A Biological Assessment of the
Warmwater Fish Community in
Lake Washington
STATE OF WASHINGTON October 2017
Washington Department of
Fish and Wildlife
Fish Program
Fish Management
FPT 17-10
by Danny Garrett, Chad Jackson
and Steve Caromile
A Biological Assessment of the Warmwater
Fish Community in Lake Washington
Yellow perch in Lake Washington, photographed by Don Rothaus.
Danny Garrett
Warmwater Fisheries Biologist, Region 4
Washington Department of Fish and Wildlife
16018 Mill Creek Blvd
Mill Creek, Washington 98012
Chad Jackson
Fish Program Manager, Region 2
Washington Department of Fish and Wildlife
1550 Alder Street NW
Ephrata, WA 98823
Steve Caromile
Warmwater Fisheries Biologist, Region 6
Washington Department of Fisheries and Wildlife
1111 Washington Street SE
Olympia, Washington 98501
October 2017
Abstract
The limnology of Lake Washington has been studied extensively over the past 100 years, and many
changes have occurred during that time that have dramatically altered the fish community and fish
habitat. In the past two decades, researchers at the University of Washington and U. S. Fish and Wildlife
Service have conducted many research projects that broadened our understanding of food web
dynamics, trophic relationships, and impacts of predatory fishes on outmigrating salmonids. Although
extensive sampling accompanied these research projects, a whole-lake assessment of the warmwater
fish community has never been conducted.
To update our knowledge of the warmwater fish community and draw comparisons to prior sampling,
we conducted a “standardized warmwater survey” developed by the Warmwater Program (Washington
Department of Fish and Wildlife) in 1997. Using electrofishing, gill netting, and fyke netting, we sampled
a total of 248 locations and captured 40,894 individuals representing 22 species. Warmwater gamefish
comprised 73.7% of the sample by number, but only 33.7% of the sample weight. Collectively,
coldwater gamefish species including Northern Pikeminnow Ptychocheilus oregonensis, Peamouth Chub
Mylocheilus caurinus, and Largescale Suckers Catostomus macrocheilus accounted for 50.1% of the
biomass. Threespine Stickleback Gasterosteus aculeatus was by far the most abundant species
comprising 70% of the sample by number. Yellow Perch Perca flavescens was the most abundant
warmwater gamefish species sampled and comprised 19% of the sampled biomass; second to Largescale
Suckers (35.3%). Pumpkinseed Lepomis gibbosus was the second most abundant warmwater gamefish,
followed by Brown Bullhead Ameiurus nebulosus and Smallmouth Bass Micropterus dolomieu. Other
gamefish including Rainbow Trout Oncorhynchus mykiss, Coastal Cutthroat Trout Oncorhynchus clarkii
clarkii, Bluegill Lepomis macrochirus, Largemouth Bass Micropterus salmoides, and Black Crappie
Pomoxis nigromaculatus constituted a small portion of the sample. These results suggest that, similar to
other Washington lakes, the fish community of Lake Washington is dominated by “coolwater” species
that include Yellow Perch, Pumpkinseed, Smallmouth Bass, and Brown Bullhead Catfish. Comparisons to
1982 sampling suggest that Largemouth Bass and Black Crappie have declined in relative abundance
over the past 30 years, while the relative abundance of Smallmouth Bass has increased.
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
i
Table of Contents
List of Tables ................................................................................................................................................. ii
List of Figures ............................................................................................................................................... iii
Introduction .................................................................................................................................................. 1
Methods ........................................................................................................................................................ 3
Results ........................................................................................................................................................... 6
Water Chemistry ....................................................................................................................................... 6
Species Composition ................................................................................................................................. 6
Catch Per Unit Effort (CPUE) ..................................................................................................................... 8
Size Distribution Indices ............................................................................................................................ 9
Yellow Perch .......................................................................................................................................... 9
Smallmouth Bass ................................................................................................................................. 11
Brown Bullhead ................................................................................................................................... 13
Cutthroat Trout ................................................................................................................................... 15
Largemouth Bass ................................................................................................................................. 17
Pumpkinseed ....................................................................................................................................... 19
Common Carp ..................................................................................................................................... 27
Green Sunfish ...................................................................................................................................... 29
Comparisons to Survey Data from 1982 ............................................................................................. 30
Discussion.................................................................................................................................................... 32
Literature Cited ........................................................................................................................................... 36
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
ii
List of Tables
Table 1. Water chemistry data collected from Lake Washington, King County, Washington on 2
August 2005 ............................................................................................................................. 6
Table 2. Species composition by weight (kg) and number of fish captured at Lake Washington (King
County, WA) during June-July 2005 ......................................................................................... 7
Table 3. Mean catch per unit effort (number of fish per hour of electrofishing and net night),
including 80% confidence intervals, for all fishes (excluding young-of-the-year) collected
from Lake Washington during June-July 2005 ......................................................................... 8
Table 4. Proportional size distribution indices, including 80% confidence intervals, of fish collected
from Lake Washington (King County) during June-July 2005, by sampling method ............... 9
Table 5. Back calculated mean length at age (mm) of Yellow Perch collected from Lake Washington
(King County, WA) during June-July 2005 .............................................................................. 10
Table 6. Back calculated mean length at age (mm) of Smallmouth Bass collected from Lake
Washington (King County, WA) during June-July 2005 .......................................................... 12
Table 7. Back calculated mean length at age (mm) of Largemouth Bass collected from Lake
Washington (King County, WA) during June-July 2005 .......................................................... 18
Table 8. Back calculated mean length at age (mm) of Pumpkinseed collected from Lake Washington
(King County, WA) during June-July 2005 .............................................................................. 20
Table 9. Back calculated mean length at age (mm) of Black Crappie collected from Lake Washington
(King County, WA) during June-July 2005 .............................................................................. 26
Table 10. Relative abundance of gamefish species sampled by electrofishing, gill nets, and trap nets in
Lake Washington embayments during August–October 1982 (Pfeifer and Weinheimer
1992). ..................................................................................................................................... 31
Table 11. Mean electrofishing catch rates from 1982 and 2005 surveys, by region. Standard error is
reported in parentheses when two or more sites were sampled (Pfiefer and Weineimer
1992). ..................................................................................................................................... 31
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
iii
List of Figures
Figure 1 Map showing lower portion of the Cedar River Watershed including Lake Washington (A),
the Lake Washington Shipping Canal (B), Lake Union (C), and the Hiram M. Chittenden
Locks (Ballard Locks; D) ............................................................................................................ 2
Figure 2. Map showing sampling locations of warmwater survey conducted during June-July, 2005
(N=227)..................................................................................................................................... 5
Figure 3. Length frequency distribution of Yellow Perch (N=6228) sampled by gill netting (GN), fyke
netting (FN), and boat electrofishing (EB) at Lake Washington (King County) in early
summer 2005 ......................................................................................................................... 10
Figure 4 Relative weights of Yellow Perch (N=3570) sampled at Lake Washington (King County) in
early summer 2005, as compared to the national 75th percentile, Wr=100 (Anderson and
Neumann 1996) ..................................................................................................................... 11
Figure 5. Length frequency distribution of Smallmouth Bass (N=285) sampled by gill netting (GN) and
boat electrofishing (EB) at Lake Washington (King County) in early summer 2005 .............. 12
Figure 6. Relative weights of Smallmouth Bass (N=269) sampled at Lake Washington (King County) in
early summer 2005, as compared to the national 75th percentile, Wr=100 (Anderson and
Neumann 1996) ..................................................................................................................... 13
Figure 7. Length frequency distribution of Brown Bullhead (N=897) sampled by gill netting (GN), fyke
netting (FN), and boat electrofishing (EB) at Lake Washington (King County) in early
summer 2005. ........................................................................................................................ 14
Figure 8. Relative weights of Brown Bullhead (N=507) sampled at Lake Washington (King County) in
early summer 2005, as compared to the national 75th percentile, Wr=100 (Anderson and
Neumann 1996) ..................................................................................................................... 15
Figure 9 Length frequency distribution of Cutthroat Trout (N=136) sampled by boat electrofishing
(EB) and gill netting (GN) at Lake Washington (King County) in early summer 2005 ............ 16
Figure 10. Relative weights of Cutthroat Trout (N=122) sampled at Lake Washington (King County) in
early summer 2005, as compared to the national 75th percentile, Wr=100 (Anderson and
Neumann 1996) ..................................................................................................................... 17
Figure 11. Length frequency distribution of Largemouth Bass (N=53) sampled by boat electrofishing
(EB) and gill netting (GN) at Lake Washington (King County) in early summer 2005 ............ 18
Figure 12. Relative weights of Largemouth Bass (N=53) sampled at Lake Washington (King County) in
early summer 2005, as compared to the national 75th percentile, Wr=100 (Anderson and
Neumann 1996) ..................................................................................................................... 19
Figure 13. Length frequency distribution of Pumpkinseed (N=1186) sampled by boat electrofishing
(EB), gill netting (GN), and fyke netting (FN) at Lake Washington (King County) during June-
July 2005 ................................................................................................................................ 20
Figure 14. Relative weights of Pumpkinseed (N=520) sampled at Lake Washington (King County)
during June-July 2005, as compared to the national 75th percentile, Wr=100 (Anderson and
Neumann 1996) ..................................................................................................................... 21
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
iv
Figure 15. Length frequency distribution of Bluegill (N=145) sampled by boat electrofishing (EB), gill
netting (GN), and fyke netting (FN) at Lake Washington (King County) during June-July
2005 ....................................................................................................................................... 22
Figure 16. Relative weights of Bluegill (N=24) sampled at Lake Washington (King County) during June-
July 2005, as compared to the national 75th percentile, Wr=100 (Anderson and Neumann
1996) ...................................................................................................................................... 23
Figure 17. Length frequency distribution of Rainbow Trout (N=25) sampled by boat electrofishing (EB)
and gill netting (GN) at Lake Washington (King County) in early summer 2005 ................... 24
Figure 18. Relative weights of Rainbow Trout (N=25) sampled at Lake Washington (King County) in
early summer 2005, as compared to the national 75th percentile, Wr=100 (Anderson and
Neumann 1996) ..................................................................................................................... 25
Figure 19. Length frequency distribution of Black Crappie (N=26) sampled by boat electrofishing (EB),
gill netting (GN), and fyke netting (FN) at Lake Washington (King County) during June-July
2005 ....................................................................................................................................... 26
Figure 20. Relative weights of Black Crappie (N=26) sampled at Lake Washington (King County) in early
summer 2005, as compared to the national 75th percentile, Wr=100 (Anderson and
Neumann 1996) ..................................................................................................................... 27
Figure 21. Length frequency distribution of Common Carp (N=26) sampled by boat electrofishing (EB)
and gill netting (GN) at Lake Washington (King County) in early summer 2005. .................. 28
Figure 22. Relative weights of Common Carp (N=26) sampled at Lake Washington (King County) in
early summer 2005 as compared to the national 75th percentile, Wr=100 (Bister et al.
