How satellites can save sharks: conserving ocean species in a protected marine reserve

by ZSL on

By King’s College London and IOZ student Michael Williamson, who has been investigating how satellite remote sensing can be used to aid shark conservation and research as part of his PhD thesis.

Despite conservation efforts such as marine protected areas, sharks are still under threat from illegal and unreported fishing. Recent research, has estimated that illegal and unregulated fishing can reduce reef shark populations around certain reefs by up to a third during illegal fishing events. These losses are unsustainable, and protection is needed to prevent further catastrophic reductions and potential eradication of reef sharks from the region. Can modern research techniques and technologies aid the protection of shark and ray species?

Underwater photo of a grey reef shark swimming up to the camera

The British Indian Ocean Territory, also known as BIOT, is a protected marine reserve in the heart of the Indian Ocean, 500 km south of the Maldives. Made up of numerous reefs and atolls, it is a haven for a variety of marine creatures such as turtles, tuna, shark and ray species. 

As a marine protected area (MPA) commercial fishing is banned within BIOT, giving a level of protection that many oceanic areas across the globe are not afforded. However, illegal fishing still occurs in the region, and only now are we beginning to understand the seriousness of this issue to the reserve and the species found within. 

Illustration showing the different components of remote sensing and the species they monitor
The main environmental variables and applications of satellite remote sensing in shark and ray research

Monitoring how environmental factors, such as sea surface temperature, wind speed and primary productivity, drive marine animal movement is an important factor for their conservation. It can help us find out where these animals go and when they go there. If we know what is causing the movement of these populations, we can then figure out the best areas to protect, both spatially and temporally. 

Data generated image showing location of sharks in relation to temperature
Geolocations of tiger sharks in winter and summer months overlaid on sea surface temperature. Taken from Lea, et al. (2015). Repeated, long-distance migrations by a philopatric predator targeting highly contrasting ecosystems. Sci. Rep. 5, 11202 doi: 10.1
For marine species like sharks, that spend most of their lives out of sight beneath the waves, this can be particularly important. We cannot observe the large aggregations of animals such as those seen on the Serengeti, or those that regularly surface like certain whale species, so we must figure out other ways of finding out where they are likely to be. 

Satellite remote sensing can play an important role in this research. Satellite remote sensing enables monitoring of environmental variables without coming into contact with them. As well as high resolution imagery, satellites orbiting the earth at heights of 500 – 800 km can detect a wide range of different data, from temperature and salinity, to wind speed and vegetation cover, over very large areas. This allows data collection of environmental variables in remote regions of the world, which would normally be costly, both financially and in terms of human time and effort.

Shark habitat often spans very remote parts of the oceans, therefore remote sensing is increasingly playing a valuable role in shark research. Remote sensing data from satellites has been used in a variety of areas, such as migration, habitat distribution, foraging ecology and the effects of fisheries. It has been used to assess how changes in sea surface temperature cause migration in tiger sharks, what drives feeding frenzies in manta rays and how different environmental variables may affect bycatch in rays and sharks in commercial fisheries. This data vastly improves our understanding of shark and ray movement and aids management and protection efforts.

Despite current uses, there are still many potential avenues for satellite remote sensing to aid shark and ray conservation and management further. Imagery for satellites is now at such high resolution that it has been used to monitor marine populations, such as whales and penguins. There is no reason why this high-resolution imagery cannot be used to estimate shark and ray populations, particularly large species such as whale sharks, giant manta rays and basking sharks. Likewise, this imagery, or the detection of lights used to attract fish, can be used to identify illegal fishing vessels in marine protected areas.

Photograph of a grey reef shark underwater

In BIOT, enforcement to prevent illegal fishing is undertaken by a patrol vessel. However, the sheer size of this marine reserve means the protective influence of this single patrol vessel can be limited. Satellite remote sensing can be used to direct the BIOT patrol vessel to the best regions of the reserve for the protection of the shark species in the region. In addition, it could be used for real time detection of illegal vessels and provide a better assessment of the true impact of illegal fishing on shark and ray populations in the region. Ultimately, this will be used to raise awareness of illegal fishing, even within protected reserves, and hopefully emphasise the importance of increased funding and enforcement efforts for this unique region of marine biodiversity.

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