Tiny computers help track Lake
Devices to determine harvest levels
By Eric Pope
The Detroit News
MILLERSBURG -- Hundreds of salmon, trout and other fish
are swimming in Lake Huron with minicomputers implanted
inside them, helping the state collect information that
will improve Michigan's sports and commercial fishing.
Computerized devices about an inch long record the water
temperature and depth the fish prefer, adding information
to a computer model the state Department of Natural Resources
uses to determine stocking levels and harvest limits for
commercial and sport fishermen as well as the Indian fish
catch under an 1836 treaty, according to Jim Johnson,
DNR station manager at the Alpena Fishery Station.
Biologists know water temperature affects the digestion
of fish, and that data will help build a better database
for the food consumption and growth rates of fish. Professors
and students at Michigan State University are working
on the database.
The data will help scientists, for example, make more
precise adjustments to salmon stocking levels.
The study began in 1998 when biologists surgically inserted
the devices in the abdominal cavities of more than 300
lake trout in Lake Huron. The computer processors and
memory chips were programmed to record the temperature
of the water the fish were in every 75 minutes for up
to 14 months.
Biologists are now using the next generation of devices,
which cost about $300 and record water temperature and
depth for trout, salmon, white fish, lake sturgeon and
sea lamprey. This year, the Great Lakes Fishery Commission
and the U.S. Fish and Wildlife Service will spend $155,000
on the project.
That's a bargain, according to biologist Roger Bergstedt
of the U.S. Geological Survey, who runs the study from
the Hammond Bay Biological Station.
"It would cost millions to get the data with research
vessels, if you could get it at all," he said. "The
fish are getting the information for you."
There's a $100 reward for the data-laden fish, which
have a tag near the dorsal or pelvic fin. So far, 85 of
700 lake trout with the recording devices have been returned.
The program so far has given scientists more information
on the sea lamprey, a nonindigenous species that sucks
blood from much larger lake trout, killing many. Recovered
thermometer tags show that the lake trout strain from
New York's Finger Lakes live at an average temperature
of 44.6 degrees during the late summer, compared to 47.3
degrees for native Great Lakes strains.
"We know that sea lampreys attack and kill fewer
Finger Lakes trout," said Bergstedt, noting that
sea lamprey also consume less blood at lower temperatures.