2000) ...................................................................................................................................... 28
Figure 23. Length frequency distribution of Green Sunfish (N=10) sampled by boat electrofishing (EB),
gill netting (GN), and fyke netting (FN) at Lake Washington (King County) in early summer
2005 ....................................................................................................................................... 29
Figure 24. Relative weights of Green Sunfish (N=10) sampled at Lake Washington (King County) in
early summer 2005 as compared to the national 75th percentile, Wr=100 (Bister et al.
2000) ...................................................................................................................................... 30
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
1
Introduction
Covering 22,138 acres and spanning 18.4 miles, Lake Washington is the second largest natural
lake in Washington State (Figure 1). Given its size and close proximity to large metropolitan
areas, including Seattle and Bellevue, Lake Washington is a popular destination for recreational
boaters, water skiers, swimmers, jet skiers, and anglers. Throughout the year, Lake Washington
offers some of the State’s best recreational fishing opportunities. Popular fisheries in the lake
include cutthroat trout, smallmouth bass, yellow perch, and sockeye salmon. In 1981, an
estimated 88,500 Lake Washington anglers lived in the greater Seattle area (Bradbury and Pfeifer
1992). From 1981 to 1982, the estimated monetary value of the coldwater and warmwater
fisheries in Lake Washington averaged $1,681,947 and $812,514, respectively. Arguably, both
angler use and the value of the fisheries in Lake Washington have increased over the past 20
years. Proper management of these valuable fisheries is critical to maintaining them for future
users.
Although the limnology and food web dynamics of Lake Washington have been studied
somewhat intensively (Eggers et al. 1978; Costa 1979; Edmondson 1994; Edmondson and
Lehman 1981; Beauchamp et al. 2004; Tabor et al. 2004; McIntyre et al. 2006; Overman et al.
2009), the resident fish community, comprised largely of nonnative species, remains poorly
understood. The most recent whole-lake stock assessment survey of the resident fish community
in Lake Washington was conducted in 1982 (Pfeifer and Weinheimer 1992). Given that change
is a fundamental aspect of fish communities, updating our information on the resident fish
community has become increasingly important. For many resident species, information on size
structure, age structure, condition, growth, and most importantly, relative abundance is not
known. Current data to produce these fishery statistics is useful in guiding management
strategies for several species, identifying future research needs, and fulfilling information
requests from the public and other governmental natural resource agencies.
At nearly 22,000 acres with an average depth of 33 meters and a heavily urbanized shoreline,
Lake Washington is a very difficult lake to sample in its entirety. Consequently, past research
conducted on Lake Washington focused on localized areas and extrapolated the data to the entire
lake (Pfiefer and Weineimer 1992). This strategy can produce results that do not represent the
entire fish community, especially in large lakes which have an uneven distribution of habitat.
Here, we provide a whole-lake assessment of the resident fish communities that use the littoral
zone of Lake Washington. Fishery statistics collected include species composition (numerical
and biomass), relative abundance (catch per unit effort; CPUE), size and age structure, and
relative weight (condition). Catch rate data from specific sites was compared to Pfiefer and
Weineimer (1992) to examine potential changes that have occurred to the fish community.
Information collected from this survey may be used by state, tribal, federal and municipal natural
resource agencies to guide future management decisions.
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
2
Figure 1 Map showing lower portion of the Cedar River Watershed including Lake Washington (A), the
Lake Washington Shipping Canal (B), Lake Union (C), and the Hiram M. Chittenden Locks (Ballard Locks;
D). Bold bars delineate lake boundaries, the furthest extent of warmwater sampling conducted in 2005.
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
3
Methods
During June 26–July 1, 2005, eight 3-person crews from the Washington Department of Fish and
Wildlife sampled the shoreline of Lake Washington. We used standardized sampling protocols
developed for Washington lakes by Bonar et al. (2000), which incorporate random sampling and
multiple gears types to obtain the best representative sample of warmwater species and their
respective size classes.
Fish were captured using three sampling techniques: electrofishing, gill netting, and fyke netting.
Electrofishing was conducted using four 16-foot and four 18-foot Smith-Root 5.0 GPP
electrofishing boats set to a DC current of 60 cycles/second at 4-6 amps. Gill nets (45.7 m long
X 2.4 m deep) consisted of four sinking panels (two each at 7.6 m and 15.2 m long) of variable-
size monofilament mesh (13, 19, 25, and 51 mm stretched). Fyke nets were constructed of a
single 30.4-m lead and two 15.2-m wings of 130 mm nylon mesh with the body of the nets
stretched around four 1.2-m aluminum rings in each of two section.
Sampling locations were chosen by dividing the shoreline into 400-m sections. Of the 301
sections, 120 were randomly selected for electrofishing, 64 for gill netting, and 64 for fyke
netting (Figures 2 and 3). In some cases, multiple gear types were used at the same sampling
locations. At each electrofishing section, the boat was maneuvered adjacent to the shoreline
(depth range = 0.2 - 2 m) for 600 seconds. Electrofishing was conducted only during evening
hours to maximize the size and number of fish captured. Electrofishing is more effective at night
because some fish species seek shelter during the day and move freely at night (Reynolds 1996;
Dumont and Dennis 1997). The total electrofishing effort (“pedal-down” time) for the lake was
72000 seconds (20 hours). Gill nets were set perpendicular to the shoreline with the small mesh
end attached nearshore and the large mesh end anchored offshore. Fyke nets were set
perpendicular to the shore with the lead net anchored onshore and the wing nets set at 45-degree
angles to the trap. Fyke nets were set so that the trap was no deeper than three meters (Bonar et
al. 2000). Both gill nets and fyke nets were set at dusk and retrieved the following day (net-
night; 16-20 hours). Total lake effort was 64 net nights for gill nets and 64 net nights for fyke
nets.
Catch per unit effort (CPUE) of each sampling gear was determined for each species collected.
The CPUE of electrofishing was determined by dividing the number of fish captured by the total
amount of “pedal-down” time recorded from the GPP. CPUE of gill netting and fyke netting
was determined by dividing the number of fish captured by the total time the nets were deployed
(net-night; 16-20 hours).
Relative weight (Wr) was used to evaluate the condition of warmwater gamnefish in Lake
Washington. As presented by Anderson and Neumann (1996), a W
r
of 100 generally indicates
that the fish is in a condition similar to the national average for that species and length. The
index is defined as W
r
= W/W
s
× 100, where W is the weight (g) of an individual fish and W
s
is
the standard weight of a fish of the same total length (mm). W
s
was derived from a standard
weight-length (log10) relationship which was defined for each species of interest in Anderson
and Neumann (1996). Minimum lengths were used for each species as the variability can be
significant for small fish (young-of-the-year).
