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Protect New Jersey’s Waters


Invasive Alert

Shawn Crouse, Principal Fisheries Biologist


In last year’s Freshwater Fishing Digest, New Jersey Division of Fish and Wildlife published an “invasive alert” to inform anglers about several aquatic invasive species. Featured was information on invasive plants and animals that could plaque waterbodies—or are already. In that alert we highlighted interesting characteristics, field identification and what anglers can do to help control the spread of these invasive species.

Since then, scores of anglers eagerly responded to notify Fish and Wildlife of their observations made while on the water. And although we know of many locations for numerous invasive species, new sightings are being made across our state on a weekly basis as anglers see, first-hand, an invasive species’ ability to spread rapidly. For years, we have known New Jersey anglers to be “our best eyes and ears” for what’s happening in our waters, and once again you prove that to be true. We are grateful.

Recent Invasive Fish Reports

  • Green sunfish are becoming more widespread. These fish can wreak havoc on the waterbody’s ecological balance once they establish and multiply.
  • Snakeheads are now confirmed in the Delaware River and its tributaries spanning a 20-mile distance from Mantua Creek, Gloucester County, upriver to Dredge Harbor, Burlington County.
  • Flathead catfish have been caught by anglers in the Delaware River from Lambertville, Hunterdon County, upriver into New York.

Recent Invasive Plant Reports

  • Didymo (rock snot) has not been confirmed in New Jersey.
  • Plants like hydrilla and Eurasian water milfoil are found in many of our lakes statewide.
  • Since the fall of 2010, known locations of the invasive water chestnut have increased from two waterbodies to at least 13 waterbodies, spanning nine counties.

Water Chestnut Sightings



Amwell Lake


Pascale Farm Pond


Baldwin Lake


Gold Run


Katzenbach School Lake


Grovers Mill Pond


Oradell Reservoir


Perth Amboy Waterfront


Lake Assunpink


Lake Musconetcong


Lake Hopatcong


Lake Wawayanda


Clark Reservoir


Robinson’s Branch


Shadow Lake


Willever Lake


Fish and Wildlife Invasive Containment Activities

  • Electrofishing efforts to reduce the Asian swamp eel population in Silver Lake, Camden County continue.
  • Agency biologists assisted the New Jersey Conservation Foundation to eradicate bighead carp and grass carp (diploid), non-sterile, in a series of former aquaculture ponds located on the Wickicheoke Creek Preserve.
  • Herbicide treatment of water chestnut in Baldwin, Amwell and Assunpink Lakes were completed by our Bureau of Land Management.
  • Field sampling to document distribution of snakeheads in the Delaware River and its tributaries from Gloucester to Camden counties.

Water Chestnut

water chestnuts 0113.tif

strongly toothed leaves. Nut-like fruit with four sharp spines.

p32_Water chestnut seed pod_revised.tif

Portions of Lake Musconetcong (Morris County) are choked with the invasive water chestnut.

The future of New Jersey’s waters is in your hands!


Invasive Fish

Fish identification can be easy for species that you catch often, however this may not be the case for species new to New Jersey waters. An untrained eye can easily mistake species that look similar.

Bowfin are native species, actually dating back 250 million years and should be released unharmed. However, snakeheads are invasive and should be destroyed and submitted to the Division of Fish and Wildlife for verification. Snakeheads have recently been found in the lower Delaware River and some of its tributaries.

American eels are a diadromous native species, using both fresh and marine waters during their lifecycle. These eels are found in nearly every waterbody in New Jersey. American brook lamprey are a harmless native species that serves as an indicator of clean substrate. The Asian swamp eel is an invasive species with documented presence in Silver Lake, a 10-acre waterbody located in Gibbsboro.

Although not a native species, channel catfish are stocked by Fish and Wildlife in select locations as it is a desirable recreational and food species. They do not reproduce in most waters, and in the few where they do, populations do not reach problematic proportions. The flathead catfish is considered an invasive species capable of causing ecological damage by out-competing other recreationally important species for food and habitat. Flatheads have been confirmed in the middle section of the Delaware River. >

Snakehead – Invasive


Long anal fin.

Bowfin – Native


Short anal fin.

American Brook Lamprey—Native

brook lamprey - Responsible Angler.tif

No pectoral fins; gill slits present.

American Eel—Native

American eel - Responsible Angler.tif

Pectoral fins present; no gill slits.

Asian Swamp Eel—invasive

swamp eel - Responsible Angler.tif

No pectoral fins; no gill slits.

Channel Catfish – Stocked

Channel CatfishT.tif

Upper jaw protrudes past lower jaw; tail deeply forked.

Flathead Catfish – Invasive


Lower jaw protrudes past upper jaw; tail not deeply forked.

Painting: Susan Trammell

Zebra mussels.TIF 

Invasive Mussels—Zebra Mussels

How to Identify Zebra Mussels

  • Look like small clams with a yellowish or brownish “D”–shaped shell, usually with alternating dark and light colored stripes.
  • Up to two inches long, but most are under an inch.
  • Usually grow in clusters
  • Zebra mussels are the ONLY freshwater mollusk that can firmly attach itself to solid objects—rocks, dock pilings, boat hulls, water intake pipes, etc.

What to Do If You Find a Zebra Mussel

  • Note the date and precise location where the mussel or its shell was found.
  • Take the mussel (several if possible) with you and store in rubbing alcohol. Do not throw it back in the water.
  • Immediately call Dr. Peter Rowe, New Jersey Sea Grant Headquarters, (732) 872-1300 extension 31, or write

Keep on Reporting

The most effective way to succeed in containing aquatic invasive species is to continue to report each encounter. As a reminder, New Jersey’s Potentially Dangerous Fish Species regulation adopted in 2010 prohibits the possession or release of live fishes including: flathead catfish, snakehead, Asian swamp eel, brook stickleback, oriental weatherfish, green sunfish and warmouth, bighead carp, silver carp and grass carp (diploid). Anglers must destroy these species if encountered while fishing and are directed to submit specimen(s) to the Bureau of Freshwater Fisheries personnel for verification. Fish and Wildlife’s fisheries biologists can be reached at (908) 236-2118 for north Jersey and at (856) 629-4950 for south Jersey.

Regulations in red are new this year.

Purple text indicates an important note.

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