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Ongoing project seeks to examine feeding habits and study area expansion into Cape Cod Bay.
By Greg Skomal, PhD, Recreational and Diadromous Fisheries Program Leader  |  August 19, 2019
DMF shark biologist, Greg Skomal, using a GoPro to observe a white shark that was spotted off the shore in Orleans. (Photo courtesy of MA DMF)

As another summer is upon us, white sharks are returning to feed in Massachusetts waters. Since 2009, DMF biologists have been examining the movement ecology, behavior, natural history, and population dynamics of this species through its Shark Research Project. To date, agency staff have tagged more than 170 white sharks with a variety of high tech devices to study their fine- and broad-scale movements. Most of these sharks (93%) were tagged off Cape Cod, but others were tagged off New York, Florida, New Jersey, and South Carolina. The sharks ranged in total length from 4.0-17.5 ft and were comprised of juveniles, subadults, and adults of both sexes.

The agency has also been working with UMass Dartmouth’s School for Marine Science and Technology to examine the relative abundance and population size of white sharks off the coast of Massachusetts using spatial capture-recapture models. The objective of this project has been to estimate the abundance and relative density of white sharks off Cape Cod from photographic mark-recapture, aerial line survey, and acoustic telemetry data. To date, we have identified more than 350 individual white sharks over the last five years. The field component of this study was completed in 2018 and subsequent analyses are ongoing.

Building on its past work and in light of the growing presence of this species in our nearshore waters, DMF is intensifying its research to understand the predatory behavior of this species with particular emphasis on public safety. The aggregation of white sharks off the coast of Cape Cod is one of only a handful of hotspots in the world and unique along the east coast of the US. As such, Massachusetts and the towns on Cape Cod in particular are faced with a growing potential for negative interactions between this species and people utilizing our coastal waters. This potential has already been manifested in an increase in attacks on humans—the most recent causing fatal injury to a boogie boarder off Wellfleet in September 2018. Therefore, intensive research on the local movements and behavior of white sharks while in Cape Cod waters is warranted. Specifically, we need to know where, when, and how these sharks hunt seals, the frequency of feeding events, and environmental factors that drive the behavior of these animals. With adequate information related to these topics, we can develop, for the first time anywhere, predictive models that can be used to forecast the presence of this species so as to enhance public safety.

Fine-scale Behavior
Using a suite of tagging technologies, we are going to examine white shark residency, habitat selection, site fidelity, local offshore distribution, social interactions, and foraging behavior. The high-resolution data collected by these tags will be used to better understand fine-scale movements in areas of high shark/human overlap and will be used to identify factors correlated with both alongshore and onshore-offshore movements, which will better inform public safety practices. In doing so, we will be expanding our tagging efforts to include Cape Cod Bay, an area of increased white shark activity in recent years.

Coupled with these efforts, we will be developing a near real-time white shark forecast based on sightings, real-time detections from acoustic buoys, and the results of habitat models currently being developed. We envision the development of weekly forecast maps that could be disseminated to beach managers and posted at public beaches to alert beachgoers when conditions indicate a high likelihood of white shark presence.

In addition, data from these tags will be used to derive estimates of feeding frequency, which will provide a basis for assessing the intensity of white shark predation on gray seals. This is of certain interest to both commercial and recreational fishermen, as well as beach managers. Given our current assessment of the white shark population size, we will be able to estimate how many seals may be consumed by this species annually and the extent to which white sharks may potentially control seal population growth.

This research, when strengthened by strong collaborations such as the Atlantic White Shark Conservancy, will produce new, revelatory information about the white shark in the North Atlantic and, specifically, off the coast of Massachusetts. This information will not only provide the basis for sustainable conservation and management of this species, but also produce viable information for science-based decision making as it relates to public safety.