State of the Lake 2002State ®f the Lake — 2002
By Jack A. Stanford
Flathead Lake Biological Station (www.umt.edu/biology/flbs)
Flathead Lakers Annual Meeting
June 23, 2002
During the last two drought years, the lake stayed very clear
and warm. As I predicted the winter was foggy and overcast much
of the time around the lake because the lake was steaming, giving up
its high summer heat load. This year we have above average snow
pack and a wet, cold spring with an extended runoff from the rivers.
So far we have had three peaks in the runoff, a phenomenon not
previously observed. So, a lot of turbid water has come into the lake
from the river. The turbid water has spread over the surface lake-.
wide and is starting to gradually sink to the bottom. This is the usual
pattern on wet years as the Flathead River system is naturally erosive
and retention of fine sediments in the lake has always occurred. Of
course some sediment is being pulled out the outlet, as the spill gates
at Kerr Dam have been wide open for some time. The lake will be
colder this summer (on Monday it was 15°C (ca. 42°F) at the
surface), owing to the cold spring and extended inflow of snowmelt.
. Primary productivity, one of the key measures of water quality,
continues to increase in the lake (see attached figure). Data for 2001
are just being calculated and the preliminary estimate is 95 g C m 2,
which is below the long-term trend line for the first time in several
years. Primary productivity has increased 1/3 since the FLBS began
keeping continuous records in 1977. The increase would be greater
if controls on pollution had not been accepted for the sewage
treatment improvements in the early 1990s. However, non -point
sources of nutrients, the main pollutants of concern, continue to be a
problem in spite of the efforts by the Flathead Basin Commission
and EPA to reduce them. We need greater emphasis on installing
high quality household sewage treatment systems in rural and ex -
urban areas of the Kalispell Valley, treating street and parking lot
runoff in constructed or natural wetlands and maintaining wide
riparian forests along our rivers and streams and the lake shoreline.
A recent report by the Lakers properly designated flood plains and
alluvial aquifers along the Flathead and other valley rivers are
critical lands that require care and protection. Constant vigilance by
all citizens is required to accomplish non -point nutrient controls,
especially since our area is a focal point for developments that too
often increase non -point pollution.
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We have not observed any significant blooms of pollution
algae in the lake during the last year.
The Mysis (opossum shrimp) population in the lake was stable
as in 1999-00 at about 35 per m2 in our fall 2001 census. Lake trout
and lake whitefish populations remains robust based on net sets done
State and Tribal biologists, a phenomenon we have long associated
with the establishment of Mysis in the lake. Station graduate student,
Craig Stafford, who completed his Ph.D. work this spring, showed
through analysis of ear bones that growth of young fish in years 1 to
3 were similar before and after Mysis established in the Lake. But
growth declined in ages 4 to 10 post Mysis. These results suggest
that increased growth was not the mechanism by which lake trout
populations expanded post Mysis. However, the Mysis foraging
behavior tends to shuttle surface productivity to the lake bottom
which likely has increased the opportunities for small lake trout and
lake whitefish to forage in deep waters, thereby reducing predation
risk and increasing the survival rate of young fish.
Stafford also found that fish growth rate. was much less
important than fish diet in determining mercury levels in lake trout
and lake whitefish and contamination increased with the foraging
depth of the fish. These findings strongly suggest that individual
fish have long term preferences in foraging depth, and that
individual differences in dietary mercury intake explains variation in
contamination levels.
We do not know the source of mercury and other carcinogenic
pollutants that have been identified in Flathead Lake fishes.
Certainly, oil spills, contaminated soils eroded by the river or dust
from within and outside the basin and two cycle engines on some jet
skis and boats are likely sources. We monitored the pollution from
the construction barge that sank multiple times during the last year
and verified a long list of organic pollutants over large areas.
Enforcement of water quality laws and agency response
preparedness to spills needs your support. But, in comparison to
other big, developed lakes around the world, the contamination in
Flathead Lake fish is not high enough to be of great concern.
Indeed, Flathead Lake is one of the cleanest lakes in the world and
fishers should not hesitate to eat some of their catches.
Biological Station scientists will continue to conduct research
on the lake and describe it in context with water problems locally,
nationally and internationally. However, we need your help to
continue the detailed monitoring program. Bob Keenan, Stan
Fischer, John Brueggeman and other Flathead legislators and the
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•2,
Montana DEQ have worked hard to fund the FLBS water quality
monitoring program. But, this year for the first time in two decades,
I had to cut back the monitoring program due to insufficient funding.
Therefore, FLBS has established an endowment fund for lake
monitoring and research. I urge all those interested in maintaining a
clean lake to contribute to this fund. Any amount helps. Contact
Erika Binger or me at the Station (982-3301) if you are interested in
this important effort.
Check the FLBS website for updates on this report and other
activities of your Biological Station.
Primary productivity , off
quality declines as primary productivity increases.
Yellow Bay monitored continuously since 1978 by FILBS. Water
`F"#
1
t t
77 79 81 83 85 87 89 91
Water Year
LOTC
• • • •
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