Completion Form

2023

At Pleasant Creek, a total of 17 sites were sampled within 15 stations; sampling was conducted at one or more sites at each station. Sampling was conducted by two three-person field crews, using Smith-Root LR-24 battery-powered electro-shockers; the voltage was set at a pulsing current pattern to minimize native fish mortality and injury. Surveys were qualitative and consisted of shocking upstream (starting and ending at a shallow riffle or other control feature) until the species captured appeared to be representative for that station; additional sites were surveyed within a station if species diversity was low. Stations were 500 m in length and were located in the field using Garmin GPS units, aerial photographs, and topographic maps. Individual site lengths varied according to discharge, stream size, and habitat type. Additional data recorded included shocking time (seconds), start/end times, water/air temperatures, and station UTM's (NAD 83). For each site, average depth and the proportion of habitat type sampled within the wetted channel was recorded and classified into the following types: run, riffle, pool, or backwater. Fish captured were placed in buckets and processed after sampling was completed to avoid recapturing individual fish within a site. All fish captured were identified to species and total length was measured to the nearest 1.0 mm; natives were returned to the river and non-natives were removed.

At Sulphur Creek, the study reach included the lower 6.4 km (4.0 mi) from upstream of the lower waterfall downstream to the confluence of the Fremont River. Stratified random sampling stations (n=4) were established 1.6 km (1.0 mi) apart, using digitized aerial photographs. Stations were approximately 500 m (0.3 mi) in length. The top of each station was located in the field using GPS units and/or aerial photographs and topographic maps. Field crews were comprised of three to four people. A total of 20 sites within each station were sampled. Sites that could be seined effectively were selected in proportion to the availability of habitat within a station (e.g., run, riffle, pool). Three-pass depletion seining was conducted, in which three consecutive seine hauls were pulled at each site, moving downstream, using 1.2 x 4.6 m knotless nylon seines (3.2 mm mesh). The second and third seine hauls duplicated the first seine haul as closely as possible. Fish captured during each seine haul were placed in separate buckets and processed independently to avoid recapturing individual fish within a site and to evaluate the effectiveness of depletion efforts. Native and non-native fish were identified and total length was measured to the nearest 1.0 mm; all fish were returned to the river. Length frequency histograms were generated for each species if >20 individuals were captured. Abundance was used to compare fish numbers among stations and was calculated for each site as the number of fish/100 m3 of stream (number of fish captured, divided by the total volume sampled); abundances were calculated for Flannelmouth Sucker and Bluehead Sucker. For each station, an average abundance was calculated for each sucker by summing fish/100m3 at each site and dividing it by the number of sites sampled. At each site field crews recorded habitat (run, riffle, pool, backwater) and dominate substrate (silt, sand, gravel, cobble, boulder, bedrock); a substrate was considered dominant if it comprised >50% of the total substrate composition. Substrates were considered mixed if two substrate types each comprised an equal percent of the total composition. The length (m), width (m), and depth (ft) of the area sampled was measured using hand-held meter tapes; if the habitat was larger than the area sampled, then the length (m) and width (m) of the habitat was also measured. These data were later used to calculate the volume (m3) of sites sampled. Additional data collected at each station included Air and water temperatures (ÃÂ°C) for each station at the beginning and end of sampling. Photographs were taken at the upstream (looking downstream) and downstream (looking upstream) ends of each station.

The presence of native fish in Pleasant Creek was encouraging, especially since sampling hasn't been conducted in this tributary for 15 years. On August 16, the lower 11 miles of stream (stations 1-11) were dry, due to water diverted at Notom Diversion. This diversion obviously influences native fish distribution; Bluehead Sucker were limited to the upstream portion of Pleasant Creek, between Site 14b in Station 14 and Station 19, while Flannelmouth Sucker were captured only in Station 1, just upstream of the confluence with the Fremont River. Multiple age classes of Bluehead Sucker were captured including young of year (YOY) and adult which indicated a self-sustaining population while Flannelmouth Sucker captures included only YOY.

On the night of August 16, Pleasant Creek reconnected to the Fremont River due to flash flooding, thus allowing sampling of the lower stations; however, Station 3 and stations 6-10 were not sampled due restricted access on private property. Following the flooding, one or more native fish species were captured in all of the lower stations sampled. This demonstrates the ability of native fish to re-populate Pleasant Creek after periods of drying. Overall, Speckled Dace were the most common and widely distributed native fish and were captured in 15 of the 17 sites sampled.

Non-native fish captures in Pleasant Creek were rare during sampling, with the exception of stations 20 and 21, where captures consisted entirely of non-native trout. Downstream of Station 20, the stream channel began to transition from shallow and wide with low velocity habitat to narrow and deep habitat with overhanging vegetation in stations 20 and 21. The transition of aquatic habitat and a waterfall between stations 20 and 21, likely limits the upstream distribution of native fish in Pleasant Creek.

When comparing 2022 Pleasant Creek fish distribution with previous sampling in 2006-2007, there was a change in distribution for Bluehead Sucker and Flannelmouth Sucker. Bluehead Sucker distribution in 2022 extended approximately 1.6 km (1.0 mi) upstream from the upstream extent in 2006 (Figure 4). However, Bluehead Sucker were absent in the lower stations in 2022, where in 2006 they were distributed throughout Pleasant Creek. This was likely due to lack of streamflow downstream of the Notom Diversion for an unspecified amount time prior to sampling in 2022, while flows were above average for the drainage in 2006. Flannelmouth Sucker distribution in 2022 was also affected by drying, with captures only occurring in the furthest downstream station. In 2006, Flannelmouth Sucker were distributed in the lower 12.9 km (8.0 mi) of Pleasant Creek with multiple age classes represented.

Efforts in 2022 represent the first fish surveys conducted by UDWR on Sulphur Creek as part of distribution sampling in the Fremont River Basin. Bluehead Sucker and Speckled Dace were the most abundant and widely distributed native fish species during sampling with captures occurring in stations 1, 2, and 3 while Flannelmouth Sucker were the least abundant and only distributed in stations 1 and 2. There were no fish captured in Station 4 during sampling. The absence of fish is likely due to the waterfall located near the top of Station 3; the approximate 10 foot drop below the waterfall acts as a barrier to upstream movement and limits distribution. The majority of fish captures (n=1,227) during sampling occurred in Station 1. This result was not surprising as Station 1 was the nearest sampling site to the confluence of the Fremont River where native fish are abundant.

Bluehead Sucker captures during Sulphur Creek sampling consisted of two age classes and included young of year (YOY) and adult. The presence of multiple age classes of Bluehead Sucker was encouraging and indicates a self-sustaining population is present. All Flannelmouth Sucker captured were YOY with no other age classes being represented (e.g., juvenile and adult). The aquatic habitat in Sulphur Creek consists largely of low velocity, shallow runs and riffles with gravel dominated substrates and is not conducive to the preferred habitat type of Flannelmouth Sucker during juvenile and adult life stages. However, the high numbers of YOY Bluehead Sucker and Flannelmouth Sucker captured during sampling indicates that Sulphur Creek is likely critical habitat during reproduction of both species and serves as rearing habitat for larval fish.

Non-native fish captures (n=128) during Sulphur Creek sampling were rare and accounted for 8.1% of total fish captures (n=1,582). Southern Leatherside Chub were the most common non-native species captured with multiple age classes represented including YOY, juvenile, and adult.

Kevin Wheeler

08/28/2023 10:15:31