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Summary 

In 2015 through 2019, the U.S. Fish and Wildlife Service (USFWS) evaluated juvenile 

Chinook salmon (Oncorhynchus tshawytscha) use in two small nonnatal streams (Mapes and 

Taylor creeks) within the City of Seattle. The lower 130 m (427 ft) of Mapes Creek was 

daylighted (stream channel was reconfigured from an underground culvert to a more natural 

stream channel at the surface) in 2014 to provide habitat for juvenile Chinook salmon, and thus 

the surveys were conducted post-construction. For Taylor Creek, we conducted pre-restoration 

monitoring of the lower 165 m (541 ft) (downstream of Rainier Ave.). The primary sampling 

technique for both streams was nighttime visual surveys which included a combination of 

snorkeling (pools, glides, delta area, and lakeshore reference sites) and surface observations 

(glides and riffles). In 2015-2017, both streams were sampled twice a month (February to May) 

with the first survey in late January and the last survey in early June. In 2018 and 2019, surveys 

were conducted monthly from January to June. Because the riffles in Taylor Creek were mostly 

too turbulent to observe fish, a subsample of riffles was sampled with electrofishing gear once a 

month. 

On a few occasions, beach seine sampling was conducted to determine if juvenile 

Chinook salmon move into the stream delta areas following rain events to forage on prey 

displaced downstream. Each year we also conducted one single-pass electrofishing survey of 

each study stream section in June to collect some detailed information on the abundance, 

distribution, and size of other fish species in each stream. To provide further data on pre-project 

conditions, we also conducted a summer single-pass electrofishing survey of two stream sections 

in upper Taylor Creek (stream reaches above Rainier Ave) in 2018 and 2019. Previous sampling 

results of these two stream sections from 2005, 2010, and 2012-2013 were also combined with 

2018 and 2019 results to provide a longer-term dataset to be used to compare to post-project 

monitoring. 

Juvenile Chinook salmon were generally common in Mapes Creek from February to 

April and were found throughout the restored reach. For 2015-2017, peak abundances occurred 

in early March with an overall peak abundance of 244 fish observed (0.94 fish/m2

) on March 6, 

2017. In April and May, the density of juvenile Chinook salmon declined sharply and was 
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usually lower than a nearby lakeshore reference site. In 2019, juvenile Chinook salmon were not 

common in Mapes Creek until April and overall numbers were lower than in 2015-2017. 

In lower Taylor Creek, juvenile Chinook salmon were predominantly found on the delta 

or in the L-1 section of our study reach. Only a few were observed in the L-2 and L-3 section. 

In 2015-2017, a small rock barrier that separated the L-2 and L-3 sections appeared to be a 

complete barrier to juvenile Chinook salmon as well as a partial barrier to migratory sculpins 

(Cottus spp.). In 2018 and 2019, this rock barrier was no longer present and some juvenile 

Chinook salmon and large numbers of coastrange sculpin (C. aleuticus) were upstream of the 

barrier location. Most fish collected during June electrofishing surveys were sculpins. Prickly 

sculpin (C. asper) were collected primarily in the slow-water habitats (convergence pool and 

glides) and coastrange sculpin were collected primarily in riffles. Fish in upper Taylor Creek 

(stream reaches above Rainier Ave) consisted primarily of cutthroat trout (O. clarkii) and in most 

years they were the only species present. In earlier sampling in 2005 and 2010, juvenile coho 

salmon (O. kisutch) were also present, which were likely from outplanting events because the 

downstream culvert under Rainier Avenue is an anadromous barrier. 

Similar to other nonnatal streams in Lake Washington or Lake Sammamish, the delta area 

of Taylor Creek appeared to have some valuable habitat for juvenile Chinook salmon. The 

northwest part of the delta area, where the main streamflow was located, provided preferred 

habitat conditions (fluvial fan with shallow areas and sand substrates). The northeast and 

southeast part of the delta area had no streamflow and was primarily composed of coarse gravel 

and cobbles. The abundance of juvenile Chinook salmon in this part of the delta was generally 

low and substantially less than along the northwest part where the streamflow was located and 

sand substrates were present. 

Unlike Taylor Creek, few juvenile Chinook salmon were observed on the delta area of 

Mapes Creek likely because this area did not have preferred habitat conditions. Diet analysis of 

juvenile Chinook salmon from Taylor Creek delta indicated they preyed primarily on small 

invertebrates from Lake Washington similar to other lake-dwelling Chinook salmon. Prey from 

Taylor Creek did not appear to be used extensively except after rain events when Taylor Creek 

invertebrates were likely displaced downstream. 
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The number of juvenile Chinook salmon in Mapes Creek from 2015 to 2017 was often 

greater than that in Taylor Creek even though Taylor Creek is a larger stream and is located over 

2 km (1.2 miles) closer to the Cedar River (the natal stream). For example, the total number of 

juvenile Chinook salmon observed was 1.9 times higher in Mapes Creek than in Taylor Creek in 

2015, 2.1 times higher in 2016, and 1.6 times higher in 2017. Additionally, the maximum 

number observed in Mapes Creek was 244 (0.94 fish/m2) while it was 157 (0.64 fish/m2) in the 

lowest two stream sections (L-1 and L-2) of Taylor Creek. The steeper gradient and possibly the 

large number of cutthroat trout in Taylor Creek could be limiting the use of Taylor Creek by 

juvenile Chinook salmon. Based on results from Mapes Creek and other nonnatal streams (Lake 

Washington basin and other systems), we recommend the gradient in Taylor Creek be less than 

2% following restoration construction. Because juvenile Chinook salmon appear to use different 

habitats as they grow, we recommend the Taylor Creek restoration should aim to create diverse 

habitat conditions including pools, glides, riffles, overhanging vegetation, and instream woody 

debris. Additionally, Taylor Creek restoration designs should consider fish passage of smallbodied fishes such as juvenile Chinook salmon and migratory sculpins. In conclusion, results 

from both streams further support the concept that small nonnatal tributaries play a valuable role 

in providing nursery habitat for rearing juvenile Chinook salmon, and thus should be a priority to 

protect and/or restore when possible. 

 
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Introduction 

Small nonnatal tributaries play a valuable role in providing nursery habitat for rearing 

juvenile Chinook salmon (Oncorhynchus tshawytscha; Murray and Rosenau 1989; Scrivener et 

al. 1994; Scarnecchia and Roper 2000; Bradford et al. 2001; Daum and Flannery 2011; Tabor et 

al. 2011b; Gregersen 2019). These small streams provide juvenile Chinook salmon with instream habitat as well as shallow, sandy delta areas that offer valuable rearing and refuge habitat. 

Additionally, nonnatal streams may be a source of prey for lake-dwelling juvenile Chinook 

salmon, especially during rain events (Tabor et al. 2011b). Nonnatal tributaries used extensively 

by juvenile Chinook salmon tend to be streams that have a low gradient (i.e., <2%), are small to 

medium-sized (i.e., < 2 cfs baseline discharge), are close to the natal stream, and have a large 

delta area (Tabor et al. 2011b). 

Identification and restoration of nonnatal streams is particularly important for Puget 

Sound Chinook salmon because these fish are currently listed as threatened under the 

Endangered Species Act (ESA; Federal Register 64 FR 14208, March 24, 1999) and often occur 

in highly altered environments. Land use changes in some areas have significantly reduced 

access to small, nonnatal streams in the Puget Sound. In prioritizing stream restoration projects, 

the potential juvenile Chinook salmon use is often an important consideration. Both pre- and 

post-restoration monitoring are needed to determine project effectiveness. 

Puget Sound Chinook salmon are primarily ocean-type Chinook salmon which typically 

emigrate to the marine environment as subyearlings. During their juvenile freshwater phase of 

three to five months, juvenile Chinook salmon can inhabit a wide range of habitat types 

including large rivers, small streams, lakes, and estuaries (Healey 1991). Ocean-type Chinook 

salmon commonly have two groups of emigrants; a group that moves downstream as fry and 

rears in estuaries, coastal ocean habitats, or lakes, and another group that rears in the river and 

emigrates as parr or smolts (Healey 1991). In some cases, fry may move into a nonnatal system 

(Murray and Rosenau 1989; Scarnecchia and Roper 2000; Tabor et al. 2011b). Primarily, 

Chinook salmon from the Lake Washington watershed immigrate to the lake in late January 

through early June and most migrate through the Lake Washington Ship Canal towards Puget 

Sound by mid-July (Lisi 2019). 
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In the Lake Washington system, there are several small, independent tributaries to Lake 

Washington and Lake Sammamish that do not provide spawning habitat but can be important as 

juvenile Chinook salmon rearing areas (Tabor et al. 2011b).  Two potential south Lake 

Washington nonnatal tributaries within the City of Seattle are Mapes and Taylor creeks. Both 

streams are small to medium-sized (< 2 cfs baseline discharge) and are relatively close to the 

Cedar River (the major Chinook salmon spawning river for this system). In 2014, the lower 130 

m (427 ft) of Mapes Creek was daylighted (stream channel was reconfigured from an 

underground culvert to a more natural stream channel at the surface) to provide stream habitat 

for juvenile Chinook salmon. The lower reach of Taylor Creek is slated to be restored within the 

next few years and pre-project evaluation and monitoring has been conducted since 2015. 

 The objective of this study was to assess the effectiveness of the restoration efforts at 

Mapes Creek, as well as determine pre-restoration conditions in Taylor Creek to provide both 

restoration design recommendations and the ability to assess project performance (by comparing 

pre- to the post-restoration conditions). Our primarily objective was to determine the abundance 

and distribution of juvenile Chinook salmon in both streams from January to June when they 

could be present. This was accomplished through nighttime visual surveys (snorkeling and 

surface observations). Additionally, we collected information on how juvenile Chinook salmon 

use the delta areas of both creeks. This included beach seining during base flow (no rain) and 

high (rain) flow conditions to determine if the abundance of juvenile Chinook salmon increases 

during rain events (Tabor et al. 2011b). We also assessed the diet of juvenile Chinook salmon to 

determine if lake-dwelling Chinook salmon feed on prey that originated from the two streams, 

especially during rain events. Lastly, backpack electrofishing surveys of both streams were 

conducted during the summer low flow period to collect some basic information on the 

abundance and distribution of other fish species. This included sampling in the upper reaches of 

Taylor Creek to document pre-project conditions. 

 
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Study Site 

The two study streams are two small independent tributaries to the southwest part of Lake 

Washington (Figure 1). This general area is located in the lower Lake Washington watershed 

which is in the central east part of the Puget Sound region. The watershed has three major 

Chinook salmon spawning tributaries: Cedar River, Bear Creek, and Issaquah Creek as well as 

two large lakes, Lake Washington (9,495 ha [23,462 acres]; 33 m [108 ft] mean depth) and Lake 

Sammamish (1,980 ha [4,893 acres]; 17.7 m [58 ft] mean depth), all of which provide rearing 

areas for juvenile Chinook salmon. In both lakes, juvenile Chinook salmon commonly inhabit 

shallow, nearshore areas (i.e., < 1 m [3.3 ft] bottom depth) from January to May (Koehler et al. 

2006; Tabor et al. 2011a) and may move into several nonnatal tributaries (Tabor et al. 2011b). 

Besides naturally-produced fish, juvenile Chinook salmon in this watershed also come from the 

Issaquah Creek Hatchery, which are typically released in May. In May and June, naturallyproduced juvenile Chinook salmon use deeper waters (Tabor et al. 2011a) and together with 

hatchery-produced juvenile Chinook salmon appear to be widely dispersed throughout Lake 

Washington before emigrating through the Lake Washington Ship Canal to Puget Sound with a 

peak emigration in June. 

Mapes Creek (mouth, 47.523639°, -122.262678°). -- Mapes Creek is a small tributary (stream 

length, 2.0 km [1.2 miles]) to Lake Washington and is located in the southeast part of Seattle. 

The stream’s drainage basin is roughly 37 ha (91 acres) and is in a highly urbanized area and the 

entire lower 900 m (2,952 ft) of the stream was located in a culvert until 2014, when the lower 

130 m (427 ft) of the stream was daylighted (Figures 2 and 3). Beside daylighting the stream, 

the restoration project included substrate and rootwad enhancement, and riparian planting to 

increase overall habitat productivity for juvenile Chinook salmon. Before 2014, the lower 130 m 

(426 ft) of stream was located over two meters underground in a culvert. Because of poor light 

conditions in the deep culvert and the culvert being below their preferred depth, we assumed that 

juvenile Chinook salmon did not use Mapes Creek. Upstream sections (upstream of the main 

culvert) of Mapes Creek are generally small with mostly fine, sandy substrates (Tabor et al. 

2010). Electrofishing surveys of upper Mapes Creek in 2006, found the only fish species present 

upstream of the culvert was threespine stickleback (Gasterosteus aculeatus) (Tabor et al. 2010). 
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FIGURE 1.- South end of Lake Washington displaying the two study streams (Mapes and Taylor creeks), as 

well as Johns Creek, another nonnatal stream commonly used by juvenile Chinook salmon. Red ovals indicate the 

study reaches. The downstream oval on Taylor Creek indicates the primary study reach (lower Taylor Creek) while 

the upstream oval indicates the additional stream reach (upper Taylor Creek) used only for summer electrofishing 

surveys. The lower section of the Cedar River (primary Chinook salmon spawning river) is also shown.

Lower Taylor Creek reach

Upper Taylor Creek reach
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FIGURE 2.- Photo of Mapes Creek shortly after the completion of the stream daylighting restoration 

project. Photo taken 1/21/2015 by Roger Tabor. 

FIGURE 3.- Photo of Mapes Creek and established bank vegetation. Photo was taken 5/19/2017 by Roger 

Tabor. The photo was taken a few meters upstream from where the photo in Figure 2 was taken (note the walking 

bridge in both photos). 
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Taylor Creek (mouth, 47.512271°, -122.246217°).-- Taylor Creek is also a small tributary 

(stream length, 4.3 km [2.7 miles]) to Lake Washington (Figure 4) in the southeast part of the 

City of Seattle and is located roughly 1.6 km (1 mile) southeast of Mapes Creek (Figure 1). The 

stream’s drainage basin is roughly 250 ha (618 acres). A large restoration project (Taylor Creek 

Culvert Replacement C399015) is planned for the lower section of the stream. This project will 

replace a failing culvert under Rainier Avenue S with a fish passable culvert, improve fish 

passage by removing other barriers, as well as provide improved habitat conditions for juvenile 

Chinook salmon in the lower channel, mouth, and delta. The Taylor Creek Culvert Replacement 

project will also maximize floodplain storage in the lower creek and help address storm-related 

flooding, restore a more balanced sediment transport regime to reduce the rate of coarse 

sediment deposition at the mouth of the creek, and improve instream and riparian habitat. The 

culvert under Rainier Avenue is considered an impassable barrier to upstream movement of all 

fish. Upstream, pools are infrequent and those that are present are usually small and shallow. In 

the headwaters, the stream splits into two forks (East and West forks). Electrofishing surveys of 

Taylor Creek in 2006, found a variety of fish species were present downstream of Rainier Ave 

but only cutthroat trout (O. clarkii) and juvenile coho salmon (O. kisutch); were present upstream 

of Rainier Avenue S (Tabor et al. 2010). Because of the impassable barrier under Rainier 

Avenue, juvenile coho salmon were believed to be from some type of outplanting, such as a 

school class project. 

