the Way Bocaccios Move
by Julie Zeidner Russo
| The prized bocaccio, a large, edible
rockfish of American Pacific waters, which gets its name from
an Italian word meaning ugly mouth, is now sending a message
to researchers at Moss Landing Marine Laboratories (MLML).
| Bocaccios are named for their protruding jaws.
| Rockfish have
been caught since the late 1800s. Today, they are one of the
most popular commercial and recreational fish on the West coast.
They also fascinate fisheries biologists because of their diversity
and longevity--there are 57 species of rockfish in Pacific waters
alone, and some can live to be more than 100 years old. "Fishing
effort for rockfishes and landings have increased dramatically
over the last forty years," said marine biologist Richard Starr
of the California Sea Grant Program. "Historically rockfish
landings have been high especially in Monterey Bay area, but
there are now indications that numbers and size composition
are decreasing for some species." The bocaccio population is
less than 20 percent of what it was in 1970, according to the
National Marine Fisheries Service, and the World Conservation
Union considers bocaccio at high risk of extinction.
Rockfish fascinate fisheries biologists because of their
diversity and longevity--there are 57 species of rockfish in
Pacific waters alone, and some can live to be more than 100
| At one time, rockfish were
hard to get to by line or net. Their preferred habitat
of deepwater rocky outcroppings and pinnacles made them
less prone to exploitation, and they could flourish within
Monterrey Bay's natural harvest refugia. But as local
stocks of rockfish have become depleted, the Monterey
fleet is going greater distances and depths to find them.
Fisheries managers are now in a race to establish marine
fisheries reserves and parks to protect rockfish. "A number
of reserves, which serve as undisturbed areas of research
or protection where fishing is prohibited, exist in California,"
said John Heine, a research biologist with the Moss Landing
Marine Laboratories, "but their effectiveness in fisheries
management is largely untested."
| Finding out how bocaccios
move is a critical piece of information in establishing
marine reserves to protect them. With support from the
National Undersea Research Program, a novel technique
of tagging rockfish underwater and observing their movements
is underway by researchers Starr and Heine, MLML fisheries
scientist Gregor Cailliet, and California Sea Grant research
technician Jason Felton. The project has already yielded
some interesting results that could be used by researchers
and managers in the study and management of rockfish as
well as other fisheries.
Traditionally, fish have been tagged with visual external
ID tags or at shallow depths where they are brought
to the surface, tagged with an external marker, and
released, the scientists said. "Researchers then wait
for tag recoveries to return via the commercial or recreational
fishery," Heine said. "Such studies provide long-term
movement data, but little information about short-term
movements." However, few researchers have successfully
tagged deepwater species. Since bocaccio live at depths
of up to 300 m or more bringing them to the surface
without bursting their swim bladders would be difficult.
Methods of tagging deepwater fish have also met with
poor results since fish enticed to swallow sonic tags
tend to regurgitate them and surgical methods of attaching
the tags externally may traumatize the fish and affect
| Last summer, scientists performed
a new six-minute procedure they developed and tested at
the Monterey Bay Aquarium to surgically insert an acoustic
transmitter inside rockfish. A commercial fisherman assisted
in bringing the rockfish up to a 20 m depth using longline
gear, then SCUBA divers descended to the depth of the
captured fish, anesthetized them one at a time, and surgically
implanted the acoustic transmitters in the bocaccio.
| Rick Starr and Jason Felton
prepare to surgically
implant a sonic tag into a bocaccio.
| Sixteen bocaccios--each outfitted
with its own unique frequency tag--released on the bottom
at the location of the catch sent radio signals back to
researchers showing their individual locations. Several
weeks after the fish were tagged, the scientists used
the Delta submersible to place six recording receivers
on the seafloor to assist in the tracking of vertical
and horizontal movements of the fish. This would be the
first time researchers had developed techniques to obtain
semi-continuous information about fish movement during
a three month period, Heine said.
||The Delta is a
two-person submersible that dives to 370 m.
Schools of up to 100 rockfish
at 150 m depth--and amazingly, three of the tagged bocaccio
located by the hydrophone-- were observed by the scientists
during their underwater excursion. What the researchers
discovered was that the rockfish tended to move up the
rock walls during the day and move down at night in
a range of about 10 to 20 m, Felton said. Occasionally,
the bocaccio dove much deeper in dives that exceed 200
m for unknown reasons, he said. Their horizontal movement
was more illusive since they may have hidden under rock
ledges or inside canyons. The bocaccios' range--as much
as several kilometers in either direction-- also surprised
scientists who thought their horizontal movements would
be smaller. "Results of this work should provide important
information related to home range and frequency of emmigrations
from harvest refugia," Starr said. The researchers are
already applying the techniques used for studying the
movement of bocaccio to other species like the prickly
shark, with the hope that it improves the design of
future marine reserves.
|For more information see the
Web sites of:
Moss Landing Marine Laboratories
and the West Coast
& Polar Regions NOAA's Undersea Research Center
August 24, 2004