New Jersey’s rivers are vastly different throughout the state; from the Atlantic coastal rivers and Pinelands streams to the large tidal tributaries of the Delaware River.  These unique habitats support a wide variety of native, invasive and recreationally important fish species.  The geographic location of a waterbody in most cases dictates surface water quality classification and ultimately the fish species that biologists would expect to find.  Waters throughout the state categorized as non-trout or warmwater fisheries have water temperatures that exceed the thermal tolerance of trout.  Some of the state’s larger river systems may have headwaters cold enough to support trout populations but as one travels further downstream, waters become increasingly too warm and only support warmwater fisheries.

Large non-wadeable rivers are most often sampled by boat electrofishing.  Wadeable rivers and streams are sampled by either backpack or tote barge electrofishing equipment.  Electrofishing is the most common non-lethal method of fish collection by fisheries biologists in both lakes and rivers.  Surveys are conducted on rivers throughout the state for many reasons.  Open river systems are more complex and challenging to evaluate than lakes and ponds.  A few recent surveys that were completed on river systems include:  The Passaic River was electrofished in recent years to evaluate the Northern Pike fishery.  Future sampling is anticipated for the non-tidal Delaware River to assess the Walleye and Muskellunge stocking programs in the Delaware River.  The tidal Delaware River from Trenton downstream to the Philadelphia region has been sampled regularly since 2008 to monitor the expansion of the Northern Snakehead population. During these snakehead surveys, Largemouth Bass were also collected to evaluate this recreationally important population.  The Mullica River was sampled for migratory river herring during their spring spawning migration.  Electrofishing is effective in many types of rivers but occasionally biologists need to use other techniques.  Alternative gears such as gill nets and seines can be used where appropriate.  Gillnets are effective in large rivers but generally have higher mortality rates that other non-lethal methods.