FIGURE 4.- Photo of the mouth of Taylor Creek and delta habitat with Lake Washington in the background. 

The concrete slab in the bottom right of the photo is severely undercut and was consistently used by juvenile 

Chinook salmon. Photo taken 3/23/2017 by Roger Tabor. 
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Methods 

Standard Chinook Salmon Abundance Surveys 

 From 2015 to 2017, lower Mapes Creek, lower Taylor Creek, and reference sites were 

surveyed twice per month from late January to early June to determine the abundance of juvenile 

Chinook salmon. In 2018 and 2019, lower Taylor Creek was surveyed once a month. Lower 

Mapes Creek was not surveyed in 2018 due to the water quality concerns of snorkeling. 

However, Mapes Creek was surveyed again in 2019 (once a month) but only consisted of 

walking surveys with no snorkeling. Visual surveys were conducted at night when juvenile 

Chinook salmon are relatively inactive and more easily observed and counted. This also allowed 

us to have minimal impact on juvenile Chinook salmon and limit the need to handle fish. Visual 

observations in deep water habitats (pools, glides [Taylor Creek only], stream deltas, and lake 

reference sites) were conducted by a snorkeler who slowly moved upstream and counted fish 

with the aid of an underwater light. Because shallow areas are difficult to snorkel effectively, we 

conducted surface observations in these habitats. Observers slowly walked upstream and 

counted fish with the aid of high-powered lights. The use of surface observations has been 

shown to be effective for studying juvenile salmonid habitat use in lotic systems where there is 

little surface turbulence (Heggenes et al. 1990). Fish observed were identified to the lowest 

possible taxonomic level and counted. Trout were categorized as fry, small, medium, or large 

based on their size. Based on length frequencies, we thought these four size categories were an 

approximation of year classes: 0+, 1+, 2+, and 3+. Trout fry were not observed until March and 

were generally 25 to 40 mm FL in March and April but could be as long as 80 mm FL in June. 

For small trout, we used the lower size limit of this size class as 60 mm FL in January through 

April but switched to the lower size limit of 80 mm FL in May and June. We used 130 mm FL as 

the upper limit of this size class. Medium-sized trout were those 130-200 mm FL and large trout 

were those > 200 mm FL. We assumed all trout observed during these visual nighttime surveys 

were cutthroat trout because all trout collected during electrofishing sampling were cutthroat 

trout. Sculpin (Cottus spp.) were split into two categories, small (< 75 mm TL) and large (> 75 

mm TL). Other species observed were categorized as juvenile, sub-adult, or adult. 

Because riffles in Taylor Creek were steep and difficult to visually count fish, we also 

sampled three or four short riffle sections (each 2 to 5 m long) once a month (February-May) 
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with electrofishing equipment. Two frame nets were used to allow stunned fish to float 

downstream into the net with the current. After sampling was completed in each riffle section, 

captured fish were placed in an anesthetizing bath of MS-222 (tricaine methanesulfonate). Fish 

collected were identified, counted, and fish lengths were measured (total length for sculpin [TL], 

fork length for all other fish [FL]). 

Before surveys were conducted each year, we divided each stream reach into habitat units 

(pools, glides, and riffles) based on physical characteristics (Appendices 1-3). The pool created 

at the stream mouth, caused by backed up water from the lake level, was classified as a 

convergence pool. Other pools upstream of the convergence pool had a maximum depth ≥ 0.35 

m (1.15 ft). Glides or shallow pools were other slow water habitats that had a maximum depth < 

0.35 m (1.15 ft). Riffles were areas that had noticeable surface turbulence with increased water 

velocities. The length of each site was measured along the thalweg. The wetted width was 

measured at 25%, 50%, and 75% of the length of the habitat unit to obtain an average wetted 

width. The maximum depth and tailout depth were measured in each pool and glide. Substrate 

was categorized by visually identifying substrate types and estimating the percentage of each 

substrate category within each habitat unit. Substrate categories were sand (< 2 mm [0.1 

inches]), fine gravel (2-12 mm [0.1-0.5 inches]), coarse gravel (12-64 mm [0.5-2.5 inches]), 

cobble (64-256 mm [2.5-10 inches]), and boulder (> 256 mm [> 10 inches]). Additional habitat 

surveys were conducted as needed to document the habitat changes because the lake level rose 

approximately 0.6 m (2 ft) each year from January to June and because of two high-flow events 

in 2017 that altered some habitat units. Stream gradient was measured once on May 18, 2017 

(Table 1) using a 7.6-m (25 ft) long plastic tube (10-mm inside diameter) filled with water to 

serve as a leveling device. Readings (vertical drop and distance between ends of plastic tube) 

were taken along the entire length of each study reach. The method is similar to that described 

by Walkotten and Bryant (1980). 

 
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Stream

 Section Gradient (%)

Mapes 1.04

Taylor 3.25

 L-1 2.60

 L-2 2.59

 L-3 3.46

TABLE 1. - Stream gradient (%) for lower Mapes Creek and three study sections of lower Taylor Creek, 

May 18, 2017. An overall gradient value is also given for lower Taylor Creek (all three stream sections combined). 

The stream habitat in lower Taylor Creek was divided into three stream sections (L-1, L2, and L-3) to help evaluate juvenile Chinook salmon distribution (Figure 5). The L-1 stream 

section (≈ 45 m long [148 ft]) included the convergence pool and a series of small pools, glides 

and riffles. Habitat conditions in this section changed as the lake level rose each year. The L-2 

stream section (≈ 52 m long [170 ft]) began at the downstream end of a long riffle (≈ 42 m long 

[138 ft]) and also included a glide (within a culvert) and a plunge pool at the upstream end. The 

L-3 stream section was approximately 42 m (138 ft) long for 2015 surveys and for the first few 

2016 surveys. After April 21, 2016, this section was expanded about 23 m (75 ft) upstream to 

include additional habitat units. 

A small barrier separated the L-2 and L-3 stream sections. In 2015-2017, the barrier 

consisted of a ≈ 0.24 m (0.79 ft) hydraulic drop over a large boulder that was presumably placed 

in the stream for some aesthetic reason (Figure 6). In late 2017 or early 2018, this small barrier 

was substantially reduced because sediments accumulated behind the passable culvert (Figure 5) 

located 3 m downstream of this barrier. The sediments caused the water level to rise in the 

plunge pool below the barrier, effectively allowing complete fish passage (Figure 6). 

 
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FIGURE 5.- Overhead photo of the lower reach of Taylor Creek displaying the three stream sections (L-1, 

L-2, and L-3) used to evaluate juvenile Chinook salmon abundance and distribution. The locations of the two delta 

snorkel transects are also displayed (Delta A was the main delta transect while Delta B was used a lakeshore 

reference transect). The location of a rock barrier that was a partial barrier to small-bodied fishes is indicated. The 

downstream end of the L-1 stream section is an area of the stream where habitat conditions changed with lake level. 

In January-March, this section was mostly a riffle and as the lake level rose in March to June, it progressively 

became a large convergence pool.
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FIGURE 6.- Before (left side) and after (right side) views of the rock barrier that was a small partial fish 

barrier (Figure 5) on lower Taylor Creek. In 2018, sediments accumulated upstream of a culvert located 

immediately downstream of the plunge pool shown in the photos which caused the water level to rise and eliminate 

the barrier. The yellow line in the upper left photo represents the approximate change in water level from 2006 to 

2019. The location of this site is shown in Figure 5. All photos were taken by Roger Tabor.

 

April 13, 2006 January 30, 2019

June 9, 2015 January 30, 2019
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Besides stream habitats, we surveyed the delta of each creek to determine how 

extensively they are used by juvenile Chinook salmon. The delta-transect length at Mapes Creek 

did not vary and was always 11 m long (36 ft) (Figure 7). The delta-transect (Delta-A) length at 

Taylor Creek varied from 12 to 18 m (39-59 ft) with lake level. Also, we surveyed an additional 

lakeshore transect to help compare the abundance of juvenile Chinook salmon along the 

lakeshore with abundances at the delta and in the nonnatal tributary. At Mapes Creek, we also 

surveyed two nearby boat ramps (total length, 22.4 m [73.5 ft)) at Be’er Sheva Park to serve as a 

reference site (Figure 7). We chose this site because of its easy access and in earlier surveys, 

juvenile Chinook salmon appeared to be more abundant at this site than other nearby locations 

(Tabor et al. 2004). At Taylor Creek, we surveyed the outside area of the delta (Delta-B; length, 

26-39.5 m [85-130 ft]) which was not under the influence of streamflow from Taylor Creek 

(Figure 5). For all the delta and other lakeshore transects, the snorkeler swam parallel to the 

shore along the 0.4-m (1.3 ft) depth contour. Transect widths were standardized at 2.5 m (8.2 ft). 

Snorkelers visually estimated the transect width and calibrated their estimation at the beginning 

of each survey night by viewing a pre-measured staff underwater. Stream and lakeshore 

temperature were also recorded on each survey night. 

FIGURE 7.- Overhead photo of the lower reach of Mapes Creek in Be’er Sheva Park displaying the stream 

section used to evaluate juvenile Chinook salmon abundance and distribution. The locations of the delta and 

reference site transects (Be’er Sheva Park boat ramps) are also displayed. The orange circle is the outlet of the 

culvert (dotted orange line) that runs under Seward Park Avenue S and S Henderson Street. The approximate upper 

extent of the convergence pool is shown with a yellow dotted line. The size of the convergence pool varied with lake 

level; it was not present in January and reached its upper extent in May or June. 
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Delta Rain Event Surveys 

Beach seine sampling was conducted periodically in 2015 through 2017 to determine if 

juvenile Chinook salmon move (primarily from other lakeshore areas) into the stream delta area 

following rain events, presumably to forage on prey displaced downstream (Tabor et al. 2011b). 

Beach seining was conducted shortly after or during a rain event if stream discharge became 

noticeably higher. We used discharge levels at Kelsey Creek (east Lake Washington tributary; 

USGS gauge 12120000) and weather forecasts to determine when would be an appropriate time 

to sample (Table 2). Seining was also repeated several days later, after stream discharge returned 

to baseline conditions. For each sampling event, 2 to 3 beach seine hauls were conducted at the 

stream mouth, as well as at a nearby reference site on the lake shore. We used the Be’er Sheva 

Park boat ramps as the reference site for Mapes Creek and used the outside delta area (Delta B) 

as the reference site for Taylor Creek. The seine was deployed offshore and set parallel to shore 

so the stream mouth could be encircled by the seine. The seine was then pulled to shore towards 

the two corners of the delta habitat unit or lake reference site. We used a small beach seine that 

was 6-m (20 ft) long and 1.3-m (4.3 ft) deep with a 1.15-m (3.8 ft) deep by 1.3-m (4.3 ft) long 

bag in the middle (Figure 8). The mesh size in the wings was 8-mm (0.3 inches) stretch mesh 

while the bag was 4-mm (0.16 inches) stretch mesh. Fish collected in the seine were counted, 

identified to species, and their length measured. 

In 2017, we also collected diet samples to determine if lake-dwelling Chinook salmon use 

prey that is displaced downstream during rain events. For each date and location, we collected 

diet samples from a maximum of five Chinook salmon to minimize handling of this ESA-listed 

fish. These Chinook salmon were anaesthetized with MS-222, the fork length was measured, and 

their stomach contents were removed through gastric lavage (Figure 8). Stomach contents were 

put in plastic bags, placed on ice, and froze. In the laboratory, each stomach sample was thawed 

and examined under a dissecting microscope. Stomach contents were separated into major prey 

taxa. Aquatic insects and crustaceans were identified to order while other invertebrate prey 

items were identified to a convenient taxonomic group. Additionally, the order Diptera was 

divided into Chironomidae and other Diptera because Chironomidae often represents the most 

important prey group (Koehler et al. 2006; Tabor et al. 2011b). Each prey group was enumerated 

and then blotted for 10 seconds on a paper towel and weighed to the nearest 0.0001 g. After 

processing, samples were placed in vials with 70% ethanol and stored for reference. 
17

To describe the diet of juvenile Chinook salmon, we calculated the mean percent by 

number (MN), mean percent by weight (MW), and frequency of occurrence (%O) for each major 

prey category (Chipps and Garvey 2007). To help compare the diet of juvenile Chinook salmon 

between different locations and weather conditions (rain versus no rain), we also calculated 

Schoener’s diet overlap index (Schoener 1971): 

      Cxy 5 pxi pyi 1 0.

where Cxy is the index value, pxi is the proportion of major prey taxa i (MWi) used by Chinook 

salmon at site x and pyi is the proportion of major prey taxa i (MWi) used by Chinook salmon at 

site y. Diet overlap index values can range from 0 (no overlap) to 1 (complete overlap). 

Researchers commonly use an overlap index level of 0.6 or less to indicate a significant 

difference in diet (Zaret and Rand 1971; Johnson 1981). Additionally, a diet breadth index (B; 

Levins 1968) was calculated to determine if Chinook salmon utilize a wider variety of prey types 

at the tributary mouths in comparison to the lake shore: 

 

 2

1

pi

B

where pi is the proportion of the diet represented by food type i. Diet breadth index values can 

range from 1 (only one prey item in the diet) to infinity. 

TABLE 2. Peak discharge levels (cfs) at Kelsey Creek (east Lake Washington tributary; USGS station 

12120000, a.k.a. Mercer Creek) that were used to determine when high and low discharge conditions should be 

present at Taylor and Mapes creeks. Beach seining at the deltas of Taylor and Mapes creeks was conducted on these 

dates to determine if there was a numerical response by juvenile Chinook salmon to increased discharge levels.  

Date Treatment Discharge (cfs) 

March 15, 2015 Rain (high flow) 313

March 26, 2015 No rain (low flow) 20

March 1, 2016 Rain (high flow) 112

March 4, 2016 No rain (low flow) 22

February 15, 2017 Rain (high flow) 223

February 28, 2017 No rain (low flow) 34

March 7, 2017 Rain (high flow) 81

March 20, 2017 No rain (low flow) 32

March 23, 2017 No rain (low flow) 21

April 5, 2017 Rain (high flow) 69

April 15, 2017 No rain (low flow) 22
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FIGURE 8.-- Photographs of the Chinook salmon diet sampling effort. Top photograph: Zachary Moore, 

Roger Tabor, and Matthew Webster pulling in a seine haul at the mouth of Taylor Creek. Bottom photograph: 

Zachary Moore lavaging a juvenile Chinook salmon. Both photographs taken on 3/7/2017 by Jennifer Fields, 

USFWS. 
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Chinook Salmon Diet - 2018 

In 2018, additional diet samples were collected to examine differences in the diet of 

Chinook salmon between the major areas of Taylor Creek. Of particular interest was whether 

Chinook salmon at the delta were using prey from Taylor Creek (e.g., mayflies, stoneflies, and 

caddisflies) or from the lakeshore (e.g., zooplankton). Samples were collected in the stream, 

delta, and at a lakeshore reference site (Be’er Sheva boat ramp). Diet samples were collected on 

three occasions: April 5, May 3, and May 14. For each date and at each site, we attempted to 

collect 10 diet samples. Chinook salmon were collected with either beach seines, electrofishing 

equipment, or dip netting at night with the aid of hand-held lights. Field and laboratory methods 

as well as data analyses were the same as for the delta rain event samples (see above). 

