2001–2002 - California Sea Grant - UC San Diego

Sonograms of the Seafloor
On land, wildlife habitats are
usually, and obviously, defined by
flora, climate and altitude. In the inky depths
of the sea, habitats are delineated quite
differently—by substrate type, water depth
and seafloor geomorphology.
Since seawater covers these habitat areas,
how do scientists “see” what is on the bottom?
Right now, techniques rely on bouncing
sound waves off the seafloor and “listening”
to their echoes.
The modern techniques for imaging the
seafloor began in the early 1990s in Monterey
Bay National Marine Sanctuary, as NOAA,
NOAA Fisheries, the U.S. Geological Survey
and others began characterizing the complex
canyon topography and associated rockfish
habitats at the sanctuary.
In the mid-1990s, Sea Grant, the
Monterey Bay National Marine
Sanctuary and the California
Department of Fish and Game supported the
newly formed Center for Habitat Studies at
Moss Landing Marine Laboratories to
characterize fish habitats around the Big
Creek Ecological Reserve. By the late 1990s,
the Seafloor Mapping Laboratory of California
State University was established.
More recently Sea Grant, in collaboration
with the California Department of Fish and
Game, has funded scientists to digitize and
interpret geophysical data collected by oil
companies, data that up until recently were
proprietary and not available for
scientific study.
Why are the maps of use? Many
reasons. Top among them: the
California Department of Fish and
Game Commission in September of
2002 adopted the state’s first
Nearshore Fisheries Management
Plan for 19 species of finfish, most
of them rockfish. The maps that are
being produced will help resource
managers identify areas that
support these species. There is also
a federal mandate to protect
“essential fish habitats.”
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Multibeam bathymetric data help scientists distinguish
steep rocky ledges and gentler sedimented slopes in
Soquel Canyon in the Monterey Bay National Marine
Sanctuary. The contours demark lines of constant
water depth. Imaging: Center for Habitat Mapping,
Moss Landing Marine Laboratories
The Essential Fish Habitat mandate represents a new
recognition by Congress, the fishing industry,
conservation groups, and the general public that
habitat quantity and quality is critical to the health and
productivity of fish populations.
—NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION
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