Tue. Apr 20th, 2021

When Demian Chapman and his colleague first started setting up underwater cameras on reefs in 2015, the aim was to capture a lot of shark video. But sometimes they got moray eels instead. Particularly at reefs where sharks were no longer present. “It was feast or famine,” Chapman, associate professor in the department of biological sciences at Florida International University (FIU), told Mongabay in an interview. “On reefs with sharks, you would see no eels. On reefs without sharks, that’s when you started seeing eels.” After collecting years of anecdotal evidence, Chapman and a team of international researchers embarked on a study: they wanted to see if data would back up their assumptions that eels were indeed present on shark-free reefs. The resulting paper, which was recently published in iScience, found that nearby markets had a negative impact on sharks and other reef fish in the Caribbean region, but didn’t have the same effect on moray eels. Consequently, eels were more abundant in places where sharks weren’t. In the paper, this phenomenon is referred to as “market gravity.” The closer a reef is to a city, the fewer fish that reef will have. This is due in part to people fishing and harvesting species from nearby reefs, but also because non-target species have to travel further away to find their own food sources when nearby reefs become depleted. “When you look at the sharks, they follow the same pattern as all other reef fish — you tend to find them…This article was originally published on Mongabay
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