Summer Electrofishing Surveys 

Each year (2015-2109), one complete single-pass electrofishing survey in June was 

conducted to provide detailed information on fish species presence and distribution in the lower 

Taylor Creek and lower Mapes Creek study reaches. In 2018 and 2019, additional single-pass 

electrofishing surveys were conducted in the upper Taylor Creek to provide further data on preproject conditions (Figures 1 and 9). To increase our sample size for later comparisons, we used 

two stream sections (U-2 and U-3) in upper Taylor Creek that had been sampled previously as 

part of other studies (Tabor et al. 2010; King County 2015). The U-2 section is 55-m (180 ft) 

long and is located between a culvert on 68th Ave S and a culvert on Holyoke Way S. This 

section was originally sampled in 2005 (Tabor et al. 2010). The U-3 stream section is 150-m 

(492 ft) long and is located immediately upstream of the culvert on Holyoke Way S. This 

section was originally sampled once a year during the summer in 2010 and 2012 to 2013 (King 

County 2015). In 2011, a different stream section (U-1) was sampled as part of the King County 

surveys (King County 2015). This section is 150-m (492 ft) long and located along the north 

part or 68th Ave S and included five small bridges (i.e., driveways) over the stream. We also 

present data from this section to give a more comprehensive review of recent pre-project 

sampling efforts. 

Electrofishing surveys were conducted during the summer low flow period in June or 

July to minimize the risk of stunning and handling protected Chinook salmon or to coincide with 
20

previous sampling efforts. We collected fish with a Smith-Root Model 12® electrofisher 

system. Electrofishing was conducted with pulsed DC current set at 300 volts. Electrofishing 

was conducted in an upstream direction with one or more netters following behind or alongside 

the electrofisher operator to collect stunned fish. In pools and glides, stunned fish were removed 

from the stream with long handle dip nets. In riffles, one or two frame nets was also used to 

allow stunned fish to float downstream into the net with the current. Once fish were captured, 

they were placed in a recovery bucket with an aerator to await processing. 

After sampling was completed in each habitat unit, captured fish were placed in an 

anesthetizing bath of MS-222 (tricaine methanesulfonate). Fish collected were counted, 

identified, and fish lengths were measured. Fish were identified and measured for fork length 

(salmonids and threespine stickleback) or total length (TL: nearest mm; sculpin and western 

brook lamprey [Lampetra richardsoni]) and many were weighed (nearest 0.1 g). The percent of 

fish weighed varied depending on time constraints. Once fish were processed, they were placed 

in a recovery bucket with an aerator until they were recovered and then they were placed back 

into the same general area where they were collected. A few unidentifiable small sculpin were 

retained for identification in the laboratory. 

In addition to determining the number of fish caught, we also estimated the total weight 

of all fish captured. To estimate the weight of fish that were not weighed, we used the following 

regressions developed from fish from stream monitoring efforts of Taylor Creek and other Puget 

Sound streams (King County 2015): western brook lamprey, weight (g) = 0.00000342TL2.856 (r2

= 0.93; n = 1,282); cutthroat trout, weight (g) = 0.00001601FL2.916 (r2

 = 0.99; n = 231 [Taylor 

Creek only]); coho salmon, weight (g) = 0.00001351FL2.978 (r2 = 0.96; n = 5,501); threespine 

stickleback, weight (g) = 0.00000814FL3.082 (r2 = 0.96; n = 373); coastrange sculpin (C. 

aleuticus), weight (g) = 0.00000419TL3.241 (r2 = 0.97; n = 6,047); prickly sculpin (C. asper), 

weight (g) = 0.00000632TL3.142 (r2

 = 0.98; n = 424). 

For habitat measurements of lower Mapes Creek, lower Taylor Creek, and the U-2 site in 

upper Taylor Creek, we used existing habitat data collected from the standard Chinook salmon 

abundance surveys. Habitat measurements at the U-3 site followed the protocols of WDOE 

(2009) which were used in 2010 and 2012-2013 surveys (King County 2015). 

 
21

FIGURE 9.- Overhead photo of upper Taylor Creek displaying the three stream sections (U-1, U-2, and U-3) 

used to evaluate fish distribution.
22

Results 

Standard Chinook Salmon Abundance Surveys 

Mapes Creek.— For all the Mapes Creek sites from 2015 to 2017 combined, a total of 1,805 

juvenile Chinook salmon were observed which included 1,503 in the stream, 46 along the delta 

transect, and 256 along the Be’er Sheva boat ramp transect (Table 3). In 2019, only the stream 

was surveyed and a total of 90 juvenile Chinook salmon were observed. The annual pattern of 

juvenile Chinook salmon use of Mapes Creek was consistent from 2015 to 2017. The abundance 

increased sharply from January through February with a peak in early March and then declined 

sharply in April and May (Figure 10; Appendix 4). The peak abundance of 244 fish (0.94 

fish/m2) occurred on March 6, 2017. The peak number of Chinook salmon observed in Mapes 

Creek increased each year from 70 in 2015 to 244 in 2017 (Table 3). Unlike the 2015-2017 

surveys, few Chinook salmon were observed in the February and March 2019 surveys (Figure 

10). The 2019 peak count of 57 Chinook salmon occurred on April 24. 

During 2015-2017 surveys, juvenile Chinook salmon were well distributed throughout 

the 130 m (427 ft) restored reach (Figure 11). However in 2019, most of the juvenile Chinook 

salmon were found in the lower part of the stream in the deep, convergence pool. This likely was 

because few were present until April when they were larger and primarily used the deeper waters 

of the convergence pool. Overall, juvenile Chinook salmon were found primarily in glides (range 

of maximum depths, 0.13 to 0.26 m [0.43-0.85 ft]) in January through March and then shifting to 

deeper water habitats (i.e., convergence pool [range of annual maximum depths, 0.42 to 0.59 m 

(1.3-1.9 ft)] and a pool at the upstream end [range of annual maximum depths, 0.41 to 0.5 m 

(1.3-1.6 ft)] in May. In comparison to the lakeshore reference site (nearby boat ramps), the 

density of juvenile Chinook salmon in Mapes Creek was generally higher in January through 

March but in April through June the density was usually higher at the lakeshore reference site. 

Juvenile Chinook salmon were also observed at the delta of Mapes Creek but their density was 

almost always lower than the lakeshore reference site at the Be’er Sheva Park boat ramps (Figure 

10). 

In addition to juvenile Chinook salmon, other salmonids also used the restored reach of 

Mapes Creek, albeit at lower densities than Chinook salmon (Figure 12). Both cutthroat trout 

(74% of the other salmonids observed) and coho salmon (26% of the other salmonids observed; 
23

Location 

aaaYear

Number of 

surveys

Number of 

Chinook 

observed

Peak Number 

of Chinook 

observed

Number of 

surveys

Number of 

Chinook 

observed

Peak Number 

of Chinook 

observed

Stream

2015 9 193 62 8 92 23

2016 10 380 133 10 168 44

2017 10 930 244 10 590 157

2018 0 - - - - 4 401 123

2019 5 90 57 5 264 145

Total 34 1,593 244 37 1,515 157

Delta

2015 9 7 5 8 30 12

2016 10 21 8 10 76 16

2017 10 18 6 10 113 46

2018 0 - - - - 4 142 81

2019 0 - - - - 5 24 7

Total 29 46 8 37 385 81

Lakeshore reference

2015 9 43 18 8 11 7

2016 10 76 18 10 27 7

2017 10 137 47 10 82 19

2018 0 - - - - 4 27 18

2019 0 - - - - 5 9 7

Total 29 256 47 37 156 19

Mapes Creek Taylor Creek

subyearlings and yearlings) were observed in Mapes Creek. For all 34 surveys combined (2015-

2017, 2019) in Mapes Creek, we observed 368 cutthroat trout, and 124 coho salmon. Overall, 

54% of the total other salmonids were observed in the plunge pool at the upper end of the 

restored reach. Of those, 79% were cutthroat trout and 21% were coho salmon; however, water 

visibility conditions in that pool often made it difficult to accurately identify the fish and the 

relative difference in abundance between the two species may not be accurate. We did conduct 

one electrofishing survey of the plunge pool on February 28, 2016 to check the species 

composition and 7 cutthroat trout (range, 72-111 mm [2.8-4.4 inches] FL) and 4 coho salmon 

(range, 79-109 mm [3.1-4.3 inches] FL) were collected. This ratio was similar to what we 

typically observed when we snorkeled the plunge pool. 

TABLE 3. -- Summary of the total number and peak number of juvenile Chinook salmon observed during 

standard nighttime abundance surveys in Mapes Creek and Taylor Creek. These surveys were a combination of 

surface (riffles and glides) and snorkeling observation (pools) surveys. The lakeshore reference sites were the Be’er 

Sheva boat ramps for Mapes Creek and the Delta-B transect for Taylor Creek. The Delta site for Taylor Creek was 

the Delta A transect. Mapes Creek was not surveyed in 2018. 

 
24

FIGURE 10.-- Juvenile Chinook salmon density (Chinook /m2

) in lower Mapes Creek and along two lake 

transects: Mapes Creek delta and a lakeshore reference site (Be’er Sheva Park boat ramps), 2015-2017. For the lake 

transects (reference and delta), surveys were all snorkeling surveys; while for the stream, surveys were a 

combination of surface (riffles and glides) and snorkeling observations (pools) surveys. Note that the density scale 

is different for 2017 when fish density was substantially higher. 
25

FIGURE 11.—Cumulative percent of the number of juvenile Chinook salmon in lower Mapes Creek 

(dashed lines and solid symbols) and lower Taylor Creek (colored solid lines and open symbols) from the stream 

mouth to the upstream end of their distribution. Each data point represents the midpoint of a habitat unit. For each 

year, data are from the survey date with the highest abundance in the stream (Mapes Creek – 3/10/2015, 3/8/2016, 

3/6/2017, and 4/24/2019; Taylor Creek – 3/10/2015, 2/23/2016, 3/20/2017, 2/12/2018, and 4/24/2019). 
26

FIGURE 12. -- Density of other salmonids (fish/m2) observed in lower Mapes Creek and along two lake 

transects: Mapes Creek delta and a reference site (Be’er Sheva Park boat ramps), 2015-2019. For the lake transects 

(reference and delta), surveys were all snorkeling surveys; while for the stream, surveys were a combination of 

surface (riffles and glides) and snorkeling observations (pools) surveys. Other salmonids observed included 

cutthroat trout and juvenile coho salmon. We assumed all trout observed during these visual nighttime surveys were 

cutthroat trout because all trout collected during electrofishing sampling were cutthroat trout. 
27

Native, non-salmonids observed in Mapes Creek were primarily sculpins and threespine 

stickleback although no threespine stickleback were observed in 2017. Additionally, three dace 

(Rhinichthys sp.) were observed in 2015. Nonnative fishes were occasionally observed in Mapes 

Creek, which included 13 unidentified sunfish (Lepomis spp.), 4 juvenile smallmouth bass 

(Micropterus dolomieu), 3 rock bass (Ambloplites rupestris), and 1 yellow perch (Perca 

flavescens). Most of these fish were observed in the convergence pool. 

Taylor Creek.– For all the Taylor Creek sites, a total of 2,056 juvenile Chinook salmon were 

observed which included 1,515 in the stream, 385 along the delta (Delta A transect), and 156 

along the lakeshore reference site (Delta B transect; Table 3). Similar to Mapes Creek, the annual 

pattern of juvenile Chinook salmon use of Taylor Creek from 2015 to 2018 was generally 

consistent from year to year. The abundance increased sharply from January through February, 

with a peak in February or March, and then declined in April and May (Figure 13 and Appendix 

5). In 2019, the annual pattern was different than the previous four years with few juvenile 

Chinook salmon present until April. 

On all survey dates except one, the L-1 section of Taylor Creek had a higher density of 

juvenile Chinook salmon than in the L-2 section (Figure 13). Unlike Mapes Creek, juvenile 

Chinook salmon in Taylor Creek were concentrated near the stream mouth (Figures 11 and 14). 

Similar to Mapes Creek, densities were highest in 2017. Peak densities occurred in either 

February or March. The overall peak abundance of 157 fish occurred on March 20, 2017. The 

highest concentration of juvenile Chinook salmon was usually in a pool near the mouth of the 

stream (Figures 4 and 14). Overall, 51% (38% if the delta is included) of all juvenile Chinook 

salmon observed in Taylor Creek were observed in this pool. Within this pool, juvenile Chinook 

salmon were concentrated in the tailout, under a concrete slab on the right bank, or within 

emergent vegetation on the left bank (Figures 4 and 14). 

In 2015-2017 (rock barrier present), no Chinook salmon were found upstream of the 

barrier between the L-2 and L-3 stream sections. A few juvenile Chinook salmon were observed 

either immediately downstream of the rock barrier or a few meters farther downstream but never 

upstream of the rock barrier. In 2018 and 2019 (rock barrier absent), a few Chinook salmon (2 in 

2018 and 5 in 2019) were observed in the L-3 stream section. Observations of Chinook salmon 
28

in the L-3 stream section were in either late April or May surveys. The farthest upstream a 

Chinook salmon was observed was 155 m upstream of the confluence with Lake Washington, a 

few meters downstream from the upper end of the lower Taylor Creek survey reach. 

Juvenile Chinook salmon were also commonly observed along the Delta A (main delta 

area) transect; however, their density at this site varied widely among and within years (Figure 

13). Substrate along this transect was a mixture of sand, fine gravel, and coarse gravel. In 

general, juvenile Chinook salmon appeared to be concentrated in parts of this transect where 

there was some streamflow and sand was the predominant substrate. Along the Delta B (outside 

delta area or lakeshore reference) transect, densities were generally low and substantially less 

than along the Delta A transect. There was little to no streamflow along this transect and the 

substrate was predominantly coarse gravel and cobbles. 

Other salmonids observed in Taylor Creek were primarily cutthroat trout (Figure 15). 

