Sharks of all sizes are vital to coral reef ecosystems, both as predators and prey. Shark populations have rapidly declined worldwide due to fishing operations, legal and illegal. The real impact of these declines is difficult to quantify due to the scope and span of global activities and discrepancies in reporting.
However, a new study published in Nature this week details the scale of shark disappearance from coral reefs. According to the survey, sharks were not observed on nearly 20% of the reefs surveyed. An article from Science Magazine refers to this as “the greatest decline of reef sharks ever recorded.”
Global FinPrint led this study. According to their website, Global FinPrint is a global survey that uses baited remote underwater video systems (BRUVS) to record marine animals on coral reefs. BRUVS, sometimes referred to as “chum cams,” consists of a video camera with bait. Global FinPrint includes more than 120 researchers worldwide. According to Global FinPrint, this study was launched in 2015, and most of the surveys occurred in 2016 to 2017.
Florida International University researchers are part of the Global FinPrint team. According to an article published by FIU regarding the study, this project surveyed 371 reefs in 58 nations. Science Magazine reports that the camera was held underwater for about 90 minutes, and videos were taken 35 to 50 times around a reef in areas about one to two kilometers wide. The BRUVS captured more than 15,000 hours of video from these reefs. The video below is an example of the footage recorded by the BRUVS.
After analyzing the videos, the team determined that on many of the world’s reefs, sharks are “functionally extinct.” According to FIU, this means that they are “too rare to fulfill their normal role in the ecosystem.” FIU reports that “essentially no sharks were detected on any reefs in the Dominican Republic, the French West Indies, Kenya, Vietnam, the Windward Dutch Antilles, and Qatar.” From 800 survey hours of these locations, only three sharks were observed.
The study cites overfishing as the key impact on shark populations on coral reefs. Demian Chapman, Global FinPrint co-lead and FIU professor and researcher, stated, “it’s clear that the central problem exists in the intersection between high human population densities, destructive fishing practices, and poor governance.”
FIU states that the study shows where shark conservation is working, and which actions are successful. In the FIU article, Chapman says, “we found that robust shark populations can exist alongside people when those people have the will, the means, and a plan to take conservation action.” The Global FinPrint team hopes to use this information to review shark conservation statuses and take the next steps for population recovery.
Sources: Nature, Science Magazine, FIU, Global FinPrint