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Sharks are essential to a healthy ecosystem, and their disappearance would have far-reaching consequences. In this article, we look at the threats they face. Because the better we understand our environment, the more effectively we can protect it.

Bycatch & ghost nets

Bycatch is the term used to describe all non-intentional fishery products. In other words, everything that ends up in the net but is not intended by the industry and is usually not wanted [8]. The majority of the worldwide catch - studies speak of more than 40% - is thrown overboard again to save space in the holds of the ships [8]. By then it is usually too late for the animals. They have died in the nets and on the longlines of non-selective fishing.

Longline fishing (actually targeting tuna or swordfish) in the open ocean is particularly problematic for high seas species, as it often overlaps with their migration routes. Survival rates are highly species-specific; tiger sharks (Galeocerdo cuvier) usually cope well with fishing stress, while mortality is much higher for other species [9]. Due to insufficient global monitoring of the fishing industry, accurate data on mortality rates and bycatch composition are scarce. However, for many shark species, the bycatch issue represents an additional anthropogenic stress to which they are exposed.

Ghost nets - lost or otherwise discarded fishing gear including nets, lines and hooks - account for 10% of marine plastic pollution [10]. Although they are no longer actively managed by fishermen and their vessels, they continue to serve their intended purpose: catch whatever gets in their way. The often large-scale nets drift unseen through the oceans. As with bycatch, marine megafauna - everything from sharks and rays to turtles and marine mammals - suffer the most. Once caught in the net, one of three fates awaits the animals: suffocation, starvation or being eaten.

Tourism

Wildlife tourism is one of the fastest growing sectors of the tourism industry. It often follows a strong economic boost for the region. However, it has the potential to severely alter the natural environment and behaviour of the animals concerned.

A striking example of this is the Oslob region in the southwest of the Philippines. Before 2011, the quiet tropical bays were known for their beautiful reefs and sporadic visits by whale sharks (Rhincodon typus). By the following year, the situation had changed dramatically. Oslob had become the whale shark capital of the world - practically overnight.

What was a true economic miracle for the region inflicted considerable damage on the whale sharks over the course of the next few years. These, in fact, did not spontaneously change their migration routes, but were lured in - with a never-ending supply of frozen shrimp [11]. Just in time for sunrise, a whole fleet of former fishermen goes out into the bays to feed the already waiting sharks. A second fleet follows closely - hundreds of tourists flock to the region to watch the spectacle from the water or from a boat. The holidaymakers pay good money for their "Whalesharks guranteed" trip to come home with Instagram-worthy photos. But the sharks pay too, whether through malnutrition due to the unbalanced diet, behavioural and migratory changes, or - increasingly - injury. Unfortunately, it is not uncommon to see sharks with severed dorsal fins or propeller wounds [12]. The "whale shark" business is booming, there is rarely enough time for conservation or compliance with rules of conduct.

Many of these problems are localised, but together they form a deadly mosaic that the sharks do not stand a chance against. One threat, however, is global - ever-increasing climate change. We think of sweaty summers, unpredictable and extreme weather phenomena or surprisingly mild winters; but the oceans are also noticeably affected. It is not only rising water temperatures that should worry us, but also the impact on marine life. Sharks, which have difficulty adapting to changing conditions thanks to low reproduction rates, need intensive attention.

Join us & help SHARKPROJECT to prevent one of the main reasons for the declining population numbers of sharks. Ohne Dich Geht's Nicht - Your vote for an EU-wide ban on the trade in loose shark fins --> https://eci.ec.europa.eu/012/public/#/screen/home

Sources can be found here:.

 


atlantic lemon and tiger shark at the Bahama Bank (c) Gerald Nowak

Atlantic Lemon and Tiger Shark at the Bahama Bank (c) Gerald Nowak


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