Estimating Salmon Abundance in the Kuskokwim River Using Sonar, 2017
Estimating Salmon Abundance in the Kuskokwim River Using Sonar, 2017

Author: Keegan O. Birchfield

Publisher:

Published: 2019

Total Pages: 40

ISBN-13:

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In 2017, sonars were operated on the Kuskokwim River to estimate the abundance and run timing of Pacific salmon Oncorhynchus spp. following recommendations from a 2014–2016 feasibility study. After identifying a location with a suitable bottom profile, split-beam and imaging sonar were deployed on the gentle sloping left bank and an imaging sonar was deployed on the steep right bank. Species-specific fish passage abundance estimates were generated using a 3-step process. First, all fish passing the site were estimated, without regard to species. Second, species compositions were estimated and adjusted using selectivity parameters. Finally, species composition estimates were applied to total passage estimates to create species-specific abundance estimates. An unadjusted estimate of 2,531,397 fish passed the sonar site between June 1 and July 26. However, right bank vertical sonar coverage was incomplete in 2017 due to late installation of a spreader lens. An expansion based on 2016 and 2017 left bank counts was used to produce estimates of right bank missed passage by species. Despite adjustments, there were still substantial differences between sonar estimates and Kuskokwim River run reconstruction and mark–recapture projects estimates of Chinook salmon Oncorhynchus tshawytscha that may be due to abnormal river conditions in 2017 (i.e., low water levels).

Estimating Fish Abundance in the Kuskokwim River Using Sonar, 2021
Estimating Fish Abundance in the Kuskokwim River Using Sonar, 2021

Author: Keegan O. Birchfield

Publisher:

Published: 2023

Total Pages: 0

ISBN-13:

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Sonars were operated on the Kuskokwim River in 2021 to estimate the inseason abundance of Pacific salmon Oncorhynchus and nonsalmon species. After identifying a location with a suitable bottom profile, split-beam and imaging sonar were deployed on the gentle sloping left bank, and an imaging sonar was deployed on the steep right bank. Species-specific fish passage abundance estimates were generated using a 3-step process. All fish passing the site were estimated without regard to species. Species composition was estimated and adjusted using net selectivity parameters. Species composition estimates were then applied to total passage estimates to create species-specific abundance estimates. An estimated 2,704,816 fish passed the sonar site between June 1 and August 26. The Chinook salmon O. tshawytscha passage estimate was 102,552 fish (95% CI 84,438–120,666). The sockeye salmon O. nerka passage estimate was 745,037 fish (95% CI 696,241–793,833). The chum salmon O. keta passage estimate was 25,689 fish (95% CI 14,550–36,828). The coho salmon O. kisutch passage estimate was 237,285 fish (95% CI 209,320–265,250). The pink salmon O. gorbuscha passage estimate was 41,912 fish (95% CI 30,758–53,066). All nonsalmon species totaled 1,552,341 fish (95% CI 1,415,098–1,689,584).

Estimating Salmon Abundance in the Kuskokwim River Using Sonar, 2016
Estimating Salmon Abundance in the Kuskokwim River Using Sonar, 2016

Author: Keegan O. Birchfield

Publisher:

Published: 2019

Total Pages: 72

ISBN-13:

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A 3-year study was initiated in 2014 to assess the feasibility of using sonar, in combination with drift gillnetting, to estimate salmon abundance in the Kuskokwim River. This report presents the results of the final year of feasibility assessment in 2016. After identifying a location with a suitable bottom profile, split-beam and imaging sonars were deployed on the gentle sloping left bank and an imaging sonar was deployed on the steep right bank. A range of drift gillnet mesh sizes were deployed along both banks to apportion sonar counts to species. Following a late project start, there were few interruptions in apportionment and sonar counts. Consistent fishing and sonar operation allowed estimation of daily and total passage of most salmon and whitefish species. A general comparison was made between the 2016 sonar, Bethel test fishery, Kuskokwim River Chinook salmon mark-recapture, and weir escapement projects. Run timing tracked well between Bethel test fishery and the Kuskokwim River sonar with small discrepancies between chum to sockeye salmon ratios that may be due to the differing mesh sizes employed by each project. Chinook salmon was the only species assessed by other projects for drainagewide estimates; a comparison was made between sonar passage estimates (with annotations concerning harvest) and run size estimates from the mark-recapture project and escapement estimates from the run reconstruction model. When considering the shorter sonar sampling season, preliminary total passage estimates of Chinook salmon were within 90% CI across all projects. When including the modifications recommended by the feasibility study, sonar has the potential to accurately estimate salmon and whitefish abundance, in real time, on the Kuskokwim River for future management purposes.

