Use of High Definition Imaging Sonar as a Methodology for Evaluating Reclamation Fish Passage Structures
1) Are species of special concern spawning in areas below Vandalia Dam, 2) What are the characteristics of these areas if spawning is occurring, 3) Can these spawning areas be reproduced as part of a mitigation strategy in the event of a listing? This scoping proposal seeks to explore Dual Frequency Identification Sonar (DIDSON) as a methodology for providing important spawning information concerning these species to managers by addressing these questions. Reclamation's Milk River Project in north-central Montana currently delivers unimpeded water to its constituents throughout the Milk River Basin. Several (4) Species of Special Concern utilize the lower Milk River below Vandalia Diversion Dam, and their presence in the river is attributed to historic spawning runs. Federal listing of any of these species under the Endangered Species Act could curtail water delivery in this basin.
Need and Benefit
Reclamation's Milk River Project provides water for over 52,000 irrigated hectares. The basin and associated water storage and irrigation diversions are critical to north-central Montana, and by extension, to Reclamation's mission in this area.
Fish assemblages in the Milk River basin are receiving higher levels of attention due to tribal and international water rights issues, basin storage expansion, and the presence of 4 Montana listed Species of Special Concern (SSC). These four species (blue sucker, sauger, shovelnose sturgeon, and paddlefish) are suspected to both spawn and rear below the lowest diversion in the basin, Vandalia Dam.
SSC listing is considered a precursor to federal listing under the Endangered Species Act (ESA). Currently, the federally endangered pallid sturgeon is the only ESA listed fish species in the Missouri River immediately downstream of Fort Peck Reservoir and Dam, but its presence has already led to operational changes in water delivery (the Milk River is a tributary to the Missouri River, joining several miles below Fort Peck).
Continued and unimpeded water delivery in the Milk River basin may be predicated on finding ways to prevent federal listing for these SSC.
Three of these SSC species, blue sucker, shovelnose sturgeon, and paddlefish, and the endangered Pallid sturgeon, are part of a biological monitoring program associated with flow modification to Fort Peck Reservoir and have been instrumented with combination acoustic and radio tags. These fish are trackable as they move into the Milk River for spawning runs, and would be detectable using Dual Frequency Identification Sonar. The sonar is capable of recording viewable behavior in turbid water, and can be used in conjunction with fine mesh egg traps to verify spawning of fish observed. If spawning can be confirmed, the characteristics of the area where it occurred can be recorded and perhaps reproduced in the event of a listing under the Endangered Species Act.