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Northern California is home to the red abalone, the world's largest abalone species. Red abalone
populations support a viable free-diving only sport fishery from San Francisco to the Oregon
border. Current regulations include seasonal and area closures, minimum size limits, gear
restrictions, and daily and yearly bag limits.
The information obtained from Department dive surveys is used in conjunction with other
sampling methods including: on site diver and shore picker interviews for catch and
effort information, phone surveys, recruitment module monitoring, and analysis of your abalone
report cards. All these methods are used to determine the current status of the abalone
population.
The Department of Fish and Wildlife conducts dive surveys at eight index sites on a triennial
period. Index sites are located in both Sonoma and Mendocino counties; the heart of the red
abalone populations, and where more than 95% of the sport fishery occurs.
Abalone densities are used in managing the fishery under the guidance of the Abalone
Recovery and Management Plan. If abalone densities reach target levels outlined in the ARMP,
regulatory changes may be proposed to adjust the yearly take by sport fishermen. For more
information on the adaptive management of the red abalone fishery, a full electronic
version of the ARMP can be viewed on the department's web page.
Diving in northern California is usually very challenging. The seas are often rough, and
the water is almost always cold and surgy with low visibility. Typically divers will
make 3 to 4 dives per day with about three hours of bottom time.
Dive surveys require a tremendous amount of planning, coordination, and organization.
Survey participants are certified scientific divers trained in transect methods and species
identification, and are well briefed to ensure that the data collected are precise.
Index site dives are conducted on random points based on rocky reef habitats. Transects are
further stratified by depth ranges from 5-60 feet. Survey points are found using a GPS
unit and a surface buoy is deployed to mark the location. Divers record counts and sizes
of abalone as well as sea urchin and other large invertebrates. Habitat and algal information
are also recorded.
Dive teams carry measuring calipers, a data board, and a 30 meter transect tape. The zero
end of the tape is tied to the kelp or a rock, and is deployed following a compass heading
over rocky habitat. Each diver surveys one side of the transect and records data one
meter out from the tape. This type of survey is called an emergent survey in which divers
only count abalone that can be seen without the aid of a flashlight or turning over rocks.
Therefore, emergent survey data typically does not include counts of very small, cryptic
abalone that occur deep in crevices and under boulders.
The survey area of a transect is further illustrated in this figure. The white, solid line shows
the zero end and the thirty end of the transect tape. The dotted white rectangle shows the
total area surveyed, going out to one meter on each the right and the left sides. The
red dots represent each of the abalone counted and measured in the sixty square meters of
area on the transect.
Abalone are measured along the greatest extent of their shell, and measurements are recorded
to the nearest millimeter. Sea urchins are measured using greatest test or shell width
excluding the spines. Pinto and flat abalone are not as commonly found as red abalone,
but they are also counted and measured.
The Department conducts various types of surveys to measure recruitment of newly settled or
juvenile abalone, which estimates the reproductive success for that particular year. A long time
series of recruitment data can show periods of strong or weak recruitment that may help
manage the fishery.
Recruitment modules replicate ideal baby abalone habitat. They allow us to count and measure
individuals without disturbing the natural substrate.
Invasive surveys, or using lights and turning over rocks to search for abalone, give us
counts on smaller abalone that we normally would not see in an emergent study.
Substrate collections are sometimes used to find microscopic abalone on algae encrusted
rocks, which gives us an idea of the strength of the recruitment event for that year.
Tagging adult abalone can be useful in determining the movement and growth of abalone in a particular
area.
This has been a brief overview on the Department's north coast abalone dive methodology. For
more information on other department activities, please visit the Department of Fish and Wildlife's
website at wildlife.ca.gov.