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HomeMy WebLinkAboutUW-FRI_Knutson Creek Report_lowresSpawning Ground Survey of Upper Knutson Creek, Iliamna Lake, Alaska Curry J. Cunningham, PhD University of Washington, Alaska Salmon Program cunninghamcurry@gmail.com 907-360-4217 Summary The purpose of this project was to quantify sockeye salmon (Oncorhynchus nerka) abundance and spawning condition, and qualitatively evaluate the availability and suitability of spawning habitat in upper Knutson Creek. Surveys were conducted by Dr. Cunningham and UW-FRI personnel near the peak of spawning reported by Demory et al. (1964), on 15-Aug-2016 and again ten days later on 25-Aug-2016. The surveyed region of Knutson Creek extended ~4 km from the downstream (59.81007° N, 154.12872° W) to upstream (59.82596° N, 154.10931° W) limits of the proposed bypass reach. The survey region was broken into 200-meter long survey sections for better spatial resolution in recorded salmon abundance. The stream survey was conducted on foot moving upstream along the stream-left (southeast) bank, with the survey crew maintaining as close a proximity to the waterline as terrain allowed. Using tally counters one person visually enumerated salmon in the stream while also noting salmon behavior (i.e. holding vs. spawning). A second person followed counting any sockeye salmon carcasses on the near and far banks of the stream and categorizing these as bear-killed or post-spawn mortality. The third person noted travel distance with handheld GPS. At the top of each survey section, the number of live fish, the number of dead fish by category and a general description of the spawning habitat were recorded, and reference photographs were taken. In addition to the formal stream survey, the four largest spawning areas (Sites #1-4) were identified and marked with fixed rebar posts for later observation. Spawning areas were designated based on the presence of fish, condition of fish, and spawning behavior (i.e. paired individuals, male-male competition, female redd digging). The four spawning sites were marked with four rebar posts (Rebar #1-4) on the stream-left bank. Horizontal distance from the rebar marker to the actual salmon spawning location was measured using a laser rangefinder and recorded along with the direction of view toward the spawning site. Where possible, two horizontal distance measurements were taken to allow for precise triangulation of the spawning site. GPS coordinates were recorded for the rebar posts and pictures were taken of both the spawning sites and the rebar marker locations. Survey Results Visibility during both surveys was good, with water clear and low turbidity. Water velocity and gradient caused some distortion due to trapped air bubbles, but overall the probability of failing to observe a significant number of sockeye was quite low. Throughout the 4 km upper Knutson Creek survey region, in total 249 live sockeye were observed on 15-Aug and 192 observed on 25-Aug. The majority of sockeye present in upper Knutson Creek were observed in section #2 (200 – 400 m upstream of the survey start), during both surveys (Survey 1: 67.1%, Survey 2: 66.2%). Survey section #2 included a side channel at stream-left that forms a deep pool where the channel encounters and slows at a cut bank, in the location where the trail from Pedro Bay meets Knutson Creek (see Site #1 and Site #2 below; 59.81112° N, 154.12437° W). Nearly all spawning activity was observed in this pool, as evidenced by paired sockeye, active redd digging, male-male competition, and the presence of nearly senescent and post-spawn sockeye. Few dead sockeye were observed (Tables 1 and 2), and of these the vast majority were bear-killed individuals found on the banks of the spawning pool in Section #2. Spawning conditions in the mainstem of Knutson Creek throughout the survey region