Shark ecotourism is booming, with operators around the world offering divers and snorkelers the chance to see these iconic predators up close. But some tourists want more than just the opportunity to swim with these animals or see them through the bars of a cage… they want to take it a step further and ‘feed the beast.’ Yes, a major draw now for tourists is shark feeding, where food is provided to attract sharks to a predictable location. Shark ecotourism as a whole has often been framed as a win-win scenario — it provides economic benefits to coastal communities and promoting conservation by giving sharks a tangible value. But many argue that the impact of artificial feeding on shark health and reproduction has been largely overlooked. New research on blacktip reef sharks (Carcharhinus melanopterus) in Mo’orea, French Polynesia, suggests that tourism-driven feeding might be doing more harm than good, with physiological markers pointing to poor nutrition, metabolic changes, and reproductive disruptions that could have long-term consequences for the population.
Blacktip reef sharks are small, coastal sharks commonly found in the shallow waters of coral reefs across the Indo-Pacific. Recognizable by the distinctive black markings on the tips of their fins, these sharks typically grow to about 5.2 feet (1.6 meters) in length. They are highly ‘site-attached,’ meaning they tend to stay within the same reef system rather than migrating long distances. Opportunistic predators, they feed on small fish, crustaceans, and cephalopods, and play a crucial role in maintaining the health of coral reef ecosystems by regulating prey populations. Despite their widespread distribution, they face threats from habitat degradation, overfishing, and climate change – like many other shark species.
A team recently analyzed blood samples from 117 adult blacktip reef sharks at both feeding and non-feeding sites around Mo’orea. A small island in French Polynesia, it is a well-established shark ecotourism industry spot due to the presence of site-attached blacktip reef sharks. The scientists looked at multiple physiological indicators, including haematocrit levels (a measure of overall health), insulin and glucose (which reflect metabolism and nutrition), and sex hormones like testosterone and estradiol (which indicate reproductive investment). The findings raise concerns about whether feeding sites are providing a reliable food source — or if they are, in fact, an ecological trap.
One of the most striking results was lower haematocrit levels in sharks at feeding sites, suggesting a general decline in health. Insulin levels, a proxy for metabolism, were also lower in males at these sites. This could indicate that the food being provided isn’t as nutritionally beneficial as natural prey, leading to changes in how sharks process energy. The impacts were more pronounced in females, particularly during the breeding season, when their energy demands are highest. Females at feeding sites also had lower glucose levels, suggesting they weren’t getting the consistent, high-quality nutrition they needed. Even more concerning, their estradiol levels — important for reproduction — were lower compared to females at non-feeding sites. That means these sharks may be investing less energy in reproduction, potentially leading to fewer successful pregnancies. Male sharks at feeding sites, on the other hand, showed the opposite trend. They exhibited higher testosterone levels during the breeding season, possibly due to increased competition at these sites or other stress-related factors that affect hormone levels. While the exact implications of these hormonal shifts aren’t fully understood, any disruption to reproductive cycles in a population could have cascading effects on its long-term stability.
Clearly, the effects of shark feeding aren’t uniform. Sex and season both play a role in how sharks respond to artificial feeding, meaning broad generalizations about its impacts could be misleading. It makes sense, since a shark’s needs vary throughout the year, and a food source that seems beneficial at one time might be harmful at another. But it seems female sharks, which require stable, nutrient-rich food during pregnancy, are particularly vulnerable in this scenario. If tourism feeding fails to meet the nutritional needs of these animals, it could weaken individuals and disrupt breeding patterns.
The team argues that these latest findings highlight the need for more careful regulation of shark-feeding ecotourism. If sharks are going to be fed, the nutritional quality of the food needs to be considered — random scraps are not be a suitable replacement for their natural diet! They also stress that operators should also evaluate whether feeding locations are being used by site-attached individuals that rely too heavily on this unpredictable food source. Without proper management, what was intended as a conservation tool could instead become a stressor that harms the very species it’s meant to protect. And nobody wants that.
While shark tourism does raise awareness and reduce direct fishing pressure, it shouldn’t come at the cost of local population’s health. If ecotourism is truly meant to support conservation, then practices like shark feeding must be carefully scrutinized to ensure they do more good than harm.
