Biological Monitoring for MoCo

Field Reports from Department of Environmental Protection Staff

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  • Photos of Critters in Our Backyard in Montgomery County, MD

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Rapidfire Fish ID

Posted by mocobio on August 20, 2009

How many distinct fish species do you think there are in Montgomery County? How many do you think you could identify by sight?

County biologists have documented more than 60 species of freshwater in Montgomery County streams. They commonly encounter upwards of 25 different species (comprising more than a thousand individuals) during summer fishing surveys at a healthy stream site.  In contrast, at poor quality stream sites they may only find 1–2 species and low numbers of individuals.

Example of five different species of fish. From top to bottom: river chub, rosyface shiner, swallowtail shiner, spotfin shiner, and silverjaw minnow. Can you see the differences?

Example of five different species of fish. From top to bottom: river chub, rosyface shiner, swallowtail shiner, spotfin shiner, and silverjaw minnow. Can you see the differences?

It takes special background and skill to properly and efficiently identify freshwater fish.   Staff training and experience helps in identifying species by examining body shape and type, mouth orientation, finnage, coloration, and overall size. Occasionally, a biologist will need to carefully count scales or fin rays to distinguish one species from another.  Biologists check each fish for anomalies such as parasites, deformities, or signs of illness. If a question on fish identification or anomaly type arises, multiple biologists examine the specimen to come to a consensus. Published fish identification keys can be consulted when necessary.  If a consensus cannot be reached in the field, the fish is taken back to the laboratory so that key features can be examined under a microscope.

A yellow bullhead catfish, distinguished by its fin shape and yellow bottom whiskers (also known as barbels). A brown bullhead looks similar but has all brown whiskers. This one has ulcers in its mouth which would be noted as an anomaly. He looks happy nonetheless.

A yellow bullhead catfish, distinguished by its fin shape and yellow bottom whiskers (also known as barbels). A brown bullhead looks similar but has all brown whiskers. This one has ulcers in its mouth which would be noted as an anomaly. He looks happy nonetheless.

With fish sampling, speed is of the essence. Two important indicators of stream health are species diversity and biomass (total weight of the biological sample).  Once the total biomass of the fish sample is recorded, fish are quickly transferred to nets and placed in a bucket with a bubbler. It is important that the fish get enough oxygen while they wait to be processed.

Buckets with aerators provide oxygen to fish as they wait to be counted.

Buckets with aerators provide oxygen to fish as they wait to be counted.

Large individuals are typically processed first or transferred to their own bucket or live well (a bucket or other container with holes to allow water to flow through). If a fish individual is able to survive and grow large in a stream or river, it means that all of its needs are being met and even exceeded. Some large and long-lived species, such as brown trout, have very specific habitat and water temperature requirements. Thus finding a large individual frequently means that the stream is healthy enough to support them well as other age classes.

These two individual fallfish from the Little Paint Branch watershed represent different age classes indicating that this stream is supporting longevity and reproductive success in this population.

These two individual fallfish from the Little Paint Branch watershed represent different age classes indicating that this stream is supporting longevity and reproductive success in this population.

When we handle fish to identify them, it is important that our hands are wet to minimize damage to their scales and fins. Typically, it is acceptable to hold a fish out of the water for brief periods at a time to get a clear look at its key features. Sometimes it is helpful to put the fish in a plastic ziplock bag with water to examine for longer periods. Digital photos help us to document fish species and their identifying features to reference later.

A handful of fish to identify.

A handful of fish to identify.

Biologists call out fish species counts and any observed anomalies to another crew member who tallies and calls back to verify the information as we go.  (This is similar to the process used to place coffee drink orders at a Starbucks coffee bar with a long queue of customers). Using this approach, we identify accurately but rapidly, and get fish back into the water to reduce their stress.  At our most diverse and populated fish sites, it can sometimes take up to two hours to count and identify all the fish collected in the buckets.

Biologist and interns processing fish. Fish are counted, identified, recorded on the data sheet, and then released back into the stream.

Biologist and interns processing fish. Fish are counted, identified, recorded on the data sheet, and then released back into the stream.

 Additional Resources:

Fish Anatomy: EPA Resource on the Basics of Fish Anatomy

Freshwater Fish Identification Key: MD Department of Natural Resources technical key for identifying Maryland freshwater fish.

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2 Responses to “Rapidfire Fish ID”

  1. […] Link: Rapidfire Fish ID « Biological Monitoring for MoCo […]

  2. your posts are brilliant please post more health news!

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