Five-year white shark population project wraps up in Cape Cod

by | Jan 2, 2019

After five years of being on the water every week in the summer and fall months tagging and cataloguing white sharks, Dr. Greg Skomal of the Massachusetts Division of Marine Fisheries, working with the Atlantic White Shark Conservancy and the University of Massachusetts Dartmouth School for Marine Science and Technology, has now wrapped up the field component of a five-year study. The study aims to estimate the size and relative abundance of the white shark population off Cape Cod, which in part uses OTN’s global receiver infrastructure.

During the study, the research team catalogued more than 320 individuals during the first four years. The 2018 data is expected to push that number much higher. Thousands of videos were collected during the five-year study and are still being processed.

“We try to keep up with compiling and analyzing the data each year and we did fairly well for the first few years,” explains Skomal. “But over the course of the next 12 months we are going to be really crunching the data.”

Seals as snacks of choice

As the seal population has been booming, it’s without question the team has seen the white sharks taking notice and increasing in the area as well. What was surprising to Skomal was that they were seeing a broad size range including adults, sub-adults (more than one year old, but not yet breeding), and juvenile sharks in the local waters. Often, researchers don’t think of juveniles feeding on seals, but they could be targeting small seals or taking advantage of robust fish stocks in the area. Indeed, charter captains have reported seeing white sharks eat striped bass right off their lines.

As more and more white sharks moved into the area, Skomal and team expanded their acoustic receiver array to monitor the 140 tagged individuals throughout the region. White sharks were now being seen routinely from the southern tip of Monomoy Island all the way up to Provincetown and into Cape Cod Bay.

Public safety top priority for researchers

While the results of this study will be published in multiple scientific papers, Skomal believes it is even more critical to get the information out to beach managers, public safety officials, and the general public.

“We will certainly be sharing this information as we crunch the data so the public remains well-informed,” said Skomal.

OTN-MDMF Shark Research Program data collaboration

After recent tragedies involving white shark interactions with swimmers, which included the first fatal attack in Massachusetts since 1936, Skomal is certain beach managers will be interested in the team’s results. He also emphasizes that although the population study is coming to a close, research into the fine- and broad-scale movements of this species, which started in 2009, and population monitoring will continue. As part of that work, research into the predatory behaviour of the white shark in this region will be intensified. He hopes that a better understanding of how, when, and where white sharks prey upon seals will ultimately enhance public safety.

Written by Robyn Morris