Bay Whales

San Francisco Bay.  The recovery of the eastern Pacific gray whale is one of the great conservation success stories of the century. The population now stands at roughly 25,000 animals - some say near pre-whaling numbers - and the populations was recently removed from the US Endangered Species List. Seemingly part of that recovery, the numbers of whales visiting the San Francisco Bay has increased dramatically in the last two years, such that seeing whales in the bay has become an almost daily event for springtime boaters.

To better understand this change, we launched a long-term study to determine how many whales visit the bay each year, how long they stay here, whether they forage in the bay, and which areas of the bay are favored by the whales. The fact that the bay is home to millions of humans has been a mixed blessing.

By networking with the multitude of bay users such as ferry captains, recreational boaters, and the public at large, we have now received over 100 reliable reports from many parts of the bay from the San Mateo Bridge up through the Carquinez Straits to the town of Antioch - about 80 km from the mouth of the Golden Gate. The downside is that the people bring with them centuries of contamination, including massive quantities of mercury contaminated sediment deposited by the 49ers in addition to shipyard and petroleum contamination from more recent activities.

These contaminants are especially important to the gray whales as they forage on bottom-dwelling invertebrates - animals that are known to bioaccumulate these contaminants and pass them along to their predators. And we've that most of the animals we've encountered at close range here in the bay are actively foraging. In concert with the numbers of live whales in the bay, the numbers of stranded gray whales has gone up dramatically over the same time period - by June of 2000 there were already 18 whale strandings in the bay alone. Although the cause of these strandings and their importance to the overall gray whale population remain unclear, our hope is that understanding the events here in the bay will not only aid in local management and development decisions, but shed some light on the broader picture of gray whale population health.