were marginal, with high water velocity, large cobble, and evidence of extreme spring flow events. The habitat may broadly be defined as a combination of large cobble (>30 cm) riffles (Fig. 1) and intermittent terraced step-pools (Fig. 2) occurring in locations where Knutson Creek becomes confined by the valley or larger bedrock rock structures resulting in higher stream gradient. Sockeye observed in the mainstem were most often found holding near the bank or in larger pools, where current was slowed. Despite the absence of spawning habitat in the mainstem of Knutson Creek, a side channel at stream-right, departing the mainstem in section #18 (see Site #3 below) and rejoining in section #15 (Fig. 3; 59.82236° N, 154.11165° W) seemed to provide suitable off-channel spawning habitat. During the 15-Aug survey 5 sockeye were observed holding in a pool of the side channel before it rejoined the mainstem. While not actively spawning, the physical appearance of these fish indicated some were in post-spawn condition. Sockeye were present in this side channel where it departs from the mainstem in section #18 (Site #3) during both surveys. Water velocity and channel structure in both portions of the stream-right side channel visible from across the mainstem, suggested suitable spawning habitat was present. The presence of sockeye spawning in both the upper stream-right and lower stream-left side channels indicates that the water velocity in the mainstem of upper Knutson Creek is likely too high to permit extensive spawning. The extent to which the stream channel and distribution of sockeye within it change from annually is unknown, given that surveys were only conducted in 2016. Also unknown is the full extent of sockeye utilization of the upper stream-right side channel (Sections #15 – 18) for spawning, given the inability of the survey crew to cross the Knutson Creek mainstem. Survey 1: August 15, 2016 Table 1. Observations of live and dead (post-spawn and bear-killed) sockeye from the 15-Aug survey, by 200-meter section. Distance upstream (meters) and coordinates (latitude and longitude) describe the location of the upstream extent of each section, and picture numbers reference the digital appendices. Section Distance Upstream (m) Live Dead Latitude (°N) Longitude (°W) Picture Post- spawn Bear-kill Total 1 200 16 0 0 0 59.81059 154.12589 2 400 167 0 3 3 59.81152 154.12389 3 600 9 0 0 0 59.81286 154.12309 4 800 6 0 0 0 59.81429 154.12239 5 1000 1 0 0 0 59.81544 154.12210 2-4 6 1200 1 0 0 0 59.81624 154.12161 6-8 7 1400 5 0 0 0 59.81664 154.11877 11-15 8 1600 6 0 0 0 59.81774 154.11705 16-18 9 1800 5 0 0 0 59.81811 154.11665 21-24 10 2000 2 0 0 0 59.81814 154.11499 31,32,36,37 11 2200 0 0 0 0 59.81900 154.11491 38,39 12 2400 0 0 0 0 59.81990 154.11401 40-43 13 2600 0 0 0 0 59.82082 154.11284 46-48 14 2800 6 0 0 0 59.82188 154.11226 49-51 15 3000 8 0 0 0 59.82257 154.11038 52-62 16 3200 0 0 0 0 59.82338 154.10962 63-65 17 3400 0 0 0 0 59.82427 154.10909 69-74 18 3600 7 0 0 0 59.82534 154.10899 82-85 19 3800 10 0 0 0 59.82586 154.10860 86-89 Total 249 0 3 3 Survey 2: August 25, 2016 Table 2. Observations of live and dead (post-spawn and bear-killed) sockeye from the 25-Aug survey, by 200-meter section. Distance upstream (meters) and coordinates (latitude and longitude) describe the location of the upstream extent of each section, and picture numbers reference the digital appendices. Section Distance Upstream (m) Live Dead Latitude (°N) Longitude (°W) Picture Post- spawn Bear-kill Total 1 200 16 2 1 3 59.81059 154.12589 95-97 2 400 127 2 14 16 59.81152 154.12389 98-100,102 3 600 7 0 0 0 59.81286 154.12309 103-105 4 800 8 0 0 0 59.81429 154.12239 106-110 5 1000 3 0 0 0 59.81544 154.12210 111-113 6 1200 3 0 0 0 59.81624 154.12161 114-116 7 1400 5 0 0 0 59.81664 154.11877 117-119 8 1600 0 0 0 0 59.81774 154.11705 120-122 9 1800 3 0 0 0 59.81811 