Coho salmon (Figure 16) were occasionally encountered. On average, 47.8 cutthroat trout were 

observed on each survey night. For all 37 surveys combined (2015-2019) in Taylor Creek, we 

observed 1,768 cutthroat trout, and 68 coho salmon. All four size classes of cutthroat trout were 

commonly observed throughout Taylor Creek. Cutthroat trout fry (0+ fish) were typically 

observed during the April-June surveys and their abundance varied widely between years. Peak 

counts ranged from 70 in 2016, 33 in 2019, 10 in 2015, 7 in 2017, and 1 in 2018. Overall, the 

small size-class (80-130 mm FL [3.1-5.1 inches]) made up 47.8% of the trout observed while the 

medium and large size-classes made up 27.2% and 8.6%, respectively. In the L-3 stream section, 

cutthroat trout were by far the most abundant fish, representing 93% of the fish observed. 

Cutthroat trout densities in the L-3 stream section were consistently higher than in the other two 

sections (Figure 17). Unlike the L-1 and L-2 stream sections, the L-3 section had several glides 

and pools and each of these habitats usually had at least one cutthroat trout (mean, 2.95; 

maximum, 14). 

 
29

FIGURE 13.-- Juvenile Chinook salmon density (fish /m2) observed in five sections of lower Taylor Creek 

from 2015-2019. Surveys were a combination of surface (riffles) and snorkeling observations (glides and pools). 

Juvenile Chinook salmon were only observed in the L-3 stream section in 2018 and 2019. Note that the density 

scales are different for each year, and fish density was substantially higher in 2017 and 2018. Locations of the 

different sections are shown in Figure 5. 
30

FIGURE 14. – Juvenile Chinook salmon in the lower section of Taylor Creek. Photo was taken by Roger Tabor 

during the day (3/23/2017) in the lower stream section near the concrete slab shown in Figure 4. 
31

 

FIGURE 15. – Photographs of a juvenile (top photo) and an adult (bottom photo) cutthroat trout in lower 

Taylor Creek. Photos were taken by Roger Tabor during night snorkel surveys (top photo, 5/13/2019; bottom photo, 

6/6/2017). 
32

FIGURE 16. - Juvenile coho salmon in the plunge pool at the upstream end of the L-2 section of lower 

Taylor Creek. Photo taken by Roger Tabor during a night snorkel survey on 6/6/2017. 
33

FIGURE 17. -- Cutthroat trout density (fish /m2) observed in three sections of lower Taylor Creek (2015-

2019) during visual nighttime surveys that were a combination of surface (riffles) and snorkeling observations 

(glides and pools). We assumed all trout observed during these visual nighttime surveys were cutthroat trout 

because all trout collected during electrofishing sampling were cutthroat trout. Sharp increases in cutthroat trout 

density in June 2015 and May-June 2016 were due to the increased presence of fry. Few cutthroat trout were 

observed on the delta transects and those data are not displayed. 
34

Similar to Mapes Creek, native non-salmonid fishes observed in lower Taylor Creek were 

primarily sculpins (Figure 18) and threespine stickleback (no threespine stickleback were 

observed in 2017-2019). In 2015-2017 (rock barrier present), only one sculpin was observed 

upstream of the rock barrier (i.e., in the upper section); whereas in 2018-2019 (rock barrier 

absent), a total of 26 sculpin were observed upstream of the rock barrier. Adult peamouth 

(Mylocheilus caurinus; n = 30) were also observed in lower Taylor Creek (in all three stream 

sections) and were all observed on May 22, 2017 and presumably were part of a seasonal 

spawning run from Lake Washington. Nonnative fishes were rarely observed in lower Taylor 

Creek, which included 1 bluegill (Lepomis macrochirus), 1 rock bass, and 4 yellow perch. All of 

these fish were observed in the L-1 stream section close to the stream mouth. 

FIGURE 18. Coastrange sculpin in the plunge pool at the upstream end of the L-2 section of Taylor Creek. 

Photo taken by Roger Tabor during a night snorkel survey on 6/6/2017. 

 
35

Length

Year Section surveyed (m) Chinook Cutthroat trout Trout fry Coastrange sculpin

2015 L-1 13.5 0 1 4 24

L-2 15 0 5 1 35

L-3 24.2 0 4 1 0

2016 L-1 12.4 1 3 14 28

L-2 25 0 6 2 59

L-3 37.4 0 6 16 3

2017 L-1 5.7 9 2 0 49

L-2 30 1 7 2 85

L-3 36.9 0 10 0 1

2018 L-1 5 5 0 0 16

L-2 35 0 9 0 82

L-3 37.7 0 4 0 11

2019 L-1 25 3 1 25 23

L-2 25 0 4 8 17

L-3 27.2 0 2 3 36

Totals 355 19 64 76 469

Number of fish

Riffles in Taylor Creek were sampled with electrofishing equipment on 20 occasions. A 

total of 19 juvenile Chinook salmon were collected and most were caught in the L-1 stream 

section (Table 4 and Appendix 6). No Chinook salmon were ever collected upstream of the rock 

barrier (L-3 stream section). A total of 140 trout were also collected and most were relatively 

small trout with only 13 fish > 100 mm FL (3.9 inches) (15.5%). Trout ≥ 60 mm FL (2.4 inches) 

(n = 64) were all identified as cutthroat trout and collected all five months. Trout ≤ 55 mm FL 

(2.2 inches) (n = 76) were primarily collected in May (75%) and considered 0+ trout fry, which 

we assumed were all cutthroat trout. The only sculpin species collected in the riffle 

electrofishing surveys was coastrange sculpin which represented 75% (469 of 628 fish) of all 

fish collected. In 2015-2017 (rock barrier present), a total of 280 coastrange sculpin were 

collected downstream of the rock barrier (stream sections L-1 and L-2) and only four (< 2% of 

total) were collected upstream of the rock barrier (stream section L-3). In 2018 and 2019 

combined (rock barrier absent), 138 coastrange sculpin were collected downstream of the old 

rock barrier location (stream sections L-1 and L-2) and 47 (34% of total) were collected 

upstream of the old rock barrier location (stream section L-3). Additionally, 2019 was the first 

year that more coastrange sculpin were collected in stream section L-3 than in either of the other 

two stream sections (Table 4).

TABLE 4.-- Number of fish collected in three stream sections during riffle electrofishing surveys in lower 

Taylor Creek, 2015-2019. 

 
36

Delta Rain Event Surveys 

Overall, we did not observe a numerical response of juvenile Chinook salmon to 

increased discharge levels at the deltas of Mapes or Taylor creeks. The number of juvenile 

Chinook salmon collected in delta beach seine sets following a rain event was higher than during 

no rain conditions (low flow) in only three of the five sampling periods in Taylor Creek and none 

in Mapes Creek (Figure 19). Catch rates among all treatments (delta and lakeshore) were highly 

variable and there was no apparent trend. Other fish species collected at both areas included 

primarily sockeye salmon (O. nerka) fry and sculpin (Table 5). 

FIGURE 19. -- Number of juvenile Chinook salmon collected per beach seine set during rain event sampling 

in Mapes and Taylor creeks from 2015-2017. ND = no data. Lakeshore reference sites were the Be’er Sheva boat 

ramps for Mapes Creek and the Delta B site (southeast part of fluvial fan without any streamflow) for Taylor Creek.

0

5

10

15

20

25

30

35

March 2015 March 2016 February 2017 March 2017 April 2017

# Chinook / set 

Taylor Creek

Delta - Rain

Delta - No Rain

Lakeshore - Rain

Lakeshore - No Rain

ND ND ND

0

5

10

15

20

25

30

35

March 2015 March 2016 February 2017 March 2017 April 2017

# Chinook / set 

Mapes Creek

ND ND ND
37

TABLE 5. -- Total number of juvenile Chinook salmon and other fishes captured with beach seine sets in 

Mapes and Taylor creeks from 2015-2017. Other salmonids include coho salmon and cutthroat trout. Other fish 

includes brown bullhead (Ameiurus nebulosus) and bluegill. Lakeshore reference sites were the Be’er Sheva Park 

boat ramps for Mapes Creek and the Delta B site (southeast part of fluvial fan without any streamflow) for Taylor 

Creek. 

  

The diet of most juvenile Chinook salmon collected in 2017 consisted largely of 

chironomids (primarily pupae and emerging adults; Table 6). At Mapes Creek, diet overlap 

values (C) among the delta-rain, lakeshore-rain, and lakeshore-no rain were all > 0.6 thus 

indicating their diets were relatively similar (Table 7). However, juvenile Chinook salmon from 

the delta-no rain sample also consumed several amphipods and one relatively large leech in 

addition to chironomids, which resulted in low diet overlap with other samples (C < 0.5) and the 

diet breadth was higher (B = 3.6 while the other samples ranged from 1.1 to 2.4). At Taylor 

Creek, diet overlap values (C) between the delta-rain sample and the no rain samples were 0.18, 

thus indicating their diets were significantly different (Table 7). Juvenile Chinook salmon had 

consumed several oligochaetes and ephemeroptera nymphs following the rain event, which 

represented 64% of the diet by weight and subsequently diet breadth index values (B) increased 

from 1.1 during no rain conditions to 3.4 following the rain event. 

Stream 

ffiiffffSample type Chinook Sockeye fry

Other 

salmonids Sculpin Stickleback Other fish

Mapes Creek

Delta - Rain 13 1 1 33 1 1

Delta - No rain 102 5 0 19 4 0

Lakeshore - Rain 48 3 1 0 0 0

Lakeshore - No rain 127 2 0 0 0 0

Total 290 11 2 52 5 1

Taylor Creek

Delta - Rain 63 3 6 12 0 0

Delta - No rain 101 32 2 7 0 0

Lakeshore - Rain 2 1 0 0 0 0

Lakeshore - No rain 20 32 0 4 0 1

Total 186 68 8 23 0 1

Number of fish collected 
38

TABLE 6.-- Diet composition of juvenile Chinook salmon at the delta of two Lake Washington nonnatal 

tributaries and two nearby lakeshore reference sites, March-April 2017. Samples were taken shortly after a rain 

event (high flow conditions in the streams) and when there had not been significant rain in the past 24 h (base flow 

conditions in the streams). MN = mean percent by number, MW = mean percent by weight, and %O = frequency of 

occurrence; n = the number of stomach samples that contained prey items.

Stream

   Location

       Prey category MN MW %O MN MW %O

Mapes Creek

   Delta

      n4 7

      Insects 78.69 74.20 100.00 30.00 58.47 100.00

         Chironomids 67.86 50.15 100.00 25.00 11.25 42.86

         Other aquatic insects 8.33 11.21 75.00 5.00 0.05 14.29

         Terrestrial insects 2.50 0.47 25.00 0.00 0.00 0.00

         Misc. insect parts 12.37 50.00 47.17 71.43

      Crustaceans 10.24 3.81 50.00 50.00 15.87 57.14

      Annelids 11.07 21.98 75.00 5.00 13.24 14.29

      Fish Eggs 0.00 0.00 0.00 15.00 12.42 14.29

   Lakeshore

      n8 7

      Insects 99.25 99.26 100.00 77.84 77.35 100.00

         Chironomids 95.78 77.16 87.50 69.57 40.52 100.00

         Other aquatic insects 2.54 0.89 25.00 0.65 0.95 14.29

         Terrestrial insects 0.93 1.43 25.00 7.62 3.16 42.86

         Misc. insect parts 19.78 37.50 32.72 85.71

      Crustaceans 0.00 0.00 0.00 22.16 22.65 71.43

      Annelids 0.75 0.74 12.50 0.00 0.00 0.00

Taylor  Creek

   Delta

      n7 5

      Insects 49.56 48.28 100.00 98.35 98.12 100.00

         Chironomids 27.11 19.28 85.71 93.36 71.87 100.00

         Other aquatic insects 20.25 20.75 57.14 0.00 0.00 0.00

         Terrestrial insects 2.20 0.28 14.29 4.99 2.90 60.00

         Misc. insect parts 7.97 57.14 23.36 80.00

      Crustaceans 11.34 5.61 71.43 0.91 0.75 20.00

      Annelids 35.74 43.02 71.43 0.00 0.00 0.00

      Fish Eggs 2.26 3.09 14.29 0.00 0.00 0.00

      Other 1.10 0.01 28.57 0.74 1.13 20.00

   Lakeshore

      n0 5

      Insects 100.00 89.50 100.00

         Chironomids 90.00 51.27 80.00

         Other aquatic insects 5.00 0.18 20.00

         Terrestrial insects 5.00 4.19 40.00

         Misc. insect parts 33.86 60.00

      Plant Material 10.50 20.00

Rain event No rain event
39

TABLE 7.-- Diet overlap index values (C) of juvenile Chinook salmon between stream deltas and lakeshore 

sites during different weather conditions, March-April 2017. Samples were taken shortly after a rain event (high 

flow conditions in the streams) and when there had not been significant rain in the past 24 h (base flow conditions in 

the streams). Diet overlap index numbers in bold indicate where there was little diet overlap (i.e., significant 

difference in diet; C < 0.6). ND = no data. 

1) Mapes Creek

Delta Lakeshore

No rain Rain No rain Rain

Delta   No rain  ‐‐‐‐‐‐  0.36 0.46 0.13

    Rain    ‐‐‐‐‐‐  0.63 0.62

Lakeshore   No rain      ‐‐‐‐‐  0.60

    Rain        ‐‐‐‐‐ 

2) Taylor Creek

Delta Lakeshore

No rain Rain No rain Rain

Delta   No rain  ‐‐‐‐‐‐  0.18 0.96 ND

    Rain    ‐‐‐‐‐‐  0.18 ND

Lakeshore   No rain      ‐‐‐‐‐  ND

    Rain        ‐‐‐‐‐ 
40

Chinook Salmon Diet - 2018

A total of 76 juvenile Chinook salmon were collected in 2018 for diet analysis. We were 

able to get a good sample (n ≥ 7) for each location and date except for the May 14 stream sample 

when we were only able to collect one sample. Similar to the 2017 diet sampling, the overall 

diet of juvenile Chinook salmon consisted largely of chironomids (primarily pupae and emerging 

adults; Table 8). The stream samples included more terrestrial insects and other aquatic insects 

than in the other samples. In contrast, the delta and lakeshore reference sites often included more 

microcrustaceans (cladocerans and copepods) than the stream site. Overlap index values (C) 

were all similar for the April 5 sample; however, the stream diet samples had a marginally 

significant difference (C = 0.5-0.6) from the other two sites for the May 3 and May 14 samples 

(Table 9). Diet index values (C) between the delta and lakeshore reference index were similar 

for all three dates. Because the diet consisted largely of chironomids, the diet breadth index 

values (B) were generally low (Table 10). The stream diet breadth index values (B) for May 3 

and May 14 were a somewhat higher due to the variety of terrestrial insects and other aquatic 

insects in the diet. 

 
41

TABLE 8.-- Diet composition of juvenile Chinook salmon in the stream area and delta of Taylor Creek and 

at one lakeshore reference site (Be’er Sheva boat ramps), April-May 2018. MN = mean percent by number, MW = 

mean percent by weight, and %O = frequency of occurrence; n = the number of stomach samples that contained prey 

items. 

