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map of AMNET sampling sites



  Bureau of Freshwater & Biological Monitoring





In 1992, the Bureau of Freshwater & Biological Monitoring initiated its Ambient Macroinvertebrate Network (AMNET).

AMNET established sampling stations in each of the 20 freshwater Watershed Management Areas, statewide, where the health of in stream benthic macroinvertebrate (sometimes called bottom-dwelling "bugs") communities are evaluated using a USEPA-developed statistical methodology referred to as Rapid Bioassessment Protocol (RBP). Under AMNET, each of the State's five major Water Regions is sampled for benthic macroinvertebrates (bottom dwelling organisms visible to the naked eye) on a rotational schedule of once every five years. Visual observations, Stream Habitat Assessments and limited physical/chemical parameters are performed on each site. To date, over 760 non-tidal sampling sites have been established.

The AMNET results have been incorporated into the National Environmental Performance Partnership System (NEPPS) as a primary environmental indicator of water quality impairment. Statewide AMNET monitoring is a commitment in the NEPPS PPA with EPA Region 2, and a key element of NJ's Long-term Water Monitoring and Assessment Strategy. Other uses of the AMNET data include:

The biological and habitat ratings are available from this web site for Round 1, Round 2, Round 3, and Round 4 data. The chemical and biological data is also available from federal and State databases.  Data retrieval links can be found here:

Ambient Macroinvertebrate Network (AMNET)

1997 - 2016 Data Comparison Table

This table displays and compares assessment ratings for sampling from Rounds 2, 3, and 4 for all five (5) regions (Basins) throughout NJ in which this ambient biological monitoring is conducted. It also contains the results for Round 5 for four of the basins (Lower Delaware data still not yet analyzed). Round 2 data were collected from 1997 to 2001 while Round 3 data were collected from 2002 to 2007. Round 4 data were collected from 2007 to 2012. Currently, the table contains the Round 5 results for the Northeast basin, the Northwest basin (Upper Delaware), the Raritan basin and the Atlantic basin. The Lower Delaware basin data is not yet completed. As additional data becomes available, it will be added to this web site.

For comparison purposes, earlier round results have been recalculated using recently adopted genus level multi-metric indices. Round 1 raw data was recorded for each site at the family level, rather than genus level taxonomy. Therefore, assessments could not be accurately recalculated and compared to the genus level multi-metric indices used in subsequent rounds. Because of this, Round 1 assessments were not added to this table. A Standard Operating Procedure is available for all aspects of the AMNET program including a summary of the index development and scoring criteria.

This table contains results only. Summary information is contained in the appropriate basin Summary Reports. The assessment of these results may be found in the NJ Water Quality Assessment reports.

A Key for the Assessment Ratings used in the table below is available. For questions or additional information, please feel free to contact us at 609-292-0427.

Multi-Metric Indices

AMNET employs a multimetric index approach for assessment of biological condition, and regulatory thresholds for use attainment. New Jersey benthic macroinvertebrate communities can be statistically grouped into three distinct structures based on geographical regions: high gradient (above the Fall Line), low gradient (Coastal Plain excluding the Pinelands), and Pinelands. To accurately assess biological condition, an index was developed for each distinct region using guidelines outline in USEPA's Rapid Bioassessment Protocols (RBP) for Use in Wadeable Streams and Rivers. The indices assess sites from two perspectives: the condition of the macroinvertebrate community and the regulatory use attainment. An assessment framework was outlined to address both concerns, and a development report was prepared for each index: High Gradient Macroinvertebrate Index (HGMI), Coastal Plain Macroinvertebrate Index (CPMI), and the Pinelands Macroinvertebrate Index (PMI).

A Standard Operating Procedure (SOP) is available for all aspects of the AMNET program including sampling, analysis, assessment, and a summary of the index development and scoring criteria.

Probabilistic Water Quality & Biological Network (PWQBN){Using Macroinvertebrates}


The objectives of the PWQBN are to:

  • establish a probabilistic network of sites to determine statewide estimates of biological impairment in a statistically sound manner

  • collect habitat and biological samples (macroinvertebrates) at co-located Ambient Surface Water Quality Monitoring Network (ASWQMN) probabilistic sites in order to link biological conditions to water quality.

Data obtained will also be used by NJDEP in the generation of the biennial Integrated Water Quality Monitoring and Assessment Report (includes 305(b) report and 303(d) list).


Fifty (50) probabilistic sites were selected for ASWQMN using a Generalized Random Tessellation Stratified (GRTS) survey design.  Fifty new probabilistic sites will be re-selected every two years over a ten-year period enabling a comprehensive statewide statistical analysis for 250 stations.  Macroinvertebrates will be sampled at co-located ASWQMN probabilistic sites  where sampling protocols are applicable for macroinvertebrate sampling, i.e. wadeable and non-tidal. This will be determined upon the initial visit for macroinvertebrate sampling. 


Biological Nutrient Correlation Project


The Project collects Total Phosphorus (TP) and Total Nitrogen (TN) water quality information at biological sites in the Ambient Macroinvertebrate Network (AMNET), Fish Index of Biotic Integrity Network (FIBI), and the Headwaters Index of Biotic Integrity Program (HIBI).  Total Nitrogen will be considered the sum of Nitrite- Nitrate (NO2-NO3) and Total Kjeldahl Nitrogen (TKN) concentrations.

According to the USEPA, human activities over the past century have dramatically increased the amount of nutrients (nitrogen and phosphorus, in particular) that are introduced to our Nation's rivers, lakes, and coastal waters. This change has adversely affected the health of the natural environment and, in some cases, poses risks to human health.


Data will be used to statistically correlate nutrient concentration with biological impairment.  Prior to 2014,  nutrient parameters were not sampled routinely at biological monitoring sites at the time of organism collection.  This project will continue routine TP and TN collection within a timeframe that biological samples are collected to meet the objective of using this nutrient data to establish possible relationships between nutrient concentrations and biological impairment for each of BFBM’s biological monitoring network.  Statistical analysis will include establishing relationships, if any, between nutrient concentration and biological communities, individual metric scores, and index scores.  


Nutrient samples are collected on the same day as biological sampling, or within 3 weeks prior to biological sampling.  Sampling index period and site lists can be found in the respective AMNET, FIBI, and HIBI QAPPs.  This project will serve to coordinate nutrient sampling, assessment, and data management between these networks.


Stressor Identification Investigations

The Stressor Identification process , based on USEPA's "Stressor Identification Guidance Document" (2000), is a systematic protocol to determine the likely stressor or stressors causing biological impairments. While biological information, such as benthic macroinvertebrate data, can determine the condition of an aquatic resource, the data do not identify the likely cause(s) of impairments. The ability to accurately identify stressors and support those findings is a critical step in developing appropriate strategies and corrective measures to improve the quality of aquatic resources.

The purpose of a Stressor Identification (SI) investigation is to determine the most likely cause(s) of the impaired benthic macroinvertebrate community, as identified through the AMNET program. AMNET sites, with a rating of "Poor" or "Fair" are considered impaired, and therefore, not supporting the Aquatic Life use goals of the federal Clean Water Act. A cause of impairment can be viewed most simply as a stressor or agent that negatively impacts aquatic life. These causes may include: chemical or physical pollutants (e.g. toxic chemicals, nutrient inputs, oxygen-consuming wastes); habitat degradation (e.g. loss of in-stream structure such as riffles and pools due to sedimentation, loss of bank and root mass habitat due to channel erosion); and hydrologic modifications (e.g. low base flow, flashy stream flow).

Available reports of completed Stressor Identification investigations.


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Last Updated: January 9, 2018