The objective of this project is to deploy an acoustic observation network around the main grey seal colonies in the Iles de la Madeleine region in order to facilitate the detection of the great white shark and to provide data concerning its critical habitat. This project also aims to document the search for food and estimate the quantity of cod consumed by the grey seal in the Magdalen Islands region and the interactions between the grey seal and the great white shark.
Grey seals are suspected of contributing to the non-recovery of certain groundfish stocks in the southern Gulf of St. Lawrence. It is essential to learn more about their diet and foraging behavior. We have more than 500 samples collected from grey seals in the southern Gulf of St. Lawrence over the past decade. However, we still only have a few samples from the Magdalen Islands region, which is a key region for both grey seals and cod. It is therefore essential to acquire information in this region in order to improve our knowledge of the diet of the grey seal, as well as its reproduction rate, information necessary for population models.
Grey seal colonies are an important food source for endangered great white sharks. Several white sharks are equipped with acoustic transmitters as part of various tagging programs and their presence is recorded each time they pass within range of an acoustic receiver. Despite the presence of several acoustic receivers at key locations in the Gulf of St. Lawrence, there are none near the grey seal colonies. Local knowledge, fishermen and the tourist industry, tells us that sharks are used to frequenting the sites of Brion Island, Deadman Island and Bird Rock. It is important to further document the frequentation of the great white shark seals near colonies of grey seals on the Magdalen Islands. This information could lead to the creation of a great white shark tagging program in the Gulf of St. Lawrence.
The objectives will be achieved by 1) the capture of 8 live grey seals on which satellite transmitters and VMTs will be placed in fall 2023; 2) by deploying 12 acoustic receivers in the Magdalen Islands when capturing grey seals and recovering the acoustic receivers no later than December 15, 2023; 3) tagging of up to 8 great white sharks in September 2023.
