Snake River White Sturgeon Conservation Plan ... - Idaho Power

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Status and Habitat Use of Snake River White SturgeonIdaho Power Companythe pool, while fish movement in the free-flowing sections of the Snake River remained morelocalized. Lepla and Chandler (1995a) speculated that these differences in movement patternswere related to the differences in feeding behaviors between riverine and reservoir environments.In free-flowing sections, food items carried by the river currents could settle out in habitats usedby sturgeon; in a reservoir, sturgeon had to search more actively. Overall, sturgeon movementduring IPC’s monitoring efforts was fairly localized, with the majority (61–91%) of fishtraveling less than 10 river miles from their initial capture locations (Figure 2). Based on alltelemetry observations, the average distance traveled by Snake River sturgeon ranged from 0.4 to4.0 river miles. Coon (1978) observed similar localized movement patterns: sturgeon greater than183 cm below Hells Canyon Dam often moved only among pools that were close to each other.He noted that smaller sturgeon tended to move downstream but averaged only around 7 km peryear.RL& L Environmental Services (2000) reported similar movement behavior for white sturgeonin the Fraser River, an undammed river system. Telemetry data for female and male whitesturgeon in various stages of maturity and segments of the Fraser River showed meanmovements of 0.4 to 3.3 river miles for Stock Group 1 (SG1), 0.0 to 1.8 river miles for SG2,0.2 to 6.7 river miles for SG3, and 0.06 to 0.4 river miles for SG5. The authors also noted thatseveral sturgeon exhibited extensive movement exceeding 25 river miles: some of these sturgeontraveled more than 43 river miles between monitoring efforts. Overall, sturgeon monitoredduring their telemetry studies displayed localized movements that most commonly ranged lessthan 6 river miles. This finding suggests that discrete sections of the Fraser River providedsuitable white sturgeon habitats for several life history functions. In the Nechako River, atributary to the Fraser River, sturgeon commonly traveled more than 9 river miles (maximummovements ranged in direction from 38 river miles upstream to 45 river miles downstream).These movements are thought to be an adaptation of a feeding strategy that exploits the sockeyesalmon migration through this river system. Similar large-scale movements that appear to benecessary because of the geographic separation between habitats suitable for various lifefunctions—such as feeding, spawning, and overwintering—have also been observed in otherriver systems, such as the Kootenai River (Apperson and Anders 1991) and Lake Roosevelt(Brannon and Setter 1992).The most notable movement patterns IPC investigators observed in the Snake River weregenerally associated with spawning, and the distance sturgeon traveled depended on theproximity of suitable spawning habitat (Lepla and Chandler 2001). This behavior wasparticularly evident among sexually mature sturgeon traveling from reservoir to riverineenvironments. In C.J. Strike Reservoir, located 37 miles upstream of Swan Falls Dam,reproductive adults (tags S2633, S2426, S2354, S2353, S249, and S258) often left the pool asspawning temperatures approached and, depending on their capture location in the pool, traveledabout 16 river miles upstream of the pool to stage and spawn near RM 521.8 (Figure 3). Similarupstream spawning movements, although typically less than a few miles, were observed amongsturgeon below C.J. Strike and Oxbow dams as they sought suitable spawning conditions thatgenerally occurred only near the tailraces (Figure 4 and Figure 5b) (Lepla and Chandler 2001).Spawning-related movements in the river canyon corridors below Bliss, Swan Falls, andHells Canyon dams were often less defined than those we observed in the reaches belowC.J. Strike and Oxbow dams. These lesser defined movements are likely due to the presence ofPage 8Hells Canyon Complex
Idaho Power CompanyChapter 4: Conceptual Design for White Sturgeon Passage Facilitiesnumerous pools with nearby high-velocity runs for staging and rapids that are suitable forspawning; such pools are absent in the reaches below C.J. Strike and Oxbow dams. The distancesthat spawners traveled varied by reach: sturgeon traveled 0.3 to 9.0 river miles between KingHill and Bliss Dam (S3335 and S275) (Figure 3), 1.5 to 6.0 river miles below Swan Falls Dam(S339 and R133) (Figure 5a), and 0.0 to 2.0 river miles below Hells Canyon Dam (S249, S248,and S294) (Figure 6). None of the telemetered spawners in these river segments traveledupstream to the dam tailraces (Lepla and Chandler 2001).Lepla and Chandler (2001) also observed that several spawners exhibited post-spawningbehavior by departing, generally downstream, from spawning areas within a few weeks, althoughthis behavior also varied. For instance, spawners from C.J. Strike Reservoir typically returneddownstream to the reservoir by late May (S2633, S2354, S2426, and S249) (Figure 3). BelowHells Canyon Dam, we observed similar behavior in two female sturgeon that departeddownstream. The distance these fish moved downriver ranged from 13 to 61 river miles,followed by return movements back upstream (24–31 river miles) by the middle of summer(S249 and S294) (Figure 6). Still other sturgeon remained at spawning sites and displayed nodiscernable post-spawning movement at all (S3335, S2534 [Figure 3], S114, S105 [Figure 4],S339 [Figure 5a], and S248 [Figure 6a]). Overall, the predominantly localized movement byreproductive and nonreproductive sturgeon suggested that several sections of the Snake Riverprovide suitable habitat for various life history functions, including feeding, rearing,overwintering, and spawning (Lepla et al. 2001).As mentioned already, movements of most sturgeon were highly localized, although somejuvenile and adult white sturgeon have moved downstream past dams in reaches of the middleSnake River. Lepla and Chandler (1995a, 1997) recaptured 15 hatchery sturgeon below BlissDam and 6 sturgeon (4 wild and 2 hatchery) below C.J. Strike Dam that had been originallystocked or tagged upstream of these projects. In contrast, no sturgeon (wild or hatchery) that hadoriginally been tagged above the HCC have been sampled downstream of Hells Canyon Damduring IPC’s sturgeon surveys. Based on the mark-recapture data, IPC estimated that 2% of theBliss Reach sturgeon population, on average, move downstream past C.J. Strike Dam annually(K. Lepla, pers. comm.). This estimate is comparable with the rate of annual downstreammovement (2%) estimated for sturgeon marked and released in the four lower Columbia Riverreservoirs (ODFW, unpubl. data).The environmental cues that drive older life stages of sturgeon to move downstream from onereach to another are poorly understood. These sturgeon may be seeking additional rearing andfeeding habitats. For instance, the Idaho Department of Fish and Game released 2,211 hatcheryrearedsturgeon (age 1) in the 13-mi segment between Lower Salmon Falls and Bliss damsduring 1989–1990 (Patterson et al. 1992). Movement by some of these stocked fish into the nextdownstream reach may have been related to searching for additional rearing habitat for whichthere was less competition. Still, other sturgeon from these stockings remained and wererecaptured at the same release point (the Lower Salmon Falls tailrace) 5 years later (IPC, unpubl.data).Hells Canyon Complex Page 9
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