LAKE ERIE
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A>lAl>J AGEMENT
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Lake Erie Lakewide Management Plan (LaMP)
Technical Report Series
Degradation of Fish Populations
Roger Knight and Phil Ryan
October 1999
Lake Erie LaMP Technical Report No. 4

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Approach
The IJC listing criteria states that fish populations are impaired,"when fish management
programs have identified degraded fish populations. In addition, this use will be
considered impaired when relevant, field-validated, fish and wildlife bioassays with
appropriate quality assurance/quality controls confirm significant toxicity from water
column or sediment contaminants".
Toxic contaminant impairment to fish is partially addressed in the Fish Tumors or Other
Deformities assessment. However, the LaMP has identified a comprehensive assessment
of impairments to fish reproduction (including impacts due to toxics and endocrine
disruptors) as a gap. An assessment of fish reproduction has been placed on the LaMP
parking lot for action in the future. Consequently, this assessment will focus on aspects
of degraded fish populations that are not toxics related.
On Lake Erie, the Lake Erie Committee (LEC) of the Great Lakes Fishery Commission
represents the 5 fishery management programs on Lake Erie. The LEC has defined
degraded fish populations through the Lake Erie Fish Community Goals and Objectives
which are endorsed by all 5 programs. Based on input from LEC member agencies, the
following terms of reference were developed for assessment of the Lake Erie fish
community:
1)	A healthy fish community is defined as consisting of not only "commodity" or
"highly-valued" species, but other necessary species as well, so as to lend balance
and stability to the entire community.
2)	Impairment to the beneficial use of Lake Erie fishes occurs when economically
viable fisheries are unsustainable due to unhealthy conditions in the fish
community.
3)	Impairment is assessed in relation to the following issues:
>	Biodiversity (i.e., loss of native species);
>	Harvestable Surplus Fish Production;
>	Keystone Predators (species whose predatory actions can structure the overall
aquatic community);
>	Food Web Dynamics (stability, structuring, efficiency of energy transfer)
>	Forage Fish Availability; and
>	Reproduction (physiology, loss of habitat, early life stage mortality).
4)	Consistent with all of the "ecological" impairment assessments, these issues are
assessed in relation to the following benchmarks:
• examination of historical and current status of key fish species;

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•	evaluation of the fish community relative to Fish Community Goals and
Objectives, as established by to the Lake Erie Committee, Great Lakes
Fishery Commission; and
•	Food web function - factors (i.e., predation, weather, lake trophic status) that
have structured the fish community of Lake Erie historically (i.e., across
"ecological eras") and comparisons of Lake Erie fish community dynamics to
those of other water bodies.
Assessments were based on field data (where available) along with synthesis of
information from the scientific literature. Impairment conclusions that are speculative,
i.e., are based on our best professional judgment but lack conclusive supporting evidence,
are italicized (see Table 2).
Historical and current status of key fish species
A number of fish species were identified as important "commodity" species or as species
that contribute significantly to the ecology of the community. Background population
"status" reports were generated for 28 species (or groups of species) to examine changes
in populations over time. In general, five "ecological eras" were examined: a) pre-1900;
b) 1900-1930; c) 1930-1972; d) 1972-1986; and e) 1986-present.
Both historical and current abundance trends for 26 species are summarized and grouped
in Table 1 according to thermal and feeding preferences (i.e., position in the food chain)
that characterize the ecological role of each species in the fish community. Species not
included in this summary were the non-native trout and Pacific salmon species and
several others classified as threatened, endangered, special concern, extirpated, or extinct.
These species were excluded from this summary due to insufficient information at the
species level.
Historically, fish population declines were most apparent for planktivores, piscivores, and
for cold-water fishes, and were least evident for benthivorous, warm-water species (Table
1). Populations of many benthivores increased in recent years. Historically, the most
significant stresses on the Lake Erie fish community were fishery exploitation, habitat
degradation (especially from cultural eutrophication), and exotic species, but the relative
importance of these factors varied among species.
From this exercise, impairments to beneficial use (Table 2) included a loss of native
species (sauger, blue pike, lake trout, lake herring) that reduced biodiversity, surplus fish
production, and overall community stability. The loss of lake herring also reduced prey
fish availability to top (keystone) piscivores. Degradation and loss of spawning/nursery
habitat led to reproductive failures for many fish species.