Date

 Prey category MN MW %O MN MW %O MN MW %O

April 5

 n 8 10 10

 Insects 88.80 95.03 100.00 99.25 97.90 100.00 60.83 85.24 100.00

 Chironomids 79.84 88.45 100.00 97.21 95.51 100.00 51.16 76.44 100.00

 Other aquatic insects 5.50 4.31 37.50 1.63 0.50 40.00 5.75 2.82 40.00

 Terrestrial insects 3.46 2.16 25.00 0.40 0.37 10.00 3.92 4.79 30.00

 Misc. insect parts 0.11 25.00 1.52 30.00 1.20 10.00

 Microcrustaceans 11.00 2.16 25.00 0.00 0.00 0.00 39.17 5.91 80.00

 Fish 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

 Fish Eggs 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

 Other 0.20 2.81 50.00 0.75 2.10 60.00 0.00 8.84 60.00

May 3

 n 7 10 10

 Insects 83.62 77.34 100.00 63.30 90.11 100.00 60.71 85.19 100.00

 Chironomids 16.30 36.73 100.00 62.80 88.31 100.00 57.03 75.34 100.00

 Other aquatic insects 2.08 1.33 71.43 0.10 0.00 10.00 0.46 0.57 40.00

 Terrestrial insects 65.24 21.96 85.71 0.41 1.26 50.00 3.22 3.88 80.00

 Misc. insect parts 17.32 85.71 0.54 50.00 5.40 90.00

 Microcrustaceans 14.47 1.54 71.43 36.21 9.85 100.00 38.06 10.37 90.00

 Fish 0.00 0.00 0.00 0.00 0.00 0.00 0.31 0.69 10.00

 Fish Eggs 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

 Other 1.91 21.11 85.71 0.48 0.05 30.00 0.92 3.75 70.00

May 14

 n 1 10 10

 Insects 100.00 76.55 100.00 64.40 89.50 100.00 55.88 77.11 100.00

 Chironomids 61.54 43.72 100.00 59.78 83.75 100.00 50.13 62.62 100.00

 Other aquatic insects 23.08 29.01 100.00 0.13 0.01 10.00 0.95 1.99 40.00

 Terrestrial insects 15.38 1.63 100.00 4.48 5.48 60.00 4.79 8.72 100.00

 Misc. insect parts 2.19 100.00 0.25 40.00 3.78 70.00

 Microcrustaceans 0.00 0.00 0.00 33.68 8.47 100.00 42.70 17.29 100.00

 Fish 0.00 0.00 0.00 0.14 0.24 10.00 0.25 1.32 10.00

 Fish Eggs 0.00 13.31 100.00 0.00 0.00 0.00 0.00 0.02 20.00

 Other 0.00 10.14 100.00 1.78 1.80 100.00 1.17 4.26 80.00

Stream Delta Lakeshore
42

1) April 5

Stream Delta Lakeshore

Stream ----- 0.91 0.86

Delta ----- 0.86

Lakeshore -----

2) May 3

Stream Delta Lakeshore

Stream ----- 0.54 0.57

Delta ----- 0.88

Lakeshore -----

3) May 14

Stream Delta Lakeshore

Stream ----- 0.51 0.52

Delta ----- 0.78

Lakeshore -----

Location April 5 May 3 May 14

Stream 1.23 3.11 2.62

Delta 1.03 1.25 1.36

Lakeshore 1.37 1.50 2.00

Date

TABLE 9.-- Diet overlap index values (C) of juvenile Chinook salmon among stream area and delta of 

Taylor Creek and one lakeshore reference site (Be’er Sheva boat ramps), April-May 2018. All samples were taken 

under base flow conditions. Diet overlap index numbers in bold indicate where there was little diet overlap (i.e., 

significant difference in diet; C < 0.6).

TABLE 10.-- Diet breadth index values (B) of juvenile Chinook salmon among stream area and delta of 

Taylor Creek and one lakeshore reference site (Be’er Sheva boat ramps), April-May 2018. All samples were taken 

under base flow conditions. Diet breadth index values can range from 1 (only one prey item in the diet) to infinity.

 
43

Summer Electrofishing Surveys 

Mapes Creek.– Salmonids (cutthroat trout, coho salmon, and Chinook salmon) only 

comprised 5.7% of the catch (Table 11). Cutthroat trout ranged in size from 104 mm to 194 mm 

FL. Coho salmon consisted of both juveniles (range, 65 mm to 92 mm FL [2.6-3.6 inches]) and 

smolts (range, 120 mm to 162 mm FL [4.7-6.4 inches]). Juvenile coho salmon were collected 

primarily in the pool at the upstream end of the study reach while smolts were primarily 

collected in the convergence pool. Only one juvenile Chinook salmon (120 mm FL [4.7 inches]) 

was collected during the four surveys. 

Of the 618 fish collected in Mapes Creek (all years combined), sculpins made up 82.8% 

of the fish collected and were present throughout the stream reach (Table 11). Sculpins consisted 

of coastrange sculpin and prickly sculpin. Overall, coastrange sculpin made up 77.6% of the 

total number of sculpin collected and prickly sculpin made up 22.4%. Prickly sculpin 

represented 37.7% of the sculpins in slow-water habitats (convergence pool, other pools, and 

glides), while they only made up 3.8% of sculpins in riffles. In the convergence pool, prickly 

sculpin made up 45% of the sculpin but only 9% farther upstream. Although the total number of 

sculpin collected did not vary considerably from year to year, there was a noticeable reduction of 

1+ and older sculpin in 2019 (Figure 20). Additionally, the overall weight of all fish collected 

per area of 0.49 g/m2

 in 2019 was the lowest level of the four survey years and was substantially 

lower than the weight collected per area in both study reaches of Taylor Creek (Table 12). 

Besides salmonids and sculpins, the only other fish species collected in Mapes Creek 

during electrofishing surveys was threespine stickleback, which included 57 fry (range, 14-29 

mm FL) and 14 adults (range, 57-79 mm FL). The number of threespine stickleback fry 

collected is likely a large underestimate of the total because the fry were small and thus difficult 

to see and some may have slipped through the dip net mesh. Also, they may have been less 

affected by the electrofishing than larger fish. 
44

TABLE 11.-- Number of fish collected in lower Mapes Creek and lower Taylor Creek (L-1, L-2, and L-3 combined) 

from June single-pass electrofishing surveys, 2015-2019. 

 

Stream

 Fish group

 Species 2015 2016 2017 2018 2019 Total

Mapes

 Salmonids

Chinook salmon 1 0 0 ND 0 1

Coho salmon - juveniles 6 1 5 ND 6 18

Coho salmon - smolts 1 2 1 ND 0 4

Cutthroat trout - 1+ and older 3 2 6 ND 1 12

 Sculpins

Coastrange sculpin 91 82 102 ND 82 357

Prickly sculpin 44 24 21 ND 14 103

Unidentified sculpin fry (< 30 mm TL) 1 0 48 ND 3 52

 Other native species

 Threespine stickleback - fry 12 43 0 ND 3 57

 Threespine stickleback - adults 6 7 0 ND 1 14

Taylor

 Salmonids

Chinook salmon 0 0 0 1 0 1

Coho salmon - juveniles 2 1 7 4 15 29

Coho salmon - smolts 3 2 2 0 7 14

Cutthroat trout - juveniles (0+) 47 159 25 2 77 310

Cutthroat trout - 1+ and older 30 26 40 19 14 129

 Sculpins

Coastrange sculpin 78 38 124 166 82 488

Prickly sculpin 9 9 4 9 0 31

Unidentified sculpin fry (< 30 mm TL) 18 0 41 9 0 68

 Other native species

 Threespine stickleback - adults 1 3 0 0 0 4

 Western brook lamprey - adults 0 0 0 2 3 5

 Nonnative

Rock bass 1 0 0 0 0 1

Number collected
45

Site Year Date Area (m2) Number of fish Number/m2 Weight (g) g/m2

Lower Mapes Creek

2015 June 9 245.6 165 0.67 448 1.82

2016 June 8 285.3 161 0.56 411 1.44

2017 June 6 323.5 183 0.57 643 1.99

2019 June 20 289.8 109 0.38 141 0.49

Lower Taylor Creek (L‐1, L‐2, and L‐3 combined)

2015 June 8 159.1 189 1.19 1,564 9.83

2016 June 8 178.3 238 1.33 1,720 9.65

2017 June 7 206.2 243 1.18 2,054 9.96

2018 June 20 203.6 212 1.04 1,358 6.67

2019 June 18 191.2 198 1.04 1,157 6.05

Upper Taylor Creek ‐ U‐1

2011 September 1 239.6 105 0.44 1,334 5.57

Upper Taylor Creek ‐ U‐2

2005 June 30 87.5 60 0.69 391 4.47

2018 July 18 102.9 24 0.23 434 4.22

2019 July 18 98.3 14 0.14 224 2.28

Upper Taylor Creek ‐ U‐3

2010 August 10 496.7 54 0.11 1,136 2.29

2012 August 23 475.4 121 0.25 2,175 4.57

2013 July 10 397.8 77 0.19 1,738 4.37

2018 July 18 388.5 51 0.13 1,210 3.11

2019 July 18 388.5 109 0.28 1,165 3.00

FIGURE 20. – Number of sculpin fry (0+) and larger sculpins collected in lower Mapes Creek during June 

single-pass electrofishing surveys, 2015-2017, 2019. Based on length frequencies, sculpin species that were < 38 

mm TL were considered sculpin fry (0+). 

TABLE 12.-- Number and total weight estimates of fish in lower Mapes Creek and Taylor Creek sites from 

summer single-pass electrofishing surveys. Fish caught in lower Mapes Creek and lower Taylor Creek consisted 

primarily of salmonids, sculpins, and threespine stickleback; whereas most fish caught in upper Taylor Creek sites 

were cutthroat trout. 

 
46

Lower Taylor Creek.– In lower Taylor Creek, 44.7% of the fish collected were salmonids (439 

cutthroat trout, 43 coho salmon, and 1 Chinook salmon). Of the cutthroat trout, 70.6% were ≤ 80 

mm FL (3.1 inches) and based on length frequencies, all these fish were likely age 0+ (Figure 

21). This size class was particularly abundant in 2016 and 2019 (2016, n = 159; range 27-70 mm 

FL [1.1-2.8 inches]; 2019, n = 77; range 26-80 mm FL [1.0-3.1 inches]) and made up 85.9% and 

84.6%, respectively of the cutthroat trout caught in those two years. Older cutthroat trout ranged 

in size from 90 mm to 262 mm FL (3.5-10.3 inches). Seventy-one percent of age 0+ cutthroat 

trout were collected in riffles while only 11.6% of the older cutthroat trout were collected in 

riffles. Cutthroat trout lengths were significantly different among habitat types (Kruskal-Wallis 

test; P < 0.001 and Conover-Inman pairwise comparisons) but were not significantly different 

among stream sections (Kruskal-Wallis test; P = 0.11) (Figure 22). 

Coho salmon were primarily associated with pools and consisted of both juveniles (range, 

60 mm to 97 mm FL [2.4-3.8 inches]) and smolts (range, 111 mm to 224 mm FL [4.4-8.8 

inches]). Only one juvenile Chinook salmon (110 mm FL [4.3 inches]) was collected during the 

five surveys. Overall, salmonids made up 12% (2018) to 79% (2016) of the total number of fish 

collected; however, they comprised 74% (2018) to 89% (2016) of the fish by weight. 

Similar to Mapes Creek, sculpins in Taylor Creek consisted of coastrange sculpin and 

prickly sculpin. Overall, they made up 54.4% of all fish collected (Table 11). Prickly sculpin 

only represented 5.9% of all sculpin collected and were only found in the L-1 and L-2 stream 

sections. They made up 12% of the sculpins in slow-water habitats but none were collected in 

riffles. In 2015-2017 when the rock barrier was a partial fish barrier, only a few coastrange 

sculpin (n = 11; 6.8% of total upper section fish catch) were collected upstream of the rock 

barrier; however, after the rock barrier was absent in 2018 and 2019, large numbers of 

coastrange sculpin (n = 141; 75.8% of total upper section fish catch) were collected and were 

present throughout the upper section (Figure 23). In 2015-2017, coastrange sculpin in the L-3 

section were longer than those in the other two stream sections while in 2018-2019, there was 

little difference among three stream sections (Figure 24). 

Besides salmonids and sculpins, other fish species collected in Taylor Creek were adult 

western brook lamprey (Lampetra richardsoni) (n = 5; range, 140-160 mm TL [5.5-6.2 inches]), 
47

adult threespine stickleback (n = 4; range, 73-77 mm FL [2.9-3.0 inches]), and juvenile rock bass 

(n = 1; 45 mm FL [1.8 inches]). 

FIGURE 21.-- Yearly length frequencies (10-mm increments) of cutthroat trout in lower Taylor Creek from 

June single-pass electrofishing surveys, 2015-2019. 

FIGURE 22.-- Fork length box plots (range, 25 and 75% quartiles, and median) of cutthroat trout by habitat 

type (left panel) and by stream section (right panel) in lower Taylor Creek from June single-pass electrofishing 

surveys, 2015-2019 combined. The number of fish collected and measured is given above each box plot. Cutthroat 

trout lengths were significantly different among each habitat type (left panel, Kruskal-Wallis test; P < 0.001 and 

Conover-Inman pairwise comparisons) but were not significantly different among stream sections (right panel, 

Kruskal-Wallis test; P = 0.11). 
48

FIGURE 23 -- Abundance (number/m2) of migratory adult sculpin species (coastrange sculpin and prickly 

sculpin) in lower Taylor Creek in relation to the rock barrier, 2015-2019. Data are from a single-pass electrofishing 

survey in June. Downstream (L-1 and L-2 stream sections combined) and upstream (L-3) represent study stream 

sections downstream and upstream of the rock barrier. The dashed vertical lines separates before and after the rock 

barrier was eliminated. 

FIGURE 24. -- Length frequencies (10-mm increments) of sculpins collected in three sections of lower 

Taylor Creek during June single-pass electrofishing surveys, 2015-2017. 
49

Upper Taylor Creek.– Of the 60 fish collected in 2005 at the U-2 stream section, 51 were 

juvenile coho salmon and 9 were cutthroat trout (Figure 25). In 2018 and 2019, all fish collected 

at this site were cutthroat trout. There was only one pool in this stream section in 2018 and 2019 

and many of the fish were collected in this pool. 

For the five years combined, a total of 408 cutthroat trout were collected in the 150-m 

long U-3 stream section. Of those, 35.3% (144 of 408) appeared to be 0+ trout (< 80 mm FL 

[3.1 inches]; Figure 26). For three of the five years, the number of 0+ trout collected was less 

than or equal to 12; however, the number caught was considerably higher in the other two years: 

2012 (n = 40) and 2019 (n = 72). The number of 1+ and older cutthroat trout varied from 39 in 

2010 to 82 in 2014. 

Besides cutthroat trout, the only other fish species collected was juvenile coho salmon 

which were only collected in 2010 (n = 4; range, 63-91 mm FL [2.5-3.6 inches]). In addition to 

the fish collected, 2 northwestern salamanders (Ambystoma gracile) and 1 Pacific giant 

salamander (Dicamptodon tenebrosus) were collected in the 2019 survey. 

