Marine Mammals

Large and charismatic, marine mammals are often perceived as signs of a “healthy” ecosystem. Alaska’s marine regions support a rich assemblage of seals, sea lions, walrus, whales, dolphins, porpoises, sea otters, and polar bears.

They are found throughout the ocean, with ranges that often overlap with major fisheries and other human activities.

To ensure the long-term health and sustainability of this very visible component of the marine ecosystems off Alaska, NPRB funds research that attempts to answer questions such as:

• What are the preferred habitats, foraging locations, and prey of key species of marine mammals?
• How can humans use the abundant fisheries resources and still provide for sustainable marine mammal populations?
• How can we reduce bycatch, entanglement, and disturbance of marine mammals during fishing operations?
• How does predation control marine mammal populations?
• What will climate change do to those populations, and can we distinguish those effects from natural variability and other changes we may create?  

Marine mammal research topics are consistent with those outlined in the NPRB Science Plan.

Research Highlights

Project 719: Analysis of acoustic and oceanographic data from the Bering Sea

(December 2008) The murkiness of the Bering Sea -- as well as its large size -- makes detecting undersea mammals difficult. For researchers at sea, sometimes hearing animals can be the next best thing to actually seeing them.

In the winter and spring of 2006-07, scientists doing research for NPRB Project 719 deployed hydrophones to record the under-ice sounds of bowhead whales, bearded seals and walrus.

The three locations chosen for this work correspond to long-term oceanographic mooring sites in place since 1995. The resulting acoustic data provide an unprecedented survey of the current status of North Pacific right whales and other endangered marine mammals in the Bering Sea.

When collated with oceanographic data, they will also let scientists include large whales in Bering Sea ecosystem models.

Follow the bouncing spectrogram

A spectrogram (right) is a visual representation of sound. Brighter colors mean louder sounds. Here's how it works:

1. LOOK at a larger image of the spectrogram.
2. LISTEN to the three-species "concert" to "follow along" with the sound. For example, the tapping sounds of walrus can be seen as vertical lines in the spectrogram.