Some are disarmingly named, like the cutesy Chinese mitten crab. Others have names more indicative of their undesirable nature, like rock snot, an algae that slimes up cool forest streams.

They are some of more than 100 invasive species that conservationists must battle in New York State, which teems with a growing number of plants, birds, fish, insects, mosses, molds and fungi that actually belong somewhere else.

An aquatic weed is creeping across the Great Lakes region that grows really fast and is very hard to kill. Scientists don’t know a lot yet about starry stonewort, but they’re hurrying to find out more. The plant, which forms dense surface mats in lakes, first turned up in North America in 1978 in the St. Lawrence River in New York state. Researchers think it probably arrived in ballast water from ships entering the Great Lakes.

The arrival of spiny waterflea is bad news for North American fisheries.