Study Title Characterizing Movement and Spatial Occupancy of Northern Bering Sea 

Pacific Halibut 

Report Title Characterizing Movement and Spatial Occupancy of Northern Bering Sea 

Pacific Halibut 

Report Number(s) (OCS 

Study) BOEM 2024-026 

Completion Date of 

Report May 2024 

Number of Pages 29 

Award Number(s) M21AC00013 

Sponsoring OCS Region 

or Office Alaska 

Applicable Planning 

Area(s) 

Norton Basin, Hope Basin, St. Matthew-Hall Basin, St. George Basin, 

Navarin Basin 

Fiscal Year(s) of Study 

Funding FY21-24 

Costs by Fiscal Year FY21: $2,191; FY22: $33,146; FY23: $81,350; FY24: $23,259 

Cumulative Project Cost $139,946 

Project Manager(s) Andrew Seitz 

Affiliation of Project 

Manager(s) University of Alaska Fairbanks, College of Fisheries and Ocean Sciences 

Address of Project 

Manager(s) 

PO Box 757220, Fairbanks, AK 99775-7220 

Principal Investigator(s) Andrew Seitz 

Keywords Pacific halibut, PSAT, Bering Sea, Ocean, Migration, Depth, 

Temperature 

ABSTRACT: The spatial dynamics and occupied habitat of large female Pacific halibut in the Northern 

Bering Sea (NBS) were investigated using pop-up satellite telemetry tags. Tagged individuals remained 

within the NBS and central Bering Sea, but crossed multiple Outer Continental Shelf (OCS) lease planning 

area boundaries, as well as the Russian maritime border, during annual spawning migrations to the 

continental shelf edge. Individuals also returned to their tagging location the following year, indicating 

inter-annual site fidelity to summer foraging areas within Norton Basin in the NBS. No Pacific halibut 

were tracked entering the Hope Basin planning area in the southern Chukchi Sea, despite the presence of 

thermal conditions that are similar to those currently occupied in the NBS. Results indicate that Pacific 

halibut occupy multiple OCS planning areas throughout the year, but that occupied areas vary seasonally 

and are restricted to the Bering Sea. 

BACKGROUND: Warming ocean temperatures have resulted in Pacific halibut exhibiting a northward 

shift into the NBS, and potentially the southern Chukchi Sea. The recent expansion of Pacific halibut into 

the NBS has resulted in an understudied region of its range, leaving an information gap in understanding 

its movements and spatial dynamics. Understanding the spatial occupancy of Pacific halibut is critical for 

management and conservation measures, as the species is both highly migratory and a valuable food source, 

supporting important commercial and subsistence fisheries in the NBS. Additionally, their expansion into 
the NBS provides the potential for Pacific halibut to interact with human activities in the region, such as 

resource exploration, extraction, and development. Identifying the potential areas where halibut may 

interact with future human activities and the timing will provide valuable benchmark information that will 

aid in understanding possible interactions between this important food source and human activities. 

OBJECTIVES: The objectives of this study were to use satellite tagging methods to assess movements 

and spatial occupancy of halibut in the NBS, including 1) identifying Outer Continental Shelf (OCS) 

planning areas in the NBS and potentially in the Southern Chukchi Sea that Pacific halibut currently occupy 

throughout the course of a year, 2) examining the timing and pathways of Pacific halibut movements among 

OCS planning areas, as well as the duration of occupation within a given planning area, 3) characterizing 

Pacific halibut spawning events to identify spawning grounds and the OCS planning areas in which they 

occur, and 4) characterizing the depths occupied by Pacific halibut to determine the potential exposure risk 

to disturbance events such as an oil spill, under the pretext that Pacific halibut are not exclusively benthic. 

METHODS: We attached pop-up satellite archival tags (PSATs) to mature female Pacific halibut (n = 16 

in 2019; n = 25 in 2020; n =18 in 2021, and n = 25 in 2022) in the NBS. While externally attached to a fish, 

the tags measured and recorded temperature, depth, and ambient light intensity data every 5 seconds. On 

pre-programmed dates, the tags released from the fish, floated to the ocean surface, and transmitted 

summarized archived data to overhead Argos satellites. Movements, habitat occupancy, and spawning 

behavior were described by examining deployment end locations, most likely movement tracks, and both 

depth and temperate occupancy of tagged fish. 

