Invasive Species Prevention

At a Glance

Threats from Home Aquaria

No Release

Releasing plants or animals from home aquaria can introduce invasive species

Prevention Protocol for Boats

3 Steps

Clean · Drain · Dry — required every time you move a boat

Once Established

Permanent

Most aquatic invasive infestations cannot be fully eradicated

NH Lake Host Program

Lake Hosts inspect watercraft and educate boaters at the Elkins Boat Launch during peak season.

What to Expect at the Launch

Trained Lake Hosts may inspect incoming watercraft at the Pleasant Lake ramp. They check for hitchhiking plants and help ensure boats from other lakes are clean.

NH Lake Host inspection at the Elkins Boat Launch

1. Clean

Remove all plants, animals, and mud from boat, trailer, and gear before leaving. Inspect hull, propeller, anchor, bilge, live well — especially crevices and undercarriage.

2. Drain

Drain bilge, live well, bait well, and all compartments before leaving. Run the motor briefly on land to drain cooling water.

3. Dry

Let everything dry completely — at least 5 days. Or use high-pressure hot water (140°F+) at an NH DES wash station for faster decontamination.

Why Prevention Is the Only Strategy

Once established, invasives rarely leave. Act before the first fragment arrives.

Ecological Collapse

Dense mats of invasive plants shade out natives, deplete oxygen, and disrupt the food web. Fish, waterfowl, turtles, and amphibians suffer. Our shorelines are also threatened by Japanese Knotweed, which can crowd out all other plants.

Economic & Recreational Harm

Infestations reduce property values and tourism. Dense weeds make swimming miserable, foul propellers, and tangle lines.

Near-Impossible to Reverse

Eradication is extraordinarily rare. Management is expensive and ongoing. Prevention: minutes per boat launch. Management: can be hundreds of thousands of dollars per year.

Variable-leaf Milfoil (Myriophyllum heterophyllum)

Most widespread in NH. Feathery reddish-stemmed leaves in whorls of 4–6; variable shape. Spreads from tiny stem fragments. Forms thick surface mats.

Eurasian Watermilfoil (Myriophyllum spicatum)

Similar to variable-leaf milfoil; more uniform leaves in whorls of four. Highly aggressive. Propeller fragments can establish new infestations miles away.

Fanwort (Cabomba caroliniana)

Bright green fan-shaped leaves in opposite pairs. Thrives in still water; forms impenetrable beds. Often sold as an aquarium plant. NEVER release any aquarium plants or animals into natural waters!

Japanese Knotweed (Reynoutria japonica)

A shoreline plant widespread in the Pleasant Lake watershed and throughout NH. Stems are similar to bamboo, with heart-shaped leaves. Grows over 10 feet tall with very deep and expansive roots, and can spread from a tiny root or shoot fragment. One of the most difficult species to eradicate. Japanese Knotweed guidance (PDF).

Spiny Water Flea (Bythotrephes longimanus)

Tiny crustacean with long barbed tail spine. Spreads via fishing and anchor lines, water in bait buckets, bilge, and wet gear. Devastates zooplankton that eat cyanobacteria and that are food for juvenile fish.

How Invasives Spread

Boats and gear are the primary vectors. A fragment on a trailer or water in a baitwell is all it takes.

Boats & Trailers

Fragments, seeds, and eggs cling to hulls, props, anchors, and trailers. One boat from an infested lake can transfer invasives to Pleasant Lake.

Gear, Bait & Live Wells

Live wells, bilges, bait buckets, and wet gear can carry invasives. Never transfer bait or water between water bodies.