FIGURE 25.-- Yearly length frequencies (10-mm increments) of fish collected in the U-2 stream section in 

upper Taylor Creek from summer single-pass electrofishing surveys, 2005 and 2018-2019. The total number of fish 

collected is given for each year. 
50

FIGURE 26.-- Yearly length frequencies (10-mm increments) of cutthroat trout in the U-3 stream section in 

upper Taylor Creek from summer single-pass electrofishing surveys, 2010, 2012-2013 and 2018-2019. The total 

number of cutthroat trout collected is given for each year. 

 
51

Discussion 

Standard Chinook Salmon Abundance Surveys

Surveys of lower Mapes Creek demonstrated that juvenile Chinook salmon were 

commonly using the recently-restored stream channel. Results were consistent with surveys of 

other nonnatal tributaries of Lake Washington and Lake Sammamish (Tabor et al. 2011b). Also, 

densities of juvenile Chinook salmon in Mapes and Taylor creeks compare favorably with 

densities observed in nonnatal tributaries from other systems (Table 13). Small, low-gradient 

streams that are close to the mouth of a natal stream (e.g., Cedar River) appear to be particularly 

valuable habitat for rearing juvenile Chinook salmon. Restoring Mapes Creek appears to have 

successfully added this valuable rearing habitat. Taylor Creek is substantially closer to the 

mouth of the Cedar River than Mapes Creek, and thus improving habitat conditions on the delta 

and in the lower channel is expected to have a strong positive effect on rearing conditions for 

juvenile Chinook salmon and should result in higher densities than those observed in Mapes 

Creek. 

TABLE 13.-- Maximum densities (fish/m2) of juvenile Chinook salmon observed in this study (bolded) 

compared to other nonnatal tributaries. The method used to assess fish density is also displayed. For all sites, the 

exact distance from the natal site to the nonnatal stream is not known. However for the Cedar River (Lake 

Washington) nonnatal streams, the distance is at least the distance from the mouth of the Cedar River to the nonnatal 

stream (1.2 to 4.5 km [0.7-2.8 miles]). Two values are given for Johns Creek, one for the entire stream and the other 

(in parentheses) excludes the convergence pool, which was a large deep slough that was not used extensively by 

juvenile Chinook salmon. The Taylor Creek value does not include the upper section because a rock barrier 

prevented juvenile Chinook salmon from moving farther upstream. 

Maximum

Natal system Stream name density (fish/m2

) Method Reference

Lower Fraser River Brunette 0.22 Multiple-pass electrofishing Murray and Rosenau 1989

Nathan 0.68 " "

Scott 0.33 " "

Squakum 0.14 " "

Wade 0.06 " "

West 0.13 " "

Whonnock 0.06 " "

Upper Fraser River Hawks 0.76 Mark-recapture with seining Scrivener et al. 1994

South Umpqua River Buckeye 0.01 Day snorkeling Scarnecchia and Roper 2000

Boulder 0.02 " "

Deadman 0.01 " "

Dumont 0.01 " "

Francis 0.01 " "

Stouts 0.01 " "

Yukon River Croucher 0.49 Mark-recapture with electrofishing Bradford et al. 2001

Cedar River (Lake Washington) Johns 0.54 (1.18) Day snorkel/surface observations Tabor et al. 2011b

Mapes 0.94 Night snorkel/surface observations this study

Taylor 0.64 " this study (lower and middle sections)
52

In lower Mapes Creek, juvenile Chinook salmon were distributed throughout the restored 

reach while in lower Taylor Creek they were concentrated in the lower section of our study reach 

and rare farther upstream (Figure 11). A major difference between the two streams is the 

gradient. We estimated the overall gradient to be about 1% in Mapes Creek and 3% in Taylor 

Creek for our study reaches (Table 1). Tabor et al. (2011b) also found that the nonnatal 

tributaries used extensively by juvenile Chinook salmon in the Lake Washington system had a 

gradient less than 1%. Studies from other systems have also found the nonnatal tributaries used 

extensively by juvenile Chinook salmon have a low gradient; ranging from <0.25% to 2% 

(Murray and Rosenau 1989; Scrivener et al. 1994; Bradford et al. 2001). The proposed 

restoration project for Taylor Creek should attempt to reduce the gradient to < 2%, ideally by 

adding more sinuosity to the stream. Unfortunately, the City of Seattle property is relatively 

narrow (approximately 34 m at the widest portion), which does not provide much room to 

meander the stream. Under current conditions the middle section of the study reach primarily 

consists of a long riffle (≈ 50 m [164 ft] long) within a single thread channel. Ideally the newly 

constructed channel will provide some slow-water habitats to the channel downstream of Rainier 

Avenue, not only to benefit upstream movements of juvenile Chinook salmon, but also to 

maximize rearing and refuge habitat. Suggested approaches include: adding hydraulic 

complexity, providing off-channel habitat, and/or splitting the single thread channel into multiple 

channels. 

Another major difference between the two streams was the abundance of cutthroat trout 

which appeared to be abundant in Taylor Creek, and relatively infrequent in Mapes Creek. 

Taylor Creek is a larger stream than Mapes Creek and even in its currently degraded condition, 

the lower reach of Taylor Creek has more pool habitat than lower Mapes Creek (Appendix 3) 

and thus is able to support several medium-sized and large cutthroat trout (e.g., > 150 mm FL 

[5.9 inches]). These larger cutthroat trout may affect the distribution of juvenile Chinook salmon 

through predation risk. In some situations, cutthroat trout can be a predator of juvenile Chinook 

salmon (Nowak et al. 2004). Additionally, cutthroat trout are often larger than juvenile Chinook 

salmon and may be dominant over them for space and food. Fish size has been shown to be an 

important variable affecting foraging and agonistic behavior in salmonids (Abbott et al. 1985; 

Sabo and Pauley 1997). However, snorkel observations from Taylor Creek and Johns Creek 

indicate cutthroat trout and juvenile Chinook salmon often occupy different habitats or different 
53

areas within the same habitat which may reduce their interactions (R. Tabor, personal 

observations). The relatively more diverse habitat conditions (pools, glides, riffles, woody 

debris, overhanging vegetation, etc.) in Taylor Creek likely allowed cutthroat trout and juvenile 

Chinook salmon to coexist. 

Over the first three years of surveys (2015-2017), the Chinook salmon abundance in 

Mapes Creek increased each year; however in 2019, the abundance was substantially lower than 

the first three years. It is unclear if this variability was due to differences in the annual 

abundance of juvenile Chinook salmon in Lake Washington, differences in our sampling 

protocol, or changes in habitat conditions. The relative annual differences among years in Mapes 

Creek was generally similar as that observed in Taylor Creek. For example, the abundance of 

juvenile Chinook salmon in Taylor Creek was highest in 2017 similar to Mapes Creek and in 

2019, they were rare in both creeks until April. Thus it is likely that much of the differences 

among years was due to annual differences in Chinook salmon abundance along the southwest 

shorelines of Lake Washington. During the first three years, we surveyed twice a month, whereas 

in 2019 we only surveyed once a month and perhaps we could have more easily missed periods 

when juvenile Chinook salmon abundance was high. Alternatively, habitat conditions (increased 

riparian vegetation and prey availability) in Mapes Creek may have progressively improved over 

the first three survey years and it is possible the stream could have supported larger numbers of 

juvenile Chinook salmon. Also, the quality of habitat conditions in Mapes Creek may have been 

reduced in 2019 because large amounts of emergent vegetation (Figure 27) may have reduced the 

amount of available habitat and increased embeddedness (Figure 28) may have reduced prey 

availability. 

For both streams, the abundance of juvenile Chinook salmon did not appear to be related 

to the annual number of fry entering the lake from the Cedar River (2015 – 326,901 fry; 2016 – 

941,443 fry; 2017 – 151,262; 2018 – 492,574; 2019 – 186,407 (Lisi 2019; P. Lisi, WDFW, 

unpublished data) (Figure 29). In particular, the lowest abundance of fry entering the lake 

among our five survey years was in 2017 yet it had one of the highest numbers of Chinook 

salmon observed in both Mapes and Taylor creeks. In addition to the number of fry entering the 

lake, there are likely a number of other factors (e.g., lake entry date, direction of stream flow on 

the Cedar River delta, water temperature and clarity, weather patterns including strong rain 

events, prey availability, Chinook salmon size, predator abundance) that influence the annual 
54

number of Chinook salmon at a particular site in south Lake Washington during their rearing 

period (January to May). Other than they appear to be more concentrated in areas close to the 

mouth of the Cedar River (Tabor et al. 2004), little is known on the movement patterns of 

juvenile Chinook salmon once they enter the lake and the various factors that influence their 

movement and relative abundance in the lake nearshore area and in nonnatal tributaries.

FIGURE 27. Photos of Mapes Creek (looking upstream) and the pedestrian bridge to show the changes in 

riparian vegetation from 2015 to 2019. 

June 9, 2015

October 1, 2019
55

FIGURE 28. Photos of the substrate in Mapes Creek including inserts to show close-ups of cobbles. Both 

photos were taken in approximately the same location (note the rootwad in the top center part of the photos). Red 

arrows highlight the change in embeddedness. Conditions during October 2019 appeared to be similar to June 2019 

(no photo available) when we our fish collections were undertaken. 

October 1, 2019

June 9, 2015
56

FIGURE 29.—Relationship between the annual number of Chinook salmon fry entering Lake Washington 

from the Cedar River and the annual peak snorkel count of juvenile Chinook salmon in two nonnatal streams 

(Mapes and Taylor creeks), 2015-2019. The dashed regression line is for Taylor Creek and the solid regression line 

is for Mapes Creek. 

For 2015-2017, the numbers of juvenile Chinook salmon in Mapes Creek declined 

sharply in April while the numbers concurrently increased at the nearby lakeshore reference site 

(Be’er Sheva Park boat ramps). In Mapes Creek, some of this is likely because the requirements 

of juvenile Chinook salmon for space and food increase as they grow (Chapman 1966) and there 

should be some level of self-thinning due to intense competition (Elliot 1993; Dunham and 

Vinyard 1997). Additionally, habitat conditions in Mapes Creek may not support larger juvenile 

Chinook salmon because there are few pools (Appendix 3). In Johns Creek (another nonnatal 

tributary in Lake Washington) in late March and April, juvenile Chinook salmon shifted from 

inhabiting shallow-water habitat (glides) to using deeper-water habitats (pools) (Tabor et al. 

2011b). In contrast to Mapes Creek, juvenile Chinook salmon at the lakeshore reference site 

were able to progressively move to deeper waters as they grow (Tabor et al. 2011a). The 

restoration project in Mapes Creek included the placement of several rootwads to provide cover 

and create scour pools. Over time, habitat conditions for larger Chinook salmon may improve if 

scour pools are created. If not, resource managers should consider exploring options for 

increasing the number of pools. 
57

In contrast to Taylor Creek, few juvenile Chinook salmon were observed on the delta 

area of Mapes Creek in comparison to a nearby shoreline transect or in the stream. Delta habitat 

conditions are markedly different between the two streams. At Taylor Creek, part of the delta 

area (roughly 25%) has gentle slopes with fine, clean sand substrates that are preferred by 

juvenile Chinook salmon (Tabor et al. 2011a, b). In contrast, there is no delta fan at Mapes 

Creek and the habitat at the mouth of the stream does not appear to be different than adjacent 

shoreline areas. There is also some rip rap along the shore at the Mapes Creek delta area and 

thus the amount of preferred shallow beach habitat is reduced. Lastly from our limited 

observations, wave action from prevailing winds seemed to be stronger at the Mapes Creek delta 

than at Taylor Creek and perhaps the Mapes Creek delta is not a preferred location for juvenile 

Chinook salmon. The stream channel at Mapes Creek was just constructed in 2014 and it may 

take several years for a fluvial delta fan to develop. However, because the stream is relatively 

small and perhaps because wave action from prevailing winds may continually move deposited 

sand from Mapes Creek; it is possible that a fluvial delta fan will not develop to any degree at 

this site. 

The Taylor Creek delta area (also called fluvial fan) covers a relatively large area; 

however, juvenile Chinook salmon appeared to only extensively use part of this area where there 

was a combination of streamflow and sand substrate. In January and February when the lake 

level was low, this preferred area was roughly 25% of the 41 to 58 m long outside edge of the 

delta area (Delta-A and Delta-B combined). Much of the remaining delta (primarily Delta-B) 

available to Chinook salmon was composed of coarse gravel and cobble with no streamflow and 

few juvenile Chinook salmon were present. As lake levels rose starting in March, the delta area 

was composed of the outside edge (Delta-A and Delta-B combined) as well as a convergence 

pool. Juvenile Chinook salmon commonly used both the outside edge (Delta A) and the 

convergence pool where there was streamflow and sand substrate. The percent of the total delta 

area that provided preferred habitat conditions varied widely with lake level. A rough estimate 

would be that, at highest lake level, half of the delta area (west side of delta area; see Figure 5) 

provided preferred habitat conditions. Observations of juvenile Chinook salmon in other areas of 

south Lake Washington indicated juvenile Chinook salmon prefer sand and gravel substrates 

(Tabor et al. 2011a) and thus replacing coarse gravel and cobble in areas where there is no 

streamflow with finer substrates would improve habitat conditions. However, restoration efforts 
58

also need to consider substrate preferences of sockeye salmon that spawn annually in either the 

delta area and/or lower channel areas of Taylor Creek (Wild Fish Conservancy 2008). Some 

combination of fine and coarse gravels will likely provide adequate habitat conditions for both 

species. The east side of the delta contains a high percent of cobbles and removal of substrates in 

that area would seem to be beneficial to both species. However, the west side of the delta has 

predominantly sand and gravel and likely does not warrant major changes. 

The small rock barrier (approximately 100 m [328 ft] upstream from the mouth) in Taylor 

Creek appeared to have a strong effect on the distribution of small-bodied fishes in 2015-2017. 

After the rock barrier was eliminated prior to 2018 sampling effort, small-bodied fishes were 

able to inhabit the entire study stream section up to Rainier Avenue. In 2015-2017, juvenile 

Chinook salmon were occasionally observed just downstream of the rock barrier but never 

upstream of it. Sculpin were abundant downstream of the rock barrier but rare upstream of the 

rock barrier and the sculpin found upstream of the rock barrier tended to be larger individuals. 

Recent studies of several other streams in the Puget Sound region have also found the 

distribution of migratory sculpins can be impacted by small barriers (i.e., > 15 cm perch height) 

and generally only large individuals are found upstream of these barriers (LeMoine and 

Bodensteiner 2014; Tabor et al. 2017). The proposed restoration project will reconstruct the 

channel and remove any potential barriers. Full-spanning log weirs and other drop structures are 

often used to improve fish habitat conditions (e.g., increase pool depth and frequency), but can 

have the unintended consequence of reducing the upstream movements of small-bodied fishes, 

including juvenile Chinook salmon (Tabor et al. 2017). In our upper Taylor Creek monitoring 

sites at the lower end of the U-2 stream section there is a channel-spanning log weir (0.3 m [1 ft] 

perch height) that will likely limit upstream movements of small-bodied fishes. If upstream 

movements of small-bodied fishes is a part of the overall fish restoration objective then this 

structure and perhaps other similar structures will need to be modified. Other types of instream 

restoration features have been recommended such as roughened channels/constructed riffles and 

porous weirs instead of log weirs and other drop structures (Cramer 2012). 

