USING INTRA-GRAVEL WATER TEMPERATURES TO MODEL CURRENT SOCKEYE SALMON INCUBATION AND PROJECT INCUBATION DURATION UNDER VARIABLE CLIMATE WARMING IN LAKE CLARK AND KATMAI NATIONAL PARKS

Water temperature is a primary driver for the development of salmonid embryos. Surface water temperature is often used as a proxy for the thermal regimes that salmon redds experience during incubation. However, this proxy may be inadequate for some habitats. We explore differences in Sockeye salmon incubation duration in Lake Clark National Park and Preserve and Katmai National Park and Preserve in southwest Alaska by comparing incubation durations modeled using surface and intra-gravel water temperatures across nine sites. Six of the nine sites examined are stream or riverbeds, and three are lake beaches. Paired surface water and intra-gravel water temperature data have continually been collected at the nine sites since 2014 as part of a long-term monitoring effort. We compare the differences in water temperature at the nine sites and use an empirical model, the Effective Value Model, to estimate incubation duration for the two thermal regimes. Additionally, we project future intra-gravel water temperatures using a generalized additive model and maximum air temperatures from twenty Global Climate Models, with ten of the Global Climate Models representing the moderate, RCP 4.5, emissions scenario and ten of the Global Climate Models representing the high, RCP 8.5, emissions scenario to explore the potential impacts of climate warming on incubation duration.

Our results indicate that intra-gravel water temperatures are warmer than surface water temperatures during the winter. The increased winter intra-gravel temperatures result in shorter incubation duration, with the hatch date modeled to occur 20 days earlier on average at lake beaches and 29 days earlier on average at river and stream bed habitats. Projections of future intra-gravel temperatures suggest shortened incubation duration due to continued warming under the moderate and high emissions scenarios.