batch_auto_20260713 202607131256465730 BOEM ESP geoESPIS ESPIS@boem.gov Bureau of Ocean Energy Management Ocean Migration and Behavior of Steelhead Kelts in the Northern Gulf of Alaska, Examined with Satellite Telemetry College of Fisheries and Ocean Sciences University of Alaska Fairbanks Although steelhead Oncorhynchus mykiss is an iconic species found throughout the North Pacific rim, little is known about this species' oceanic ecology. Understanding the marine distribution of steelhead in the North Pacific Ocean is important for understanding the potential interactions between human activities and this fish species. Oil and gas exploration and development may eventually occur in offshore areas throughout the North Pacific Ocean, including the Gulf of Alaska, Aleutian Arc, and the Bering Sea. If steelhead occupy these areas, these individuals may be directly exposed to habitat disturbance as a result of these human activities. Given the generally low abundance of this species and the potential for interactions with human activities, understanding the marine migration patterns and behavior of steelhead is important to understand potential impacts on this species. To provide insights into migratory routes and habitat occupied by steelhead in the North Pacific Ocean, we attached pop-up satellite archival tags (PSATs) to steelhead kelts (n = 16 in 2018; n = 12 in 2019, and n = 35 in 2020) from a prominent Alaskan population, the Situk River. While externally attached to a fish, the tags measured and recorded temperature, depth, and ambient light intensity data every two minutes. On pre-programmed dates, the tags released from the fish, floated to the surface of the ocean, and transmitted archived data to overhead Argos satellites. Movement, habitat occupancy, behavior, geolocation, and mortality of steelhead were described by examining end locations, migration routes, depth occupancy, and temperature occupancy of tagged fish. 213084 U.S. Department of the Interior, Bureau of Ocean Energy Management, Environmental Studies Program https://doi.org/10.13039/100012475 M20AC10005 10.67297/9A1E48 https://boem.gov/awardpages/100296