Freshwater invasions in the Hudson Valley: overview and

management

David Strayer, Cary Institute of Ecosystem Studies

Outline

• Overview of freshwater invasions in the Hudson Valley

• Invasion pathways: how freshwater invaders get around

• What you can do to reduce the negative effects of freshwater invaders

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Freshwater invasions in the Hudson Valley (1) are numerous, (2) began long ago, and

(3) are continuing

Number of established, non-native species in freshwater parts of the Hudson River basinupdated from Mills et al. (1996)

Many of the most prominent species in our fresh waters aren’t native

…and some of these species cause problems

New invaders continue to arrive

Images from USGS

…or are on the way

Clockwise from upper left: silver carp, grass carp, black carp, ruffe; all from USGS

… and climate change will allow species to move in from the south

How do non-native freshwater species get here?

Be very, very careful about deliberate introductions

“but that so fine a plant as this, with its handsome leafy rosettes, and edible nuts, which would, if common, be as attractive to boys as hickory nuts now are, can ever become a nuisance, I can scarcely believe”

Water-chestnut

…and releases from gardens and aquaria

• Each year, ~10,000 individual fish (dozens of species) and ~3000 aquatic plants (dozens of species) are released from aquaria into the wild in the city of Montreal (252 species of fish and 138 species of plants were for sale within the city)

• In a Minnesota study, “93% of orders received from aquatic plant vendors contained a plant or animal species not specifically requested; misidentified plants were found in 18% of the orders; unordered seeds in 43%.”

• Presumably, similar issues here in the Hudson Valley

What can I do to lessen the negative effects of freshwater invaders?

• Deal with today’s problems

– Local management

• Prevent tomorrow’s problems

– Responsible individual behavior

– Community programs

– Political engagement

Dealing with today’s problems

• No need to kill a species that is well-established in the region just because it isn’t native– Many non-native species don’t cause problems, and even provide

benefits– Match management to specific goals: don’t try to eradicate if your

actual goal is local control– Views of multiple stakeholders may need to be reconciled

• Control often not feasible– Cost– Side effects– Legality!

• Design the control program to match goals and constraints

www.saveblacklake.org/

Reduce future problems: responsible individual behavior

• Don’t move living plants or animals or untreated water between bodies of water!– Don’t dump aquaria

– Don’t dump bait buckets or live wells

– Don’t deliberately move species you like

– Clean trailers

– Clean waders

• Don’t buy new species of plants for your water gardens

Reduce future problems: community programs

•Boat stewards•Community outreach and education

(61% of aquarium owners, 54% of water-gardeners, and 46% of boaters know nothing about invasive species (Connelly et al. 2015))

Reduce future problems: Political engagement

• Little political pressure for better policies– Prevention of invasions usually far more effective

than management after invasion

• Effective industry opposition to new policies

• “Think locally, act globally”– If we wait for a non-native species to become a

problem locally, many of the best options are gone

• Could weigh in on proposed regulations or contact state and federal lawmakers

Conclusions

• Freshwater invaders are numerous, and have had large effects (some of them bad) on local ecosystems

• Many more invaders are poised to come to the Hudson Valley, but…

• We can reduce negative impacts by thoughtful collective action and responsible individual behavior