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
4
Age and growth of five species (Smallmouth Bass, Largemouth Bass, Yellow Perch,
Pumpkinseed, Black Crappie) in Lake Washington were evaluated using procedures described by
Fletcher et al. (1993). All samples were evaluated using both the direct proportion method
(Fletcher et al.1993).
The proportional size distributions (PSDs) of six species (Smallmouth Bass, Largemouth Bass,
Yellow Perch, Pumpkinseed, Black Crappie, and Common Carp) were determined following
procedures outlined in Anderson and Neumann (1996) with terminology refined by Guy et al.
(2006; 2007). PSDs use two length measurements to provide information about the proportion
of various size fish in a population. PSDs are calculated by using the number of quality-size
(PSD), preferred-size (PSD-P), memorable-size (PSD-M), and trophy-size (PSD-T) fish,
dividing by the number of stock-size fish, and multiplying by 100. PSD length categories, which
vary by species, are based on percentages of world-record lengths: stock (20-26%), quality (36-
41%), preferred (45-55%), memorable (59-64%), and trophy (74-80%).
Water chemistry data were collected at 1-meter increments in the east channel of Lake
Washington (Lat 47.54972 N, Long 122.20365 W) on August 2, 2005. A Hydrolab
©
was used to
collect information on temperature (ºC), dissolved oxygen (mg/L), pH, and conductivity
(µS/cm). A Secchi disk was used to record Secchi depth, a unit of measure representing water
clarity.
The timing of a fishery survey can affect the quality of data collected (Bettross and Willis 1988;
Guy and Willis 1991). In Washington, standardized warmwater sampling generally occurs
during late May/early June or late September/early October, when water temperatures are
between 16–22 ºC. However, there is a high risk of encountering ESA-listed juvenile Chinook
Salmon and Steelhead during these sampling periods in Lake Washington. As a result, June 23–
27 was selected as a compromise between sampling efficiency and risk to ESA-listed species.
Biological information recorded from sampled fishes included identification of species (except
Cottidae spp.), total length (mm) and weight (g). Ageing structures (scales and otoliths) were
collected from a subsample (up to eight per 10-mm size class) of select species. From this data
we calculated species composition and relative abundance (by weight and number), catch rates
for each species by gear type (CPUE), age and back-calculated length at age, and size structure
(i.e., length frequency and proportional stock densities).
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
5
Figure 2. Map showing sampling locations of warmwater survey conducted during June-July, 2005 (N=227).
Due to the spatial randomization of sampling within each gear type, some stations were sampled using
multiple gear types.
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
6
Results
Water Chemistry
Water chemistry data was collected from the east channel of Lake Washington (Lat
47.54972 N, Long 122.20365 W) on August 2, 2005. Water quality parameters included
temperature, dissolved oxygen, pH, and conductivity (Table 1). Secchi depth was measured at
6.2 meters.
Table 1. Water chemistry data collected from Lake Washington, King County, Washington on 2 August
2005. Data were collected in the east channel, south of I-90 (Lat 47.54972 N, Long 122.20365 W).
Depth
(m)
Temperature
(°C)
DO
(mg/L)
pH
Conductivity
(µS/cm)
0
23.3
9.51
7.88
79
1
23.23
9.17
7.92
78.7
2
23.18
9.26
7.96
79.1
3
23.13
9.45
7.97
79
4
23.07
9.27
7.99
78.7
5
23
9.36
7.99
78.7
6
22.99
9.22
8
78.8
7
22.96
9.27
8
78.9
8
22.89
9.24
7.98
78.6
9
19.66
8.97
7.53
76.6
10
17.38
8.14
7.24
75.8
11
16.45
7.8
7.1
75.6
12
15.15
7.25
6.98
75.7
13
14.34
6.69
6.86
75.2
14
13.96
6.6
6.83
75.3
15
13.18
6.04
6.75
75.4
16
12.85
5.55
6.7
75.4
17
12.11
5.8
6.7
75.1
18
11.47
5.75
6.67
74.8
19
11.12
4.53
6.58
75.1
Species Composition
A total of 21 fish species and one family (Cottidae: Sculpins) were collected during
sampling efforts on Lake Washington. Warmwater gamefish comprised 73.7% of the sample by
number, but only 33.7% of the sample weight (Table 2). Collectively, coldwater species
including Northern Pikeminnow, Peamouth, and Largescale Suckers accounted for a large
portion of the biomass sampled, (50.1%). Threespine Stickleback (TSS) was by far the most
abundant species comprising 70% of the sample by number (Table 2). Yellow Perch was the
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
7
most abundant warmwater gamefish species sampled (50.8% of the sample by number,
excluding TSS) and comprised 19% of the sampled biomass; second to Largescale Suckers
(35.3%). Pumpkinseed was the second most abundant warmwater gamefish (10.2% of the
sample by number, excluding TSS). Smallmouth Bass and Brown Bullhead comprised 5.7% and
6.1% of the biomass of fish sampled, respectively. Other gamefish including Rainbow Trout,
Cutthroat Trout, Bluegill, Largemouth Bass, and Black Crappie constituted a small portion of the
sample (3.2% by number excluding TSS; 1.2% by weight).
Table 2. Species composition by weight (kg) and number of fish captured at Lake Washington (King County,
WA) during June-July 2005. Percent composition by number is also shown without the Threespine
Stickleback (TSS).
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
8
Catch Per Unit Effort (CPUE)
Fyke netting captured the most fish (n=28,643), though Threespine Stickleback (TSS) comprised
the majority of the catch (n=26,155; Table 3). Excluding TSS, gill netting captured the most fish
(n=6,693), followed by electrofishing (n=5,555) and fyke netting (n=2,488). Gill netting catch
rates were highest for Yellow Perch (60.38 fish/net-night), TSS (22.47 fish/net-night), Northern
Pikeminnow (6.89 fish/net-night), and Largescale Sucker (3.86 fish/net-night). Electrofishing
catch rates were highest for Yellow Perch (74.55 fish/hour), Sculpin (Cottidae spp.; 62.82
fish/hour), TSS (44.04 fish/hour), Largescale Sucker (25.71 fish/hour), Pumpkinseed (21.35
fish/hour), and Brown Bullhead (17.45 fish/hour).
Table 3. Mean catch per unit effort (number of fish per hour of electrofishing and net night), including 80%
confidence intervals, for all fishes (excluding young-of-the-year) collected from Lake Washington during
June-July 2005.
Species Electrofishing (# fish/hr) Gill Net (# fish/net night) Fyke Net (# fish/net night)
Yellow Perch
74.55 ± 9.56 60.38 ± 10.29 16.13 ± 5.04
Sculpin (Cottidae spp. ) 62.82 ± 6.43 0.17 ± 0.08 1.37 ± 0.45
Threespine Stickleback 44.04 ± 6.69 22.47 ± 4.99 425.40 ± 144.33
Largescale Sucker 25.71 ± 3.59 3.86 ± 0.69 --
Pumpkinseed 21.35 ± 9.68 1.4 ± 0.47 12.15 ± 3.7
Brown Bullhead 17.45 ± 6.04 1.49 ± 0.59 7.6 ± 7.15
Northern Pikeminnow 10.46 ± 3.15 6.89 ± 1.09 0.26 ± 0.19
Smallmouth Bass 9.8 ± 2.36 1.54 ± 0.31 --
Cutthroat Trout 5.71 ± 1.03 0.43 ± 0.11 --
Chinook Salmon 2.63 ± 0.64 0.14 ± 0.06 0.1 ± 0.08
Peamouth 2.52 ± 0.79 4.97 ± 0.91 0.06 ± 0.07
Largemouth Bass 2.31 ± 1.08 0.14 ± 0.08 --
Rainbow Trout 1.21 ± 0.67 0.03 ± 0.03 --
Black Crappie 0.68 ± 0.3 0.21 ± 0.09 0.05 ± 0.04
Tench 0.37 ± 0.35 0.22 ± 0.11 0.08 ± 0.07
Coho Salmon 0.36 ± 0.2 0.05 ± 0.05 0.02 ± 0.02
Oriental Weatherfish 0.32 ± 0.34 0.03 ± 0.04 0.03 ± 0.03
Bluegill 0.26 ± 0.15 0.05 ± 0.05 2.21 ± 2.48
Common Carp 0.21 ± 0.16 0.24 ± 0.08 --
Green Sunfish 0.16 ± 0.12 0.01 ± 0.09 0.02 ± 0.02
Longnose Sucker 0.11 ± 0.09 -- --
Sockeye Salmon 0.11 ± 0.09 0.46 ± 0.15 --
Unidentified salmonid (Salmonidae spp. ) 0.11 ± 0.13 -- --
Gear Type
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
9
Size Distribution Indices
According to Gustafson (1988), sample sizes of 55 and 120 stock size fish provide
proportional size distribution (PSD; Guy et al. 2007) estimates with confidence intervals of ±10
at the 80 and 95% confidence limits, respectively. Electrofishing sample sizes for stock-length
Brown Bullhead, Yellow Perch, Smallmouth Bass, and Pumpkinseed were high, and permitted
the calculation of reliable confidence intervals at the 80% confidence limit (Table 4).
