DNR Study: Other Fish Species Declined After Arrival of Chesapeake Channa in Maryland Waters

Fish communities changed significantly in the Blackwater River drainage

Maryland Department of Natural Resources biologists perform winter fyke net surveys in the Little Blackwater River in 2019. Maryland DNR photo by Stephen Badger,

Chesapeake Channa adults were first documented in Maryland, thousands of miles from their native habitat in East Asia in 2002. Subsequent illegal introductions and natural dispersal in the decades since their arrival in Maryland expanded the species range. A new study by the Maryland Department of Natural Resources confirms the negative impact this invasive species has on other fish and the ecosystem.

A comparison of fish communities in the Blackwater River drainage near Cambridge before and after the introduction of non-native Chesapeake Channa, also known as northern snakehead, found lower relative abundances for 19 of 22 resident species observed, resulting in differences in community structure and biodiversity after the introduction.

Department of Natural Resources fisheries biologist Dr. Joe Love, and co-authors Joshua J. Newhard and Meghan Walker, published their findings in the online early edition of the Journal of Fish and Wildlife Management in November 2024.

Since their arrival, Chesapeake Channa have colonized an average of three new Chesapeake Bay subwatersheds per year, according to a 2018 study by Love and Newhard. 

“We know that this is an opportunistic, predatory species that could impact native fish populations, but before this study, whether their predation has changed the composition of aquatic communities was unknown,” said Love. 

A factor that helps them efficiently establish populations is reproduction. A recent study conducted by Love found these fish can release tens of thousands of eggs and could spawn more than once a year.

The authors recognized an opportunity to compare the fish communities in the Blackwater River drainage before and after the predator’s introduction because an inventory of fishes was conducted in that area in the early 2000s. Chesapeake Channa were first reported in Blackwater in 2012 and today it is a popular recreational fishing area for them, with some limited commercial harvest. 

During a 2018 survey, fisheries biologists Joseph Love and Jim Thompson (right to left) examine a Chesapeake Channa caught in the Blackwater River near Harriet Tubman State Park. Maryland Park Rangers Dana Paterra and Angela Crenshaw (left to right), then managers of the state park, observe. Maryland DNR photo by Stephen Badger.

In 2018 and 2019, biologists sampled six sites using the same methods as the fish community studies performed in Blackwater in 2007 and 2008 to learn if the number of species or the proportion of those species had changed. They conducted additional surveys between 2021 and 2023 to substantiate their findings. 

Before the introduction of the Chesapeake Channa, the three most abundant species, in order, were white perch, brown bullhead, and black crappie. Six years afterward, the three most abundant species were common carp, gizzard shad, and then white perch. While most species studied experienced declines, the biologists noted the greatest decreases were in popular prey for Chesapeake Channa such as black crappie, white perch, bluegill, and pumpkinseed.

The authors found that changes in water quality conditions could not explain the changes observed in the fish community. Instead, predation or displacement likely explained the changes observed.

Managing invasive species costs the United States more than $100 billion per year. In Maryland, aquatic wildlife like blue crabs and striped bass play important roles in the economy and culture, and invasive species could impact these industries and local ecosystems. Other studies have shown that once invasive fishes are established they cause widespread reductions in biomass. This study examined changes in one waterway where Chesapeake Channa has flourished, but impacts may not be the same everywhere. Impacts from an invasive species depend upon its abundance and the ecosystem, both of which greatly differ across rivers and lakes of the Chesapeake Bay watershed. 

Sportfishing and commercial harvesting for invasive fishes have become popular in Maryland and help the state manage the population. Chesapeake Channa and blue catfish both taste mild and have a firm texture, making them great fish to eat. Chesapkeae Channa is available on menus and at local seafood markets seasonally in spring and summer. There is no season or limit for harvesting Chesapeake Channa, and Maryland DNR has many resources available on its website for anglers interested in learning more.