Hi folks - Saw this info from the Seattle Parks & Rec, and wondered whether
(or how much) the introduction of a large, predatory, exotic fish species
would have any impacts on the avian community of Green Lake? Muskellunge
and pike are well-known for preying on the young of waterfowl and marsh
birds (coots, grebes, etc.). Is the potential predation on carp worth the
effects on other components of the lake?

Jon. ('just wondering') Anderson
Olympia, Washington
festuca at olywa.net
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Tiger muskies introduced to help
balance Green Lake ecology

SEATTLE* As part of a larger effort to improve water quality and
recreational fishing in Green Lake, the Washington Department of
Fish and Wildlife (WDFW) plans to stock the lake with 150 tiger
muskies in early November to thin populations of stunted perch
and sunfish and to control common carp.

The tiger muskies, a non-reproducing hybrid of northern pike
and muskellunge, have been used successfully since the 1980s
for similar purposes on other state waters, including Mayfield
Reservoir in Cowlitz County and Lake Tapps in Pierce County
as well as other areas of the country.

Now about 18 inches long, the tiger muskies will be legal catch
as game fish themselves once they reach a minimum 36 inches,
in about a year. But in the meantime they are expected to improve
fishing in the lake by thinning perch, rock bass, bluegill and
pumpkinseed sunfish populations. Those species, all non-natives,
have overcrowded the lake and have become stunted. They also
compete with seasonally stocked rainbow trout. The lake's heavy
weed growth prevents bass from preying effectively on the over-
populated perch and sunfish. By contrast, tiger muskies are
effective predators in shallow, weedy waters such as Green Lake.

Besides balancing fish populations and thus improving fishing
opportunities for urban anglers, the tiger muskies may also improve
the lake's water quality by eating some of the lake's common carp
which stir up bottom sediment.

The City of Seattle's Parks Department has made other efforts to
improve Green Lake water quality, including weed mowing and
phosphorus treatments.

Because Green Lake has no inlets or outlets to other waters, and
because the tiger muskies are sterile, WDFW fish managers are
confident the introduced fish will not pose an environmental threat
in the 255-acre Lake or other waters.

Tiger muskies can live about 10 years and can reach lengths of 50
inches here under ideal conditions. The fish to be planted in Green
Lake were reared at WDFW's Columbia Basin Hatchery in Moses Lake.
# # #

FACT SHEET

Tiger muskellunge stocking
at Green Lake

Summary

Green Lake in Seattle has suffered for many years from diminished water
quality, excessive vegetation growth and unbalanced fish populations.
These problems have in turn reduced recreational opportunity. A number
of organizations, including the Seattle Department of Parks and Recreation
(SDPR) and Washington Department of Fish and Wildlife (WDFW) have
an interest in improving these conditions for the benefit of the local
community and the general public. A number of projects have already
been implemented in Green Lake to address these concerns. For example,
a lake-wide phosphorus reduction treatment and mechanical aquatic plant
harvesting program were implemented based on recommendations arising
from consulting firm and WDFW research. The next project implemented
by WDFW with support from SDPR will be the stocking of the sterile apex
predator, tiger muskellunge (commonly known as "tiger muskie"), to control
the dominant and deleterious common carp population and to restore balance
to the fish community. Following are additional details describing the
background, goals, and objectives of this project, and basic facts regarding
the biology of tiger muskellunge.

Background

1)Green Lake historically provided substantial fishinrecreation within the
urban region of Seattle
2) Water diversions from the lake and widespread introductions of non-
native species have impacted water quality, altered lake productivity and
decimated this once-popular fishery
3) For years SDPR and WDFW have struggled with various approaches
to solving these problems and restoring fisheries in Green Lake, which
would be accessible to large numbers of urban youth and local citizens.
4) Following recommendations outlined in a 1995 lake restoration study,
a lake-wide alum treatment was applied to Green Lake. This treatment was
intended to bind the critical algal nutrient, phosphorus, and make it
unavailable in the sediments, thus reducing incidents of lake-wide blooms.
While a small and temporary measure of success was achieved, the loading
of phosphorus into the sediments has shifted lake productivity from algae
to aquatic plants, which now dominate the extensive littoral zone of this
shallow lake.
5) Further exacerbating these water quality problems, a large population
of common carp has expanded unchecked in the lake and now dominates
the biomass of the fish community, reducing resources for more desirable
species such as trout, bass, and catfish. Common carp stir the sediments
extensively through their foraging activities and resuspend the phosphorus.
This behavior combined with the excretions of these fish is thought
significantly diminish water quality. Furthermore, because of their rapid
growth, Green Lake common carp rapidly reach sizes that make them
invulnerable to the lake's resident predators.

Goals

1) Restore recreational mixed-species fisheries to Green Lake
2) Improve water quality
3) Create angling opportunities for urban youth

Objectives (Phase I)

1) Reduce carp populations, relieve competition for resources for other
fish species, reduce internal phosphorus loading, and restore ecosystem
function by stocking the sterile apex predator, tiger muskellunge
2) Provide an additional angling opportunity to fish for these desirable
game fish

Tiger Muskellunge biology

1) Tiger muskellunge are a sterile hybrid of northern pike and muskellunge
2) Tiger muskellunge grow rapidly, attaining a length of 20 inches in their
first
year and 30 inches in their second year. Growth slows dramatically after
they
reach 36 inches but some individuals may attain a length of 50 inches under
ideal growth conditions. Although there are records of these fish living as
long as 15 years, few have been observed to live longer the eight to ten
years.
3) Tiger muskellunge prefer shallow, weedy habitats characterized by dense
aquatic vegetation in summer and fall and tend to move into deeper water
during winter months.
4) Numerous studies have revealed that these fish are ambush predators
feeding primarily on other fish, and show distinct preferences for carp
where
these fish are present.
5) Like all esocid species, tiger muskellunge are reclusive and avoid
contact
with humans.
6) The WDFW has stocked tiger muskellunge in a number of lakes in both
eastern and western Washington.
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