Native or Naturalized?

The fish populations of New Jersey’s rivers and streams look vastly different than they did 200 years ago. Most of today’s freshwater game fish are non-native and were brought to New Jersey to increase recreational opportunities for anglers. As a result, many of our state’s native fish have been extirpated or their ranges significantly reduced.

Many species that previously thrived throughout the state are now found exclusively or largely in the Pine Barrens. Because of the acidity of Pine Barrens waters, rivers and streams in this region serve as refuge for native fish from non-native predators that cannot tolerate high acidity. Many predatory species can survive in acidic waters as adults, but their young are unable to survive and grow under those conditions.

Brown Trout, South Branch Raritan River

Our beloved brown trout? Largemouth bass? Smallmouth bass? All are non-native. But that doesn’t necessarily mean they are invasive. Over the course of over 100 years, these species have become naturalized in New Jersey and are reproducing in the wild. Our stream systems are fully functional with these species occupying a unique ecological role.

But there are places where biologists must work to manage overlapping fish populations to protect native fish. For example, the NJ Division of Fish & Wildlife’s Bureau of Freshwater Fisheries recently added protections for brook trout – New Jersey’s only native trout species.  The state altered the stocking of rainbow trout to help increase the success of brook trout, and created a Brook Trout Conservation Zone where all anglers who catch these fish must immediately and carefully release them unharmed. Other new fishing regulations are designed to increase the survival chances of brook trout if caught and released.

Brook Trout, South Branch Raritan River

Our state’s native and naturalized fishes are all important. Fish are often used as indicators of water quality, so a stream with a diversity of fish species is a stream with clean, healthy water.

Naturalized species, like smallmouth bass and brown trout, are important recreational targets for anglers. Recreational fishing is good way to get people engaged with nature and in tune with their local stream. As Raritan Headwaters is located in the heart of the Brook Trout Conservation Zone, helping people learn about their local streams can be both important and rewarding.

Our region does have some invasive fishes – such as green sunfish and oriental weatherfish – that can be potentially dangerous to other native or naturalized species. One way to avoid spreading invasive fish species is to never release live bait or transport fishes between water bodies. 

The New Jersey Bureau of Freshwater Fisheries lists all potentially dangerous fish species and how to handle them here.

RHA Fishes of The Upper Raritan Fact Sheets:

Green Sunfish


American Eel

Coming Soon! Brook Trout