Harbor seals and the changing environment of the Bay
Harbor seals are found throughout the northern hemisphere in the nearshore waters of the Atlantic and Pacific Oceans. Their need to regularly haul-out on land to rest and nurse pups ties them to coastal feeding areas, which are often contaminated with industrial and municipal pollution. In the Bay, many of their haul-out sites have been lost to shoreline development in the last 100 years. It is increasingly difficult for seals to find the key features they need from the shoreline: isolation from predators or humans and easy access to water. In fact, since the natural harbors preferred by seals have been replaced with human-made ones, they have now moved in with humans, attracting hosts of tourists at Pier 39 in San Francisco.
Harbor seals are primarily bottom feeders, eating a variety of fish and mollusks that live near the ocean floor. As such, they are at risk from environmental pollution and toxins. These threats from industrial chemicals, while invisible to the human eye, are responsible for damage to the seals’ immune systems, reducing the seals’ ability to fight off disease and infection. A factor which has been implicated in the great seal epidemic that devastated the seal population in the Wadden Sea and parts of the North Sea along the north coast of Europe in 1988, killing over 18,000 harbor seals.