Electrofishing and fyke netting produced similar PSD values for Yellow Perch and
Pumpkinseed. Gill netting produced considerably higher PSD values for Smallmouth Bass and
Yellow Perch than electrofishing and provides additional insight into the true size structure of the
population. Although we report size distribution values for Largemouth Bass and Common
Carp, these values must be interpreted as representing our sample and not the population given
the low sample size (<55 individuals). High size distribution values (>30 PSD) were recorded
for Yellow Perch (all gear types), Smallmouth Bass (electrofishing and gill netting), and Brown
Bullhead (electrofishing and fyke netting).
Table 4. Proportional size distribution indices, including 80% confidence intervals, of fish collected from
Lake Washington (King County) during June-July 2005, by sampling method. Asterisks denote insufficient
sample sizes for calculating reliable confidence intervals. Species with sample sizes of stock size fish <10 are
not included.
Yellow Perch
Yellow Perch sampled from Lake Washington ranged from 11 to 353 mm total length
(Table 2; Figure 3) and ranged in age from 1 to 6 years (Table 5). The growth of Yellow Perch
exceeded the statewide average for all year classes. Relative weights of Yellow Perch less than
140 mm total length were highly variable and clustered around the national average. For Yellow
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
10
Perch greater than 140 mm total length, relative weights were generally below the national
average (Figure 4).
Table 5. Back calculated mean length at age (mm) of Yellow Perch collected from Lake Washington (King
County, WA) during June-July 2005. Values were calculated using the direct proportion method (Fletcher et
al. 1993).
Figure 3. Length frequency distribution of Yellow Perch (N=6228) sampled by gill netting (GN), fyke netting
(FN), and boat electrofishing (EB) at Lake Washington (King County) in early summer 2005.
Year Class # Fish 1 2 3 4 5 6
2004 33 85
2003 43 90 168
2002 41 82 164 223
2001 3 120 157 206 241
2000 14 80 162 209 237 260
1999 1 107 206 262 302 330 349
Weighted Mean 135 89 165 219 241
265 349
State Average 60 120 152 193
206
Mean total length (mm) at age
0%
2%
4%
6%
8%
10%
12%
50
70
90
110
130
150
170
190
210
230
250
Percent Frequency (%)
Total Length (mm)
EB (N=1423)
GN (N=3802)
FN (N=1000)
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
11
Figure 4 Relative weights of Yellow Perch (N=3570) sampled at Lake Washington (King County) in early
summer 2005, as compared to the national 75th percentile, Wr=100 (Anderson and Neumann 1996). Dashed
line denotes the linear regression line (R²=0.1374).
Smallmouth Bass
Smallmouth Bass sampled from Lake Washington ranged in length from 78 to 521 mm
total length (Table 2; Figure 5) and ranged in age from 1 to 10 years (Table 6). The growth of
Smallmouth Bass exceeded the statewide average for year classes 1-7. A reliable length-at-age
average for fish older than 7 years has not been developed due to lack of data. The relative
weights of Smallmouth Bass varied greatly among individuals (i.e., W
r
61–168) and were not
correlated to fish size (Figure 6).
0
20
40
60
80
100
120
140
160
180
0 50 100 150 200 250 300 350 400
Relative Weight (Wr)
Total Length (mm)
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
12
Table 6. Back calculated mean length at age (mm) of Smallmouth Bass collected from Lake Washington
(King County, WA) during June-July 2005. Values were calculated using the direct proportion method
(Fletcher et al. 1993).
Figure 5. Length frequency distribution of Smallmouth Bass (N=285) sampled by gill netting (GN) and boat
electrofishing (EB) at Lake Washington (King County) in early summer 2005.
Year Class # Fish 1 2 3 4 5 6 7 8 9 10
2004 19 102
2003 54 93 188
2002 27 92 194 306
2001 8 84 163 260 350
2000 16 83 146 219 310 378
1999 4 103 164 238 326 378 410
1998 8 92 171 254 319 368 412 441
1997 4 94 174 238 303 359 395 430 455
1996 6 85 172 261 323 373 409 440 462 483
1995 7 88 177 254 339 398 428 450 470 483 496
Weighted Mean 153 92 179 264 323 377 412 442 464 483 496
State Average 70 146 212 268 334 356 393
Mean total length (mm) at age
0%
1%
2%
3%
4%
5%
6%
7%
70
110
150
190
230
270
310
350
390
430
470
Percent Frequency (%)
Total Length (mm)
EB (N=185)
GN (N=98)
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
13
Figure 6. Relative weights of Smallmouth Bass (N=269) sampled at Lake Washington (King County) in early
summer 2005, as compared to the national 75th percentile, Wr=100 (Anderson and Neumann 1996). Dashed
line denotes the linear regression line (R²=0.1117).
Brown Bullhead
Brown Bullhead sampled from Lake Washington ranged from 71–338 mm total length
(Table 2; Figure 7). Aging structures such as pectoral spines were not collected from Brown
Bullhead, so no age data is reported. The condition of Brown Bullhead varied greatly among
individuals (i.e., W
r
38–194) and was not correlated with fish size (Figure 8).
0
50
100
150
200
250
0 100 200 300 400 500 600
Relative Weight (Wr)
Total Length (mm)
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
14
Figure 7. Length frequency distribution of Brown Bullhead (N=897) sampled by gill netting (GN), fyke
netting (FN), and boat electrofishing (EB) at Lake Washington (King County) in early summer 2005.
0%
2%
4%
6%
8%
10%
12%
70
90
110
130
150
170
190
210
230
250
270
290
310
330
Percent Frequency (%)
Total Length (mm)
EB (N=332)
GN (N=94)
FN (N=471)
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
15
Figure 8. Relative weights of Brown Bullhead (N=507) sampled at Lake Washington (King County) in early
summer 2005, as compared to the national 75th percentile, Wr=100 (Anderson and Neumann 1996). Dashed
line denotes the linear regression line (R²=0.0011).
Cutthroat Trout
Cutthroat Trout sampled from Lake Washington ranged in length from 21 to 546 mm
total length (Table 2; Figure 9). Aging structures were not collected from Cutthroat Trout. The
condition of Cutthroat Trout varied greatly among individuals (i.e., W
r
30–135) and was not
correlated with fish size (Figure 10).
0
50
100
150
200
250
0 100 200 300 400
Relative Weight (Wr)
Total Length (mm)
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
16
Figure 9 Length frequency distribution of Cutthroat Trout (N=136) sampled by boat electrofishing (EB) and
gill netting (GN) at Lake Washington (King County) in early summer 2005.
0%
2%
4%
6%
8%
10%
12%
14%
16%
18%
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
540
Percent Frequency (%)
Total Length (mm)
EB (N=109)
GN (N=27)
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
17
Figure 10. Relative weights of Cutthroat Trout (N=122) sampled at Lake Washington (King County) in early
summer 2005, as compared to the national 75th percentile, Wr=100 (Anderson and Neumann 1996). Dashed
line denotes the linear regression line (R²=0.0041).
Largemouth Bass
Largemouth Bass sampled from Lake Washington ranged in length from 95 to 393 mm
total length (Table 2; Figure 11) and ranged in age from 1 to 3 years (Table 7). The growth of
Largemouth Bass exceeded the statewide average for all year classes. The relative weight of
Largemouth Bass varied greatly among individuals (i.e., W
r
82–193) and was not correlated to
fish size (Figure 12).
0
20
40
60
80
100
120
140
160
0 100 200 300 400 500 600
Relative weight (Wr)
Total Length (mm)
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
18
Table 7. Back calculated mean length at age (mm) of Largemouth Bass collected from Lake Washington
(King County, WA) during June-July 2005. Values were calculated using the direct proportion method
(Fletcher et al. 1993).
Figure 11. Length frequency distribution of Largemouth Bass (N=53) sampled by boat electrofishing (EB)
and gill netting (GN) at Lake Washington (King County) in early summer 2005.
Year Class # Fish 1 2 3
2004 23 104
2003 10 100 224
2002 6 93 238 350
Weighted Mean 39 101 229 350
Western WA average 60 145 222
Mean total length (mm) at age
0%
2%
4%
6%
8%
10%
12%
14%
90
110
130
150
170
190
210
230
250
270
290
310
330
350
370
390
Percent Frequency (%)
Total Length (mm)
EB (N=44)
GN (N=8)
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
19
Figure 12. Relative weights of Largemouth Bass (N=53) sampled at Lake Washington (King County) in early
summer 2005, as compared to the national 75th percentile, Wr=100 (Anderson and Neumann 1996). Dashed
line denotes the linear regression line (R²=0.1434).
