Category: General Article
Date: Friday, September 1, 2017
One of the questions I get asked most often is — what is the biggest threat to sharks? The greatest pressure on shark populations comes from fishing. It has been estimated that up to 25% of shark and ray species are threatened with extinction, largely based on declines caused by fishing. Sharks are captured in a wide variety of fisheries including those that aren’t targeted toward catching sharks (this is called incidental by-catch). It is important to note that sharks have a range of uses: in many locations shark meat is used as a food source, fins are used in soup, skin is made into leather, teeth are sold as curios. The wide use of shark products drives the retention of sharks in fisheries even if they are not targeted. While some species are very vulnerable to fishing pressure and decline quickly, other species are able to support targeted fishing if proper management policies are in place.
Another threat to sharks is habitat loss and degradation. As you will have seen from my posts about shark movements, many individuals have home areas where they spend large amounts of time, possibly their entire life. This is especially true for many of the coastal species. This means our coastal habitats are very important to the survival of these sharks. If we pollute these areas or alter them by developing ports or other structures we may be putting species at risk. If the altered habitat isn’t suitable, the sharks will be forced to leave or may not survive. In thinking about shark conservation we also need to think about their need to have healthy areas to live and enough food to survive. So protecting our coastal areas and keeping them free of litter, plastic, pollution or other damage is very important.
Climate change is also an issue for animals and habitats around the world. In the last two years, the Great Barrier Reef has undergone significant bleaching events due to high water temperatures. Corals have a symbiotic relationship with algae which give the coral their color. If water temperatures are too high the algae will be expelled leaving the white coral skeleton exposed. After bleaching many corals die or become diseased which is damaging to the health of the reef and the animals that rely on coral to survive. We do not understand whether bleaching will affect the sharks that live on the reef, only time will tell. As the climate changes and water temperatures also change, we may see sharks having to use different areas, or if reefs are damaged we may see declines in these populations. All of these changes and damage to habitat create an uncertain future for sharks.
Given the pressures on the marine environment and shark populations, there is a great need for science. My role in shark conservation is to create information that can be used by Australian managers to decide how best to protect our habitats and animals. There are so many questions about sharks. So many things we don’t know. Science plays a big role in answering these important questions so wildlife managers — and the rest of us, too — can make better decisions to help protect our oceans and everything in them.