Estimating Fish Abundance in the Kuskokwim River Using Sonar, 2020
Estimating Fish Abundance in the Kuskokwim River Using Sonar, 2020

Author: Keegan O. Birchfield

Publisher:

Published: 2023

Total Pages: 0

ISBN-13:

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Sonar was operated on the Kuskokwim River in 2020 to estimate the inseason abundance of Pacific salmon Oncorhynchus and nonsalmon species. After identifying a suitable bottom profile location, split-beam and imaging sonar were deployed on the gentle sloping left bank, and an imaging sonar was deployed on the steep right bank. Species-specific fish passage abundance estimates were generated using a 3-step process. All fish passing the site were estimated without regard to species. Species composition was estimated using drift gillnet catches adjusted by net selectivity. Species composition estimates were then applied to total passage estimates to create species-specific abundance estimates. An estimated 2,823,393 fish passed the sonar site between June 3 and August 25. The Chinook salmon O. tshawytscha passage estimate was 106,265 fish (95% CI 90,344–122,186). The sockeye salmon O. nerka passage estimate was 576,045 fish (95% CI 509,922–642,168). The chum salmon O. keta passage estimate was 76,369 fish (95% CI 55,954–96,784). The coho salmon O. kisutch passage estimate was 163,708 (95% CI 127,238–200,178). The pink salmon O. gorbuscha passage estimate was 19,793 fish (95% CI 12,239–27,347. All nonsalmon species totaled 1,881,213 fish (95% CI 1,742,348–2,020,078).

Estimating Fish Abundance in the Kuskokwim River Using Sonar, 2019
Estimating Fish Abundance in the Kuskokwim River Using Sonar, 2019

Author: Keegan O. Birchfield

Publisher:

Published: 2023

Total Pages: 0

ISBN-13:

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Sonars were operated on the Kuskokwim River in 2019 to estimate the inseason abundance of Pacific salmon Oncorhynchus and nonsalmon species. After identifying a suitable bottom profile location, split-beam and imaging sonar were deployed on the gentle sloping left bank, and an imaging sonar was deployed on the steep right bank. Species-specific fish passage abundance estimates were generated using a 3-step process. All fish passing the site were estimated without regard to species. Species composition was estimated and adjusted using net selectivity parameters. Species composition estimates were then applied to total passage estimates to create species-specific abundance estimates. An estimated 2,871,514 fish passed the sonar site between May 31 and July 26.

Estimating Fish Abundance in the Kuskokwim River Using Sonar, 2018
Estimating Fish Abundance in the Kuskokwim River Using Sonar, 2018

Author: Keegan O. Birchfield

Publisher:

Published: 2023

Total Pages: 0

ISBN-13:

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In 2018, sonars were operated on the Kuskokwim River to estimate the inseason abundance of Pacific salmon Oncorhynchus and nonsalmon species. After identifying a location with a suitable bottom profile, split-beam and imaging sonars were deployed on the gentle sloping left bank, and an imaging sonar was deployed on the steep right bank. Species-specific fish passage abundance estimates were generated using a 3-step process. First, all fish passing the site were estimated without regard to species. Second, species compositions were estimated and adjusted using selectivity parameters. Species composition estimates were then applied to total passage estimates to create species-specific abundance estimates. An estimated 2,060,581 fish passed the sonar site between June 2 and July 26. However, left-bank sonar counts were disabled from June 2 to June 3, and right-bank sonar counts were disabled from June 22 to June 28; expansions based on 2018 counts when sonars were operational were used to adjust estimates of missed passage by stratum and species (for a new total passage of 2,163,768 fish). The backup adaptive resolution imaging sonar (ARIS) lacked automatic tilt capability; therefore, total estimates of passage are considered underestimates. Several risk mitigating plans were proposed to prevent sonar downtime in the future. Finally, discrepancies between concurrent inseason indices and sonar estimates of chum salmon abundance led to recommendations for deeper offshore apportionment nets during high water years.