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Environmental and Protection Effects of Shark-Companion Associations Across Three Ocean Basins
Jett K Walker1, Jessica J Meeuwig1, Christopher D H Thompson1,2
1Marine Futures Laboratory, School of Biological Sciences University of Western Australia Crawley Western Australia Australia.
Ecology and Evolution
|June 12, 2026
Summary
Ecological associations between sharks and companion species are influenced by environmental factors and marine protected areas. Understanding these relationships is crucial for conserving marine biodiversity and preventing species co-declines.
Area of Science:
- Marine ecology
- Interspecies associations
- Ocean biodiversity
Background:
- Ecological interdependence significantly impacts animal fitness and ecosystem structure.
- Open ocean associations between large mobile hosts and smaller companion species are poorly understood.
- The loss of one species can lead to cascading effects and accelerated biodiversity loss.
Purpose of the Study:
- To quantify companion-host associations across seven shark species in three ocean basins.
- To investigate the influence of environmental conditions and marine protected area (MPA) status on these associations.
- To provide the first large-scale assessment of shark-associated species interactions.
Main Methods:
- Utilized a curated database from midwater Baited Remote Underwater Video Systems (BRUVS).
- Collected data on species identity, abundance, and length for sharks and their companions.
- Employed statistical models to predict companion presence and abundance based on environmental and MPA variables.
Main Results:
- Nearly half of individual sharks hosted companion species, with significant variation among shark species.
- Companion occurrence was primarily predicted by sea surface temperature, salinity, wind speed, and distance to shore.
- Companion abundance was influenced by primary productivity, wind speed, and salinity.
- Partially protected areas (IUCN IV-VI) showed higher companion occurrence, while highly protected areas (IUCN I-II) supported greater companion abundance.
Conclusions:
- Environmental factors sensitive to climate change may disrupt shark-companion associations.
- Marine protected area status influences the probability and abundance of companion species.
- Disruption of these associations risks co-declines of dependent species and impacts open ocean biodiversity.
- Effective conservation strategies must consider these interspecies linkages for ecosystem persistence.
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