Use of optical satellite imagery to estimate abundance of Narwhal (Monodon monoceros) in Makinson Inlet in the Canadian high Arctic

Remote sensing technologies have expanded methods for monitoring wildlife. Very High Resolution (VHR) satellite imagery is becoming more widely used for animal detection. This is especially important for remotely based and hard to detect species such as narwhal (Monodon monoceros Linnaeus, 1758). Narwhal are a data deficient species due to their large geographic distribution and elusive nature. During the summer, narwhal from the Baffin Bay population migrate to fiords and inlets in Canada and Greenland but their spatial use and density in fiords in the high Arctic is relatively unknown. Makinson Inlet, an inlet on Ellesmere Island in northern Canada, was surveyed using aerial methods in 2013 and estimated a surface abundance of 812 narwhal (adjusted to 2387). Another aerial survey was attempted but unsuccessful due to inclement weather in 2022; however, satellite imagery offers another method for estimating abundance of narwhal in this remote fiord. In this study the World-View 3 satellite (31 cm resolution) was tasked to obtain optical imagery from Makinson Inlet and 5752 km2 was imaged between August 2 to 5, 2022. Imagery readers with previous satellite imagery analysis experience manually analyzed the imagery and identified 406 narwhal. The estimated number of narwhal in Makinson Inlet was adjusted for availability bias to account for deeper whales that would not be visible in the imagery (>1 m deep). The adjusted estimated abundance for narwhal in Makinson Inlet was 1987 (CV = 0.12; 95 % CI: 1578-2502). This study demonstrates the first use of VHR satellite imagery as a remotely-based non-invasive method to obtain information on narwhal abundance in the Canadian high Arctic.