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Table 4.1. Thermal preference and foraging guild for selected Lake Erie fish species.
Thermal Preference
Warm nearshore"
Cool offshore"
Cold open deepwater*
Piscivore
Planktivore
Benthivore
white bass (-) i
smallmouth bass (0)
largemouth bass (0)
gizzard shad (-) ^
white perch (-) ^
walleye (0)
4. blue-pike, sauger (-)
4.	esocids (-) 4.
emerald shiner (-)
spottail shiner (-)
alewife (-)
yellow perch (-) +
lake sturgeon (-) +
round goby (+) f
lake trout (-)
burbot (-) f
sea lamprey (-)
rainbow smelt (-) i
lake herring (-)
lake whitefish (-) f
sculpins (-) i
bigmouth buffalo (+) f
smallmouth buffalo (+) ^
freshwater drum (0)
channel catfish (0) f
carp (0)
= current abundance above historical average;
= current abundance near historical average;
= current abundance below historical average;
Arrows indicate increasing or decreasing trend in abundance for recent years.
Species in bold type = native populations are no longer present. Only Lake Trout
populations are currently being rehabilitated through stocking.
= > 27 C;
= 18-27 C;
*= less than 18C
4.3 Fish community relative to the Fish Community Goals and Objectives (FCGO)
In January 1999, the Lake Erie Committee (LEC) of the Great Lakes Fishery
Commission formalized a set of FCGO with several guiding principles:
•	preference to self-sustaining indigenous species over naturalized species;
•	prevention of non-indigenous species introductions;
•	maintenance and restoration of fundamental habitats;
•	preservation of biodiversity;
•	sustenance of economically-valuable fisheries; and
•	Lake Erie's biological limit to productivity.
The objectives encompass:
¦	a west-east gradient in productivity;
¦	sustainable harvest of 50-60 million lbs. of high-valued fish species annually;
¦	nearshore habitat and associated fisheries;
¦	riverine and estuarine habitats and fish stocks that use them;

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¦	sustainable harvests for high-value fish species in each basin;
¦	contaminant issues of human consumption and reproductive inhibition in fish;
¦	fish habitat throughout the watershed;
¦	genetic diversity;
¦	rare, threatened, and endangered species; and
¦	prey base and food web structure.
The current status of fish species (Table 1) relative to FCGO suggests impairment of
beneficial use (Table 2) due to loss of native species (sauger, blue-pike, lake trout, lake
herring, pike, and muskellunge) which in turn has reduced biodiversity and fish
community stability. Surplus production for fisheries (comparing the '80s to the '90s) is
impaired for several species, including walleyes and yellow perch. Per the FCGOs, the
combination of non-indigenous species and changes in lake productivity and water
transparency has impaired overall food web structure, prey fish availability, and the
behavior of walleyes. Loss of fish habitat has affected reproduction for several species,
including walleyes and lake trout.
4.4	Food web function of the Lake Erie fish community
Analyses of the food web within Lake Erie's basins were undertaken to examine the
effects of non-indigenous species, native predators, and environmental changes on overall
system structure. The fish community has become progressively astatic from west to
east, owing to inefficient transfer and loss of energy through the pelagic food web, due to
competition between non-indigenous and native fish species, over-winter mortality on
non-indigenous species, and loss of potentially stabilizing effects from top piscivores.
The community has also been affected by the loss of nearshore habitat that is critical to
reproductive success for many species, including top predators like sauger, northern pike,
and muskellunge.
These ecological changes have impaired the biodiversity of the Lake Erie fish community
through the loss of predatory function both in nearshore and pelagic areas of the lake.
The presence of non-indigenous species (i.e., gizzard shad and alewife) has severely
impaired efficient transfer of energy from primary producers to top predators, resulting in
energy being "lost" to important fish species. As a result, the fish community has
become increasingly susceptible to further perturbations. Loss of nearshore habitat to
human development or activities adversely affects system function and impairs
reproduction of many fish species (i.e., sauger, northern pike, and muskellunge) that
serve as top predators in the community.
4.5	Impairment Conclusion
All systems have natural variability. However, the fish community of Lake Erie suffers
from an unnaturally high level of instability, due to the combination of changes in lake
productivity, inefficient use of energy within the food web (due to the introductions of
non-indigenous species and loss of native species), and loss of critical nearshore habitat.
Some members of the pristine Lake Erie fish community are gone (i.e., blue pike,

