true

ISRA FACTSHEETS

NORTH AMERICAN PACIFIC

ISRA FACTSHEETS

NORTH AMERICAN PACIFIC

Buldir Shelf Break ISRA

16/68

Buldir Shelf Break ISRA

Buldir Shelf Break

Summary

Buldir Shelf Break is located in Alaskan waters of the United States of America. It sits west of Buldir Island and next to the Buldir Pass, in the western part of the Aleutian Archipelago. The area is characterised by sandy and rocky substrates, coral and sponge communities, and strong eddy activity that promotes primary productivity. Within this area there are: reproductive areas (Whiteblotched Skate Bathyraja maculata).

Buldir Shelf Break

Buldir Shelf Break

DESCRIPTION OF HABITAT

Buldir Shelf Break is located in Alaskan waters of the United States of America. It is situated west of Buldir Island and sits next to the Buldir Pass, in the western part of the Aleutian Archipelago (Zimmermann & Prescott 2020). This is the largest (~130 km) pass in the region and separates the Aleutian Trench (Pacific Ocean) and the Bering Sea (Hunt & Stabeno 2005; Khudyakova et al. 2025). The area is characterised by sandy and rocky substrates with sponge and coral communities (Rooper et al. 2014; NOAA-AFSC 2026).

This area is influenced by the Alaska Stream, an intense boundary current flowing westward along the shelf break and the Aleutian Trench (Budyansky et al. 2022). This current enters into the Bering Sea through the deepest straits of the Aleutian Archipelago, including Near Strait (Khudyakova et al. 2025). It has strong eddy activity that transports relatively warm, salty, and nutrient-rich waters promoting primary production and defining the water flow through all the straits in the Aleutian Islands (Rogachev & Shlyk 2018; Mordy et al. 2023). Bottom water temperature ranges ~3.5–4.5°C (NOAA-AFSC 2026)

This Important Shark and Ray Area is benthic, subsurface, and is delineated from 140–260 m based on the depth range of Qualifying Species in the area.

CRITERION C

SUB-CRITERION C1 – REPRODUCTIVE AREAS

Buldir Shelf Break is an important reproductive area for one ray species.

Between 1982–2025, the Alaska Fisheries Science Center (AFSC) – National Oceanic and Atmospheric Administration (NOAA) conducted trawl surveys during the late boreal spring and summer in the Bering Sea, the Aleutian Islands, and the Gulf of Alaska (NOAA-AFSC 2026). Temporal coverage of the surveys varied per region with most surveys conducted annually (e.g., continental shelf surveys in the Bering Sea), or biennially (e.g., Gulf of Alaska) since 1999 (Hoff 2016; Siple et al. 2024; Markowitz et al. 2025; Dowlin et al. 2026). The continental slope survey in the Bering Sea stopped in 2016 (Markowitz et al. 2025). Surveys are conducted at fixed stations or following a stratified random survey design and covering depths from 0–1,000 m divided in multiple depth strata across 300–500 stations per region. In general, otter trawls of ~25 m headrope and ~34 m footrope were used and tows lasted between 15–30 minutes at a speed of ~3 knots. Catch-per-unit-effort (CPUE) was estimated as the number of individuals/number of egg cases per square kilometre (no/km2) and the area swept (km2) as the linear distance towed, multiplied by the mean net width (Hoff 2016; Siple et al. 2024; Markowitz et al. 2025; Dowlin et al. 2026).

Between 2008–2024, the presence of Whiteblotched Skate egg cases was recorded in 46 tows during trawl surveys across the whole region, five (10.9%) of which were recorded inside this area in July 2018 and 2024 at depths of 141–257 m (NOAA-AFSC 2026). The second highest CPUE (mean = 516.3 egg cases/km2; 150.4–1,816.7) of Whiteblotched Skate egg cases was recorded in this area compared to the whole region surveyed (mean CPUE outside the area = 67.6 egg cases/km2; 25.1–265.4) after Stalemate Bank (mean CPUE = 712.0 egg cases/km2; 158.1–4,329.9).

Buldir Shelf Break

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