Pumpkinseed
Pumpkinseed sampled from Lake Washington ranged from 11–234 mm total length
(Table 2; Figure 13) and ranged in age from 1 to 4 years (Table 8). The growth of Pumpkinseed
exceeded the statewide average for all year classes. The condition of Pumpkinseed varied
greatly among individuals (i.e., W
r
50–148) and was not correlated to fish size (Figure 14).
0
50
100
150
200
250
0 100 200 300 400 500
Relative Weight (Wr)
Total Length (mm)
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
20
Table 8. Back calculated mean length at age (mm) of Pumpkinseed collected from Lake Washington (King
County, WA) during June-July 2005. Values were calculated using the direct proportion method (Fletcher et
al. 1993).
Figure 13. Length frequency distribution of Pumpkinseed (N=1186) sampled by boat electrofishing (EB), gill
netting (GN), and fyke netting (FN) at Lake Washington (King County) during June-July 2005.
Year Class # Fish 1 2 3 4
2004 13 51
2003 27 51 111
2002 12 49 118 155
2001 1 35 84 134 160
Weighted Mean 53 50 112.0 153.0 160.0
State Average 24 72 102 122
Mean total length (mm) at age
0%
2%
4%
6%
8%
10%
12%
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
210
220
230
Relative Frequency (%)
Total Length (mm)
EB (N=442)
GN (N=68)
FN (N=676)
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
21
Figure 14. Relative weights of Pumpkinseed (N=520) sampled at Lake Washington (King County) during
June-July 2005, as compared to the national 75th percentile, Wr=100 (Anderson and Neumann 1996).
Dashed line denotes the linear regression line (R²=0.0003).
Bluegill
Bluegill sampled from Lake Washington ranged from 33–143 mm total length (Table 2;
Figure 15). The condition of Bluegill varied greatly among individuals (i.e., W
r
43–206) and
was not correlated to fish size (Figure 16).
50
60
70
80
90
100
110
120
130
140
150
0 50 100 150 200
Relative Weight (Wr)
Total Length (mm)
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
22
Figure 15. Length frequency distribution of Bluegill (N=145) sampled by boat electrofishing (EB), gill netting
(GN), and fyke netting (FN) at Lake Washington (King County) during June-July 2005.
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
30
40
50
60
70
80
90
100
110
120
130
140
Percent Frequency (%)
Total Length (mm)
EB (N=5)
GN (N=3)
FN (N=137)
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
23
Figure 16. Relative weights of Bluegill (N=24) sampled at Lake Washington (King County) during June-July
2005, as compared to the national 75th percentile, Wr=100 (Anderson and Neumann 1996). Dashed line
denotes the linear regression line (R²=0.1117).
Rainbow Trout
Rainbow Trout sampled from Lake Washington ranged from 147–318 mm total length
(Table 2; Figure 17). The condition of all Rainbow Trout was poor (i.e., W
r
59–78) and was not
correlated with fish size (Figure 18).
0
50
100
150
200
250
0 50 100 150 200
Relative Weight (Wr)
Total Length (mm)
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
24
Figure 17. Length frequency distribution of Rainbow Trout (N=25) sampled by boat electrofishing (EB) and
gill netting (GN) at Lake Washington (King County) in early summer 2005.
0%
5%
10%
15%
20%
25%
30%
140
150
160
170
180
190
200
210
220
230
240
250
260
270
280
290
300
310
Percent Frequency (%)
Total Length (mm)
EB (N=23)
GN (N=2)
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
25
Figure 18. Relative weights of Rainbow Trout (N=25) sampled at Lake Washington (King County) in early
summer 2005, as compared to the national 75th percentile, Wr=100 (Anderson and Neumann 1996). Dashed
line denotes the linear regression line (R²=0.2548).
Black Crappie
Black Crappie sampled from Lake Washington ranged in length from 86 to 210 mm total
length (Table 2; Figure 19) and ranged in age from 1 to 2 years (Table 9). The growth of Black
Crappie was similar to the statewide average for all year classes. The condition of Black Crappie
varied greatly among individuals (i.e., W
r
103–166) and did not appear to be related to fish size
(Figure 20).
40
60
80
100
120
140
160
100 150 200 250 300 350
Relative Weight (Wr)
Total Length (mm)
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
26
Table 9. Back calculated mean length at age (mm) of Black Crappie collected from Lake Washington (King
County, WA) during June-July 2005. Values were calculated using the direct proportion method (Fletcher et
al. 1993).
Figure 19. Length frequency distribution of Black Crappie (N=26) sampled by boat electrofishing (EB), gill
netting (GN), and fyke netting (FN) at Lake Washington (King County) during June-July 2005.
Year Class # Fish 1 2
2004 13 86
2003 5 86 183
Weighted Mean 18 46 111
Western WA average 46 111
Mean total length
0%
2%
4%
6%
8%
10%
12%
14%
16%
80
90
100
110
120
130
140
150
160
170
180
190
200
210
Percent Frequency (%)
Total Length (mm)
EB (N=13)
GN (N=13)
FN (N=3)
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
27
Figure 20. Relative weights of Black Crappie (N=26) sampled at Lake Washington (King County) in early
summer 2005, as compared to the national 75th percentile, Wr=100 (Anderson and Neumann 1996). Dashed
line denotes the linear regression line (R²=0.0011).
Common Carp
Common Carp sampled from Lake Washington ranged in length from 300 to 785 mm
total length (Table 2; Figure 21). The condition of Common Carp varied greatly among
individuals (i.e., W
r
87–156) and did not appear to be related to fish size (Figure 22).
0
20
40
60
80
100
120
140
160
180
200
60 110 160 210 260
Relative Weight (Wr)
Total Length (mm)
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
28
Figure 21. Length frequency distribution of Common Carp (N=26) sampled by boat electrofishing (EB) and
gill netting (GN) at Lake Washington (King County) in early summer 2005.
Figure 22. Relative weights of Common Carp (N=26) sampled at Lake Washington (King County) in early
summer 2005 as compared to the national 75th percentile, Wr=100 (Bister et al. 2000). Dashed line denotes
the linear regression line (R²=0.0117).
0%
5%
10%
15%
20%
25%
<440
440
460
480
500
520
540
560
580
600
620
640
660
680
700
720
740
760
780
Percent Frequency (%)
Total Length (mm)
EB (N=4)
GN (N=15)
40
60
80
100
120
140
160
180
0 200 400 600 800 1000
Relative Weight (Wr)
Total Length (mm)
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
29
Green Sunfish
Green Sunfish sampled from Lake Washington ranged in length from 65 to 192 mm total
length (Table 2; Figure 23). The condition of Largemouth Bass varied greatly among individuals
(i.e., W
r
79–177) and did not appear to be related to fish size (Figure 24).
Figure 23. Length frequency distribution of Green Sunfish (N=10) sampled by boat electrofishing (EB), gill
netting (GN), and fyke netting (FN) at Lake Washington (King County) in early summer 2005.
0%
5%
10%
15%
20%
25%
30%
35%
60
70
80
90
100
110
120
130
140
150
160
170
180
190
Percent Frequency (%)
Total Length (mm)
EB (N=3)
GN (N=6)
FN (N=1)
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
30
Figure 24. Relative weights of Green Sunfish (N=10) sampled at Lake Washington (King County) in early
summer 2005 as compared to the national 75th percentile, Wr=100 (Bister et al. 2000). Dashed line denotes
the linear regression line (R²=0.1795).
Comparisons to Survey Data from 1982
Relative abundance data for warmwater fish species reported by Pfeifer and Weinheimer (1992)
are shown in Table 10. Mean electrofishing catch rates for warmwater species from eight
locations in Lake Washington are reported for 1982 and 2005 surveys. Mean electrofishing
catch rates of Smallmouth Bass, Pumpkinseed, and Brown Bullhead were higher in 2005 across
all sampling locations, with the exception of Pumpkinseed at Andrews Bay. Catch rates for
Yellow Perch, Largemouth Bass, and Black Crappie varied greatly among surveys and sampling
locations.
40
60
80
100
120
140
160
180
200
0 50 100 150 200 250
Relative Weight (Wr)
Total Length (mm)
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
31
Table 10. Relative abundance of gamefish species sampled by electrofishing, gill nets, and trap nets in Lake
Washington embayments during August–October 1982 (Pfeifer and Weinheimer 1992).
Species
Relative Abundance
(by number)
Yellow Perch
57.01
Brown Bullhead
15.65
Black Crappie
12.69
Largemouth Bass
10.83
Pumpkinseed
2.58
Rainbow Trout
0.95
Smallmouth Bass
0.29
Table 11. Mean electrofishing catch rates from 1982 and 2005 surveys, by region. Standard error is reported
in parentheses when two or more sites were sampled (Pfiefer and Weineimer 1992).
