The Anne Arundel County Fish Atlas: An Introduction

In 2004, Anne Arundel County began the Countywide Biological Monitoring Program (Program) to better understand the health of the County’s non-tidal streams and rivers and the biological communities they support. In the beginning, only stream insect community health was assessed; however, in 2017, the Program expanded to include the fish community. The sampling work underpinning this Story Map, and the related “An Atlas of the Freshwater Fishes of Anne Arundel County, Maryland” document, occurred between 2017 and 2021.

It is not cost-effective or necessary to sample every stream in the County to describe Countywide stream conditions. The Program employs a random sampling approach to characterize aquatic communities in an unbiased, scientifically rigorous way using tried and true methods based on those developed by the State of Maryland. Details about the methods used by the Program can be found here:

Because not every stream reach is sampled, it is possible that a fish species not observed in a particular watershed during our sampling effort could still be present in that watershed. The random sampling approach, however, makes the chances of it occurring in large numbers likely quite low. During the five-year assessment period, 49 individual fish species were identified across the County’s 13 major watersheds.

In this Story Map, we showcase ten different species that were observed during the project. Of these ten, three are the most commonly found in the County and three are among the least commonly found. Three other species showcased are among the median number of fish found and another is an invasive fish. It is our intention to update this Story Map when more data is available in subsequent projects.

Most fish species are typically found in particular places in streams and rivers. The homes (aka habitats), which certain species choose, are not random. Since many species are only found in certain parts of the stream, the distribution and abundance of high quality habitat conditions are important in maintaining fish populations. Features like pools, riffles, woody debris jams and beaver dams, undercut banks, and submerged aquatic vegetation are some of the features used by County fishes.

In addition to stream-specific habitat conditions, the large scale geological and climatological characteristics where a river system is located can have a great impact on the distribution of fishes. In Maryland, there are several of these  physiographic regions , with two sharing the northwestern-border of the County: the Piedmont and the Coastal Plain.

While the 49 non-tidal fish species are discussed in “An Atlas of the Freshwater Fishes of Anne Arundel County, Maryland," ten species (Eastern Blacknose Dace, American Eel, Eastern Mudminnow, Longnose Dace, Mummichog, Redfin Pickerel, Brook Trout, Rock Bass, White Crappie, and Snakehead) are highlighted here.

The ten species were chosen based upon their abundance in County streams. Where these species are most often found, which County streams have their preferred habitat, or where ecological threats might occur are just several of the insights to be learned from the known fish distribution in our nontidal County streams. For example, the distribution of our most abundant species (Eastern Blacknose Dace, American Eel, and Eastern Mudminnow) tells us that most watersheds in the County have stream habitat suitable for these fish. On the other hand, the least abundant species’ (Brook Trout, Rock Bass, and White Crappie) distribution tells us that either most habitat in the County may not be suitable for these fish, or that the habitat may only be found in one place. Insights such as these can inform recommendations for streams that may be in need of restoration or enhancement to maintain or increase levels of fish diversity.

While the Atlas and this Story Map attempt to use as little jargon and technical language as possible, the descriptions sometimes use technical terms to describe different parts of fish that are useful in identifying a particular species. The diagram below provides a guide to these terms for your reference. You can find a brief description, life history, and location map of each of the ten fish below.

These three fish were among the least observed in the County during the project. All three fish were found in only one location, although it is possible that they could reside elsewhere.

One invasive species was found during the project: the Northern Snakehead (Channa argus).