From: fak9957@ritvax.isc.rit.edu (Frank Kruppenbacher)
Subject: Lake Ontario Forage Fish Population Declines
Reply-To: fak9957@ritvax.isc.rit.edu
Organization: Rochester Institute of Technology
Date: Tue, 28 Jul 1992 15:31:58 GMT

Sunday July 26, 1992

Fewer 'forage' fish in Lake Ontario
by Diana L. Tomb
Rochester Democrat & Chronicle

     Lake Ontario's alewife population - a fish eaten by the big
game species such as salmon - is falling so much it could force
cutting the number of game fish being stocked, monitoring of the
lake suggests.
     A group of scientists from the United States and Canada will
meet in Kingston, Ontario, on Tuesday and Wednesday to discuss the
recent findings of the U.S. Fish and Wildlife Service, with an eye
toward advising the decision-makers.
     "The implications are tough if we've got a serious decline in
the sawbellies," Ned Holmes, a biologist with the state Department
of Environmental Conservation's [region 8] office in Avon [NY],
told a panel of fishery people in Monroe County last week. Sawbelly
is a common nickname for the alewife.
     The big concern is that a decline in alewives could cause a
crash in the lake's sport fishery like the one that hit Lake
Michigan in the mid 1980s.
     The Lake Ontario fishery already is experiencing some stress
because the poor economy has reduced the numbers of people taking
fishing charters.
     "A lot of signs are saying the system isn't functioning the
way it used to," federal fisheries biologist Robert O'Gorman
said."If you've got predators out there eating your prey, you
should replace them. If you want the system to work well, you
should replace them fast."
     Today in Lake Ontario, that's not happening.
     Two key differences do exist between the conditions in Lake
Ontario now and what happened to Lake Michigan.
     Scientists here have been on the lookout for a crash since
Lake Michigan lost its fishery and may bale to act in time to
prevent a die-off.  In addition, bacterial kidney disease - perhaps
more easily spread in an underfed population - was the big killer
of Lake Michigan salmon.  That disease hasn't been found so far in
Lake Ontario fish.
     The non-native alewives were at unmanageable levels in the
early 1970s - they'd die off in huge, smelly piles on Great Lakes
beaches. The predatory chinook and Coho salmon, and lake trout,
were introduced to control them.
     The recent bad news about alewives comes from trawls performed
twice each spring since 1978 by the federal and state governments.
     After this spring's trawls, O'Gorman came up with a seven
point list of concerns - and they basically pointed to fewer
alewives, with the remaining ones in poor condition.
     * Large alewives and large smelt, another forage fish,
appeared in record low numbers from 1990 to 1992. The monitoring
involved trawling for fish in 12 sections of the New York side of
Lake Ontario, taking samples from six to 12 different depths in the
water column and distances from shore.
     "The disappearance of the large fish in any population is
generally thought to be a sign of predation. The point is how low
do you want to get," O'Gorman said.
     * Alewives who are in their second year of life grew poorly
from 1986 to 1990.
     "They aren't growing much," O'Gorman said. This could be due
to lack of food for the alewife.
     Holmes suggested the improvements in pollution control -
reducing the amount of phosphorous, for example - has made the lake
less productive.  Phosphorous feeds algae, which is fed upon by
phytoplankton.  Those microscopic organisms are food for
zooplankton which are eaten by alewives.
     Because there are so many links in the food web below
alewives, that connection may be tough to track down than the
effect of predation on alewives, O'Gorman said.
     * Alewife populations are down, yet they're in terrible
shape," O'Gorman said. Usually, the physical condition of the
alewife population improves when there are fewer of them competing
for food.
     Dave MacNeill, with the Brockport office of the National Sea
Grant College Program, said the alewives may be scrawny because
they're suffering from excessive predatory pressure.  They're
getting chased around a lot, and may not be able to feed as well.
     * There was a modest die-off of alewives last winter, even
though winter conditions were milder than normal.  Because the fish
are not native to the lake, they aren't well equipped to withstand
its cold temperatures. But usually the winter has to be harsher to
see the kind of die-off that happened this year, O'Gorman said -
because fewer fish usually have more to eat, which makes them
heartier.
     * Adult alewives were almost absent from the northeastern New
York waters of Lake Ontario. Canadian surveys found abnormally low
numbers of alewives in easternmost waters there, too.
     "As the alewife population get lower, you're going to have
pockets in the lake where there aren't any fish," O'Gorman said.
The samplings was taken before cormorants - waterfowl that eat the
fish - migrated back to the lake, ruling them out as a possible
cause of the decline.
     * Four dead or dying chinook salmon and one dead Coho salmon
were collected in the western lake trawls this spring.
     "We've been doing these surveys all these years and we very
rarely find dead salmon.  When you do find one there's usually an
obvious cause of death," O'Gorman said.  These fish weren't
emaciated, but didn't have another obvious cause of death. Lab
analysis ruled out the Lake Michigan killer - bacterial kidney
disease.
     * The biomass, or combined weight, of smelt caught in the 1992
trawls was the lowest since the monitoring began in 1978. The
biomass of adult alewives was the lowest since 1979.
     "I wouldn't say they're in a crash but they might be in a
downward spiral," O'Gorman said.
     As a researcher, O"Gorman is cautious about suggesting a
course that should be taken to arrest the alewife decline. Others
have been less reticent, though.
     "There is enough evidence to suggest perhaps reducing the
number of predators stocked in the lake," MacNeill said last week.
     Not many options are available, though, said a Canadian
fishery biologist.
     "Certainly the only real obvious management option," is
reducing the numbers of stocked predatory fish, said Michael L.
Jones, from the Ontario Ministry of Natural Resources. "If one
accepts predation is the problem and accepts that reduction in
stocking would solve the problem, that is really the only serious
management option."
     So far there hasn't been a matching decline in the numbers of
predatory fish.
     But O'Gorman noted that the number of lake trout that survive
for a year after they are stocked has declined by 50 percent
recently.  In that year, they usually grow from 4 or 5 inches to 7
or 8 inches, the size of an adult alewife.  The fingerling lake
trout may be taking the place of alewives as forage for the larger
fish.
     "If alewives and smelt are down, the likelihood of a fish
(eating) a recently-stocked predator is high," O'Gorman said.
     DEC spokeswoman Barbara Allen said her agency expects to make
some decisions early next month.