Port Wells-College Fjord is an important movement area for Pacific Sleeper Sharks.

Pacific Sleeper Sharks seasonally move through this area, connecting deep waters at the entrance to the Fjord system with shallow areas near the glaciers (Bishop et al. 2026). Fourteen individuals were tagged in the southern end of the fjord system near Whittier and Cochrane Bay between June–August 2022. Animals ranged in size from 229–343 cm total length (TL). The size-at-maturity of 400 cm TL for males and 370–430 cm TL for females indicates that they were juveniles (Ebert et al. 2021; Bishop et al. 2026). Pop-up archival satellite tags were deployed on all sharks, with deployment durations of 365 days (n = 13) and 730 days (n = 1). Thirteen of these tags transmitted successfully, and 10 were physically recovered, providing high-resolution archival data. Additionally, 12 of the same sharks were also tagged with two mark-report pop-up tags programmed to detach after 120 days and 240 days. These tags provide the location of the sharks when they detach and transmit their signal via satellite. In high-latitude and demersal species, traditional satellite tracking using light levels to infer location does not work, and hence a Hidden Markov Model based on known locations from tag deployment, intermediary pop-up locations from mark-report tags, and final pop-up locations from satellite tags, as well as swimming depth and bathymetry was used to estimate daily location probabilities.

All mark-report tags popped up inside the area suggesting that tracked Pacific Sleeper Sharks remained in the fjord system over the tracking duration (Bishop et al. 2026). One shark likely left the fjord system briefly, indicated by deeper swimming depths than what is available within the system. The Hidden Markov Model indicated that in July/August, sharks were generally near the tagging locations in the southern end of the area near the mouth where Port Wells connects to Prince William Sound. The only report of a Pacific Sleeper Shark on the citizen science platform iNaturalist recorded in the wider region is also from this location in August 2024 (iNaturalist 2026). Tagged sharks then moved northward in November/December, reaching areas near active glaciers, such as in College Fjord, at the northern end of this area, in March/April. By July/August, tagged sharks were again in the southern end of the area. The intermediary pop-up locations from mark-report tags strongly support this seasonal movement pattern (Bishop et al. 2026).

A cluster analysis of depth and temperature data showed that tracked Pacific Sleeper Sharks made large diel vertical movements from shallower and warmer waters at night to deeper, colder waters during the day between October–January when they were in the central section of the area. In winter, they shifted to deep (300–400 m) and cold waters with minimal vertical movement between September–April. In spring and summer between March–August, they then either used intermediate depths (100–300 m) or shallow depths (50–250 m) during the day, when they were near the glaciers and back near the tagging locations. Although the area extends only ~80 km, the clear seasonal pattern suggests that this is an important movement area that connects different bathymetric habitat. Historical and contemporary evidence from Prince William Sound shows that multiple, or even large numbers, of individuals are sometimes captured in a fishing set, indicating that they may aggregate (Matta et al. 2024). The horizontal and vertical seasonal movements of tracked Pacific Sleeper Sharks suggest that they may shift from pelagic foraging to benthic scavenging and also balance foraging with resting (Bishop et al. 2026). This movement area thus likely connects different foraging and resting habitats.