 
59

Delta Rain Event Surveys

 

 We did not observe any numerical response of juvenile Chinook salmon to increased 

storm-related increases in discharge levels at the deltas of Mapes or Taylor creeks. Based on 

earlier sampling in Lake Washington tributaries, we had expected to see an increase in catch 

rates (Tabor et al. 2011b). Catch rates in this study were quite variable and may have been 

related to several factors, thus requiring a larger sample size to fully explore the role of nonnatal 

streams as feeding areas for juvenile Chinook salmon following storm events. Similar to earlier 

sampling, it’s possible the small beach seine could easily have missed fish that are in deeper 

waters. In addition, high turbidity levels following rain events may allow juvenile Chinook 

salmon to move into deeper waters when predation risk is lower. For example, Tabor and 

Wurtsbaugh (1991) found juvenile rainbow trout (O. mykiss) moved offshore during periods of 

high turbidity to feed on large zooplankton presumably because risk from visual predators was 

lower. Juvenile Chinook salmon are often in schools during the day and beach seine catches 

may be extremely variable depending if a school is encountered or not. Most of our sampling 

was done during the day and because juvenile Chinook salmon appear to have a crepuscular 

feeding pattern (Tabor et al. 2011a), we may have missed the time of the day when there is a 

numerical response to the high discharge event. The duration and magnitude of the high 

discharge event further complicates sampling because it may also influence the numerical 

response by juvenile Chinook salmon. 

Similar to previous sampling on Lake Washington tributaries (Tabor et al. 2011b), we 

observed a shift in the diet of juvenile Chinook salmon with increased discharge levels at the 

delta of Taylor Creek. Instead of Chinook salmon diet being almost entirely composed of prey 

that likely originated from the lake shoreline (e.g., chironomids), they switched to prey from 

Taylor Creek (e.g., oligochaetes and mayflies). The high discharge event likely displaced a large 

number of invertebrates downstream (referred to as invertebrate drift) that they were able to 

consume. Invertebrate drift typically increases during high discharge events (Anderson and 

Lehmkuhl 1968), and it is this phenomenon that is expected to draw juvenile Chinook salmon to 

nonnatal streams following peak discharge events. Salmonid foraging success in the main 

channel of Taylor Creek may be reduced due to increased turbidity levels (Sweka and Hartman 

2001) and water velocities (Piccolo et al. 2008). However, once the stream enters the lake 
60

following a rain event, there will be a wide range of water velocities and turbidity levels from 

turbid, high velocity conditions near the stream mouth to clear, low velocity conditions in the 

lake and juvenile Chinook salmon may be able to find the ideal location that provides good 

foraging conditions and still minimizes risk to visual predators. 

Unlike Taylor Creek, we did not observe any major shift in the diet of juvenile Chinook 

salmon at the Mapes Creek delta following a rain event. Mapes Creek is a smaller and lower 

gradient stream than Taylor Creek and there may not be as many displaced invertebrates moving 

downstream. Also, there may be differences in the abundance of macroinvertebrates between the 

two streams because Mapes Creek watershed is located in a heavily-urbanized area and may 

have poor habitat conditions (e.g., long culverted stream sections, predominately sand substrates; 

Tabor et al. 2010). 

Chinook Salmon Diet - 2018

Diet sampling in 2018 indicated juvenile Chinook salmon at the Taylor Creek delta fed 

more similarly to lakeshore-dwelling Chinook salmon than to stream-dwelling Chinook salmon. 

Bioenergetics analysis of juvenile Chinook salmon collected from the nearshore areas of Lake 

Washington indicated they grow well and prey appears to be abundant (Koehler et al. 2006); 

therefore, feeding on prey that originated in the lake may be preferred. It is unclear if prey 

availability is better in the stream or the lake. Perhaps the stream has lower prey availability but 

is attractive to juvenile Chinook salmon because of reduced predation risk. The high density of 

juvenile Chinook salmon on the delta may be due to the presence of ideal habitat conditions 

(sand substrates and shallow waters) and proximity to good foraging conditions along the 

lakeshore. 

Summer Electrofishing Surveys 

The numbers of cutthroat trout caught during summer electrofishing surveys in lower and 

upper Taylor Creek varied widely among years. Much of the variability was due to the large 

differences in the numbers of 0+ age cutthroat trout caught. For example, in lower Taylor Creek 

in 2018 only two were caught yet 159 were caught in 2016 and 77 were caught in 2019. Egg 

survival rates likely varied widely among years due in large part to differences in physical 

factors such as the amount of fine sediments and physical displacement from scour caused by 
61

high flow events (Quinn 2018). In the lower reach in 2016 and 2019 when 0+ cutthroat trout 

were abundant, peak streamflows appeared to have been much lower (based on USGS Kelsey 

Creek February-April stream gage measurements) than in 2015, 2017, and 2018 when numbers 

were substantially lower (Figure 30). In the upper reach, the highest number of 0+ cutthroat 

trout collected was also the year when peak streamflows in Kelsey Creek were the lowest among 

the five survey years; however, the relationship between peak streamflow and the number of 0+ 

cutthroat trout was not as strong as for the lower reach. 

FIGURE 30.—Relationship between peak streamflow (February-April, Kelsey Creek USGS stream gauge) 

and the number of 0+ cutthroat trout collected during an annual single-pass electrofishing survey in two reaches of 

Taylor Creek. The lower reach (L-1, L-2, and L-3 combined) surveys were conducted in June while the upper reach 

(U-3) surveys were conducted in July or August. 
62

Cutthroat trout appear to successfully spawn in the lower and upper study reaches of 

Taylor Creek; however, there was no evidence of successful spawning of cutthroat trout in 

Mapes Creek. During June electrofishing surveys, only a total of five cutthroat trout > 150 mm 

(5.9 inches) FL were collected in Mapes Creek; whereas in lower Taylor Creek, 55 cutthroat 

trout > 150 mm (5.9 inches) FL were collected. Mapes Creek is a smaller and shallower stream 

than Taylor Creek (Appendix 3) and may not have adequate habitat conditions for spawning 

adults. Additionally, Mapes Creek has a lower gradient and appears to have a higher level of 

embeddedness than Taylor Creek which may result in poor egg survival rates if spawning did 

occur. 

 The two sculpin species present in both Mapes Creek and Taylor Creek were both 

migratory sculpin. Both species are generally widespread in lowland lakes, estuaries, and the 

lower reaches of streams and rivers and have small planktonic larvae that drift downstream to 

slow-water environments after hatching. After larvae grow for a few weeks, they assume a 

benthic existence and then migrate upstream to inhabit lower reaches of rivers or streams. 

Because of their planktonic larval stage, they can quickly invade new habitats such as coastal 

streams opened from glacier retreat (Milner et al. 2008). Similarly, migratory sculpins appeared 

to have colonized Mapes Creek soon after the restoration project was completed. Electrofishing 

of upstream sections of Mapes Creek in May 2017 (part of this study) and July 2005 (Tabor et al. 

2010) indicated that sculpin were not present. Thus migratory sculpin likely had to colonize 

Mapes Creek from Lake Washington. The restoration project was completed in September 2014 

and we observed sculpin in the new stream channel during our first surveys in February 2015 and 

they appeared to be abundant when we did our electrofishing survey in June 2015. 

The relative distribution between the two species of migratory sculpins in Taylor Creek 

and Mapes Creek was consistent with results from other studies. Coastrange sculpin were 

substantially more common in riffles (faster-water habitats) than prickly sculpin in both study 

streams. Several other studies have found that prickly sculpin and coastrange sculpin are 

spatially segregated with prickly sculpin primarily inhabiting pools and coastrange sculpin 

inhabiting riffles (Taylor 1966; Mason and Machidori 1976; White and Harvey 1999; Tabor et 

al. 2007). Because coastrange sculpin inhabit faster waters than prickly sculpin, they are likely 

better adapted for moving upstream through riffles and thus are typically found farther upstream 

(Mason and Machidori 1976; Tabor et al. 2017). Only one prickly sculpin was ever collected in 
63

the middle section of Taylor Creek whereas some coastrange sculpin were collected in the upper 

section. In Mapes Creek, coastrange sculpin were well distributed throughout the study reach 

while prickly sculpin were primarily found in the lower part of the study reach in the 

convergence pool. 

In 2019, the catch of 1+ and older sculpin in Mapes Creek was considerably lower than 

during 2015-2017 surveys. Reduction of the catch of these sculpin was likely due to major 

changes in habitat conditions including 1) increased embeddedness (Figure 28), and 2) increased 

levels of riparian vegetation (Figure 27). In general, large substrates that have abundant 

interstitial spaces with little embeddedness appear to support larger sculpin populations than 

areas with small substrates or high embeddedness (Hawkins et al. 1983; Brown 1991; Haro and 

Brusven 1994; Knaepkens et al. 2002; Davey et al. 2005). During the 2015-2017 surveys, many 

of the 1+ and older larger sculpin were caught in areas near the rootwads where cobbles were 

positioned (Figure 28). In 2019, few sculpin were collected around these cobbles presumably 

because of the high level of embeddedness. Habitat conditions have also changed dramatically 

because of the increase in riparian vegetation (Figure 27); however, it is unclear exactly how this 

affects sculpin catch rates. Increased levels of riparian vegetation may reduce capture efficiency 

because some areas are difficult to shock and/or see the stunned fish. Additionally, increased 

levels of riparian vegetation might reduce the amount suitable habitat for sculpins or perhaps 

reduce the availability of macroinvertebrates, their primary prey base. Results from Mapes 

Creek highlight the need to monitor habitat conditions as well as fish populations for several 

years to determine the long-term effectiveness of each restoration project; a critical process that 

is not universally conducted. 

During the five years of June electrofishing surveys, the only nonnative fish collected 

was one rock bass in lower Taylor Creek. Additionally, nonnative fish were occasionally 

observed during our standard juvenile Chinook salmon in both streams and represented a small 

fraction of the total number of fish observed. Most nonnative species found in the Lake 

Washington basin primarily inhabit lentic systems and slow-moving streams and rivers and 

Mapes and Taylor creeks may not have preferred habitat conditions. Additionally, nonnative 

fish may not compete well with native salmonids and sculpin that are better adapted for the 

stream habitat conditions found in Mapes and Taylor creeks. 
64

The only fish species collected in the upper reaches of Taylor Creek (above Rainier Ave) 

were cutthroat trout and coho salmon. Because there is an anadromous barrier at Rainier 

Avenue, cutthroat trout appear to have a self-sustaining fluvial population in upper Taylor Creek. 

Fluvial populations of coastal cutthroat trout have also been documented upstream of 

anadromous barriers in other small coastal streams (Northcote and Hartman 1988; Heggenes et 

al. 1991b). At both upper Taylor Creek sites, 1+ and older cutthroat trout appeared to occur 

primarily where there were deeper pools and glides. Coastal cutthroat trout that are 1+ and older 

generally show a strong preference for deeper pools (> 25 cm) and areas with some type of cover 

and lower water velocities (Heggenes at al. 1991a). 

Juvenile coho salmon were only collected in upper Taylor Creek in 2005 and 2011. 

Because of the anadromous barrier, these fish are considered from some type of an outplanting, 

likely from a local school education project. This highlights the difficulty of long term 

monitoring and evaluating barrier removal projects if additional variables such as outplantings 

are included in the overall project. Additionally, outplanting of juvenile coho salmon had 

recently been planned for Mapes Creek, which would have made it difficult to assess the use of 

the stream by juvenile Chinook salmon which could be displaced by juvenile coho salmon. 

We recommend continuing the summer surveys in upper Taylor Creek, especially the 

upstream reach, to document if other species such as coho salmon and sculpins have colonized 

the upper stream reaches and how the fish community has changed once the restoration project is 

completed. In comparing the two upper Taylor Creek stream sections, the U-3 stream section 

sppeared to be the best site to continue sampling if only one site was able to be surveyed. Unlike 

the U-2 stream section, the U-3 stream section had three years of prior sampling efforts, was 

conducted over a 150-m stream reach, and included several pools. The downside of this site is 

that it is farther upstream from the U-2 stream section and some fishes, especially small-bodied 

fishes, may not move that far upstream and could be missed in post-project monitoring. 

Therefore, some combination of sampling just upstream of Rainier Avenue and continuing to 

sample the U-3 stream section as well as lower Taylor Creek would be preferable to document 

changes in fish distribution once fish passage is improved. 

 
65

Acknowledgements

We wish to thank Steve Damm, Joe Starstead, and Katherine Lynch (Seattle Public 

Utilities (SPU)) for all of their support throughout this project. We thank Dan Lantz, (King 

County) for his assistance with all the upper Taylor Creek sampling efforts including the original 

2010-2013 surveys. USFWS employees and volunteers Alex Bell, Olivia Williams, Jeffery 

Johnson, Tim Grun, Aubrey Tingler, Michaela Lowe, Jennifer Fields, Matthew Webster, Keith 

Sweeney, Carlisha Hall, Matthew Kuo, Alex Pavlinovic, Pat DeHaan, Emma Evans, Jeffery Lee, 

Alex Schneider, Michael Elam, Amber Left-Hand Bull, Evan Lewis, Jono Grindall, and 

Samantha Heinicke assisted with the field and/or laboratory work. We also thank SPU 

employees Steve Damm, Chapin Pier, Ava Fuller, Aaron Jorgenson, Adrian Tuohy, and 

Katherine Lynch for their assistance with the field work. We thank Peter Lisi, Washington 

Department of Fish and Wildlife for providing information on Cedar River Chinook salmon fry 

migration. An earlier draft of this report was reviewed by Pat DeHaan (USFWS), Steve Damm 

(SPU), Katherine Lynch (SPU), and Joe Starstead (SPU). Funding for this project was made 

possible by Seattle Public Utilities and administered by Steve Damm, Joe Starstead, and 

Katherine Lynch. 

 
66

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70

Appendix 1. Number (#), length (m), and area (m2) of different habitat types in the Mapes 

Creek study reach during fish surveys. The start and end survey dates is the period of fish survey 

dates that corresponds to each row of habitat values. 

