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New Jersey

Freshwater Fishing

Freshwater Fishing

Invasive Fish Species Update

Principal Biologist Chris Smith with Northern Snakehead captured from the Salem Canal.
Principal Biologist Chris Smith with Northern Snakehead captured from the Salem Canal. Photo by Eric Boehm/NJDEP Fish & Wildlife.

Aquatic Invasive Species: Threatening NJ's Waterways

By Christopher Smith, Principal Fisheries Biologist

New Jersey’s picturesque rivers, lakes, and estuaries have long been a haven for native plants and animals. Yet, hidden below the surface lies the growing threat posed by numerous Aquatic Invasive Species (AIS) currently inhabiting the state. These unwelcome guests threaten to disrupt the balance of our aquatic ecosystems, jeopardizing the biodiversity, habitats, and even the economy of our state.

The Northern Snakehead has attracted considerable attention due to its rapid propagation, extensive distribution, and the frequency with which anglers encounter it. Our dedicated biologists at NJDEP Fish & Wildlife have monitored its spread since its introduction, recognizing its potential to disrupt our aquatic ecosystems.

What do all these words mean?

The terminology used to describe subtle differences in the status and impacts of various species can be confusing. First, species are either native or non-native. The term native is a synonym for indigenous, both referring to a species that naturally occurs in an area without human intervention. Non-native is a term used for species that were intentionally or unintentionally moved beyond their native range by means of human activity. Synonyms for non-native include non-indigenous, introduced, alien, and exotic. Naturalized species are non-native species that have an established population beyond their native range. Wild does not refer to a species’ historic range, but it only means that a species is born in the wild, in the case of fish it means not stocked and born naturally in the wild. Invasive species are non-native species that are naturalized and that may cause ecological or economic harm.

Potentially Dangerous Fish Regulation

In New Jersey, the term Potentially Dangerous Fish is used with regulatory purpose and indicates an elevated threat level of select invasive species. The possession or release of live, Potentially Dangerous Fish is strictly prohibited. The Northern Snakehead and Flathead Catfish are two of our commonly known species, however the following are also included: Asian Swamp Eel, Bighead, Grass (diploid), and Silver Carp, Blue Catfish, Brook Stickleback, Green Sunfish, Oriental Weatherfish, Round Goby, Warmouth and all black bass except for Largemouth and Smallmouth Bass. Anglers MUST destroy these species regulated as Potentially Dangerous Fish if encountered while fishing and should submit specimen(s) or photos to a NJDEP Fish & Wildlife fisheries biologist for verification. To reach a regional biologist, call 908-236-2118 (north), 609-223-6076 (central) or 856-629-4950 (south). Photos and reports can also be submitted to [email protected].

Diagram of Differences Between Invasive Catfish and Non-Invasive Catfish
Invasive Species Hydrilla and New Zealand Mud Snail.

Are all Non-native Fish managed as Potentially Dangerous?

No. Many non-native fish are not identified as Potentially Dangerous Fish for many reasons. Some of them have been naturalized within our ecosystems for 100 years or longer and some are valued as sport fish. Although an invasive species, Common Carp are NOT regulated as Potentially Dangerous Fish as they are already found in most waters throughout the state. As such, Common Carp do not have to be destroyed when caught by anglers. Where it gets very tricky is that some non-native species are considered invasive if found in certain habitats. Brown Trout are a prime example of a non-native species that causes ecological harm to native Brook Trout (as Brown Trout are considered invasive in some places) but are valued and managed for angling in other watersheds (not invasive in other places). For more information see Wild Browns Abound article.

What Can Be Done?

The introduction of AIS poses significant and far-reaching impacts to New Jersey's waters. They often outcompete native species for resources, alter habitats at the expense of native flora and fauna, and detrimentally affect recreational activities such as fishing and boating. They even have adverse impacts on local economies tied to tourism and outdoor activities. These interconnected consequences emphasize the critical importance of addressing and mitigating the spread of Aquatic Invasive Species in New Jersey.

NJDEP Fish & Wildlife is very concerned of the threat posed by AIS and has implemented several measures to combat this issue effectively. These efforts include the development of a Statewide Aquatic Invasive Species Management Plan that will steer future monitoring and research, control and eradication, regulations, and education and outreach.

Invasive species are likely to cause environmental harm to the state’s fisheries resources by outcompeting our native species AND our preferred game fish species, regardless of their origin. The battle against these invaders requires ongoing vigilance, cooperation from the public, and continued research and innovation. Protecting our aquatic habitats and native species is not just an environmental responsibility but also a necessity for all residents of the Garden State.

Invasive Species Red Swamp Crayfish