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DEP Home : Water : Biological Monitoring : Biological Monitoring: Fish
Fish have an important ecological role in the overall food web. Fish are an integral part of our environment and natural history and are also an important resource providing food, recreation and economic value. County biologists study fish communities to provide insight on the health and condition of County streams.
Smallmouth Bass being measured as part of DEPs sampling protocol.
Here are some important reasons why examining and monitoring fish is useful in assessing our local waterways:
Learn more about the use of freshwater fish as an indicator of water quality.
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Once numbers of individuals are summed for each species present at a stream site, a fish Index of Biotic Integrity (IBI) is calculated based on multiple metrics. The IBI is used to rank the stream in relation to reference stream conditions. To use biological data properly, water resource analysts generally compare the fish data (actually not the raw data but a multi-metric index based on the data) from the stream sites under study, to indices from stream sites in ideal or nearly ideal condition (often called a reference condition). Stream sites are then ranked against the reference condition. This helps DEP set priorities for watershed restoration and improvement.
The fish IBI is averaged with the benthic macroinvertebrate IBI to determine overall stream conditions.
Fish IBI metrics are listed below. A technical, peer-reviewed methodology is used to take raw data and develop them into an acceptable Stream Rating score.
Total number of species
Total number of riffle benthic insectivore individuals
Total number of minnow species (cyprinidae)
Total number of intolerant species
Proportion of tolerant individuals
Proportion of individuals as omnivores/generalists
Proportion of individuals as pioneering species
Total number of individuals (excluding tolerant species)
Proportion of individuals with disease/anomalies
The photos below show fish that are commonly found in Montgomery County streams. Sensitive fish are only found in high quality waterways in our County. Pollution-tolerant fish may be found in more streams including those which have been impacted by cumulative or recent pollution.
Blueridge Sculpin
Brown Trout
Northern Hog Sucker
American Eel
Greenside Darter
Longnose Dace
Rock Bass
Rosyside Dace
River chub
Rosyface shiner
Spottail shiner
Yellow Bullhead Catfish
Blacknose Dace
Brown Bullhead
Creek Chub
Green Sunfish
White Sucker
Montgomery County has tabular raw fish data and fish narrative summaries from 1994-present for most monitoring sites around the County. Also available are GIS coverages (or maps) showing fish conditions. Maps can be developed to order depending on the request. Submit a request for either raw data or data in maps.
The following tables provide an explanation of the datafields found in our raw tabular data.
STATION The station field is a nine character code that identifies the station name. The stations are a combination of the two letter code for the watershed+the two letter code for the subwatershed+ the single digit stream order code+ the sequential reach number.
SPECIES The official common name of the fish species collected during sampling.
SAMPLE_DATE The date the station was sampled.
PASS1 Number of specimens collected from the first sampling pass.
PASS2 Number of specimens collected from the second sampling pass.
ANOMALIES The total number of anomalies.
ANOMALIES_TYPE The number of anomalies found of a certain type + the two letter code for the type of anomaly found.
Station The station field is a nine character code that identifies the station name. The stations are a combination of the two letter code for the watershed+the two letter code for the subwatershed+ the single digit stream order code+ the sequential reach number.
Date The date the station was sampled.
SummaryScore The final IBI summary score (1-5).
Narrative Descriptive word to describe the condition of the stream in relation to reference streams. Narratives are either Excellent (>4.5), Good (3.3-4.5), Fair (2.2-3.2), or Poor (<2.2).
If you are interested in obtaining data or protocols, please contact DEP at askdep@montgomerycountymd.gov. In your request, please provide the following information:
Name, organization (if applicable), phone number, and/or email address Type of data requested Time frame requested Explanation for use of data (helps to personalize the data request) Preferred method of data retrieval (email, CD by mail, FTP, pick up CD or materials from DEP offices)
Fish Anatomy
Office of Water's Biological Assemblages and Protocols for Fish page
MD-DNR MBSS Fish Distributions
Information about Stronghold Watersheds in Maryland (PDF, 2 pp, 193K)
Fish Kills in Maryland - Maryland Department of the Environment (MDE)
MDE Fish Consumption Advisory - Guidelines for Recreationally Caught Fish Species in Maryland
How to Protect Your Health While Eating Fish
Fishing Fun for Kids