Factors Influencing Rainbow Smelt Entrainment Through Oahe Dam, South Dakota

This study was part of a four-year (1996-1999) project focused on gaining a better understanding of the dynamics surrounding the entrainment of rainbow smelt through Oahe Dam. Rainbow smelt are an important forage species for walleye and salmonids in Lake Oahe. Loss of rainbow smelt, from Lake Oahe through turbine entrainment could, if of sufficient magnitude, exacerbate variability in smelt population dynamics. Chapter 2 examines diel, seasonal, and annual trends of rainbow smelt entrainment and estimates the magnitude of smelt loss through Oahe Dam. Chapter 3 objectives were to better understand potential key variables that may influence Lake Oahe rainbow smelt susceptibility to turbine entrainment. Specific variables examined were water temperature, light intensity, the metalimnion, and hydroacoustic abundance of Lake Oahe rainbow smelt in close proximity to the intakes. Knowledge of how these factors may affect rainbow smelt entrainment may allow managers to forecast rainbow smelt susceptibility to entrainment as well as assess the utility of potential approaches to reduce smelt entrainment (e.g., modifying reservoir pool elevation, diel and seasonal water release patterns, strobe lights. From 1997 to 1999, rainbow smelt and other fish species were collected in the Oahe Dam tailrace (tailrace) from May through October or November with paired 1-m diameter, 1-mm (bar measure) mesh Nitex plankton nets. Additionally, water temperature, light intensity, and hydroacoustic abundance of rainbow smelt in Lake Oahe in close proximity to the intakes were measured. Abundance of entrained rainbow smelt in the tailrace was generally higher at night and varied seasonally. Age-0 rainbow smelt appeared to be most susceptible to entrainment through Oahe Dam from mid-June to mid- September while age-I and older rainbow smelt were at higher risk from June to mid-August. Mean abundance of age-1 and older rainbow smelt in the tailrace was 8. 2 ± 1.2 (± SE) RB S/1.000 m3 in 1997, 1.6 ± 0.36 in 1998, and 1.2 ± 0.20 in 1999 while age-0 rainbow smelt tailrace mean abundance was 53.1 ± 5.6 in 1997, 9.4 ± 0.79 in 1998, and 0. 21 ± 0.03 in 1999. Cumulative loss of rainbow smelt due to turbine entrainment through Oahe Dam from June through September was 439 ± 1 (± 95 Cl) million in 1997, 3 .2 ± 0.1 in 1998, and 1.8 ± 0.1 in 1999. Total estimated population loss (August through October) of rainbow smelt from the lower third of Lake Oahe due to turbine entrainment was 55% in 1997, <1% in 1998, and <1% in 1999. Tailrace abundance of entrained rainbow smelt estimated with meter nets was strongly related to smelt hydroacoustic abundance in close proximity to the intakes (r2 = 0.9361, p < 0.0001). Seasonal rainbow smelt entrainment through Oahe Dam appeared to be related to water temperature, light intensity, and the location of the metalimnion with relative to the depth of the intakes. Water temperature in the tailrace was most similar to reservoir water temperatures from O to 5 m above the depth of the intakes. Daytime light penetration was typically below the depth of the intakes, probably reducing the entrainment of most age-0 and nearly all age-I and older rainbow smelt during the day. The metalimnion was usually located at or above the depth of the intakes from June through August or September, likely exacerbating rainbow smelt entrainment. Managing rainbow smelt entrainment through Oahe dam will likely be a challenging task due to current system design, regulated use patterns of water in Lake Oahe, and the multiple objectives of numerous parties interested in the regulation of the flow regime of the Missouri River system. Overall, the best approach for reducing rainbow smelt entrainment through Oahe Dam at this time might be to examine the practicality of using strobe lights as a behavioral deterrent. Strobe lights can be turned on and off as needed without the logistical complexities that could very easily obstruct effective management of rainbow smelt entrainment based on manipulating Lake Oahe pool elevations and water release rates.

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Thesis - University Access Only

Discipline thesis:degree_discipline

Wildlife and Fisheries Science

Year

2000

Author dc:creator

• Smith, Kevin A.

Contributors dc:contributor

• Michael L. Brown

• rainbow smelt
• oahe dam
• south dakota
• environmental aspects
• Natural Resources and Conservation

Statement dc:rights

• Copyright © 2000 Kevin A. Smith. All rights reserved.

Language dc:language

en

Repository record dc:identifier

https://openprairie.sdstate.edu/etd/415

OAI identifier oai:identifier

oai:openprairie.sdstate.edu:etd-1415