Study Update Tailrace Slough Use by Anadromous Salmonids

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Vincent Cameron
5 years ago
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1 Study Update Tailrace Slough Use by Anadromous Salmonids

2 Goals and Objectives Identify what anadromous salmonids use the tailrace slough by: Life Stage (Juvenile, migrating and spawning adults) Timing Type of use

3 Study Area The tailrace slough immediately downstream of the Project tailrace terminus to its confluence with the Cowlitz River Given that the configuration of the tailrace changes frequently, the area surveyed was within the bankfull channel at the time of the study

4 Study Area X X X Right Channel X Right Channel X Tailrace Mouth Main Channel Above Split X = Study Sites Left Channel Left Channel Main Channel

5 Methods 3 m of every 16 m is snorkeled seasonally for 1 year assessing: Fish species presence Life Stage and Approximate Length Habitat Characteristics Depths Velocities Substrate Composition Habitat Types

6 Survey Issues A Spring 26 survey could not be conducted due to a period of extended high water and extreme turbidity A fall/winter survey was scheduled for Dec. 1 th. High flows and long term turbid water associated with the November, 26 flood precluded biologists from conducting a survey until January, 27. Comprehensive documentation of adult use in the tailrace slough from the Anadromous Spawning Surveys during the period from August to January (24-26) was utilized for anadromous fish presence information during the fall/winter period.

7 Survey Dates and Associated Flows July 27, 26 (Finished August 2 nd, 26) January 15, 27 April 26, 27 June 19, 27 Cowlitz River 925 cfs Tailrace 94 cfs (Snorkeled) Cowlitz River 137 cfs Tailrace 58 cfs (Electrofished) Cowlitz River 143 cfs Tailrace 44 cfs (Electrofished) Cowlitz River 23 cfs Tailrace 11 cfs (Snorkeled)

8 Results from the July, 26 Survey A total of five 3 m sites were surveyed 618 coho juveniles were observed in the left side channel 4 Chinook juveniles were observed in the left side channel 5 coho juveniles were observed in the right side channel 2 coho were observed in the channel prior to the split Other species documented include: rainbow trout whitefish sucker

9 Table 3-1 July, 26 Habitat and Fish Observation Information Habitat Percentages Depth Range (ft) Riffle Run Glide Pool Substrate Velocity Range (Fps) Number of Coho Juveniles Observed Number of Chinook Juveniles Observed Left Side Channel Study Sites Cobble/ Gravel.35/1/35.9/ Right Side Channel Study Sites 1 Sand.85/1.4.3/ Main Channel Above Split Study Sites 1 Sand/ Gravel 1.2/3.75.1/

10 Results from the January, 27 Survey The same five 3 m sites were surveyed Secondary habitat types changed as a result of flooding in November, 26. No anadromous species were observed in any of the study sites. Other species documented include: rainbow trout whitefish sucker

11 Table 3-2 January, 27 Habitat and Fish Observation Information Habitat Percentages Riffle Run Glide Pool Substrate Depth Range (ft) Velocity Range (Fps) Number of Coho Juveniles Observed Left Side Channel Study Sites Sand/ Cobble.9/1.8.1/.65 Right Side Channel Study Sites 5 5 Gravel/ Cobble.85/ /2.57 Main Channel Above Split Study Sites 1 Sand/ Cobble.65/3..97/1.73

12 Results from the April, 27 Survey The same five 3 m sites were surveyed March high water resulted in secondary habitat types being altered at the study sites 31 coho juveniles were observed in the left side channel 1 Chinook juvenile was observed in the right side channel 2 coho juveniles were observed in the main channel before the split Other species documented include: rainbow trout whitefish sucker

13 Table 3-3 April, 27 Habitat and Fish Observation Information Habitat Percentages Depth Range (ft) Riffle Run Glide Pool Substrate Velocity Range (Fps) Number of Coho Juveniles Observed Number of Chinook Juveniles Observed Left Side Channel Study Sites Gravel/ Cobble.2/1../ Right Side Channel Study Sites 1 Gravel.6/ / Main Channel Above Split Study Sites 1 Sand/ Gravel.3/3.6.12/1.6 2

14 Results from the June, 27 Survey The same five 3 m study sites were surveyed High water related to runoff altered secondary habitat types between the April and June surveys Approximately 14 coho juveniles were observed in the left side channel No fish were observed in the right channel 25 coho juveniles were observed in the main channel above the split Other species documented include: rainbow trout whitefish sucker

15 Anadromous Fish Presence No Anadromous adults were observed during the surveys Juvenile presence varied by season and channel Coho presence dominated the surveys which correlates well with anadromous spawning survey numbers seen in the tailrace slough

16 Coho Juvenile Presence Numbers in Packwood Tailrace Slough Number of Fish July January April June Month Left Side Channel Right Side Channel Main Channel Above Split

17 Habitat Conditions The left side channel has a higher gradient, varying substrate composition and much higher habitat diversity than the right channel The right channel consists of uniform habitat with very little suitable substrate for spawning and slow moving pocket water for rearing Gravel was transported into the main channel above the split as a result of the November, 26 and March, 27 high water events

18 Left Side Channel Packwood Tailrace Slough Left Channel Habitat Frequencies During Each Survey Habitat Percentage July 26 January 27 April 27 June 27 Survey Riffle Run Glide Pool

19 Right Side Channel Packwood Tailrace Slough Right Channel Habitat Frequencies During Each Survey Habitat Percentage July 26 January 27 April 27 June 27 Survey Riffle Run Glide Pool

20 Main Channel Above Split Packwood Tailrace Slough Main Channel Habitat Frequencies During Each Survey Habitat Percentage July 26 January 27 April 27 January 27 Survey Riffle Run Glide Pool

21 Conclusions The tailrace slough area is a dynamic complex that can go through dramatic hydrologic and habitat alterations as a result of high flows from the Cowlitz River Throughout these alterations, during ENW studies, the left side channel maintained its high level of spawning and rearing habitat. A majority of coho juveniles and all coho spawners were observed in the left side channel All gravel and wood that is routed into the area is a product of transport down the Cowlitz River.

22 Conclusions No coho were observed during the January, 27 survey Emergence typically occurs in April Most coho out-migrating as year 1+ (over wintering) juveniles Low flows in the late summer months likely push a majority of the juvenile coho into the mainstem Cowlitz River or other perennial side channels downstream for further rearing This movement of juveniles during the late summer combined with the November, 26 flood likely explains the lack of coho observations during the January survey. The largest number of coho juveniles were observed during the June, 27 survey, (n=14). Rearing areas in the left side channel are still wetted at this time and there is a large amount of slow moving pocket water still available.

23 Conclusions The lack of Chinook and Steelhead adults in the tailrace slough area is to some degree attributable to the following: Lower numbers of adult Chinook and steelhead spawners released above mainstem Cowlitz River Dams Fewer fish associated with an abundance of suitable spawning and rearing habitat in the upper Cowlitz River lowers the likelihood of observations in the tailrace slough Chinook spawn timing, (mid-august September) occurs during periods of low flow in the tailrace slough, likely precluding spawners from utilizing a majority of the quality habitat

Study Update Fish Distribution and Species Composition

Study Update Fish Distribution and Species Composition Goals and Study Area Gain a better understanding of fish species composition and abundance in waters associated with the Packwood Lake Hydroelectric