The Richmond Bridge Harbor Seal
Survey
Frequently Asked Questions
The Richmond Bridge Harbor Seal
Survey
Frequently Asked Questions
1) Why is Caltrans doing this study?
2) What happened to the seals when the bridge was built?
3) How is the situation at Castro Rocks different today than when the bridge was first built?
4) What is so important about the seals at the Richmond-San Rafael Bridge? I thought there were lots of seals around now?
6) Can I stop on the Richmond Bridge and look at the seals?
7)
Are these the same as the Pier 39 seals?
They don't seem to mind people being really close...
1) Why is Caltrans doing this study?
Marine mammals such as the harbor
seal are protected by the Marine Mammal Protection Act of 1972, which (among
other things) established a moratorium, with certain exceptions, on the taking
of marine mammals in U.S. waters. In this context, to 'take' is to
"harass, hunt, capture, or kill, or attempt to harass, hunt, capture or kill
any marine mammal". Caltrans is about to begin the seismic retrofit
of the Richmond-San Rafael Bridge, and there is a harbor seal
haul out site
* (called Castro Rocks
) located very close to the Bridge. Harbor seals are sensitive
to human disturbance, and harbor seals using this haul out site will almost
certainly be impacted by the increased noise, etc., associated with the retrofit
work. Therefore, Caltrans is required by the National Marine Fisheries
Service (NMFS) to monitor the seal population there, to assess potential
impact to harbor seals and to try and minimize disturbance to the seals in
any way feasible. The viability of the Bay's resident harbor seal population
depends on the integrity of only 12 terrestrial sites which they currently
use to rest and reproduce at; Castro Rocks is the largest haul out site in
the North Bay, and the second largest breeding site in the Bay.
This is where we come into the picture.
In 1998, Caltrans contracted with San Francisco State University (SFSU) to
conduct the harbor seal monitoring at the Richmond-San Rafael Bridge, and
the Richmond Bridge Harbor Seal Survey (RBHSS) came into being. Dr.
Sarah Allen of Point Reyes National Seashore and Dr. Hal Markowitz of SFSU
serve as the principal investigators on the project. It is our goal
to monitor seal numbers at the rocks, as well as levels of disturbance that
the seals are exposed to, both before and during the construction.
Two additional Bay harbor seal haul out sites -- Mowry
Slough
and Yerba Buena Island
-- are being monitored, as they may be affected by the retrofit work at
the Richmond-San Rafael Bridge. We will report on what we find, and
our data on seal reactions to this kind of work, tolerance levels, disturbance
thresholds, mitigation measures, etc. can be used for this and future Caltrans
projects involving harbor seals. In addition, we will recommend ways
for Caltrans to minimize any negative impacts on the seals at this haul out
site, while ensuring that the retrofit proceeds expeditiously.
If you would like to read more
about marine mammal protection, NMFS has a great page with more info on the
Marine Mammal Protection
Act
.
*
a haul out is an area where seals come to land to rest, breed and molt
2) What happened to the seals when the bridge was built?
Although no records exist of seals
using Castro Rocks prior to the bridge construction in 1956, we suspect that
they were probably there. No seals were mentioned in reports written
during the construction of the bridge itself. Looking at records that
were made following the completion of the construction, it appears that numbers
using this haul out site increased, very slowly, to the levels that they
are at today (maximum count of 596 seals).
3) How is the situation at
Castro Rocks different today
than when the bridge was first built?
The Richmond-San Rafael Bridge
was completed in 1956, when life was very different for seals in the San Francisco
Bay. Accelerated rates of shoreline development have meant a decrease
in the amount of available haul out space for harbor seals in the Bay --
harbor seals have abandoned at least two Bay haul out sites (that we know
of). Seals today have fewer options should one of their current haul
out sites become unusable. For example, seals abandoned a site in Richardson
Bay (Strawberry Spit) in the early 1980's, due to increased levels of human
disturbance and development in the area. In addition, the population
of San Francisco Bay is under some pressure due to water quality issues in
the Bay (in contrast to coastal seal populations). Seals in the San
Francisco Bay are subject to much higher levels of human disturbance today
(due to watercraft, foot traffic, aircraft, etc.) than they were in 1956.
And finally, the Marine Mammal Protection Act (see question #1) was passed
in 1972, and so didn't apply in 1956.
4) What is so important about
the seals at the
Richmond-San Rafael Bridge? I thought there were
lots of seals around now?
Numbers of harbor seals (and California sea lions and Northern elephant seals) on the coast of California have been increasing since the Marine Mammal Protection Act was passed in 1972. However, the number of harbor seals found in San Francisco Bay has remained steady, failing to rebound like the coastal numbers. Harbor seals are the only marine mammals to stay in the Bay year-round, and are an important part of the Bay's ecosystem. Only 600-700 harbor seals reside in the Bay, and our counts of over 500 seals using the Castro Rocks haul out represent a substantial portion of this overall number. With the increased levels of stress on the seals of the Bay, it is important to minimize disturbances whenever possible.
In addition, Castro Rocks is the
second largest pupping site in the San Francisco Bay, and in order to protect
populations, it is important to protect pupping sites. Mothers with
pups can be particularly sensitive to disturbance, and it has been suggested
that high levels of human disturbance may cause abandonment of sites.
During the course of the retrofit project, contractors working for Caltrans
observe a boat "exclusion zone" around the rocks during the pupping and molting
seasons (when numbers of seals using the haul out are at their highest).
In addition, the contractors do not work on the sections of the bridge closest
to the rocks during these two seasons (from March 15 through July 31), and
work elsewhere on the bridge during this time.
The seismic retrofit work on the Richmond-San Rafael Bridge is scheduled to end in September 2005. While any construction activity has the potential to affect the commute, Caltrans plans to maintain both eastbound and westbound traffic on the Bridge. More information about the seismic retrofit of the Richmond-San Rafael Bridge can be found at http://www.dot.ca.gov/hq/esc/tollbridge/index.html?Rich-SR/ProjectOverview.html .
It is our job to report on our
findings on an ongoing basis to Caltrans, and when possible, to suggest ways
to minimize negative impacts on the animals, should these arise. It
is one of our goals to work together with Caltrans to protect the seals at
Castro Rocks while having at most a minimal impact on the scheduling and
progression of the seismic retrofit. The retrofit of this bridge is
vital for the safety and peace of mind of Bay Area residents and bridge users
(like us!).
6) Can I stop on the Richmond
Bridge and
look at the seals?
Stopping on the Richmond-San Rafael
Bridge (or on any bridge) is strictly prohibited for any reason other than
an emergency. It is simply not safe to stop and get out of your car
to try and observe the seals. Our field biologists all have received
Caltrans safety training and wear special safety gear at all times on the
bridge (as all Caltrans employees do).
7) Are these the same as the
Pier 39 seals?
They don't seem to mind people being
really close...
The "seals" that you see at Pier
39 are actually California sea lions, a different species of Pinniped (the
group to which both seals and sea lions belong). Unlike the harbor
seals found in San Francisco Bay, who tend to be quite sensitive to human
disturbance, male California sea lions at Pier 39 are well known for their
apparent lack of concern
* about humans in their immediate environment,
not to mention their enthusiastic barking!! The Pier 39 sea lions have
become a major tourist attraction; like harbor seals and the grey whales
that migrate along the coast, these marine mammals are an important aesthetic
(and economic) asset for the city of San Francisco and surrounding Bay Area.
For more on the Pier 39 sea lions,
The Marine Mammal Center
(in Sausalito, California) has a number of pages with lots of great information
about those animals.
*
However, California sea lions (particularly females) at other sites can be
very sensitive to human disturbance.
