Most Antarctica aficionados have heard of the explorer Ernest Shackleton, and his daring voyage in a lifeboat from Elephant Island to South Georgia Island, a distance of 720 nautical miles, all to save his crew after their ship, Endurance, was crushed in the ice. Prince William Sound now has its own Shackleton - a six-foot long autonomous underwater glider currently deployed in the Sound that bears his name (and was previously deployed in Antarctica no less!). Shaped like a torpedo with wings, the bright yellow glider travels around 1 km/hr. By making small changes in its buoyancy and with the help of its wings, the glider dives slowly towards the bottom, arriving within 20 minutes. Once it is at the bottom, the glider switches to positive buoyancy and slowly climbs back up towards the surface. Every two hours, the glider surfaces and uploads data to scientists via satellite link.

The purpose of the Shackleton glider's "expedition" in Prince William Sound is to search for herring overwintering areas. Dr. Mary Anne Bishop has been acoustic-tagging herring in Prince William Sound the past four years to document their year-round movements. The acoustic tags implanted in the herring have a battery life of >2 years and emit a series of "pings" every 90-120 seconds. When a tagged herring swims near an underwater acoustic receiver, its individual code number along with the date and time are recorded.

Currently there are over 300 tagged herring potentially alive in either the Sound or the Gulf of Alaska. In addition to an assortment of oceanographic measurement devices, Shackleton is equipped with its own acoustic receiver to detect the tagged herring. Scientists at the University of Alaska Fairbanks have programmed Shackleton to repeatedly cover areas where we suspect that herring overwinter. Efforts will initially concentrate in the eastern Sound, around the Port Gravina and Orca Bay spring spawning grounds. A small number of acoustic receivers in these areas previously detected herring during winter. Being able to reprogram Shackleton to explore new routes and/or repeat areas where herring have been detected represent a new chapter in the study of herring movements in the Sound. Stay tuned for the Shackleton herring expedition results!

This project is a collaboration between the PWS Science Center, University of Alaska Fairbanks College of Fisheries and Ocean Sciences, and NOAA. Funding for herring tagging was made possible by the Exxon Valdez Oil Spill Trustee Council. Funding for the Shackleton glider "expedition" in the Sound was made possible by the Alaska Ocean Observing System.