Bering Sea

The Bering Sea is a highly productive ecosystem and supports a large commercial fishery, tribal subsistence harvests, and several species of whales that forage there seasonally. One of these, the North Pacific right whale (Eubalaena japonica), is among the most endangered whales in the world due to intensive commercial whaling in the 19th century and illegal whaling in the 1960s. There are probably only a few dozen right whales in the eastern North Pacific, and they are seen predominantly during summers in the

southeastern Bering Sea (SEBS), in shallow waters (< 200 m) over the continental shelf. Right whales eat small planktonic crustaceans, and depend on primary production and physical forcing that lead to large accumulations of their prey. Climate change is having noticeable effects on the Bering Sea ecosystem, including loss of sea ice, decreasing summer wind speeds, and increasing water temperature, and may have impacts on right whale distribution, foraging and reproductive success.

Objectives
       1. develop techniques for detecting North Pacific right whale calls in long-term acoustic            recordings
       2. investigate right whale occurrence and calling behavior
       3. understand right whale habitat use in an oceanographic context

       We deployed Acoustic Recording Packages in the SEBS in 2001, 2002, 2004, and 2005 that recorded continuously at 500 Hz sampling rate or above for 2 – 11 months per instrument (Figure 1). Deployments were at or near subsurface moorings that recorded oceanographic data including temperature, salinity, and chlorophyll fluorescence.

Results
       Right whale calls were detected in the SEBS as early as May and as late as December. Calls were usually detected on 1 - 3 consecutive days, with silent intervals ranging from 2 - 49 days. These data indicate that right whales occur in the SEBS later in the year than previously known, and suggest that they intermittently pass over the middle-shelf, usually remaining there for only a few days at a time. Peak right whale calling rates and the most days per month with calls were in late summer. We hypothesize that right whales are more abundant and remain in the SEBS middle-shelf region longer in late summer than during other times of year. Calling rates were significantly higher during darkness than during daylight, suggesting a relationship to behavior that may vary diurnally, such as foraging.
       Only a few right whale calls were detected in deep water (>1000 m) on the SEBS slope on one day in June 2005. No right whale calls were detected southeast of Kodiak Island in 2003 or within the Bering Sea outer shelf/shelf break region in 2004. Acoustic propagation of right whale calls was excellent on the SEBS middle shelf, and we were able to detect calls to distances of 50-100 km on average, with a maximum detection distance in our study of 190 km. When whales are in deep water off the shelf, their calls propagate less efficiently, and this may be one reason why we have detected so few right whale calls in recordings made off the shelf (> 200 m).
       Right whales were detected earlier in years with early ice retreat and a late spring bloom and intermittently throughout summer and fall in all years with recording effort. We hypothesize that right whale occurrence is linked to environmental variables via bottom-up control on production and distribution of copepods, their primary prey.

Collaborators:
       - NOAA/Alaska Fisheries Science Center (AFSC)
       - National Marine Mammal Laboratory (NMML)
       - Southwest Fisheries Science Center (SWFSC)
       - NOAA/Pacific Marine Environmental Laboratory (PMEL)
       - Alaska Department of Fish and Game (ADFG)

Figure 1. Map of Acoustic Recording Package deployment locations, 2000-2006. Grey shaded polygons represent NMFS-designated critical habitat for North Pacific right whales.

Outreach & Education
As a part of this project, members of the Whale Lab are excited to contribute to public education and outreach through aquarium exhibits, visits to schools, teacher workshops, and conducting hands-on and project-based learning with younger students. Past highlights include visits to Alaskan schools in the Bering Strait and Aleutians East Borough School Districts, email correspondence with elementary students in Superior, Montana, and numerous workshops and field trips for K-12 students visiting SIO and UCSD. Current outreach efforts include providing content and training for students in the SeaTech program, working with teachers who are developing marine science curricula for Alaska and San Diego schools, and connecting students from these schools to one another.

Outreach Links:
       http://www.voicesinthesea.org
       http://www.seatech4teens.org/
       http://seagrant.uaf.edu/marine-ed/curriculum/

Credit: Lisa Munger