Location 2008 1982
2008 1982 2008 1982 2008 1982 2008 1982
2008 1982 2008 1982 2008 1982
0.50
3.00
0.70
0.50
3.50
0.50
1.00
0.50
0.80
40
(31.4)
0.0
Effort (hrs)
0.33
1.58
0.50
0.60
0.50
2.40
0.50
3.0
23.9
(13.8)
0.2
(0.2)
30
(19.3)
1.0
47.8
(36.7)
0.0
2 (2)
0.0
Pumpkinseed
Sunfish
0.0
0.6
274
(274)
0.0
16 (16)
0.0
28
(22.3)
0.0
5.8
(5.8)
0.4
(0.4)
0.0
0.0
17.9
(17.9)
1.3
4 (4)
17.5
(9.39)
Smallmouth
Bass
6
(4.9)
0.0
0.0
0.0
2 (2)
0.0
0.0
0.0
0.7
(0.5)
0.0
6.0
18
(18)
1.3
Largemouth
Bass
0.0
7.0
2 (2)
27.6
0.0
6
(1.8)
26
(23.1)
10.4
0.0
60
(28.4)
27.9
(19.6)
25.9
(22.9)
27.5
(19.2)
108
(55.4)
0.0
3.0
0.9
0.0
0.0
0.0
0.2
(0.2)
3
1
3
2
Brown
Bullhead
0.0
0.0
148
(148)
0.0
10
(7.2)
3
1
3
2
3
1
# of sites
2
1
3
1
3
2
49.0
36.0
43
(35.1)
Yellow Perch
95.5
Black
Crappie
0.0
0.0
2 (2)
1.7
7.6
62.1
4.5
(0.67)
13.7
(5.8)
0.0
4 (4)
0.0
4 (4)
8.3
(0.9)
0.0
6.7
(5.5)
2 (2)
0.0
0.0
Sandpoint
Yarrow Bay
6 (4.9)
72 (55)
30 (30)
72
(27.5)
63.2
(15.4)
101.7
(38.3)
78.6
(54.7)
210
(153.5)
Andrews
Cozy Cove
Juanita Bay
Kenmore
Mercer Slough
Meydenbauer
Bay
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
32
Discussion
The standardized warmwater sampling protocols we used (Bonar et al. 2000) indicate an ideal
sampling period for spring (April-mid June) and fall (August-first week in October) surveys.
These time periods coincide with peak catch rates for warmwater species (Pope and Willis 1996;
Divens et al. 1998). We deviated from this protocol by delaying this survey till late June (June
26-July 1) to minimize take of ESA-listed salmonids during outmigration. Consequently, the
data we recorded for certain species may underrepresent the population due to seasonal shifts in
habitat use. For example, catch rates and PSD values recorded for Smallmouth Bass may have
been higher if sampled in early June when peak spawning occurs.
Lake Washington’s Yellow Perch and Smallmouth Bass populations represent the majority of
warmwater fishing opportunity in terms of relative abundance and numbers of quality-size fish.
Both species exhibited above average growth as compared to the Washington State average and
estimates of proportional size distribution (PSD) were high for electrofishing (>30) and gill
netting (>50). The higher PSD values for Smallmouth Bass and Yellow Perch from gill netting
are not uncommon, and may be attributed to these species commonly occupying deep water
habitats that are poorly sampled by electrofishing (Hamley 1975; Osborne et al. 2003). In
general, Lake Washington is characterized by a steeply sloped and highly urbanized shoreline,
with thousands of docks that are narrowly spaced. These obstructions limit boat maneuverability
which ultimately decreases electrofishing efficiency.
The high relative abundance of Yellow Perch was not unexpected. Since their first recorded
introductions into places such as the Columbia River and Silver Lake (Cowlitz County) in the
1890s (Lampman 1946; Wydosky and Whitney 2003), Yellow Perch have become one of the
most abundant fishes in Washington and often represent the dominant species in the fish
community. In the North Puget Sound region, Yellow Perch comprised the majority of fish
sampled in Lake Stevens (Snohomish County; Mueller 1999a), Lake Sawyer (King County;
Downen and Mueller 2000a), Lake Meridian (King County; Verhey and Mueller 2001); Lake
Terrell (Whatcom County; Downen and Mueller 2000b), Big Lake (Skagit County; Mueller and
Downen 1999), and Lake Whatcom (Whatcom County; Mueller et al. 1999). Yellow Perch are
highly fecund, prolific spawners and in small lakes, they tend to become overabundant and
exhibit reduced growth (Wydosky and Whitney 2003), either due to interspecific competition or
a lack of larger prey items. In Lake Washington, the diet of Yellow Perch primarily consists of
Cottus spp. and Longfin Smelt (Costa 1979; Overman et al. 2009), both of which are prevalent in
the lake, and presumably, provide a consistent source of food for Yellow Perch after they switch
to piscivory at around 200 mm total length (Overman et al. 2009).
Largemouth Bass in Lake Washington represented a small portion of the sample, but exhibited
growth and condition above the Washington state average. Although the timing of the survey
precludes us from determining young-of-the-year (YOY) abundance, the low relative abundance
of Largemouth Bass and size structure coupled with habitat characteristics of the lake suggest
low recruitment of age-0 Largemouth Bass. Many researchers have demonstrated that high, size-
selective mortality of age-0 Largemouth Bass occurs during the winter (Oliver et al. 1979;
Gutreuter and Anderson 1985; Miranda and Hubbard 1994; Garvey et al. 1998). Thus, abiotic
factors affecting the duration of first year growth can influence patterns of winter survival and
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
33
cohort strength (Garvey et al. 2002). Specifically, low temperatures during the spring and
summer can delay hatching and reduce growth rates, resulting in delayed onset of piscivory
(Olson 1996). YOY Largemouth Bass that switch to piscivory often have dramatically increased
condition and growth (Olson 1996; Ludsin and DeVries 1997). Bowles (1985) found that water
temperature and rate of warming (degree-days) affected over-winter survival of YOY in the
Coeur d’ Alene Lake system by influencing the length and quality of the growing season. He
suggested that Largemouth Bass less than 50 mm total length could not survive long winters
(Bennett et al. 1991a). In Lake Washington, the growth and condition of adult Largemouth Bass
suggests that individuals that survive their first year and switch to piscivory grow quickly, yet
high mortality of YOY bass is likely limiting the size of the population.
Tabor et al. (2004) and Tabor et al. (2007) estimated the population of Largemouth Bass and
Smallmouth Bass in the Lake Washington Shipping Canal (LWSC; a major migration corridor
for salmonids) at 2,500 and 3,400 fish, respectively. In contrast, our relative abundance
estimates (Table 2) suggests that Smallmouth Bass greatly outnumber Largemouth Bass in the
main lake portion of Lake Washington. The disparity in these results may be attributed to habitat
characteristics, e.g., gravel flats, wood cover, vegetation, and warm water, which are largely
unavailable to Largemouth Bass in the main lake and restricted to shallow embayments and the
LWSC. The amount and arrangement of Largemouth Bass habitat has been shown to regulate
population processes at the landscape scale (Irwin et al. 2002). Gravel substratum for spawning,
shoreline complexity/morphology, and adequate cover were identified as important landscape
features for Largemouth Bass production (Irwin et al. 2002).
Smallmouth and Largemouth Bass have been shown to consume native fishes including juvenile
salmonids (Bennett et al. 1991b, Tabor et al. 1993; Fritts and Pearson 2004) and remain
controversial for fisheries managers in Lake Washington where ESA-listed stocks of salmon are
present. Several studies have been conducted on the predatory impacts of Smallmouth Bass in
Lake Washington on outmigrating smolts of Chinook Salmon (Tabor et al. 2004; 2007) and
Sockeye Salmon (Fayram and Sibley 2000). Though black bass were shown to prey on
salmonids during outmigration, particularly in the Lake Washington Shipping Canal (LWSC), all
studies concluded that predation by black bass has a relatively “little” or “minor” impact on
salmon abundance (Fayram and Sibley 2000; Tabor et al. 2004; 2007). The primary forage for
Smallmouth Bass in Lake Washington is crayfish and sculpin (Overman et al. 2009; Tabor et al.
2004; 2007), both of which are highly abundant.
Although recent creel data is lacking for Lake Washington, the number of recreational bass
tournaments held annually strongly suggests that Smallmouth Bass remain the primary driver of
warmwater fishing effort. During 2010-2013, angling clubs applied for 13-17 contest permits
per year to fish for Smallmouth Bass and Largemouth Bass in Lake Washington. Given that
tournaments anglers in Washington are limited to two bass tournaments per month on each water
body, anglers are nearly maximizing their opportunities to hold fishing contests every year.
Anglers who fish Lake Washington regularly cite the quality of fish and proximity to home as
the primary reason for their trip.
Several other warmwater gamefish species occur in Lake Washington, i.e., Pumpkinseed,
Bluegill, Black Crappie, and Green Sunfish, that collectively made up a small portion of the total
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
34
biomass (11.7%; excluding Threespine Sticklebacks). Similar to Largemouth Bass, these species
spawn when water temperatures reach approximately16-18 ºC. In contrast, Yellow Perch
comprised the majority of the biomass (50.8%) and spawn at much lower temperatures (7-11 ºC).
