The lake whitefish Coregonus clupeaformis, dikameg in Anishinaabemowin, holds cultural importance, and is a mainstay of commercial, recreational, and subsistence fisheries throughout North America. In the Laurentian Great Lakes, declines in recruitment, since the early 2000s, have raised concerns among stewards and fishery managers. A more detailed understanding of the lake whitefish mating system could help resolve potential recruitment bottlenecks and thus inform appropriate stewardship actions. Herein, we describe, for the first time, a single lake whitefish spawning event captured using high-resolution underwater videography. From 94 h spent on the water, we captured and analyze a 4.5 min video clip that shows pre-mating, mating, and post-mating behaviour of a male and female lake whitefish from Lake Michigan. The clip shows a number of what we interpret as courtship, site-selection, and spawning behaviours culminating in release of about 20 eggs in a single spawning event. Behaviours that included travelling, physical contact, chasing, circling, orienting, and gamete release are described and time-referenced to a video supplement. This single observation is part of a larger project to assess lake whitefish spawning behaviour in the wild but is noteworthy in that it provides new insights into the spawning behaivour of lake whitefish and appears consistent with reproductive behaviours observed in European coregonines.

During 2022-2023, we used a Boxfish Robotics (https://www.boxfishrobotics.com) “Luna” craft to capture high-resolution underwater footage of spawning lake whitefish in lakes Huron and Michigan. The Luna craft is a next-generation drone that utilizes advanced full-frame imaging from a 4K 10-bit 4:2:2 120p Sony A7SIII camera equipped with either a Sony 16-35 mm f/2.8 or a Sony 24mm f/1.4 Zeiss lens. In shallow water, a 250-mm Nauticam glass dome port was used for the best edge-to-edge image quality, but for deepwater filming, a 200-mm Boxfish acrylic dome rated for 500 m depth was used. High sensitivity up to ISO 409,600 provided exceptional low-light camera performance. Two dimmable 8,500-lumen lights attached via adjustable arm mounts to the front of the craft provided ample illumination under all light conditions encountered. The ROV was tethered to the surface by a 300-m long, 2.7-mm diameter, lightweight, fiber-optic cable which allows recording on the surface in 4k ProRes Raw at 30p and frame stabilizing in post-production. The craft was controlled from the surface via a pilot console equipped with a 17-inch 4K monitor and a 10-inch sunlight readable secondary navigation display. The ROV carried sensors for depth, acceleration, internal humidity, temperature, and pressure and a 3D compass and precision gyroscope. A Subsea USBL transmitter and receiver provided GPS location of the ROV underwater (i.e., georeferenced on a map) and a Doppler Velocity Log sensor allowed the pilot to hold station thereby facilitating precise real-time control and adjustment of the craft and camera.