Researchers tag white shark, hope to discover key for managing the species in Nova Scotia

0

For the past ten years, OTN has worked closely with the shark unit of Fisheries and Oceans Canada (DFO) and Blue Shark Charters to tag Atlantic shark species, including dogfish, Greenland, blue, porbeagle and in more recent years, white sharks.

Dr. Heather Bowlby’s recent tracking studies at the Canadian Atlantic Shark Research Lab at DFO’s Bedford Institute of Oceanography are building on a larger program to collect valuable data on shark species in Atlantic Canada. Her work is also informing management bodies considering protection measures for sharks, namely, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) and the Species at Risk Public Registry processes.

This September, Dr. Bowlby’s team, consisting of DFO Aquatic Fisheries Technician Warren Joyce, OTN Technician Nathan Glenn, and Blue Shark Charters’ Captain Art Gaetan and first mate Cale DeLong, tagged a 16 foot female adult white shark with both a pop-up archival satellite tag and a Vemco V16 (16mm; 10 year life span) acoustic tag provided by OTN.

The crew avoided bringing the animal on board for tagging because little is known about the potential long-term impacts that result from invasive handling techniques that lift large predators out of the water. Instead, a shaft with a dart head and a detachable anchor was used to externally attach both tags at the base of the dorsal fin of the shark. This method allows scientists to work with any sized white sharks, and because a specialized vessel isn’t required, it’s also more cost-effective. 

The white shark investigates the tuna bait | Canadian Atlantic Shark Research Lab

“Given that we know very little about the long-term effects of tagging stress on this endangered species, we’re employing the most minimally-invasive techniques possible,” says Dr. Bowlby. “It’s very exciting for us to validate a methodology where animals haven’t been taken out of their natural environment in order to collect these rich data sets.”

The acoustic tags will generate data for up to 10 years whenever the tag is in range of  acoustic receivers such as those found on OTN’s Halifax Line—the longest receiver array in the world made up of more than 200 receivers spanning from Halifax to the continental slope. By contrast, the archival satellite tag will pop to the surface after a year and communicate detailed temperature, depth and location to researchers via the ARGOS satellite network.

Together, these data sets will greatly improve understanding of the distribution and migration patterns of great whites and of their use of Canadian waters–key information in determining habitat for white sharks at the northern limit of their range and answering critical conservation questions. The collaborative tagging program will yield valuable data that can advise decision makers about protection measures under the Species at Risk Act.

“We have a lot to learn about white sharks, including their use of critical habitat. Understanding this important identifier is key in informing policy and management, and also the first step in mitigating threats to their populations,” says Dr. Bowlby.

Sharks are top predators and ecosystem regulators, and face increasing pressure from climate change, overfishing and habitat destruction. OTN is supporting elasmobranch tracking studies in the Northwest Atlantic by providing expertise, field personnel, infrastructure and data warehousing to enable research programs and ultimately provide knowledge that informs policy-makers on protection measures. 

An hour after tagging, the shark swims between two floats | Canadian Atlantic Shark Research Lab

“By understanding the abundance, distribution and habitat use of this charismatic species, we’ll be able to better protect them, and in turn, also better understand the ecosystems that support commercially and culturally important fish stocks, which local communities rely on for sustenance and for their livelihoods,” says OTN Executive Director, Dr. Fred Whoriskey.


Share.

Comments are closed.