Experts call them “critters in crisis.”

A marbled salamander, an American eel, a crayfish and a few others are among the species that wildlife and water-quality experts in Montgomery County, Md., said they’ve recently put on a watch list because they’re worried about the populations and their long-term survival in the D.C. region.

Experts in Montgomery County’s Department of Environmental Protection (DEP) and Montgomery Parks showcased last week some of the amphibians, fish and insects they consider “at-risk” because their habitats are stressed because of water-quality troubles caused by development and runoff, plus a range of pollutants including fertilizers and pesticides.

“Extinction of species is happening at an accelerated rate, but we often think it is happening someplace else,” said Adam Ortiz, the director of Montgomery County’s environmental protection agency. “But because of climate change, overdevelopment and local pollution, there are species that are threatened right in our backyard.”

Many of the creatures on Montgomery officials’ list of concern already were considered unique and rare. Others are hanging on, but experts worry about their decline.

One of the creatures that experts are concerned about is the American eel, which is the only local fish that begins its life in seawater in the areas of Bermuda and the Bahamas and then swims to freshwater streams around the Chesapeake Bay area to spend its adult life. Nationally, the American eel population is shrinking, and an unhealthy environment and poor water quality could harm its habitat in the D.C. region, experts said.

There also are worries about yellow lance mussels, which are considered important for natural water systems because they filter algae, experts said. Yellow lance mussels used to be more abundant in streams around the Chesapeake Bay, but as the water quality in the area has declined, so has this bivalve’s numbers.

Rachel Gauza, the biological monitoring program coordinator for the Montgomery Parks agency, said sedimentation and erosion from land development and excess storm water can cause declines in water quality and habitat. That leaves fine particles to coat stream and river bottoms where yellow lance mussels live and can eventually lead to declines in their population.

Another species in crisis is the acuminate crayfish, which is unique to Montgomery and Prince George’s counties, experts said, and found largely in the Anacostia watershed.

To survive, Maryland’s crayfish typically need clean water in areas where there are fewer people, buildings and motor vehicles. But their habitats in the D.C. region are now home to high-density human development, so, good storm-water management is needed to keep those areas clean, experts said.

They’re also in trouble because of a larger species called the virile crayfish, which was introduced into D.C.-area waters from parts of the Mississippi watershed.

Experts say they also worry about the giant stonefly, whose presence in streams is a sign of high water quality.

But its numbers are dropping nationally, and experts worry that pollutants such as sediment and oil can foul the gills of giant stoneflies when they are in the larval stage and living in streams, threatening their survival, according to Ken Mack, a senior water-quality specialist in Montgomery County.

Another very rare creature experts are worried about in the D.C. region is the marbled salamander, which has gray and black skin and a poisonous tail that helps it fend off predators. Experts said that in 25 years of monitoring streams in the county, they have found only three marbled salamanders.

Marbled salamanders are often hard to see because they live under logs or rocks. Wildlife experts said their presence is an indicator that wetlands are in good health. But there is concern that development could degrade their habitat.

“If we change their environment and pave over wetlands, that changes how the waters move through the wetlands, and that changes the habitat and potentially the spawning for marbled salamanders,” according to Mack.

Montgomery officials urge residents to help to keep the environment clean by picking up trash and pet waste or volunteering for cleanups in area parks. They also said residents can use environmentally friendly detergents when washing vehicles at home, and in lawn care can reduce their use of pesticides and fertilizers, which are ingredients in contaminated storm-water runoff.

“People don’t always make the connection between our behaviors and local streams and rivers,” Ortiz said. But experts remind the public that when rain falls, all residue on the ground washes into creeks and streams, then into rivers and on into the Chesapeake Bay.

“We don’t expect people to live in the Garden of Eden but to be more thoughtful and try to live in a more sustainable way,” Ortiz said.