Species and Habitat Studies: Amphibian and Other Aquatic Species Research Update

Transcription

1 Species and Habitat Studies: Amphibian and Other Aquatic Species Research Update Marc Hayes 21 September 2016

2 Amphibian and Other Aquatic Species Research Update HABITATS ASSEMBLAGE 1 Chehalis Floodplain Off-channel Stillwater-breeding amphibians, many fishes, turtles & beaver 2 Chehalis Mainstem/Large Tributaries Stillwater breeding amphibians, some fishes, turtles & beaver 3 Headwater Streams Instream Riparian Stream-breeding amphibians and selected fishes Terrestrial stream-associated amphibians 1 2 3

3 Chehalis Floodplain Off-channel Habitats 156 habitat units surveyed to date (48 new) 6 amphibian and at least 29 fish species (7 new) Fish species richness increases downstream 11 exotics: 1 amphibians (bullfrog) and 10 fishes Exotic species fewer at tails of floodplain Key exotics: bullfrog, bluegill, largemouth bass Key natives: 4 amphibians, 3-spined stickleback, Olympic mudminnow, beaver Modeling reveals wetter years (2016) favor natives; drier years (2015) favor exotics Only turtles exotic red-eared sliders at two sites, no Western pond turtles Oregon spotted frog and breeding Western toads not found Exotics or newts limit native amphibians (new) 1

4 Floodplain Off-channel Habitats Impacts from Proposed Dam Alternatives AREA OF POTENTIAL IMPACT FRFA FRO Above Proposed Dam/ Within Proposed Dam/ Not applicable Not applicable Not applicable Not applicable Downstream of Proposed Dam/ 1) Seasonal inundation footprint of oviposition habitat reduced for flows below operational maximum; effect more pronounced with proximity to proposed dam; effect magnitude uncertain 2) Major freshets (10-year floods or greater) with high channel reorganization and new off-channel creation capacity eliminated 1) Seasonal inundation footprint of oviposition habitat reduced for flows below operational maximum; effect more pronounced with proximity to proposed dam; effect magnitude uncertain 2) Major freshets (10-year floods or greater) with high channel reorganization and new off-channel creation capacity eliminated

5 Chehalis Mainstem and Large Tributary Habitats RM surveyed to date; 11.4 RM resurveyed (83.0 RM since last update) Western toad limited to the upper ¼ of mainstem (upstream of RM 82) and a few larger tributaries (new) Late May to June breeding as river stage drops enough to expose protected pools Shading resulting from reduced stream size likely affecting upper distribution limit Uncertain geomorphic/flow control may be affecting lower distribution limit 2016 survey confirmed finding highest densities in proposed dam/reservoir footprint Coho fry fish species most often observed in toad breeding pools Nine other fish species (one exotic) and five other amphibian species (one exotic) also in pools 2 6

6 Mainstem and Large Tributary Habitats Impacts from Proposed Dam Alternatives AREA OF POTENTIAL IMPACT FRFA FRO Above Proposed Dam/ Within Proposed Dam/ Probably isolation of probably limited Western toad population Instream breeding habitat loss; potential gain in margins of reservoir pool uncertainty reflects dam operation Possible isolation of probably limited Western toad population Possible instream breeding habitat loss uncertainty reflects ambiguity of changes in instream habitat between reservoir fillings; reservoir pool too fluctuating to either allow breeding or survival if breeding occurs Downstream of Proposed Dam/ If flows are higher during the late May to June drop in the hydrograph than historically typical, either breeding or rearing may be disrupted by flows sweeping out unattached eggs, embryos, or larvae or protracting development with water temperature lower than typical If a release of flow following a dam closure event creates higher than typical flows during the late May to June drop in the hydrograph, either breeding or rearing may be disrupted by flows sweeping out unattached eggs, embryos, or larvae or protracting development with water temperature lower than typical

7 Headwater Stream Habitats 120 unique sites surveyed (32 new and 5 repeat surveyed sites since last update) Dunn s and Van Dyke s salamanders found at 41 and 9 unique sites, respectively More than half (n = 24) of Dunn s occupied sites in proposed dam/reservoir footprint Only 1 Van Dyke s occupied site in proposed dam/reservoir footprint Elevation breakdown reveals 26 (63%) of Dunn s sites are <750 feet (220 m) elevation In contrast, only 1 (11%) of Van Dyke s sites is <750 feet (220 m) elevation 811 incidental observations of at least 10 additional native amphibians species Incidental observation of stream-breeding amphibians restricted to tributaries 3

8 Headwater Stream Habitats Impacts from Proposed Dam Alternatives AREA OF POTENTIAL IMPACT FRFA FRO Above Proposed Dam/ Probable isolation of likely limited Dunn s salamander populations and more extensive Van Dyke s and stream breeding amphibian populations Probable isolation of likely limited Dunn s salamander populations and more extensive Van Dyke s and stream breeding amphibian populations Within Proposed Dam/ Riparian habitat loss for Dunn s and Van Dyke s salamanders; loss major for Dunn s and minor for Van Dyke s; loss of breeding habitat for tailed frogs, giant salamanders, and torrent salamanders in tributaries; new riparian around reservoir margin not suitable for Dunn s and Van Dyke s salamanders Riparian habitat loss for Dunn s and Van Dyke s salamanders; loss major for Dunn s and minor for Van Dyke s; loss of breeding habitat for tailed frogs, giant salamanders, and torrent salamanders in tributaries; unreliable development of riparian because of irregular reservoir filling Downstream of Proposed Dam/ Probable isolation of extremely limited Dunn s salamander and stream-breeding amphibian populations Probable isolation of extremely limited Dunn s salamander and stream-breeding amphibian populations

9 Questions?