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Fish Monitoring Sections

Bureau of Freshwater & Biological Monitoring

Fish Monitoring

1 backpack electrofishing
2 backpack electrofishing
barge electrofishing

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The federal Clean Water Act (CWA) section 106 (e) (1) requires states receiving water grants to monitor the quality of their waters, including biological monitoring. The U.S. EPA’s National Guidance on the 10 elements of a State Water Monitoring and Assessment Program suggest states should be using at least 2 biological community assemblages (e.g. , fish and macroinvertebrates) as core indicators to assess aquatic life use. 

In 2000 the Bureau of Freshwater and Biological Monitoring (BFBM) initiated the fish index of biotic integrity (IBI) monitoring in the northern part of the state to assess the health and condition of fish assemblages and to identify potential stressors from high gradient streams in New Jersey.  The Fish IBI is an index that measures the health of a stream based on multiple attributes (metrics) of the resident fish assemblage.  Each site sampled is scored based on its deviation from reference conditions (i.e., what would be found in an unimpacted stream) and is subsequently classified as “very poor”, “poor”, “fair”, “good” or “excellent”.   

The monitoring of stream fish assemblages is an integral component of many water quality management programs, and its importance is reflected in the aquatic life use support designations adopted by many states.  Fish assemblages can be stand-alone indicators of a waterbody’s health and/or fishability.  In addition, they may be combined with other biological and chemical indicators to assist in the identification of waters for upgrade to Category One antidegradation classification (N.J.A.C. 7:9B) based on exceptional ecological significance.

Currently, BFBM employs three IBI programs to monitor wadeable streams throughout the State.  The northern fish IBI (NIBI) is used to assess high gradient streams north of the fall line which are greater than 4-square miles in drainage size.  The southern fish IBI (SIBI) was developed for low gradient streams located in the Inner Coastal Plain which are greater than 2-square miles in drainage size.  Recently, the bureau completed the headwaters IBI (HIBI) for those small high gradient tributaries north of the fall line which are less than 4-square miles in drainage size. The headwater IBI monitors the assemblage of fish as well as crayfish, salamanders and frogs to assess aquatic life use in small headwater streams.

Fixed sites are sampled on a five year rotating basis, with monitoring focused on one water region each year. Northern IBI and Headwaters IBI monitoring occurs in three (Upper Delaware, Northeast, and Raritan) of the State's five major Water Regions on a rotational schedule of once every five years. Southern IBI monitoring occurs in one (Lower Delaware) of the State's five major Water Regions on a rotational schedule of once every five years.

The Fish Monitoring program also includes Fish Tissue Monitoring to support fish consumption use assessments and advisories.


If you are interested in more information about the IBI, please contact John Vile at 609-292-0427.


nibi region map

High Gradient IBI Sampling Area (NIBI)

hibi region map

Headwaters IBI Sampling Area (HIBI)

sibi region map

Low Gradient IBI Sampling Area (SIBI)

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Last Updated: August 10, 2017