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Halibut trails For five months, the
feisty 60-pound Pacific halibut with the nickname Lip roamed the Gulf of
Alaska, its movements monitored by a tiny computer tag anchored below its
dorsal fin. In a project that
could revolutionize the study of ocean use by important Alaska species
like halibut and salmon, the fish was among half a dozen big flatfish
successfully tracked from Resurrection Bay over the past 18 months during
a test of new miniature technology. On its travels to
and from deep water, this halibut sniffed at the surface and plunged as
deep as 1,600 feet. When it traveled farther offshore, it spent whole days
swimming hundreds of feet up and down in the water column, followed by
days of steady cruising, often about 1,000 feet down. Then, out in the
abyss, it found what passes for halibut bliss. In what could be the
first glimpse of mating by the species, the fish shot straight for the
surface on nine occasions, rising 300 to 570 feet in minutes before
plunging just as fast to its previous depth. While no one knows
for sure what the halibut was doing, observations of breeding flatfish in
the Atlantic Ocean suggest that the fish probably soared in unison with
another consenting piscivore, according to biologists from the U.S.
Geological Survey in Anchorage. "It's like a
dance," explained Jennifer Nielsen, supervisor of fisheries research
for the USGS's local biological resource division. "As a pair, they
do like a spiral ascent. It's part of its breeding behavior. Nobody is
quite sure why they do it." "Everyone has
known for a long time that (Pacific halibut) go off the shelf in the
winter to breed," added Derek Wilson, a fisheries biologist working
with Nielsen on the project. "But individual breeding behavior has
never been documented before." The halibut study
illustrates how miniature tracking technology and tiny computers have
changed field research forever, enabling scientists to gather detailed
information about where wild animals go and what they do in environments
beyond normal human scrutiny. By attaching the devices to fish, especially
salmon, scientists can begin to answer fundamental questions about habitat
use in the deep sea, Nielsen said. "I've been a
salmon biologist for 25 years, and one of the biggest questions for the
whole 25 years has been the ocean," Nielsen said. "It's been a
big black box. It's a big unknown. . . . Now the technology has opened the
opportunity to begin to ask -- at the same level that we look at rivers --
what's the ocean use by salmon?" Funded with a
$77,000 grant from the Exxon Valdez Oil Spill Trustee Council, the halibut
project was aimed at testing 14 tiny pop-up satellite tracking tags as a
way to identify critical marine habitat for any Alaska fish. Though
previously tried on tuna and marlin, the technology had never been used
this far north, Nielsen said. As designed by
Seattle-based Wildlife Computers, the 2-inch-long, bobber-shaped devices
trailed behind the halibut on a tungsten wire, constantly recording water
pressure, temperature and ambient light as the fish swam. Unless recovered
first by a fisherman, the device corrodes the wire at a programmed time,
floats to the surface and transmits its data to a satellite. By registering the
time of each day's sunrise and sunset, the tags could enable scientists to
indirectly calculate the approximate latitude and longitude of fish --
something not possible with conventional global positioning system
satellites. A poster describing preliminary results was published this
winter by Nielsen, Wilson, Andy Seitz and Sage Pelot. But the halibut
study is only the beginning. Additional satellite tags will go on halibut
this next season in the Gulf and Bering Sea. In separate projects using
nonsatellite tags that store data in memory or give off beeps underwater,
Nielsen and co-researchers Wilson, Phil Richards and Chris Zimmerman plan
to start tracking coho salmon smolts from Ship Creek, as well as steelhead
from the Ninilchik River and Deep Creek on the Kenai Peninsula. "It was always
a little weird to me (that scientists) consider salmon a freshwater fish
when they spend two-thirds of their time in the ocean," Nielsen said.
"There's a gap. . . . And that's what we're trying to get at --
knowing where they go and why." Working with Capt.
Harold Salve of the fishing vessel Rocinante, Nielsen's team caught the
first 11 halibut during two trips off Bear Glacier near the mouth of
Resurrection Bay in August 2000. Among the fish was a 50-inch 60-pounder
with a torn lip. It soon joined six other survivors at the Alaska SeaLife
Center for months of observation. That fish, named
Lip, initially didn't want to eat, said research associate Pam Parker, one
of the people who monitored the project at the center. But as its wound
healed, it began to feed with enthusiasm. "It was
superaggressive," she said. "It was just an interesting
fish." All of the flatfish
adapted fast to captive life and became popular with tourists. They would
sleep in a pile on the sandy bottom of the 10-foot-deep tank. When the
tank was drained for veterinarian checks, the fish would calmly swim in a
foot of water while the vet walked among them, Parker said. The fish even
ogled their human keepers. "They were
really curious," Parker said. "The minute we would approach the
tank, they would start swimming with their heads out of the water. They
would watch us." More important, when
the tags were surgically anchored, the animals recovered fast and ignored
one another's tags. "The bottom
line was that within a week, they were all behaving normally and there
were no critical problems with the tags, and that's what we needed to
see," Nielsen said. Over the next year,
14 halibut were equipped with the tags and released off Resurrection Bay.
In the end, seven tags succeeded in delivering data to the scientists. (A
programming error by the manufacturer set four of the tags to release 41
years in the future, and three tags simply did not respond.) Two halibut,
including the one called Lip, were caught by commercial fishermen,
allowing Nielsen to recover all of the data recorded in their tags. The
other five tags released on schedule last Nov. 15 and transmitted data to
the satellite. Two halibut had
stayed near the Kenai Fjords coast -- one swimming only a few miles away
and the other moving southwest toward the mouth of Cook Inlet. But three
halibut swam much farther out. One had traveled about 120 miles out toward
Middleton Island. The other two were in the Gulf south of the Bering
Glacier, more than 200 miles from Resurrection Bay. Doug O'Harra can be
reached at do'harra@adn.com and 907
257-4334. ON THE WEB: For details on
tracking halibut with pop-tags: www.absc.usgs.gov/research/Fisheries/Halibut/popup_tags.htm
For details on
tracking Ship Creek coho salmon: www.absc.usgs.gov/research/Fisheries/archival_tagging/coho_archivetags.htm
For other fisheries
projects by USGS in Anchorage: www.absc.usgs.gov/research/Fisheries/fish_proj.htm
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