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Aquatic Species of Concern for NY Boaters Q&A

What are some of the species I should be on the look-out for in New York State?

Plant Species:

Image of invasive species being picked up by a boat oar.

Hydrilla, Eurasian watermilfoil, water chestnut, curly-leaf pondweed, didymo, fanwort, Brazilian elodea, brittle naiad, European frogbit, parrot feather, creeping water primrose, starry stonewort, variable leaf watermilfoil.

Animal Species:

Image of a zebra mussel encrusted outboard motor.

Zebra mussel, quagga mussel, Asian clam, fishhook waterflea, spiny waterflea, bloody red shrimp, round goby, alewife, white perch.

Where can I find additional information on these species?

A wealth of information on aquatic invasive species can be found on the web. DEC provides ID and distribution information, as well as cleaning advice for these species. Also, the online New York Invasive Species Clearinghouse (leaving DEC website), a partnership with Cornell University, is a good place to learn about invasive species.

Are all waters vulnerable to zebra or quagga mussel colonization?

Image of a zebra mussel
USGS Archive
Image of a quagga mussel
A. Benson, USGS,

Zebra mussels require at least 12 mg/l (parts per million) of calcium in order to grow and survive and around 20 mg/l to flourish in a body of water. Quagga mussels require even higher concentrations to survive. This is why many hard water western and central NY waters have been colonized by one or both of these species, but other regions of the state such as the Adirondacks and Long Island with softer water have not had problems with these invasive mussels. This is the primary reason why zebra mussels have not become problematic after being introduced into Lake George.

What about Asian clam? I understand that this species can be problematic because it can cause algae blooms?

Image of an asian clam
USGS Archive, USGS,

Asian clam have been found in New York State for over 30 years, including major waters such as Seneca Lake, Owasco Lake, Otisco Lake, Canandaigua Lake and Chautauqua Lake. They are not overly abundant in any of the waters they have been found in and appear be coexisting with native clam species. Although Asian clam have been blamed for an increase in algae in certain sections of Lake Tahoe in California, no such blooms have been noted in New York waters.

Can this species be spread by boats?

Unlike zebra and quagga mussels, Asian clam do not affix to boat hulls. Larval Asian Clam also do not spend a significant time floating around in the water column and are much less likely to be sucked up in the water intake of a marine engine. They may, however, be found in the mud and sand, or vegetation scooped up by boat anchors, or possibly in water in a boat's bilge, live wells or bait wells. Asian clam were first reported in NY in small ponds on Long Island that do not permit boat use.

If it is unlikely that they are spread by boats, how are they introduced and spread?

Asian clams are a popular ethnic food item and it is believed that they may be purposefully introduced by individuals desiring to grow them for food. They are also sold as good luck clams, or golden clams in the aquarium trade and may be introduced when aquaria are dumped into a waterbody or released in ceremonies. As mentioned previously, although they do not affix to boats they can find their way into lake water found in the boat's water holding compartments and may also be found in the sediment of plants scooped up by boat anchors. Be sure to clean all boating equipment and drain and dry water holding compartments.

What about the various aquatic invasive plant species such as Eurasian watermilfoil and curly-leaf pondweed? Are all waters at risk from these species?

image of an curly-leaf pondweed
L.J. Mehroff, Univ. of Ct.,
image of an Eurasian watermilfoil
L.J. Mehroff, Univ. of Ct.,

Although many of the invasive plant species will grow in most New York waters, not all will grow to nuisance proportions. Many of these species grow best in disturbed or nutrient enriched segments of lakes (ie. outlet or inlet areas) and do best when they do not compete with other native plants. Eurasian watermilfoil, for example, prefers waters with high phosphorus levels. Many nutrient poor Adirondack lakes have had water milfoil for years and it has never reached nuisance levels. This is why it is extremely important to limit nutrient and sediment inputs to lakes from stormwater runoff and septic systems. If these inputs are not addressed, nutrients will eventually build up to the point that they can fuel AIS growth.

So just because a species known to be an AIS has been found in a lake or pond, it may not become a problem?

Correct. However, since it is very difficult to predict how an AIS will react in a body of water, it is best to prevent its introduction in the first place. In some waters, aquatic plant species can grow to such high levels that boating and swimming are virtually impossible, while in others they grow at levels similar to native plant species. Not all of the impacts associated with AIS may be considered negative by lake users. For example, zebra mussels can clog water intake pipes and can cause problems on swimming beaches due to their sharp shells. However, their ability to filter nutrients and algae can significantly improve water clarity and the aesthetic appeal of a body of water. Unfortunately this usually comes at a cost, as young fish are heavily dependent on algae for food and their growth rates can be impacted when these populations are reduced.

What kind of problems might I expect should AIS become established in a waterbody?

As mentioned previously, it is difficult to predict what the impact of an AIS introduction will be in a particular waterbody. Impacts vary by species and can be influenced by a number of factors including nutrient concentrations in the water and sediment, sediment type, water depth and competing native species. In nutrient rich (eutrophic) waters introduced plant species can grow to the point that they can restrict or prevent boating and swimming, reduce water flow and provide a habitat for surface algae blooms. Zebra mussels can cover all of the hard surfaces on a lake bottom. Their shells can be sharp and although they will not colonize sandy surfaces, shells of dead clams can cause problems on swimming beaches. Zebra mussels are filter feeders, removing plankton and nutrients from the water column and outcompeting native mussels. This can significantly increase water clarity and expand existing beds of aquatic plants. Zooplankton (microscopic animal) species such as spiny and fishhook water flea, primarily impact recreational fishing by accumulating on fishing line, clogging line guides on rods and potentially altering the food supply for certain sportfish species. Invasive fish species impact recreational fishing by outcompeting native species. Many brook trout fisheries have been destroyed in New York State by the introduction of non-native fish species.

Additional Related Questions and Answers

Questions and answers on how aquatic invasive species are spread

Questions and answers on cleaning and disinfection techniques for boaters

Questions and answers on additional aquatic invasive species information and advice for boaters

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