This pattern of fish abundance is common throughout Washington lakes, suggesting that fishes
belonging to cold- and coolwater guilds are more physiologically well-adapted to the thermal
regime of Washington lakes, e. g., degree days of warming. Temperature can influence the
relative abundance of species because the effects of temperature on year-class strength,
recruitment, growth, and survival affect each species differently depending on thermal
requirements (Shuter and Post 1990; Tonn 1990; Casselman 2002). Although the growth of
Largemouth Bass and Pumpkinseed were above the Washington average, the low relative
abundance of these species suggests that one or more abiotic or biotic factors is limiting
population growth.
Largescale Suckers and Northern Pikeminnow comprised nearly half of the biomass sampled
indicating robust populations of both species. Although the sampling methods were specifically
designed to estimate the relative abundance of warmwater fish species (Bonar et al. 2000), the
80% confidence interval around catch rates for Northern Pikeminnow and Largescale Sucker
(Table 3) suggests that comparisons of relative abundance are valid. High relative abundance of
these two species has been documented in several lakes in Washington, including Lake Spokane
(Osborne and Divens 2003), Palmer Lake (Osborne et al. 2003), and Mason Lake (Mueller
1999b), and may be linked to the simplicity of their spawning requirements and the plasticity of
their feeding ecology. Both species broadcast spawn adhesive eggs over sand, gravel, or cobble
bottom in slow to moderate currents, habitats that are widely available in Washington’s rivers
and streams (Wydosky and Whitney 2003). The feeding ecology of both species is also highly
conducive for lacustrine environments. Largescale Suckers and Northern Pikeminnow attain
large sizes relative to most species and exploit a wide variety of food items as adults such as
snails, crawfish, and sculpins. Largescale suckers can exploit many food items that other species
cannot, including periphyton algae, filamentous algae, and detritus (Wydosky and Whitney
2003). Overman et al. (2009) found the diet of adult Northern Pikeminnow across all seasons in
Lake Washington varied widely, but primarily consisted of Longfin Smelt and Sockeye Salmon.
Electrofishing catch rate data collected from 11 locations in 1982 and 2005 was reported to
investigate potential changes to the Lake Washington fish community (Table 11). The high
variability associated with catch rates, i.e., standard error, suggests that a larger sample size is
needed to make statistical comparisons among these locations in Lake Washington. Without
statistical rigor, we can only hypothesize that observed increases in catch rates of Smallmouth
Bass, Pumpkinseed Sunfish and Brown Bullhead reflect actual changes to the fish community.
During the 1980s and 1990s, anglers reported catching fewer Largemouth Bass and Black
Crappie while encountering an increasing number of Smallmouth Bass (Kurt Kraemer,
Washington Department of Fish and Wildlife, personal communication). A possible shift in the
fish community may be linked to limnological changes that occurred during the 1970s. With the
exception of combined sewer flows, sewage effluent was completely diverted from the lake by
1968 and the lake subsequently reverted to a mesotrophic state (Cooke et al. 1993). Although
many changes occurred during this time and have been elaborated by Edmondson (1994), the
most notable changes were decreases in phosphorus loading and phytoplankton abundance. This
shift from eutrophy to mesotrophy and associated changes to the plankton community may be
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
35
correlated with a reduction of Largemouth Bass and Black Crappie and an increase in
Smallmouth Bass during the 1980s and 1990s.
Similar to other north temperate lakes, Lake Washington is composed of many species with
distinct temperature preferences (i.e., warm-, cool-, and coldwater species). The size,
morphometry, and thermal-stratification of Lake Washington provides habitat for all three
thermal guilds, though changes in species distribution and abundance are likely to occur in
coming decades. Climate change, which results in a change in water temperature over time, is
becoming increasingly recognized as a factor that influences fish and aquatic communities
(Casselman 2002; Robillard and Fox 2006). Many studies that project the effects of climate
change in lake fishes have predicted declines in coldwater species (Mackenzie-Grieve and Post
2006; Jacobson et al. 2010; Herb et al. 2014). Other studies have shown positive associations
between water temperature and warmwater fish populations (Robillard and Fox 2006; Hansen et
al. 2016). In Lake Washington, current environmental conditions appear to favor coolwater
species such as Yellow Perch and Smallmouth Bass. Whether these species will continue to
thrive, or be gradually supplanted by other warmwater species, i.e., Largemouth Bass, Rock
Bass, Black Crappie, or Bluegill, will depend on the rate and degree of regional temperature
changes. Future research may focus on monitoring long-term trends in fish abundances as they
relate to changing water temperatures to better understand the relationship among abiotic and
biotic factors that continue to shape the Lake Washington fish community.
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
36
Literature Cited
Anderson, R. O. and R. M. Neumann. 1996. Length, weight, and associated structural indices.
Pages 447–482 in B. R. Murphy and D. W. Willis, editors. Fisheries Techniques, 2
nd
edition. American Fisheries Society, Bethesda, Maryland.
Bennett, D. H., D. R. Hatch, and M. D. Liter. 1991a. Managing Largemouth Bass in the
Northwest: a game of recruitment, protection, and patience. Pages 313–322 in
Warmwater Fisheries Symposium I. U. S. Department of Agriculture, Forest Service,
General Technical Report RM-207, Fort Collins, Colorado.
Bennett, D. H., J. A. Chandler, and L. K. Dunsmoor. 1991b. Smallmouth Bass in the Pacific
Northwest: benefit or liability. Pages 126–135 in D. C. Jackson, editor. Proceedings of
the First International Smallmouth Bass Symposium, Mississippi Agricultural and
Forestry Experimental Station, Mississippi State University, Mississippi State.
Bettross, E.A. and D.W. Willis. 1988. Seasonal patterns in sampling data for largemouth
bass and bluegills in a northern Great Plains impoundment. Prairie Naturalist 20, 193–
202.
Bradbury, A. and B. Pfeifer. 1992. Draft Report: Fishieries Investigations of Lakes
Washington and Sammamish, Part III. 1980–1990. Washington Department of Fish and
Wildlife, Mill Creek, Washington.
Bonar, S. A., B. D. Bolding, and M. Divens. 2000. Standard Fish Sampling Guidelines for
Washington State Ponds and Lakes. Washington Department of Fish and Wildlife, Fish
Program, Technical Report # FPT 00–28.
Casselman, J. M. 2002. Effects of temperature, global extremes, and climate change on year-
class production of warmwater, coolwater, and coldwater fishes in the Great Lake basin.
Transactions of the American Fisheries Society 32:39–60.
Cooke, G. D., E. B. Welch, S. A. Peterson, and P. R. Newroth. 1993. Restoration and
Management of Lakes and Reservoirs. Second edition. Lewis Publishers, Boca Raton,
FL. 548 pages.
Costa, H. H. 1979. The food and feeding chronology of Yellow Perch (P. flavescens) in Lake
Washington. International review of hydrobiology 64(6):783–793.
Divens, M. J., S. A. Bonar, B. D. Bolding, and E. Anderson. 1998. Monitoring warm-water fish
populations in north temperate regions: sampling considerations when using proportional
stock density. Fisheries Management and Ecology 5:383–391.
Downen, M. R., and K. W. Mueller. 2000a. 1999 Lake Sawyer Survey: The warmwater
community in a popular, unregulated fishery. Washington Department of Fish and
Wildlife, Olympia, Washington. Technical Report #FPT 00-23.
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
37
Downen, M. R., and K. W. Mueller. 2000b. 1999 Lake Terrell Survey: Potential trophy
Largemouth Bass and Channel Catfish fisheries in a lowland western Washington lake
preserve. Washington Department of Fish and Wildlife, Olympia, Washington.
Technical Report #FPT 00-12.
Dumont, S. C. and J. A. Dennis. 1997. Comparison of day and night electrofishing in Texas
reservoirs. North American Journal of Fisheries Management 17:939–946.
Edmondson, W. T. 1994. Sixty years of Lake Washington: a Curriculum Vitae. Lake and
Reservoir Management 10:75–84.
Edmondson, W. T. and J. T. Lehman. 1981. The Effect of Changes in the Nutrient Income on
the Condition of Lake Washington. Limnology and Oceanography 26(1):1-29.
Eggers, D.M., N.W. Bartoo, N.A. Rickard, R.E. Nelson, R.C. Wissmar, R.L. Burgner, and A.H.
Devol. 1978. The Lake Washington ecosystem: the perspective from the fish
community production and forage base. J. Fish. Res. Board Can. 35: 1553–1571.
Fayram, A. H., and T. H. Sibley. 2000. Impact of predation by Smallmouth Bass on Sockeye
Salmon in Lake Washington, Washington. North American Journal of Fisheries
Management 20:81–89.
Garvey, J. E., R. A. Wright, and A. R. Stein. 1998. Overwinter growth and survival of age-0
largemouth bass (Micropterus salmoides): revisiting the role of body size. Canadian
Journal of Fisheries and Aquatic Sciences 55(11):2414–2424.
