Looking for critters: How DEP monitors our streams in spring

Crayfish April 4, 2017
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The approach of spring brings a new sampling season for biological monitoring along with it. Between March 1st and April 30th, DEP will visit more than 100 stations to collect samples. This year, the baseline watershed that we focus our sampling around will be Rock Creek.  DEP biologists will also continue to monitor Special Protection Areas.



Stonefly (Order: Plecoptera)


What happens during spring stream sampling?

Looking for stream bugs

In the spring, DEP uses benthic macroinvertebrates to determine the health of streams. Benthic macroinvertebrate (AKA benthics) is the scientific name of the category of stream bugs and crayfish that live at the bottom of streams.  Based on the species types and diversity of benthics, DEP biologists can judge whether a stream section is healthy.

To sample a station for benthics, DEP biologists collect 20 samples using a very fine-meshed net from a variety of habitats in the stream such as riffles, under rocks, root wads, and more. It is important to take the samples from the best possible habitats in order to get a true representation of the benthic community of the stream.


Biological Monitoring Staff performing a spring stream sampling

Biological monitoring staff performing a spring stream sampling


One common and interesting bug that is found is the “case-maker” Caddisfly larva that builds a protective case out of small pieces of rocks and woody debris. It can then attach itself to the bottom of rocks and might stay there until it emerges as an adult.

In addition to taking benthic samples, DEP assesses the surrounding riparian habitat and in-stream habitat for presence of vegetation, erosion, sediment deposition and more. These habitat assessments provide insight as to why the benthic macroinvertebrate community is excellent, poor, or somewhere in-between.

Monitoring benthic macroinvertebrate populations is very important because it gives us information on the health and quality of our local streams that flow through our yards, parks, and communities.


Northern Two-lined Salamander in its larval life stage

Northern Two-lined Salamander in its larval life stage


Amphibians and reptiles too!

Spring is an exciting time for the herpetofauna (amphibians and reptiles) surveying aspect of monitoring. It is the beginning of mating season for frogs and toads – the part of their life that requires proximity to water – so there is a good chance of hearing a variety of species (or if you’re lucky – seeing them!).

A very common salamander to see in the spring is the Eastern Red-backed Salamander, which can be found on land under logs and rocks. When summer approaches these salamanders head underground seeking cooler temperatures.


Northern Black Racers

Northern Black Racers


DEP biologists perform timed searches for amphibians and reptiles. They search for 10 minutes on each side of the stream, and 10 minutes within the stream channel. Surveying herpetofauna is as simple as lifting logs and rocks to check underneath for salamanders, or searching wetlands and seasonal pools for frogs, toads, or eggs. These are considered to be the best available habitats, and anything that is found is recorded.

Spring is an exciting time to be out in the field to witness the change in landscape and bloom of new life in Montgomery County.


By Samantha Duthe

Samantha started as an intern with DEP’s summer biological monitoring program and now supports the Department full time, including outreach and education.  Samantha loves teaching others about County wildlife. 

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