Protecting Harbor Seals in San Francisco Bay

Pacific Harbor Seal Haul Out Sites in San Francisco Bay
A map showing Pacific harbor seal haul out sites in San Francisco Bay. Pupping may occur at any of these sites, though some locations may support only a few pups. Primary pupping sites are highlighted in red.

There is nothing cuter than a Pacific harbor seal pup.

And as it turns out, these adorable marine mammals can be heard crying “maaaa” right in our own backyard. From March to June, Pacific harbor seals pup at multiple sites along the shores of San Francisco Bay. But our lovable flippered neighbors are also highly sensitive to our presence in the Bay, and human activities both in the water and on land can have negative consequences for pupping seals.

According to National Park Service scientist Dr. Sarah Allen, Castro Rocks, Mowry Slough, and Newark Slough serve as the primary pupping sites in the Bay. Pupping in smaller numbers is also observed at other haul out locations, which include Redwood City’s Bair Island, home to an ambitious wetland restoration effort. (Click on the image above to see a map of harbor seal haul out and pupping sites in the Bay.) Mudflats, rocky intertidal zones, pocket sandy beaches, islands, and wetlands are some of the habitats used for pupping. Dr. Allen tells Save The Bay that if sufficiently deep water is located nearby and human disturbance is absent, future restored wetlands may become new pupping sites as well.

Just as we have the power to improve the condition of Bay wetlands for seals, human activity can also reduce the quality of pupping habitat. As Dr. Allen explained to Bay Nature in 2011, development can cause pupping site abandonment and contributes to the lower number of pups in the Bay compared to other coastal sites. The Marine Mammal Center, which cares for abandoned Pacific harbor seal pups, also notes that “harbor seal colonies in the Bay Area are vulnerable to human disturbance, climate change and human-produced pollutants.” The Center warns that seal moms may be frightened by humans, prompting them to desert pups or pupping sites.

According to the Marine Mammal Protection Act guidelines, a buffer equal to the length of one football field should be maintained to avoid disrupting these shy creatures. The National Park Service also advises that paddlers and people on land avoid alerting seals of their presence, move away if any behavioral disruption is observed, and refrain from trying to rescue seals. If a distressed seal is detected, contact the Marine Mammal Center at 415-289-SEAL.

In addition, we need to ensure that harbor seals and other Bay wildlife are not harmed by shoreline development. Of particular concern today is a proposed development in the South Bay city of Newark that would pave over wetlands and hundreds of acres of historic baylands in order to build an 18-hole golf course and nearly 500 houses. The shoreline area targeted for development, referred to as “Area 4,” is located directly adjacent to Mowry Slough. Pollutants originating from this development, such as pesticides from the proposed golf course, could negatively impact downstream water quality, threatening wildlife.

Harbor seals’ sensitivity to disturbance, coupled with ongoing attempts to develop the Bay shoreline, underscores the importance of supporting Bay restoration and continuing the fight to preserve wildlife habitat. Learn more about Save The Bay’s wetland restoration programs, pollution prevention efforts, and opposition to the fill of Newark’s baylands.

City’s Plan Would Pave Bay Wetlands with Golf Course, Nearly 500 Houses

Photo of Area 4
Historic Bay tidal marsh, Newark’s “Area 4,” is one of the largest areas of restorable, undeveloped baylands in the South Bay (Photo by Margaret Lewis)

Should a bayside city work to help expand the San Francisco Bay National Wildlife Refuge, restoring more than 400-football fields-worth of Bay wetlands and habitat? Or should they forever destroy that opportunity by filling in the area with an 18-hole golf course and nearly 500 single family houses?

Those are the choices right now in the City of Newark – a shoreline city of 40,000 next to Fremont. Rather than recognize the incredible opportunity to protect the Don Edwards S.F. Bay National Wildlife Refuge, endangered species, and migratory bird habitat, Newark is seeking approval to fill in over 300 acres of historic baylands, including nearly 100 acres of wetlands and aquatic habitat, sprawling the city into a FEMA-designated flood zone.

Environmental organizations and regulatory agencies have long stressed to Newark of the ecological importance of 550-acre “Area 4” – one of the largest areas of restorable, undeveloped baylands in the South Bay:

  • The 1999 Baylands Ecosystem Habitat Goals Project, the scientific roadmap for the restoration of the Bay shoreline, identifies Area 4 as being uniquely situated for the restoration of both tidal marsh and adjacent upland transition zones, two habitats critical to the health of the Bay
  • Area 4 is host to approximately a dozen special status species –including the endangered Salt Marsh Harvest Mouse – and it is directly adjacent to Mowry Slough, a primary breeding ground for San Francisco Bay Harbor Seals
  • The San Francisco Bay Regional Water Quality Control Board has stated that “large expanses of undeveloped uplands immediately adjacent to tidal sloughs are extremely rare in the south and central San Francisco Bay” and that “Area 4 represents a rare opportunity to … provide an area for tidal marsh species to move up slope in response to sea level rise”
  • Similarly, the California Department of Fish and Wildlife have stated that “this wetland is an integral component of the San Francisco Bay ecosystem,” and “critically important to waterfowl and shorebirds.”

Yet Newark has ignored these concerns, proposing to fill in these rare wetlands and wildlife habitat with 2.1 million cubic yards of fill – enough dirt to fill nearly 100 trucks a day for two years straight!

The City should focus future growth within already developed areas, near transit, shops and services, not on ecologically-sensitive, restorable baylands at risk from flooding and sea level rise.

Update 10/11/2013: 

Opposition to Newark’s plan to build as many as 500 houses and an 18-hole golf course on one of the largest pieces of restorable Bay shoreline in the South San Francisco Bay is growing. More than 2,000 Bay Area residents submitted comments to the city on its General Plan. You added your voice to the chorus of opposition from regulatory agencies including the U.S. Fish and Wildlife Service (USFWS), the Bay Conservation and Development Commission (BCDC), and the Water Board.

A letter submitted by Don Edwards San Francisco Bay National Wildlife Refuge (USFWS) staff stated, “the proposed development of Area 4 will only add to the cumulative loss of tidal wetlands in San Francisco Bay and endangered species that are dependent on that habitat.”

Your support also helped us convince several environmental organizations to send letters of opposition, including Center for Biological Diversity, Defenders of Wildlife, and Greenbelt Alliance. Thanks to you, Newark’s plan will not go unnoticed much longer. Sign up here for updates on next steps.