154.11665 123-125 10 2000 0 0 0 0 59.81814 154.11499 11 2200 0 0 0 0 59.81900 154.11491 126-129 12 2400 0 1 0 1 59.81990 154.11401 130-132 13 2600 0 0 0 0 59.82082 154.11284 136-138 14 2800 0 0 0 0 59.82188 154.11226 139-141 15 3000 2 0 0 0 59.82257 154.11038 16 3200 0 0 0 0 59.82338 154.10962 142-144 17 3400 1 1 0 1 59.82427 154.10909 145-147 18 3600 16 0 0 0 59.82534 154.10899 19 3800 1 0 0 0 59.82586 154.10860 Total 192 6 15 21 Figure 1. Knutson Creek riffle structure, with slower water near bank. Figure 2. Knutson Creek step pools. Figure 3. Upper stream-right side channel rejoins the mainstem of Knutson Creek in Section #15 (Fig. 3; 59.82236° N, 154.11165° W). Note: 5 sockeye were holding in the pool at the top of the picture, body condition indicated some were post-spawn. Spawning Habitat Determination Site 1 and Site 2 The majority of live sockeye (Survey 1: 67.1%, Survey 2: 66.2%) were observed in survey section 2 (200 – 400 meters upstream of lower survey limit), in a side channel at stream-left that forms a deep pool at a cut bank near, where the trail from the Pedro Bay meets Knutson Creek (59.81112° N, 154.12437° W). Two distinct spawning aggregations (Sites 1-2) within this side channel were observed and marked, with distances measured from two rebar posts (Rebar 1-2) to the two sites. Figure 4. Rebar #1 Figure 5. Rebar #2 Figure 6. Site #1 Figure 7. Site #2 Figure 8. Diagram of stream-left tributary in survey section #2, showing sites #1-2 and rebar #1-2. Mainstem Site 2 Site 1 Log Rebar 1 Rebar 2 9.31 m 8.68 m 25.96 m Site 3 Latitude: N 59.82522 Longitude: W 154.10898 Distance: 20.75 m (Rebar 3) Direction: NW The third spawning site was identified in section 18 during the 15-Aug survey, and subsequently marked during the 25-Aug survey. Sockeye were observed to be paired and spawning where a small side channel exits the mainstem at steam-right. Due to the depth and velocity of Knutson Creek it was not possible to cross and mark the location directly. Rebar #3 was placed on the left bank and the distance to the spawning pool was measured with laser range finder, 20.75 meters to the northwest of the marker. Figure 9. Site #3, looking to the northwest from rebar #3 across Knutson Creek. Spawning was observed in the pools beyond the mainstem, where the stream-right side channel exits. Figure 10. Site #3, view downstream. Spawning area marked in red. Figure 11. Site #3, view upstream. Spawning area marked in red. Site 4 Latitude: N 59.82582 Longitude: W 154.10849 Distance: 30.45 m (Rebar 4) Direction: NW Spawning site #4 was identified in section 19, where water from a side channel at stream- left pools before spilling over a small rock pile into the mainstem of Knutson Creek. Rebar #4 was placed on the left bank on an open rock and moss shelf and the distance to the spawning pool was measured with laser range finder, 30.45 meters to the northwest of the marker. Figure 12. Site #4, view from Rebar #4 across Knutson Creek mainstem. Spawning pool marked in red. Figure 13. View upstream from Rebar #4. Spawning pool is left of the photograph. Figure 14. Site #4, view downstream from Rebar #4. Western edge of spawning pool marked in red. Figure 15. Site #4 spawning pool. Figure 16. Site #4 spawning pool and rock shelf separating it from the Knutson Creek mainstem. Acknowledgements I would like to thank the Pedro Bay Corporation for permitting us to access their land, and our bear guards Floyd and Aaron from Pedro Bay. In addition, I would like to acknowledge the UW-FRI personnel who took part in the surveys: Jason Ching, Martin Arostegui, and Dara Yiu. References Demory, R.L., Heinle, D.R., Orrell, R.F. (1964) Spawning ground catalog of the Kvichak River system, Bristol Bay, Alaska, (Special scientific report -- fisheries ;no. 488, Vol. v, 292 pages), U.S. Dept. of Interior, Fish and Wildlife Service, Washington, D.C.