Shark ‘Fitbit’ captures rare, 1st recorded ship strike impact on 23-foot fish

In April, shortly after tagging an endangered basking shark off the coast of Ireland, researchers captured what is believed to be the first-ever video of a shark—or any large marine animal—being struck by a boat.

The footage obtained using an activity measurement device similar to a FitBit and an attached camera, offers scientists a rare chance to study the effects of vessel strikes on large marine animals, an increasingly pressing issue worldwide, according to Taylor Chapple, a shark researcher and lead author of the study.

“This is the first-ever direct observation of a ship strike on any marine megafauna that we’re aware of,” Chapple said.

“The shark was struck while feeding on the surface of the water and it immediately swam to the seafloor into deeper, offshore waters, a stark contrast to its behavior prior to the strike.”

Effect of the boat strike on the shark

The researchers were conducting a pre-planned study within Ireland’s National Marine Park to investigate basking shark foraging behavior and its relationship with environmental factors. They tagged a feeding basking shark with a camera and activity monitor system.

After tracking the shark from a safe distance for a few hours, the researchers left the area for the day. The tag was set to record autonomously until its scheduled release, after which the researchers recovered it and analyzed the data.

Approximately seven hours after the strike, the tag was released and retrieved. The data revealed that the shark did not resume feeding or any other normal behavior while it was being monitored, according to Chapple.

The tag data indicated that shortly after tagging and tracking began, the shark spent several hours at the surface, engaging in normal feeding behavior with occasional dives. It then made a sudden evasive maneuver, followed by the keel of a boat striking its back just behind the dorsal fin.

The impact caused the shark to tumble through the water and increase its tailbeat frequency as it descended to the seafloor. Camera footage showed visible skin damage, paint marks, and a red abrasion, but no open wounds or bleeding.

Protecting this endangered species

Basking sharks, the second largest fish species, often exceed 26 feet (8 meters) in length. Classified as globally endangered by the International Union for Conservation of Nature, they aggregate in large numbers in only a few locations, including Ireland.

These sharks filter-feed at the water’s surface, similar to certain whales, which increases their vulnerability to boat strikes. However, unlike whales, basking sharks often sink when killed, complicating efforts to assess mortality rates, according to Chapple.

Earlier this year, the Irish government established the country’s first National Marine Park, encompassing 70,000 acres of land and sea along the coast of County Kerry. This park aims to protect the seasonal feeding and potential mating grounds of basking sharks .

Further research

While vessel strikes are not always immediately fatal, even non-lethal injuries can have significant short- and long-term effects on the affected animal, the researchers noted.

“The fact that a shark we fitted our ‘Fitbit’ to was struck in this area within a few hours underlines just how vulnerable these animals are to boats and highlights the need for greater education in how to mitigate against such strikes,” notes co-author Nicholas Payne.

Co-author Alexandra McInturf emphasized the importance of further research on interactions between water users and basking sharks in the National Marine Park and other key areas along the Irish coast.

She pointed out that this incident raises important questions about how frequently and in what conditions sharks occupy these habitats when they are not visibly at the surface.

McInturf stressed that, given Ireland’s unique position as one of the few locations where basking sharks are consistently observed, addressing these questions is crucial for both enhancing our ecological understanding of the species and informing conservation efforts for this globally endangered shark.

The findings were just published in Frontiers in Marine Science .