Climate-driven deoxygenation elevates fishing vulnerability for the ocean's widest ranging shark
Marisa Vedor1,2, Nuno Queiroz1,3, Gonzalo Mucientes1,4
1CIBIO/InBIO, Universidade do Porto, Campus Agrário de Vairão, Vairão, Portugal.
Elife
|January 19, 2021
Summary
Climate change is shrinking the habitat of blue sharks by reducing dissolved oxygen (DO) at depth. This forces sharks into shallower waters, increasing their vulnerability to surface fisheries.
Area of Science:
- Marine Biology
- Climate Change Science
- Fisheries Management
Background:
- Ocean hypoxia is expanding due to climate change, concentrating pelagic fish.
- The impact of hypoxia and fisheries on pelagic sharks is not well understood.
Purpose of the Study:
- To investigate how climate-driven deoxygenation and fisheries interact to affect blue sharks in the eastern tropical Atlantic Oxygen Minimum Zone (OMZ).
- To determine if blue sharks' vertical habitat is compressed by these factors and assess their vulnerability to fishing.
Main Methods:
- Analysis of satellite-tracked blue shark dive depths.
- Environmental modeling within the eastern tropical Atlantic OMZ.
- Correlation analysis between fishing effort, dissolved oxygen (DO) levels, and shark catches.
Main Results:
- Blue shark maximum dive depths decreased significantly.
- Habitat compression was linked to decreasing DO, high sea surface temperatures, and increased primary production.
- Longline fishing effort was concentrated above the OMZ.
- Higher shark catches correlated with strong DO gradients, indicating aggregation.
Conclusions:
- Climate-driven deoxygenation compresses blue shark vertical habitat, increasing vulnerability to surface fisheries.
- Ocean warming and deoxygenation necessitate adaptive fisheries management strategies to protect pelagic sharks.
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