Biological Monitoring

In 1995, the West Virginia Department of Environmental Protection (DEP) established the Watershed Assessment Program to assess and report on the water quality of the State's streams and lakes. Following a period of restructuring within the agency, the program's name was changed to the Watershed Assessment Branch (WAB). The WAB is comprised of a staff of biologists and environmental scientists who measure and assess the chemical and physical properties of water, assess habitat conditions, and collect biological samples in the form of benthic macroinvertebrates and fish from streams and lakes throughout the state. As of 2020, WAB has collected 10,598 benthic macroinvertebrate samples at 6,847 stations, from 3,896 different streams. About 560 fish community samples have been collected at 501 stations, from 406 different streams. Since 1998, WAB has used the benthic macroinvertebrate data to measure the biological health of West Virginia streams. Fish community sampling in streams has been part of WAB biological monitoring since 2006.

Water Sampling
Water Sampling

Benthic Macroinvertebrates

Benthic macroinvertebrates (also known as "benthos") are small animals living among stones, logs, sediments and aquatic plants on the bottom of streams, rivers and lakes. They are large enough to see with the naked eye (macro) and have no backbone (invertebrate). Insects comprise the largest diversity of the these organisms and include mayflies, stoneflies, caddisflies, beetles, midges, crane flies, dragonflies and others. Non-insect members of the benthic macroinvertebrate community are snails, clams, aquatic worms and crayfish. To date, the WAB has collected and identified 538 different kinds (mostly Genus level identifications) of benthos from 6,202 stations on 5,530 different streams throughout West Virginia. The WAB has found the diversity of some benthos to be especially high, including mayflies (49 genera) and stoneflies (43 genera). Some benthic genera are fairly common throughout the state, while others are limited in their distribution to just a few areas. The most commonly encountered benthos is the midge Polypedilum (Family Chironomidae), found at 81% of collection stations. The caddisfly Cheumatopsyche (Family Hydropsychidae) and mayfly Baetis (Family Baetidae) have been found at 77% and 72% of the stations, respectively. The net-winged midge Blepharicera (Family Blephariceridae) is not common, found at only 1.2% of all collection stations. This sensitive organism is restricted to the steeper streams in the higher mountains of the state, where oxygen rich water cascades over waterfalls and tumbles through small rapids and riffles.


Benthic macroinvertebrates live in a wide variety of habitats and can be found from the smallest headwater streams down to the largest rivers. In West Virginia, benthic macroinvertebrates are especially diverse, having adapted to the complex array of streams that dissect the mountains and tumble through the narrow valleys. In general, benthic organisms are most diverse in the fast flowing riffle and run areas of streams. Compared to pools and glides, riffles and runs are shallower and have higher stream gradients and faster water velocities. They are composed of rough materials, such as large gravel, cobbles and small boulders that create turbulence and oxygenate the water, while providing a stable habitat for benthos to live. Many insect benthos spend the majority of their lives (anywhere from 1 month to 4 years, depending on the species) in the water and only emerge as adults for a few hours (or up to several days) to reproduce and complete their life cycle. Movement of benthos larvae includes swimming, crawling around on the stream bottom and drifting with stream currents. After emerging, adult aquatic insects can fly to new stream locations during their winged terrestrial stage.


Benthic macroinvertebrates have special adaptations that allow them to live in the stream environment. These adaptations may be unique physical features or even specialized behaviors. For example, many species have flattened bodies that allow them to hide between boulders and cobbles, thus limiting the stress of fast-moving water and allowing them to avoid some predators. Others have sharp claws, suction cups, or other grasping mechanisms on their bodies to prevent them from being swept away in the swift-flowing current. Black fly larvae (Family Simuliidae) have a silk gland and posterior hooks that are used to anchor them in place while they face upstream actively capturing food with their fan-like mouth parts. Net-building caddisfly larvae (Family Hydropsychidae) construct funnel-shaped nets, attach them to stable substrate materials, and then periodically harvest the food caught in the mesh. Some stonefly species will avoid high water temperatures by burrowing deep into the stream bottom substrate where they will diapause near the water table. One of the most important adaptations for benthos is the ability to extract oxygen from the water in which they live. Many aquatic insects accomplish this with external gills that remove oxygen from the surrounding water, while others rely upon cutaneous respiration to obtain oxygen.


Benthos are often classified based on their feeding strategy. The stonefly Pteronarcys (Family Pteronarcyidae) is in the shredder functional feeding group. These large stoneflies primarily consume decaying leaves that have fallen into the stream from trees along the forested riparian corridor. The water penny beetle (Family Psephenidae) is a scraper and can be observed grazing on algae that covers rocks and logs. The mayfly Family Baetidae is classified as a collector-gatherer, primarily feeding on fine pieces of organic material on the stream bottom. The most recognized predator in the aquatic insect world is the larval form of the dobsonfly, more commonly known as the hellgrammite (Family Corydalidae). Hellgrammites are active predators, crawling around on the large cobble and boulders in the swifter habitats of streams where they search for other benthic macroinvertebrates to eat.

Importance in Food Webs

Benthic macroinvertebrates are extremely important in aquatic food webs. In most streams, the energy stored by plants is available for consumption by benthos either in the form of leaves that fall into the water or in the form of algae that grows on the stream bottom. The energy derived by eating leaves and algae is then transferred from benthos to other life forms in and around the stream such as fish, frogs, salamanders, snakes, birds, and even fishermen. In another sense, benthos are important for recreational purposes, as thousands of trout anglers strive to "match the hatch" of many species, particularly those of mayflies.