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sauger), constituting the loss of fishery opportunity (an impairment to beneficial use).
Because the community is unstable (hence unpredictable), sustenance of extant fish
populations and associated fisheries is uncertain, and constitutes another impairment to
the beneficial use of Lake Erie fishes. The full degree of current impairment, and the
extent to which current impairment can be reversed, can only be assessed after ecosystem
objectives have been identified. And finally, due to instability of the lake system and the
changing conditions in the lake, the impairment information in this report is subject to
change.

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Table 4.2.	Impairment of the Lake Erie fish community, as identified from three approaches: 1) a historical comparison of fish population status, 2)
achievement of fish community goals and objectives (FCGO) developed by the Lake Erie Committee of Great Lakes Fishery Commission, and
3) Food web function. Items in italics are speculative. N/A= not applicable.
Item
Comments
Historical
FCGO
Food Web Function
Biodiversity
Loss of native stocks
Impaired due to losses
Impaired due to losses
Impaired due to losses and
addition of exotics
Harvestable Surplus Fish
1990s versus 1980s
N/A
Impaired for walleyes,
yellow perch, smelt, white
bass
Changes have occurred with
fish community succession
Production
Pre-1980
Impaired - loss of lake
herring, blue-pike, sauger,
lake trout
N/A
N/A
Keystone Predators
Walleye
Some stocks are impaired
due to limited spawning
habitat
Impaired as light spatially
and temporally limits habitat
volume and predatory
function relative to '80s
Reduced predatory function
due to habitat limitation may
be an impairment
(species whose predatory
actions can structure the
overall aquatic
community)
Lake Trout
Impaired - loss of native
stocks
Impaired due to lack of
natural reproduction
Profundal predatory function
restored through stocking
Northern Pike and
Muskellunge
Impaired - stocks reduced
due to loss of habitat
N/A
Impaired - reduced nearshore
predatory function
Sauger and Blue Pike
Impaired - no native stocks
remaining
N/A
Impaired : loss of predatory
function
Food Web
Stability, Structuring, and
Efficiency of energy transfer
N/A
Impaired due to presence of
exotics, loss of biodiversity
(including vector species),
and lack of full piscivore
assemblage
Impaired due to presence of
exotics, loss of biodiversity
(including vector species),
and lack of full piscivore
assemblage. Native fish
community was more
resilient than current
community.
Forage Fish Availability
Soft-rayed more important
than spiny to piscivores
Impaired: loss of species
(lake herring)
Impaired: low diversity and
productivity decline
Impaired: exotics (clupeids)
less stable than native fishes

Reproductive physiology
N/A
N/A
Thiaminase and goiterogens
issues
Reproduction
Loss of habitat
Impaired: loss of spawning
and nursery habitat
Impaired: loss of spawning
and nursery habitat
Impaired: loss of spawning
and nursery habitat

Impingement and entrainment
effects on fish eggs/larvae
Potential impairment on
local stocks
N/A
N/A

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