brown new zealand mud snails in capitol lake
TRANSCRIPT
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New Zealand mud snails(Potamopyrus antipodarum)
In Capitol Lake
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•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)
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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.
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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
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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
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Freeze results
0 1 2 3 4 5
Time (days)
0.0
0.2
0.4
0.6
0.8
1.0
Surv
ival
rate
Day 0 ~ 20,000 NZMS/m2
Day 5 ~ 400 NZMS/m2
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Saltwater back flush
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•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.
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12% mortality from backflush
Impact on NZMS
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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.
Pre-Backflush Treatment Post-Backflush Treatment0
1000
2000
3000
4000
5000
6000
7000
8000
9000
Avera
ge T
ota
l A
bundance o
f B
enth
ic M
acro
invert
ebra
te O
rgan-
ism
s/M
2
Pre-Backflush Post-Backflush
Ave
rag
e T
ota
l A
bu
nd
an
ce/M
2
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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