Brown new zealand mud snails in capitol lake

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Brown new zealand mud snails in capitol lake

  1. 1. New Zealand mud snails (Potamopyrus antipodarum) In Capitol Lake
  2. 2. • Small aquatic snail • Parthenogenic • High reproductive potential ▫ 20-120 offspring/year • High-density populations ▫ 100,000-500,000/m2 • Tolerant of moderate salinity levels (17-24 pss)
  3. 3. Impacts • Outcompete native gastropods by consuming large quantities of primary production • Do not serve as an equivalent food source – NZMS pass through fish guts undigested. • Restricted recreational opportunities. • Increased costs to aquaculture and municipal water control facilities.
  4. 4. Western Expansion
  5. 5. Vectors • Fish hatcheries and associated stocking operations • Recreational watercraft and trailers • Anglers and hunters • Sand and gravel mining, dredging • Commercial shipping • Pets, fish and wildlife • Natural resource management activities
  6. 6. Response ▫ Fish and Wildlife – state and federal ▫ General Administration ▫ Ecology ▫ Natural Resources ▫ City of Olympia ▫ Invasive Species Council • October 2009 – snails found • November 2009 ▫ Agencies notified ▫ Response work group formed ▫ Closed lake • December 2009 ▫ Partial lake drawdown + Freeze • March 2010 ▫ Lake drained and filled with water from Budd Inlet • July 2010 ▫ Survey around lake
  7. 7. Freeze results 0 1 2 3 4 5 Time (days) 0.0 0.2 0.4 0.6 0.8 1.0 Survivalrate Day 0 ~ 20,000 NZMS/m2 Day 5 ~ 400 NZMS/m2
  8. 8. Saltwater back flush
  9. 9. • 25 sites sampled • Day 1: Fill water 28.7 pss • Salinity levels declined with freshwater inputs from Deschutes River • NZMS likely exposed to salinities above 20 for 7- 8 hours.
  10. 10. 12% mortality from backflush Impact on NZMS
  11. 11. Impact on resident benthic invertebrates • Negative impact ▫ Abundance ▫ Species richness • Community could recover to similar diversity and abundance ▫ Overall community structure (based on feeding groups) remained similar before and after backflush. 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 Pre-Backflush Treatment Post-Backflush Treatment AverageTotalAbundanceofBenthicMacroinvertebrate Organisms/M2 Pre-Backflush Post-Backflush AverageTotalAbundance/M2
  12. 12. What’s next? • Continue containment • Freeze • Permanent plots established to look at long-term response • Small-scale trials of higher salt concentrations or other treatments
  13. 13. www.invasivespecies.wa.gov wendy.brown@invasivespecies.wa.gov

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