Lake Pend Oreille Research by JwbDrK8

VIEWS: 8 PAGES: 19

									 Importance of Water Level
  Management to Kokanee
and Bull Trout in Lake Pend
          Oreille
                       Lake Pend Oreille

                               Sandpoint

                                                      Hope
                Pend Oreille
                River



        Albeni
                                                             Clark
        Falls Dam
                                                             Fork
                                                             River


                                                             Cabinet
                                                             Gorge
                                                             Dam


                           Scenic Bay
                        Bayview
                                                     10 Km
                                      Idlewild Bay




Size = 38,300 ha, Maximum Depth = 351m
                    Lake elevation (m)




              624
                    625
                          626
                                627
                                      628
                                            629

       Jan
       Feb
       Mar
       Apr
        Ma
       Jun
        Jul
        Au




1935
       Sep
       Oct
       Nov
       Dec
       Jan
       Feb
       Mar
       Apr
        Ma
       Jun
        Jul
1936


        Au
       Sep
       Oct
       Nov
       Dec
                                                  Natural elevations for Lake Pend Oreille
Natural and Managed Lake Levels

                          629                                2063
                                        Managed              2061
     Lake elevation (m)




                                                                    Lake elevation (ft)
                          628
                                                             2059
                          627                                2057
                                                             2055
                          626                                2053
                          625                                2051
                                            Natural          2049
                          624                                2047
                                 Au




                                 Au
                                Nov




                                Nov
                                Apr




                                Apr
                                Oct




                                Oct
                                 Jul




                                 Jul
                                Jan




                                Jan
                                Feb


                                Jun

                                Sep



                                Feb


                                Jun

                                Sep
                                Dec




                                Dec
                                 Ma




                                 Ma
                                Mar




                                Mar

                                1935 2002        1936 2003
Why are kokanee
important to bull trout?




        •60-80% of their diet is kokanee.
        •Without kokanee, lake trout and bull
        trout would be in direct competition for
        a limited food supply.
                                         Estimates of Adult Kokanee
                                                Abundance
                               10
Kokanee abundance (millions)


                                         1952 dams were built
                                9
                                8                       1966 consistently deep lake drawdowns
                                7                               begin
                                6
                                5
                                4
                                3
                                2
                                1
                                0
                                    52

                                         56

                                              60

                                                   64

                                                         68

                                                              72

                                                                   76

                                                                        80

                                                                             84

                                                                                  88

                                                                                       92

                                                                                            96

                                                                                                 00

                                                                                                      04
                                                                         Year
  Spawning
 habitat is the
limiting factor
Gravel at Farragut
   March 2004
 Water line


Shoreline at
 low pool


Larger rocks
Can we show that a varied winter
water level will increase kokanee
          egg survival?
Winter Elevations in Lake Pend Oreille

                  2056                                                           Experimental years
                  2055

                  2054
 Elevation (ft)




                  2053

                  2052

                  2051

                  2050

                  2049

                  2048
                         1990
                                1991
                                       1992
                                              1993
                                                     1994
                                                            1995
                                                                   1996
                                                                          1997
                                                                                  1998
                                                                                         1999
                                                                                                2000
                                                                                                       2001
                                                                                                              2002
                                                                                                                     2003
                                                                                                                            2004
                                                                                                                                   2005
                                                                          Year
Methods     Fry net used on trawler


Trawling




           Hydroacoustics
Results                                            Kokanee Fry Abundance


                                16
                                                            Fry Net
                                14
     Number of Fry (millions)

                                                            Hydroacoustics
                                12
                                10
                                8
                                6
                                4
                                2
                                0
                                     1999


                                            2000


                                                   2001


                                                                 2002


                                                                        2003


                                                                               2004
                                                          Year
Wild egg-to-fry survival
                                            12




             Wild egg-to-fry survival (%)
                                            10


                                             8


                                             6


                                             4

                                                              Lowered lake level
                                             2


                                             0
                                                 0   200000   400000     600000    800000
                                                     Female kokanee spawners
Wild egg-to-fry survival
                                            12




             Wild egg-to-fry survival (%)
                                            10


                                             8
                                                              Raised lake level


                                             6


                                             4


                                             2


                                             0
                                                 0   200000   400000     600000   800000
                                                     Female kokanee spawners
Wild egg-to-fry survival
                                            12




             Wild egg-to-fry survival (%)
                                            10


                                             8                   Raised lake level


                                             6


                                             4

                                                              Lowered lake level
                                             2


                                             0
                                                 0   200000   400000     600000      800000
                                                     Female kokanee spawners
Wild egg-to-fry survival
                                            12




             Wild egg-to-fry survival (%)
                                            10



P< 0.05                                      8                   Raised lake level


                                             6




2.4 fold                                     4

                                                              Lowered lake level
                                             2
increase
                                             0
                                                 0   200000   400000     600000      800000
                                                     Female kokanee spawners
             Lake Level Management



1. Vary winter lake level 4 ft in different years.
2. Maintain a higher winter pool level for 3 years,
   then lower lake to replenish gravel.
3. Time full drawdown to coincide with years
   when kokanee numbers are low.
         Start


Is there a declared power emergency ?
    No                        Yes


Was the previous year successful for chum salmon
spawning (< ? % of redds dewatered)?
                                       Yes                                 Will this be the second year in a row the lake
                                                                 No                                                               No
                                                                           is lowered to 2051’?

                                                                                  Yes
                                        Rainfall prediction for Nov -Jan for Columbia River Basin

                              Below normal                            Equal chance, normal, or above normal


                        Are female kokanee                                                                   Are female kokanee
                        spawners above 70k?                                                                  spawners above 70k?


                  No                          Yes                                                          No               Yes


       Was lake at 2051’ each of         Was lake at 2051’ the                   Was lake at 2051’         Was lake at 2055’ each of
       previous 2 yrs?                   previous year?                          the previous year?        3 previous years?
         Yes            No              Yes         No                                     Yes          No          No            Yes




                             2055’                                                 2051’

								
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