brown new zealand mud snails in capitol lake

New Zealand mud snails(Potamopyrus antipodarum)

In Capitol Lake

•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)

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.

Western Expansion

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

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

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

Saltwater back flush

•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.

12% mortality from backflush

Impact on NZMS

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

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

www.invasivespecies.wa.gov

wendy.brown@invasivespecies.wa.gov