Impacts of Invasive Drills on Olympia Oysters in Puget Sound: Implications for Restoration. Native Oysters and Invasive Drills

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1 Impacts of Invasive Drills on Oysters in Puget Sound: Implications for Restoration Eric Buhle and Jennifer Ruesink Dept. of Biology, Univ. of Washington Seattle WA Native Oysters and Invasive Drills Gallons (x 1000) Oysters Harvested in Puget Sound data: J. White, UW Year (Ostrea conchaphila) Japanese drill (Ocinebrina inornata)

2 Drills Overlap with Native Oysters Puget Sound Pacific Ocean known current locations known Japanese drill locations data: B. Blake, WDFW map: L. McCoy, UW Drill Impact: Historical Data North Bay Fate of dead s Drilled Puget Sound Oakland Bay Other sources of mortality Seattle Little Skookum Inlet Totten Inlet Mud Bay Chapman and Banner 1949, WA Dept Fisheries

3 Why Might Drill Impacts Vary? Japanese drills s Why Might Drill Impacts Vary? Japanese drills s Predator feeding rate functional response

4 Why Might Drill Impacts Vary? Japanese drills s Predator feeding rate Prey mortality rate functional response Predator Prey Predator Prey Why Might Drill Impacts Vary? Japanese drills Predator feeding rate functional response s Alternative prey Prey mortality rate Predator Prey Predator Prey

5 Why Might Drill Impacts Vary? Japanese drills Predator feeding rate functional response s Alternative prey Prey mortality rate Increasing predator density Study Questions 1. How does the impact of drills vary in space? Is impact related to drill density? 2. Does the per capita effect of drills depend on density? Alternative prey 3. Does the per capita effect of drills depend on alternative prey density?

6 Enclosure Experiment: Drill Functional Response Feeding rate (s/m 2 /100 d) drills m 2 17 drills m 2 7 drills m 2 4 drills m density (m 2 ) density (m 2 ) Oyster mortality rate

7 Measuring Drill Impact: Oyster Transplants Measuring Drill Impact: Oyster Transplants mortality, JuneSept 2005 Total mortality Drill predation Other causes Mortality rate (d 1 ) Skookum 1 Skookum 2 Gallagher Gallagher Cove Cove Oyster Bay Liberty Bay Skookum 1 Skookum 2 Gallagher Cove Oyster Bay Liberty Bay

8 Impact Increases with Drill Density Mortality rate (d 1 ) Skookum 1 Skookum 2 Totten 1 Totten 2 Liberty Drill density (m 2 ) Drill density only model: ΔAIC c = 58.0, R 2 = 0.10 predation mortality rate = c*drill density Per Capita Effect Depends on Prey Density Mortality rate per drill (drill 1 d 1 ) Skookum 1 Skookum 2 Totten 1 Totten 2 Liberty density (m 2 ) Drill & density model: ΔAIC c = 48.2, R 2 = 0.83 c*drill density predation mortality rate = 1+ c * h* density

9 Per Capita Effect Depends on Prey Density Mortality rate per drill (drill 1 d 1 ) Skookum 1 Skookum 2 Totten 1 Totten 2 Liberty Barnacles Pacific Weighted total prey density Drill,, barnacle, & Pacific model: ΔAIC c = 0, R 2 = 0.96 c*drill density predation rate = 1+ c* h* density + b1*barnaclecover + b2* Pacific density Drill Impacts and Native Oyster Restoration Alternative prey Total drill impact density

10 Drill Impacts and Native Oyster Restoration Alternative prey Total drill impact Drill control density Drill Impacts and Native Oyster Restoration Alternative prey Total drill impact Oyster stock enhancement Drill control Current density Density with enhancement density

11 Thanks to... Jennifer Ruesink Kyla Zaret Heather Tallis Lee McCoy Cap n Eric Wagner Jackie White Brice Semmens Anne Salomon Tessa Francis Alan Trimble Isabel Gottlieb Jesús Alvarez Gena Anderson Max Whetstine Brett Bishop Russ Walker Tim McMillin Eric Hall Rod Scheffenauer Joth Davis Betsy Peabody Tristan PeterContesse Puget Sound Restoration Fund Sea Grant NSF ARCS photo: Joth Davis