Video S3 - Organic Pellet Application to Carrington Island Spawning Site

Video S3. Suppression of invasive lake trout by treatment of spawning sites with organic pellets to kill embryos in an IPM approach. Because only a few weeks are available to safely work on Yellowstone Lake following the peak of lake trout spawning each autumn, we expanded the embryo suppression research to include a comprehensive treatment of a spawning site with organic pellets by helicopter (with long line and seeder/spreader) to better understand the logistical constraints that may be faced when attempting large-scale, multi-site applications in the future. Dr. Christopher Guy of the USGS Montana Cooperative Fishery Research Unit describes the Carrington Island spawning site. During an October 2019 experimental treatment, all of the rocky substrate at this spawning site (0.5 ha) was treated with 18,000 kg of organic (soy and wheat gluten) pellets in less than one day. The pellets induce organic decomposition and decline in dissolved oxygen concentration, which is lethal to lake trout embryos, curtailing recruitment from the site. Relative to the expansive lake areas intensively gillnetted over a 22-week season (> 60 km of gill nets set daily), lake trout embryo suppression targets relatively small sites during a period of 2–3 weeks in autumn where the majority of a future year class is concentrated. Broad-scale application of pellets in autumn may reduce lake trout recruitment and enhance population suppression as part of an IPM approach targeting multiple lake trout life stages because the area of the 14 verified spawning sites is only 11.4 ha (0.03% of lake surface area).