Estimating Fish Abundance in the Kuskokwim River Using Sonar, 2018
Author: Keegan O. Birchfield
Publisher:
Published: 2023
Total Pages: 0
ISBN-13:
DOWNLOAD EBOOKIn 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.