Predicting current and future global distributions of whale sharks

Area of Science:

• Marine Biology
• Climate Change Ecology
• Conservation Science

Background:

• The whale shark (Rhincodon typus), listed as Vulnerable by the IUCN, inhabits global warm and temperate waters.
• Current and future global distribution predictions for whale sharks are lacking.
• Understanding habitat shifts is crucial for conservation efforts.

Purpose of the Study:

• To predict the present-day and future global distribution of whale sharks.
• To test if environmental covariates similarly predict whale shark occurrence across ocean basins.
• To assess the impact of climate change on whale shark distribution.

Main Methods:

• Utilized 30 years of whale shark observation data (1980-2010) from tuna purse-seiners.
• Applied generalized linear mixed-effects models with environmental predictors (sea surface temperature, chlorophyll a, bathymetry, depth, slope, distance to shore).
• Predicted 2070 sea surface temperatures using an ensemble of global circulation models under a no-policy scenario.

Main Results:

• Habitat suitability is primarily influenced by bathymetry and sea surface temperature, with slight variations across oceans.
• Warming sea surface temperatures are predicted to cause a poleward shift in suitable habitat in the Atlantic and Indian Oceans.
• A slight range contraction is anticipated, with minor changes predicted for the Pacific Ocean.

Conclusions:

• Warming sea surface temperatures may drive whale sharks away from current aggregation sites.
• The species' distribution is likely to undergo an overall redistribution.
• Conservation strategies must consider these predicted shifts in habitat suitability due to climate change.