductive and body condition indicators.
• To explore the impact of warm conditions, sea turbulence, and Ekman transport on anchovy biological processes.
• To apply advanced statistical methods to determine causality between environmental factors and anchovy dynamics.

Main Methods:

• Utilized frequency-domain Granger-causality to test statistical significance and direction of causality between time series.
• Analyzed the relationship between Pacific decadal oscillation anomalies, sea surface temperature, and anchovy biological indicators.
• Examined the synchronization of anchovy body condition with local environmental conditions.

Main Results:

• Pacific decadal oscillation anomalies were identified as significant drivers of anchovy reproductive and body condition indicators, alongside sea surface temperature.
• Warm conditions were found to potentially increase gonad development and synchronize body condition dynamics.
• The study identified causal links between environmental factors and anchovy biological processes.

Conclusions:

• Regional drivers like Pacific decadal oscillation anomalies play a critical role in the southern Humboldt Current ecosystem.
• Environmental conditions significantly influence anchovy (Engraulis ringens) reproduction and feeding, offering predictive insights.
• This research provides valuable data for predicting anchovy abundance and biological peaks in the region.