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Threats to Sharks

Updated: May 5

Author: Hunter Wortmann


Threats to Sharks


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Why are sharks in danger? Sadly, we must look at our own history to find the answer. Sharks have been on the planet for over 400 million years. Humans have only been on the planet for 300,000 years and as we have moved from hunter-gather societies to agricultural and fishing communities we have started to make large scale impacts on the place we call home. In the span of only 4 decades the shark populations have begun to dwindle. But what has caused such a rapid decline in such a recent timeline? A combination of the overfishing, bycatch and habitat destruction come together to threaten shark species all over the ocean.




Overfishing

We must look at the tools us humans have developed to support our growing population by developing ways to mass catch food from the largest food source we have: our oceans. Humans are essentially outcompeting sharks for their natural prey and in turn, removing a large percentage of shark’s food source from the ocean. The combined mass fishing that happens all around the globe is one of the largest threats that sharks face.1 Species like the Oceanic Whitetip who used to be the most abundant species in the ocean are now critically endangered largely due to indiscriminate fishing and the lack of regulations.




Bycatch

Sharks are fish too and are also interested in what is on the end of a fisherman’s hook. Unfortunately, a lot of sharks perish when hooked because they are not able to continuously swim to breath properly. Much of a fisherman’s catch goes to waste, (known as bycatch) because many other species besides the targeted catch also are interested in what’s on the end of the hook. Bycatch are the unwanted captures that happen to make their way into nets or onto hooks and suffer an unnecessary death. This is not something the fishermen intend to catch but non-targeted species like this happen to be about 40% of the world’s catch, adding up to over 60 billion pounds of wasted life per year, many of those being sharks.




Habitat Destruction

Shark habitats are at risk due to the rising global temperatures and ocean acidification. The pH of the ocean lowers due to the extra absorption of carbon dioxide from the atmosphere which becomes toxic to many species. The phytoplankton living on corals reefs are sensitive to changes in water chemistry and die off when their surrounding waters become too acidic. The corals depend on these phytoplankton for food and protection and 25% of the ocean’s species depend on the corals. Without thriving coral reefs and their dependents, sharks have a much smaller food supply. Along with coral reefs, sharks reproduce or give birth and feed in coastal and estuarine waters which is a hot spot for occurrences of oil spills, chemical waste, aquaculture, and other forms of pollution.




100 million sharks are killed every year due to the impacts of fishing and human pollution. Our ocean’s top predators like sharks are great indicators of environmental stress. We need to understand more about our impacts on these species to hopefully prevent further harm and restore balance to the ecosystem. Without sharks and their role in prey mitigation our oceans are a much scarier place.

Sources:

1. https://usa.oceana.org/blog/bycatch-spotlight-one-biggest-issues-facing-sharks-today

2.https://www.iucnredlist.org/species/39374/2911619

3. https://www.sharkconservation.org.au/threats-to-sharks-blog/2017/12/10/habitat-degradation-and-climate-change

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