Biological Indicators

Benthic macroinvertebrates provide reliable and comprehensive information on water and habitat quality and have been used as biological indicators in many parts of the world for nearly 100 years. In some cases, it may be difficult to identify pollutants and stressors in streams with chemistry data alone, which only provides information pertinent to the precise time of sampling. Even the presence of fish may not be indicative of the status of a stream because fish can swim away to avoid polluted water or unfavorable habitat conditions and then return when conditions improve. Many benthic macroinvertebrates are not as mobile as fish and cannot move to avoid pollution. Therefore, the community of benthos living in a stream may indicate the water quality conditions of the past. Additionally, benthos are excellent tools for assessing water quality because they are extremely diverse, allowing for a wide range of sensitivity and responses to stressors such as metals, nutrients and sediments. Finally, they are ubiquitous and relatively easy to collect and identify which makes them attractive to agencies and organizations searching for a practical means of assessing water quality in streams.

Collecting Benthic Macroinvertebrates

Streams in West Virginia are primarily high gradient with coarse substrate materials such as boulder, cobble and gravel. These physical conditions are responsible for the typical riffle/run habitats commonly found in most streams across the state. The Watershed Assessment Branch samples these riffle/runs for benthos by using a hand-held net, often referred to as a kick-net. Generally speaking, the net is secured to the stream bottom in a riffle/run while the cobbles and gravels upstream are cleaned and disturbed ("kicked") causing the benthos to float downstream into the net. This procedure is used statewide by the WAB in all wadeable streams with riffle/run habitats and is by far the most common type of benthic sample collected by the agency. All benthos samples are taken to the laboratory where the organisms are sorted, identified and enumerated in preparation for data analysis and interpretation.

Entities wishing to collect benthic macroinvertebrates from West Virginia streams for basic environmental research studies or permitting projects will need to obtain a scientific collection permit from the West Virginia DNR, which requires that the investigator(s) follow the methods established and used by the WAB.

Using Benthic Macroinvertebrates to Assess Biological Conditions

In order to extract and understand the information presented by a benthic macroinvertebrate sample, the WAB uses a tool commonly called an Index of Biotic Integrity (IBI). An IBI is a summary score that is comprised of several biological indicators called metrics. A metric is a characteristic of the biological community that changes in some predictable way with increases in human disturbance. For example, species richness (sometimes called diversity) generally exhibits a marked decrease as human disturbance increases. Therefore, it is one of the most commonly utilized component metrics of IBI's.

Family Level Benthic IBI

In 2000, the WAB collaborated with the United States Environmental Protection Agency (EPA) Region III to develop its own IBI, a multi-metric index for biological assessments called the West Virginia Stream Condition Index (WVSCI). The WVSCI summarizes family level identifications of benthic macroinvertebrate assemblages to assess the biological condition of wadeable streams with riffle/run habitats. This index includes six biological metrics that represent elements of the structure and composition of benthic macroinvertebrate communities. The WVSCI metrics were selected to maximize discrimination between streams with known stressors and reference streams. Reference streams have little or no human disturbances, and therefore exhibit good water quality and habitat conditions. Many of the streams that the WAB recognizes as reference sites are located on public lands, such as Monongahela National Forest and the West Virginia State Park system. The WAB used the WVSCI from 2002 to 2014 to assess the biological condition of wadeable streams in the state.

Genus Level Benthic IBI

Although the family-level WVSCI was designed using sound ecological and statistical principles and has typically met the needs of the WAB, the availability of genus-level benthic macroinvertebrate data led to the development of an updated IBI in 2011. This IBI, referred to as GLIMPSS, was developed with geographical and seasonal partitioning that resulted in separate IBI’s for the plateau and mountain regions in WV as well as spring, summer, and winter seasons. Genus-level taxonomy allowed for the selection of several additional indicator metrics with larger response ranges that could better track stressors in different seasons and within specific geographic regions.

Fish Community Assessments

Fish community assessments are an important component of many water quality management programs. These assessments can be useful for making decisions regarding biological integrity and overall stream health. Similar to benthic macroinvertebrates, samples of fish communities from streams can be assessed using an IBI. WVDEP collaborated with West Virginia University to finalize the development of fish IBIs specifically applicable to West Virginia fish communities. It was determined during the IBI development that fish communities varied regionally and therefore required region specific expectations. The end result is that IBIs were developed for 3 of the 5 distinct regions in the state. However, the performance of these IBI's was not sufficient to utilize for 303(d) assessment purposes. Additional fish community data is being collected for the purpose of improving the performance of these IBIs.

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Consumption Advisories

Human activities have allowed the discharge of chemicals, trace metals and other contaminants into the waters of the state. Fish and other aquatic organisms may bioaccumulate these contaminants in their tissues to levels much higher than those in the water and sediments. The WAB collects fish of various species from West Virginia's waterbodies in order to determine if contaminants are present in their tissues, and to what level. This information is used by the West Virginia Department of Health and Human Resources, through an interagency agreement with West Virginia's DEP and Division of Natural Resources, to develop consumption advisories for fish caught in the state. These fish consumption advisories are reviewed annually and are geared towards helping West Virginia anglers make educated choices about eating the fish they catch.

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