 

Year Convergence Pool

Length Area Length Area Length Area Length Area

start end (m) (m2

) # (m) (m2) # (m) (m2) # (m) (m2)

2015

9-Feb Mar-15 3.0 10.1 1 11.5 30.7 7 62.2 91.0 8 48.4 54.9

7-Apr 7-Apr 30.0 68.0 1 11.5 30.7 6 41.5 62.0 7 42.2 47.6

20-Apr 20-Apr 57.5 168.7 1 11.5 30.7 4 23.3 36.5 5 32.8 34.4

6-May 19-May 54.3 164.7 1 11.5 30.7 5 26.5 42.0 5 32.8 34.4

4-Jun 4-Jun 38.9 83.0 1 11.4 35.7 5 27.1 52.5 5 48.9 74.4

2016

25-Jan 25-Jan 0.0 0.0 1 10.8 30.7 6 48.9 102.1 7 75.9 120.0

16-Feb 23-Feb 0.0 0.0 1 10.8 30.7 6 48.9 98.8 7 75.9 127.9

8-Mar 22-Mar 5.8 10.6 1 10.8 30.7 6 48.9 98.8 7 70.1 118.7

5-Apr 5-Apr 28.5 61.8 1 10.8 30.7 5 37.1 76.5 6 54.4 94.0

21-Apr 11-May 44.0 95.3 1 10.8 30.7 4 23.1 51.3 5 52.9 91.1

28-May 8-Jun 46.0 112.1 1 10.8 30.7 4 23.1 51.3 5 52.9 91.1

2017

26-Jan 26-Jan 0.0 0.0 1 8.0 29.4 7 59.8 119.0 7 68.7 116.0

13-Feb 21-Feb 0.0 0.0 2 12.0 34.5 6 55.8 108.1 8 70.1 121.1

6-Mar 6-Mar 8.0 17.6 1 9.4 27.6 6 55.8 108.1 7 61.5 105.2

20-Mar 20-Mar 12.0 27.7 1 9.4 27.6 6 55.8 108.1 7 55.9 100.6

4-Apr 4-Apr 33.5 83.8 1 9.4 27.6 5 44.5 87.1 6 48.2 87.4

17-Apr 5-Jun 49.0 151.6 1 9.4 27.6 4 31.0 61.6 5 46.2 82.8

2019

30-Jan 21-Feb 0.0 0.0 1 7.5 19.5 6 49.2 82.1 8 79.7 116.2

18-Mar 18-Mar 9.5 16.5 1 7.5 19.5 6 49.2 82.1 8 70.2 101.6

24-Apr 24-Apr 44.0 96.8 1 7.5 19.5 5 34.2 60.1 6 50.7 73.3

13-May 13-May 57.7 159.6 1 7.5 19.5 4 24.7 43.7 6 46.5 67.0

Habitat type

Other pools Glides Riffles

Survey dates
71

Year

 Stream section

Length Area Length Area Length Area Length Area

 start end (m) (m2

) # (m) (m2) # (m) (m2) # (m) (m2)

2015

 L-1

23-Feb 23-Feb 11.0 58.7 1 7.2 15.4 1 3.5 3.0 2 25.5 36.0

10-Mar 10-Mar 19.0 79.7 1 7.2 15.4 1 3.5 3.0 2 25.5 36.0

26-Mar 26-Mar 19.0 79.7 1 7.2 15.4 2 12.2 29.4 1 20.0 19.3

7-Apr 19-May 16.0 96.7 2 21.8 38.9 1 3.5 3.0 1 4.0 5.6

19-May 19-May 16.0 96.7 2 22.6 41.8 1 3.5 3.0 1 5.0 7.0

 L-2

23-Feb 4-Jun 0.0 0.0 1 2.8 6.7 1 7.5 9.0 1 42.5 53.8

 L-3

23-Feb 4-Jun 0.0 0.0 3 7.8 10.8 3 8.2 12.1 5 25.9 32.7

2016

 L-1

25-Jan 23-Feb 0.0 0.0 2 18.1 12.5 1 4.5 5.3 3 41.0 84.1

8-Mar 8-Mar 32.1 120.3 2 18.1 12.5 1 4.5 5.3 3 21.6 32.3

22-Mar 22-Mar 36.7 141.7 2 18.1 12.5 1 4.5 5.3 2 17.0 16.0

5-Apr 5-Apr 16.5 151.3 2 15.6 10.1 1 4.5 5.3 2 14.0 13.4

21-Apr 21-Apr 16.5 151.3 2 21.2 15.6 1 9.5 11.2 1 4.0 4.6

11-May 6-Jun 16.5 151.3 2 31.8 26.2 0 0.0 0.0 1 4.0 4.6

 L-2

25-Jan 6-Jun 0.0 0.0 1 3.3 10.1 1 7.0 8.4 1 41.5 54.6

 L-3

23-Feb 5-Apr 0.0 0.0 5 14.2 22.1 1 7.5 10.7 4 21.3 30.5

21-Apr 6-Jun 0.0 0.0 7 18.7 31.9 1 7.5 10.7 5 36.2 57.3

2017

 L-1

26-Jan 26-Jan 7.5 16.9 2 15.4 16.4 1 2.8 2.5 4 40.4 112.7

13-Feb 20-Mar 5.0 31.8 2 17.5 27.1 1 1.4 1.9 4 33.5 107.1

30-Mar 30-Mar 10.5 73.5 2 17.5 27.1 1 1.4 1.9 4 30.4 56.2

11-Apr 24-Apr 18.7 137.1 2 17.5 27.1 1 1.4 1.9 2 15.5 17.2

8-May 8-May 16.5 151.3 1 18.2 24.0 1 5.0 6.1 2 9.0 9.2

22-May 6-Jun 16.5 151.3 1 24.3 32.1 0 0.0 0.0 0 8.0 8.0

 L-2

26-Jan 26-Jan 0.0 0.0 1 2.6 7.2 1 7.3 8.8 1 39.0 54.9

13-Feb 24-Apr 0.0 0.0 1 2.6 6.9 0 0.0 0.0 1 49.0 70.0

8-May 6-Jun 0.0 0.0 1 2.0 6.4 1 7.4 8.9 1 43.0 65.6

 L-3

26-Jan 26-Jan 0.0 0.0 6 18.9 33.0 2 5.6 7.1 6 41.3 65.3

13-Feb 24-Apr 0.0 0.0 5 14.9 28.4 3 8.1 14.1 6 42.1 70.2

8-May 5-Jun 0.0 0.0 6 16.3 30.0 2 3.6 5.5 6 44.4 75.2

Habitat type

Other pools Glides Riffles

 Survey dates

Convergence Pool

Appendix 2. Number (#), length (m), and area (m2) of different habitat types in three sections of 

the lower Taylor Creek study reach during bimonthly fish surveys (late Jan- early June, 

2015-2019. The start and end survey dates is the period of fish survey dates that 

corresponds to each row of habitat values. The L-1 stream section occasionally included 

some secondary habitat units and thus the sum of the length of habitat types is longer than 

the total stream length. 

 
72

Appendix 2, continued. Number (#), length (m), and area (m2) of different habitat types in 

three sections of the lower Taylor Creek study reach during monthly fish surveys (late 

January-May, 2018-2019. The start and end survey dates is the period of fish survey 

dates that corresponds to each row of habitat values. The L-1 stream section occasionally 

included some secondary habitat units and thus the sum of the length of habitat types is 

longer than the total stream length. 

 

Year

 Stream section

Length Area Length Area Length Area Length Area

start end (m) (m2

) # (m) (m2) # (m) (m2) # (m) (m2)

2018

 L-1

22-Feb 22-Feb 0.0 0.0 1 13.4 18.8 2 3.8 3.9 3 36.5 64.8

13-Mar 13-Mar 14.8 133.2 1 13.4 18.8 2 3.8 3.9 3 30.6 62.5

9-Apr 9-Apr 17.0 171.7 1 13.4 18.8 2 3.8 3.9 2 15.5 11.9

3-May 3-May 17.0 177.4 1 32.7 43.2 0 0.0 0.0 0 0.0 0.0

 L-2

22-Feb 3-May 0.0 0.0 1 3.2 8.5 2 11.8 16.5 2 37.7 51.6

 L-3

22-Feb 3-May 0.0 0.0 5 15.0 26.3 3 8.6 13.6 6 45.0 69.6

2019

 L-1

30-Jan 21-Feb 0.0 0.0 2 14.2 23.0 4 5.8 22.2 6 35.3 77.7

18-Mar 18-Mar 8.5 105.5 2 14.2 23.0 3 5.8 3.3 5 22.9 26.5

24-Apr 24-Apr 14.7 148.5 1 10.7 19.6 1 9.4 7.7 2 17.4 14.0

13-May 13-May 13.0 164.7 1 18.8 37.6 1 7.4 5.9 2 12.9 9.9

 L-2

30-Jan 30-Jan 0.0 0.0 1 1.9 4.5 4 14.6 19.4 3 27.2 35.0

21-Feb 13-May 0.0 0.0 1 1.9 4.5 4 12.6 16.2 3 29.2 37.6

 L-3

30-Jan 13-May 0.0 0.0 5 16.0 28.3 2 6.8 8.8 6 45.6 68.0

Survey dates

Habitat type

Convergence Pool Other pools Glides Riffles
73

Appendix 3. Maximum depth of slow-water habitats (glides and pools) in lower Mapes Creek 

and lower Taylor creeks (2015-2019). The dashed horizontal line at 0.35 m maximum 

depth is the level we used to classify each slow-water habitat unit as either a pool or a 

glide. 

   
74

Appendix 4. Number of fish observed during visual nighttime surveys in lower Mapes Creek, 

2015-2017, and 2019. Only the six primary species (sculpin is a combination of two 

species) observed are included. Coho salmon were categorized as either subyearlings 

(0+; < 100 mm FL) or yearlings (1+; > 120 mm FL). Trout were categorized as either 

small (65-130 mm FL), medium (130-200 mm FL), or large (> 200 mm FL). All trout 

collected during electrofishing sampling were cutthroat trout, thus we assumed all trout 

observed during visual nighttime surveys were cutthroat trout. 

   
75

Appendix 4, continued. Number of fish collected during riffle electrofishing surveys in lower 

Taylor Creek, 2015-2017 and 2019. Only the six primary species (sculpin is a 

combination of two species) observed are included. Coho salmon were categorized as 

either subyearlings (0+; < 100 mm FL) or yearlings (1+; > 120 mm FL). Trout were 

categorized as either small (65-130 mm FL), medium (130-200 mm FL), or large (> 200 

mm FL). All trout collected during electrofishing sampling were cutthroat trout, thus we 

assumed all trout observed during visual nighttime surveys were cutthroat trout. 

   
76

Appendix 5. Number of fish observed during visual nighttime surveys in four sections of lower 

Taylor Creek, 2015-2019. Only the six primary species (sculpin is a combination of two 

species) observed are included. Coho salmon were categorized as either subyearlings 

(0+; < 100 mm FL) or yearlings (1+; > 120 mm FL). Trout were categorized as either fry 

(< 65 mm FL), small (65-130 mm FL), medium (130-200 mm FL), or large (> 200 mm 

FL). All trout collected during electrofishing sampling were cutthroat trout, thus we 

assumed all trout observed during visual nighttime surveys were cutthroat trout. 
77

Appendix 5, continued. Number of fish observed during visual nighttime surveys in four 

sections of lower Taylor Creek, 2015-2019. Only the six primary species (sculpin is a 

combination of two species) observed are included. Coho salmon were categorized as 

either subyearlings (0+; < 100 mm FL) or yearlings (1+; > 120 mm FL). Trout were 

categorized as either fry (< 65 mm FL), small (65-130 mm FL), medium (130-200 mm 

FL), or large (> 200 mm FL). All trout collected during electrofishing sampling were 

cutthroat trout, thus we assumed all trout observed during visual nighttime surveys were 

cutthroat trout. 

 
78

Appendix 5, continued. Number of fish observed during visual nighttime surveys in lower 

Taylor Creek, 2015-2019. Only the six primary species (sculpin is a combination of two 

species) observed are included. Coho salmon were categorized as either subyearlings 

(0+; < 100 mm FL) or yearlings (1+; > 120 mm FL). Trout were categorized as either fry 

(< 65 mm FL), small (65-130 mm FL), medium (130-200 mm FL), or large (> 200 mm 

FL). All trout collected during electrofishing sampling were cutthroat trout, thus we 

assumed all trout observed during visual nighttime surveys were cutthroat trout. 

 
79

Appendix 5, continued. Number of fish observed during visual nighttime surveys in lower 

Taylor Creek, 2015-2019. Only the six primary species (sculpin is a combination of two 

species) observed are included. Coho salmon were categorized as either subyearlings 

(0+; < 100 mm FL) or yearlings (1+; > 120 mm FL). Trout were categorized as either fry 

(< 65 mm FL), small (65-130 mm FL), medium (130-200 mm FL), or large (> 200 mm 

FL). All trout collected during electrofishing sampling were cutthroat trout, thus we 

assumed all trout observed during visual nighttime surveys were cutthroat trout. 

 
80

Length

Year Date Section surveyed (m) Chinook Cutthroat trout Trout fry Coastrange sculpin

2015 March 26 L-1 5 0 1 0 12

L-2 5 0 1 0 8

L-3 10 0 1 0 0

April 7 L-1 5 0 0 2 5

L-2 5 0 2 0 6

L-3 5.7 0 2 0 0

May 5 L-1 3.5 0 0 2 7

L-2 5 0 2 1 21

L-3 8.5 0 1 1 0

2016 February 16 L-1 5 1 0 0 10

L-2 5 0 2 0 15

L-3 10.2 0 0 0 1

March 8 L-1 4.4 0 1 0 17

L-2 5 0 2 0 23

L-3 7 0 2 0 2

April 5 L-2 10 0 2 0 15

L-3 10.2 0 3 0 0

May 11 L-1 3 0 2 14 1

L-2 5 0 0 2 6

L-3 10 0 1 16 0

2017 February 14 L-1 2.3 6 0 0 30

L-2 5 0 2 0 6

L-3 10 0 4 0 0

March 20 L-1 3.4 3 2 0 19

L-2 5 1 2 0 20

L-3 10 0 2 0 0

April 11 L-2 10 0 0 0 33

L-3 6.9 0 4 0 1

May 9 L-2 10 0 3 2 26

L-3 10 0 0 0 0

2018 February 2 L-1 5 5 0 0 16

L-2 5 0 3 0 5

L-3 10 0 2 0 3

March 18 L-2 10 0 2 0 4

L-3 10 0 0 0 5

April 13 L-2 10 0 3 0 42

L-3 7.7 0 0 0 0

May 3 L-2 10 0 1 0 31

L-3 10 0 2 0 3

2019 January 30 L-1 5 0 0 0 1

L-2 5 0 2 0 5

L-3 7.2 0 0 0 2

February 19 L-1 5 0 1 0 13

L-2 5 0 0 0 1

L-3 5 0 1 0 8

March 18 L-1 5 0 0 0 2

L-2 5 0 0 0 6

L-3 5 0 1 0 8

April 24 L-1 5 3 0 13 7

L-2 5 0 2 3 3

L-3 5 0 0 1 5

May 13 L-1 5 0 0 12 0

L-2 5 0 0 5 2

L-3 5 0 0 2 13

Totals 355 19 64 76 469

Number of fish

Appendix 6. Number of fish collected during riffle electrofishing surveys in lower Taylor 

Creek, 2015-2019.