RESULTS: Winter end locations indicated large scale movements (305 to 1022 km displacements) to the 

continental shelf edge for inferred spawning purposes, where they were distributed from the Pribilof Islands 

to the Russian coast. Summer end locations suggested subsequent returns to approximate tagging locations, 

occurring as close as 14 km from the fish’s release site. Temperatures occupied by Pacific halibut while 

at liberty ranged from -1.9 to 13.0°C, while occupied depths ranged from 0.5 to 696.5 m. Pacific halibut 

predominantly occupied waters near the seafloor, but also occupied shallow waters and made short-term 

ascents into the water column. Pacific halibut most likely movement tracks were as long as 2430 km, 

during which time all individuals moved across multiple OCS leasing area boundaries within the Bering 

Sea, with many also moving across the Russian maritime border. However, no individuals moved into Hope 

Basin in the Chukchi Sea, despite availability of bottom water temperatures within the Pacific halibut’s 

occupied thermal range. 

CONCLUSIONS: Satellite telemetry data provided valuable information about Pacific halibut migratory 

movements, spawning activity, and occupied depths and temperatures throughout the year in an 

understudied region. Pacific halibut were seen seasonally occupying multiple OCS lease planning areas 

across the eastern Bering Sea shelf, but were not observed entering Hope Basin in the Chukchi Sea. This 

suggests that Pacific halibut may interact with human activities while foraging, spawning, and migrating 

in the Bering Sea, but not in the Chukchi Sea. While it does not appear as though Pacific halibut 

currently occupy the Chukchi Sea at this juncture, the potential for further northward expansion of this 

species into this region in the future remains. This study provides valuable benchmark information that 

can inform NEPA analyses and human activity planning to help minimize potential impacts to this 

important economic and subsistence. 
STUDY PRODUCT(S): 

1. Final report and image library: Seitz, A.C., Flanigan, A.J., Nielsen, J.K., Loher, T. 2024. 

Characterizing movement and spatial occupancy of northern Bering Sea Pacific halibut. Coastal 

Marine Institute Final Report for OCS Study BOEM 2024-026. 

2. Poster presentation: Flanigan, A.F., Wehde, D., Loher, T., Seitz, A.C. 2022. Understanding 

Pacific halibut (Hippoglossus stenolepis) spatial dynamics in the northern Bering Sea. Alaska 

Marine Science Symposium. Virtual. January 2022. 

3. Poster presentation: Flanigan, A.F., Wehde, D., Loher, T., Seitz, A.C. 2022. Understanding 

Pacific halibut (Hippoglossus stenolepis) spatial dynamics in the northern Bering Sea. Ecosystem 

Studies of Subarctic and Arctic Seas. Seattle, WA. June 2022. 

4. Oral presentation: Flanigan, A.F., Wehde, D., Loher, T., Seitz, A.C. 2022. Understanding 

Pacific halibut (Hippoglossus stenolepis) spatial dynamics in the northern Bering Sea. American 

Fisheries Society Alaska Chapter. Virtual. March 2022. 

5. Oral presentation: Flanigan, A.F., Wehde, D., Loher, T., Seitz, A.C. 2022. Understanding 

Pacific Halibut (Hippoglossus stenolepis) Spatial Dynamics in the Northern Bering 

Sea. American Fisheries Society University of Alaska Fairbanks Student Sub-unit 

Symposium. Fairbanks, AK. March 2022 

6. Oral presentation: Flanigan, A.F., Wehde, D., Loher, T., Seitz, A.C. 2023. Assessing spawning 

behavior at the northern extreme of Pacific halibut. PICES Annual Meeting. Busan, South 

Korea. September 2022. 

7. Oral presentation: Flanigan, A.F., Wehde, D., Loher, T., Seitz, A.C. 2023. Assessing spawning 

behavior at the northern extreme of Pacific halibut. Alaska Marine Science 

Symposium. Anchorage, AK. January 2023. 

8. Oral presentation: Flanigan, A.F., Wehde, D., Loher, T., Seitz, A.C. 2022. Assessing spawning 

behavior at the northern extreme of Pacific halibut. American Fisheries Society University of 

Alaska Fairbanks Student Sub-unit Symposium. Fairbanks, AK. March 2023. 

9. Oral presentation: Flanigan, A.F., Wehde, D., Loher, T., Seitz, A.C. 2022. Assessing spawning 

behavior at the northern extreme of Pacific halibut. American Fisheries Society Alaska 

Chapter. Fairbanks, AK. March 2023. 

10. Oral presentation: Flanigan, A.F., Loher, T., Seitz, A.C. 2023. Assessing spawning behavior at 

the northern extreme of Pacific halibut. ICES Annual Meeting. Bilbao, Spain. September 2023. 

11. Oral presentation: Flanigan, A.F., Nielsen, J.K., Loher, T., Seitz, A.C. 2023. Pacific halibut in 

the northern Bering Sea. Strait Science Series. Nome, AK. September 2023. 
MAP OF STUDY AREA: Figure 1 of report OCS Study BOEM 2024-026 

Bering Sea Outer Continental Shelf lease planning areas and Pacific halibut (Hippoglossus stenolepis) 

tagging locations near Nome, AK (pink circles) and Savoonga, AK (yellow circles).