Garvey, J. E., R. A. Stein, R. A. Wright, and M. T. Bremigan. 2002. Exploring ecological
mechanisms underlying largemouth bass recruitment along environmental gradients.
Page 7-23 in D. P. Phillip and M. S. Ridgeway, editors. Black Bass: Ecology,
Conservation, and Management. American Fisheries Society, Bethesda, Maryland.
Gustafson, K. A. 1988. Approximating confidence intervals for indices of fish population size
structure. North American Journal of Fisheries Management 8:169–141.
Gutreuter, S. J. and R. O. Anderson. 1985. Importance of body size to the recruitment process
in Largemouth Bass. Transactions of the American Fisheries Society 114:317–327.
Guy, C.S. and D.W. Willis. 1991. Seasonal variation in catch rate and body conditions for four
fish species in a South Dakota natural lake. Journal of Freshwater Ecology 6:281–292.
Guy, C. S., R. M. Neumann, and D. W. Willis. 2006. New terminology for proportional stock
density (PSD) and relative stock density (RSD): proportional size structure (PSS).
Fisheries 31(2):86-87.
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
38
Guy, C. S., R. M. Neumann, D. W. Willis, and R. O. Anderson. 2007. Proportional Size
Distribution (PSD): A Further Refinement of Population Size Structure Index
Terminology. Fisheries 32(7):348.
Fritts, A. L. and T. N. Pearson. 2004. Smallmouth Bass predation on hatchery and wild
salmonids in the Yakima River, Washington. Transactions of the American Fisheries
Society 133:880–895.
Hamley, J. M. 1975. Review of gillnet selectivity. Journal of the Fisheries Research Board of
Canada 32:1943–1969.
Herb, W. R., L. B. Johnson, P. C. Jacobson, and H. G. Stefan. 2014. Projecting cold-water fish
habitat in lake of the glacial lakes region under changing land use and climate regimes.
Canadian Journal of Fisheries and Aquatic Sciences 71:1334–1348.
Irwin, E. R., J. R. Jackson, and R. L. Noble. 2002. A reservoir landscape for Age-0 Largemouth
Bass. Page 61–71 in D. P. Phillip and M. S. Ridgeway, editors. Black Bass: Ecology,
Conservation, and Management. American Fisheries Society, Bethesda, Maryland.
Jacobson, P. C., H. G. Stefan, and D. L. Pereira. 2010. Coldwater fish oxythermal habitat in
Minnesota lakes: influence of total phosphorus, July air temperature, and relative depth.
Canadian Journal of Fisheries and Aquatic Sciences 67:2002
–2013.
Lampman, B. H. 1946. The coming of the pondfishes. Binfords and Mort., Portland, Oregon.
177 pp.
Ludsin, S. A., and D. R. DeVries. 1997. First-year recruitment of Largemouth Bass: the
interdependency of life stages. Ecological Aplications 7:1024–1038.
Mackenzie-Grieve, J. L. and J. R. Post. 2006. Projected impacts of climate warming on
production of Lake Trout (Salvelinus namaycush) in southern Yukon lakes. Canadian
Journal of Fisheries and Aquatic Sciences 63:788–797.
McIntyre, J. K., D. A. Beauchamp, M. M. Mazur, and N. C. Overman. 2006. Ontogenetic
trophic interactions and benthopelagic coupling in Lake Washington: evidence from
stable isotopes and diet analysis. Transactions of the American Fisheries Society
135:1312–1328.
Miranda, L. E. and W. D. Hubbard. 1994. Winter survival of Age-0 Largemouth Bass relative
to size, predators, and shelter. North American Journal of Fisheries Management
14(4):790–796.
Mueller, K. W. 1999a. 1997 Lake Stevens Survey: The warmwater fish community after
implementation of a minimum length rule on Largemouth and Smallmouth Bass.
Washington Department of Fish and Wildlife, Olympia, Washington.
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
39
Mueller, K. W. 1999b. 1997 Mason Lake Survey: The Warmwater Fish Community of a Lake
Dominated by Non-Game Fish. Washington Department of Fish and
Wildlife, Olympia, Washington. Technical Report.
Mueller, K. W. and M. R. Downen. 1999. 1997 Big Lake Survey: The warmwater fish
community before treatment with a selective herbicide. Washington Department of Fish
and Widlife, Olympia, Washington. Technical Report #FPT 99–11.
Mueller, K. W., M. R. Downen, amd D. H. Fletcher. 1999. 1998 Lake Whatcom Survey: The
warmwater fish community 15 years after the introduction of Smallmouth Bass.
Washington Department of Fish and Wildlife, Olympia, WA. Technical Report #FPT
99-12.
Oliver, J. D., G. F. Holeton, and K. E. Chua. 1979. Over-winter mortality of fingerling
Smallmouth Bass in relation to size, relative energy stores, and environmental
temperature. Transactions of the American Fisheries Society 108:130–136.
Olson, M. H. 1996. Ontogenetic niche shifts in largemouth bass: variability and consequences
for first-year growth. Ecology 77:179–190.
Osborne, R. S. and M. J. Divens. 2003. 2001 Warmwater Fisheries Survey of Lake Spokane,
Spokane and Stevens Counties, Washington. Washington Department of Fish and
Wildlife, Fish Program, Technical Report # FPT 03-02.
Osborne, R. S., M. R. Petersen, and C. S. Jackson. 2003. 1999 Warmwater Fisheries Survey of
Palmer Lake (Okanogan County), Washington. Washington Department of Fish and
Wildlife, Fish Program, Technical Report # FPT 00-03.
Overman, N. C., D. A. Beauchamp, H. B. Berge, M. M. Mazur, and J. K. McIntyre. 2009.
Differing forage fish assemblages influence trophic structure in neighboring urban lakes.
Transactions of American Fisheries Society 138:741–755.
Pfeifer, B. and J. Weinheimer. 1992. Draft Report: Fishieries Investigations of Lakes
Washington and Sammamish, Part VI. 1980-1990. Washington Department of Fish and
Wildlife, Mill Creek, Washington.
Pope, K. L. and D. W. Willis. 1996. Seasonal influences on freshwater fisheries sampling data.
Reviews in Fisheries Science 4(1):57–73.
Robillard, M. M. and M. G. Fox. 2006. Historical changes in abundance and community
structure of warmwater piscivore communities associated with changes in water clarity,
nutrients, and temperature. Canadian Journal of Aquatic Sciences 63:798–809.
A Biological Assessment of the Warmwater Fish Community in Lake Washington October 2017
40
Reynolds, J. B. 1996. Electrofishing. Pages 221-253 in B. R. Murphy and D. W. Willis,
editors. Fisheries Techniques, Second Edition. American Fisheries Society, Bethesda,
Maryland.
Shuter, B. J. and J. R. Post. 1990. Climate, population viability, and the zoogeography of
temperate fishes. Transactions of the American Fisheries Society 119:314–336.
Tabor, R. A., R. S. Shively, and T. P. Poe. 1993. Predation on juvenile salmonids by
Smallmouth Bass and Northern Squawfish in the Columbia River near Richland,
Washington. North American Journal of Fisheries Management 13:831–838.
Tabor, R. A., M. T. Celedonia, F. Mejia, R. M. Piaskowski, and D. L. Low. 2004. Predation of
juvenile Chinook Salmon by predatory fishes in three areas of the Lake Washington
Basin. U.S. Fish and Widlife Service Annual Report, Lacey, Washington.
Tabor, R. A., B. A. Footen, K. L. Fresh, M. T. Celedonia, F. Mejia, D. L. Low, and L. Park.
2007. Smallmouth Bass and Largemouth Bass predation on juvenile Chinook Salmon
and other salmonids in the Lake Washington Basin.
Tonn, W. M. 1990. Climate change and fish communities: a conceptual framework.
Transactions of the American Fisheries Society 199:337–352.
Verhey, P. A., and K. W. Mueller. 2001. 2000 Lake Meridian Survey: The warmwater fish
community of an oligotrophic urban lake. Washington Department of Fish and Wildlife,
Olympia, Washington. Technical Report #FPT 01-11.
This program receives Federal financial assistance from the U.S. Fish and
Wildlife Service Title VI of the Civil Rights Act of 1964, Section 504 of the
Rehabilitation Act of 1973, Title II of the Americans with Disabilities Act
of 1990, the Age Discrimination Act of 1975, and Title IX of the
Education Amendments of 1972. The U.S. Department of the Interior and
its bureaus prohibit discrimination on the bases of race, color, national
origin, age, disability and sex (in educational programs). If you believe
that you have been discriminated against in any program, activity or
facility, please contact the WDFW ADA Program Manager at P.O. Box
43139, Olympia, Washington 98504, or write to
Department of the Interior
Chief, Public Civil Rights Division
1849 C Street NW
Washington D.C. 20240
