Graduate Research Assistant - Adria Banks
NOAA/Padilla Bay NERR Research Assistantship Recipient
Harbor Seals in and around Marine Reserves
Adria Banks
M.S Candidate, Western Washington University
Marine and Estuarine Science Program
Department of Biology
Bellingham, WA
Harbor seal abundance and foraging habits within and adjacent to candidate marine reserves in Skagit County, Washington
Background
Marine reserves, defined as areas where fishing and other harvesting activities
are banned, are becoming a popular management tool used to conserve marine biodiversity
and to manage fisheries. After an area is protected from fishing, there tends to be rapid
increases in biomass, abundance, and average size of exploited species. Due to the increase
in size and quantity of exploited species in protected sites, one would expect predators to
respond by increasing their abundance and frequency of foraging in these areas of increased
prey density. Yet, there is a lack of information regarding the responses of top marine
predators to these areas of higher fish abundance.
Currently, eight marine reserve sites are being considered in Skagit County for management of bottomfish - a species complex including rockfish (Sebastes spp.) and lingcod (Ophiodon elongates) - which are of concern as stocks have decreased significantly since the 1980s. In some areas, rockfish and lingcod are also known to be important prey of harbor seals (Phoca vitulina). Harbor seals are the most widely distributed and abundant pinniped species in Washington State, with a year-round presence and well-known haul-out sites (Fig. 1). These predators, therefore, have great potential to affect local fish stocks in the San Juan Islands and surrounding waters.
Fig. 1. Harbor seals hauled out in Padilla Bay.
This project aims to answer the following questions:
- What is the current abundance of harbor seals in and around Skagit County candidate marine reserves, including Padilla Bay?
- Does harbor seal abundance vary seasonally or annually in the study area?
- Do harbor seals respond to differing prey distributions on a small spatial scale (less than 1 km)?
The answers to these questions will set the stage for continued monitoring of these sites after protected status has been awarded and will increase our understanding of fine-scale predator-prey dynamics that should be considered in marine reserve design.
Methods
Airplane- and boat-based surveys will be conducted monthly to attain a robust measure of the
number of harbor seals using a geographic area encompassing the eight candidate marine reserves,
including Padilla Bay (Fig. 2), during the pre-reproductive, pupping, and molting seasons. In
addition to total counts of seals, Adria will record time of day, sea state, and cloud cover as
environmental variables that may affect the number of seals hauled-out.
Bottomfish density will be measured by SCUBA divers three times per month in the study site. From land, scan sampling will be used to record harbor seals swimming in the water. Total count of seals observed, sea state, cloud cover, and time of day will be recorded. During scans, detected seals will be targeted with a theodolite to determine their exact positions and whether or not the seals are consuming prey. Tracking sessions of randomly chosen focal seals will determine the length of time that seals spend in the candidate marine reserves as well as to examine behavior patterns within the candidate reserve.
Fig. 2. Spatial extent of aerial survey coverage.
Significance to Padilla Bay
One of the candidate marine reserves encompasses Hat Island as well as Saddlebag, Dot, and
Huckleberry Islands, which are at the western edge of Padilla Bay. Given the number of harbor
seal haul-out sites within the Padilla Bay National Estuarine Research Reserve, and their proximity
to Hat Island, collecting baseline information on the number of seals that use Padilla Bay as a
resting area prior to protection of the candidate areas is crucial to address the more long-term
question: Do predators respond to increased prey densities in a marine reserve by increasing their
abundance? Additionally, information on the seasonal fluctuations of these marine predators within
Padilla Bay and the surrounding waters does not currently exist.
Fig. 3. Adria Banks taking photographs from a plane over the study area.
Biographical Information
Adria Banks is currently a Maters of Science Candidate in the Biology Department/Marine and Estuarine
Science Program at Western Washington University (Fig. 3). Her graduate advisor is Dr. Alejandro
Acevedo-Gutiérrez. Before enrolling at WWU, she received a BS in Zoology from the University
of Washington. Adria's research is partially funded by a Padilla Bay Research Assistantship in
Estuarine Science and Coastal Zone Management.