Curious.Judith

KQED’s “Quest” show produced a segment on the salt pond restoration which introduces the concept of adaptive management and how that will be well implemented in the fifty year project of transitioning the industrial salt ponds into a variety of restored and managed habitats in the south bay.

The July-September 2007 issue of Bay Nature has some information on the restoration of San Pablo Bay wetlands and salt marshes (ie: North Bay) The full supplement is available as a 2.2 MB PDF. The October-December 2004 issue has a south bay report that may still be of interests for background reading.

salt ponds, wetlands, san francisco bay, don edwards, Don Edwards National Wildlife Refuge, adaptive management, salt marshes

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A week or so ago, I met USFWS staff setting out a “habitat” to study Chinese mitten crabs (Eriocheir sinensis) in Stevens Creek. I knew they were considered invasives, and new the recently signed state law about dumping ballast water was meant to prevent such invasions — but now i know a good bit more about the mitten crab (and note that it might have been intentionally introduced because it’s an Asian delicacy).

From the 1995 study NONINDIGENOUS AQUATIC SPECIES IN A UNITED STATES ESTUARY: A CASE STUDY OF THE BIOLOGICAL INVASIONS OF THE SAN FRANCISCO BAY AND DELTA:

n November, 1994 a crab caught in a shrimp net in the southern end of San Francisco Bay was identified as Eriocheir sinensis by Robert Van Syoc of the California Academy of Sciences. Shrimp trawlers report that they have occasionally caught such crabs, many of them carrying eggs, in the South Bay since 1992 and in San Pablo Bay since the summer of 1994. Of 75 crabs collected from San Francisco Bay, 24 were female, and all but 5 of these were carrying eggs. Several ovigerous females collected in the winter of 1994-95 were maintained in aquaria by the Marine Science Institute of Redwood City, California, and hatched active zoeae by the first week of February. In 1995 Katie Halat found juvenile mitten crabs to be common in burrows in the upper parts of sloughs at the southern end of the South Bay.

From the 2006 Draft California Aquatic Invasive Species (AIS) Management Plan which one isn’t supposed to quote (bad Judith, bad):

Although the Chinese mitten crab, Eriocheir sinensis, had previously been found
elsewhere in the United States, San Francisco Bay was the first introduction that resulted
in the establishment of an extensive population. Burrows excavated by the crabs erode
banks and could damage levees. The crab’s sharp claws can cut through commercial
fishing nets and reduce or damage catch. The mitten crab also hosts a human parasite
known as the lung fluke, which can cause tuberculosis-like symptoms. In fall of 1998, as
many as 1 million mitten crabs were collected at the federal and state fish salvage
facilities in the south delta, which are associated with the California Aqueduct and State
Water Project. The crabs clogged the screens, holding tanks, and transport trucks used
to salvage fish from the pumping stations. The state built “Crabzilla” – an18-foot high
traveling fish screen at its Tracy fish collection facility to scoop up the crabs so they can
be hauled off and ground up for fertilizer. Mitten crab numbers declined after 1998, and
in 2005 were at very low numbers throughout the watershed.

A reference to Crabzilla can be found in this newsletter, describing the construction in more detail, and more economic details are given in this newspaper article. (Why are we using a Asian delicacy for fertilizer? Once the economic value is set, the species might be released in other estuaries.)

• Mitten crab ID Card, PDF
  • Only crab in fresh waters of North America
  • Claws equal in size and “hairy” (juveniles may not have“ hairy” claws)
  • Four lateral carapace spines (last one smaller); notch between eyes
  • Carapace up to 4 inches (100mm) wide; light brown to olive green in color
• NEMESIS database entry (nice reference/bibliography link as well as invasion history)
• Aquatic Nuisance Species Task Force: Monitoring studies — The San Francisco Bay study [1995] identified 212 introduced species, and an additional 123 species that were cryptogenic. The Columbia River survey found that most of the nonindigenous species found in San Francisco Bay are also in the Columbia River
• San Francisco Estuary Project

(more…)

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