Global FinPrint study reveals functional extinction of reef sharks on nearly 20% of surveyed reefs

In 2015, Microsoft co-founder Paul Allen launched Global FinPrint, a global survey that eventually deployed thousands of underwater cameras across coral reefs in 58 countries. The project was led by researchers at Florida International University and funded by the Paul G. Allen Family Foundation, with more than 120 researchers across the western Atlantic, the Indian Ocean, the Western Pacific and the Central Pacific. In total, more than 400 reefs were surveyed across 58 countries and territories, producing over 20,000 hours of footage. The study published in Nature, titled ‘Global status and conservation potential of reef sharks’, showed that sharks were absent from nearly 20% of the reefs surveyed. The study linked this depletion to socio-economic factors including market proximity, poor governance, and population density, while also identifying shark sanctuaries, catch limits and marine protected areas as measures associated with higher shark abundance.

Rather than using divers to conduct visual counts, the project relied on baited remote underwater video systems, or BRUVS According to Global FinPrint, researchers "usually set 30 to 100 BRUVS on a reef and record animal sightings for 60 minutes on each one." The research team drew on data from more than 15,000 standardised baited remote underwater video stations deployed on 371 reefs across 58 nations to estimate the global conservation status of reef sharks. Much of what was previously known about sharks had been inferred from industrial fishery catch records, with far less information available about sharks living in coastal habitats. The results reveal the profound impact of fishing on reef shark populations, with no sharks observed on almost 20% of the surveyed reefs. Reef sharks were found to be almost completely absent from reefs in several nations, and this depletion was strongly linked to socio-economic conditions, such as size and proximity of the nearest market, poor governance and human population density. The study's extended data further indicate that among the eight lowest-ranked nations surveyed, there was less than a 0.1% chance of a shark being present whenever a BRUVS was deployed, a level the authors describe as functional extinction. Functional extinction in this context means reef sharks are essentially absent from the ecosystem, with little to no functional role in structuring the surrounding reef fish community through predation or fear-based effects.

Despite the scale of the declines, the study identifies opportunities for conservation. Shark sanctuaries, closed areas, catch limits and the absence of gillnets and longlines were all associated with substantially higher relative abundance of reef sharks, pointing to several policy pathways for restoring reef shark populations. As per Global FinPrint, reef sharks were largely absent in nations with high human population density and poor governance of marine resources; opportunities for conservation remain in most places. National shark fishing bans, fishing regulations and no-take marine protected areas are already being used successfully in different parts of the world to prevent reef shark extinctions, and the project also identified locations where reef sharks remain common enough to seed the recovery of populations elsewhere potentially.

An estimated 100 million sharks are taken each year for their fins and meat, with many species suffering severe declines due to unregulated fishing. The organisation notes that shark fishermen in most nations use the whole animal fins, skins, cartilage, jaws and meat rather than practising "finning" alone, meaning that without careful controls, catches can exceed the ability of many shark species to replenish their populations. According to the IUCN Red List of Threatened Species, one-quarter of sharks and their relatives are threatened with extinction. The loss of these predators, according to Global FinPrint, threatens the food security of nations that rely on fish for human consumption and threatens the dive tourism industry that relies on sharks as living attractions; while their absence can also disrupt the balance of marine food webs, causing large-scale habitat changes. Building on these findings, the next phase of research seeks to improve understanding of how sharks influence other reef animals, and how the loss of sharks could disrupt the balance of coral reefs, often described as the ‘rainforests of the sea’, around the world.