Northern Snakehead Fish in Maryland
Current Research & Presentations
Preliminary Investigation of the Invasive Northern Snakehead (Channa argus) in the Howard County, Maryland Within the Ecosystem of the Little Patuxent River and Middle Patuxent River Waterways
The goal of this investigative research done with this invasive species of snakehead in the Little Patuxent River is to understand how this fish is adapting to new environments. Observing the Northern Snakehead fish in their new surroundings, such as smaller bodies of water that change based on the rain flow and not the tide, acclimating to different habitats, understanding their navigational and survival techniques, behavior changes and confirming an established presence of breeding activity was very exciting.
It cannot be confirmed at this time that the Northern Snakehead fish are negatively or positively affecting the ecosystem of the area under observation. More time is needed on this study and gut content was not used during this observational period. Data supports the notion that it is confirmed that they are adapting to their new habitat and forming new behaviors from those previously noted in Maryland’s tidal rivers. The depth and flow of this river changes greatly throughout the seasons. The snakehead fish seem to have been able to adapt to these changes in depth and flow by moving from the shallow, limited, and ever changing grassy banks with muddy substrate to the deeper water with rocky substrate that is far more abundant. The adult fish have started to gather in the middle of the river in deep pool pockets which does not have vegetation or cover. On sunny days, this behavior is visually observed. This behavior it appears to conclude that they are competing among themselves for prime habitat.
Nesting sites observed during research were not conical shaped vegetation. Since the offspring were viewed in open water near rocky banks, no nest was present. Fry were observed to follow schooling behavior. However, they have changed from the normal “up and down” descent in a safe vegetative cone to an unusual “in and out” movement towards the bank and then away from it. This was observed when fry was threatened by something in the water, such as an angler, in their new visual schooling behavior.
Previous observations show that the Northern Snakehead moves upstream during the fall, therefore they will continue until a natural hindrance or non-optimal habitat occur. Navigational techniques are still on point for what has been previously documented in Maryland. The most compelling argument for range expansion was based on angler returns. Snakehead fish are migrating upriver in the Little Patuxent River. An angler caught 12 snakehead fish in one afternoon off Piney Orchard Parkway near Wildlife Loop South, Anne Arundel County, in the Little Patuxent River. This site is approximately 10 miles away from our observational area and approximately 5 miles away from the beginning of the Little Patuxent River. This supports the previous findings by Odenkirk and Owens (2007) that Northern Snakehead fish, in the Little Patuxent River, are exploring and venturing upriver during flooding periods while still maintaining a stable population throughout previously occupied zones. Though this fish has yet to overcome the natural rocky barriers of the observational area of Savage Mills, it is likely that this population will succeed and continue upward migration patterns.
The behavior change of note on this study was that the snakehead fish favored the deep-water pockets of over 4 feet in depth without vegetation. They can be seen maintaining a top water presence instead of occupying their favored habitat conditions of being near grassy banks with muddy substrate. This seemed unusual due to the fact that it would make this fish an easy target of prey, such as predatory birds or anglers. This behavior could be the result of trying to reach top water prey such as aquatic bugs or even amphibians.
The confirmation of fry in the research area was fortunate to be observed twice during the periods of study. To see that the offspring’s’ school behavior was the same, as described by Courtenay and Williams 2004, in one area where the habitat availability are more suitable to their liking and in another area in the same river a few hundred yards away in a completely different habitat, is confirmation that this species’ is highly adaptable. There were what seemed like thousands of fry in both nesting sites. Adults fish were not visible near offspring, as described (Courtenay and Williams 2004), which might be a new behavior for the species. Since the adults are choosing to be in deep water pockets, and adults are known for eating young, the fry might be further away from their parent couple for safety. This could be another new learned behavior. The fact that the offspring are exhibiting this shows how highly adaptable and versatile they are.
Information on how to identify and properly handle this invasive fish must be made available with signage posted at state and local parks where this fish is found. It should be noted that anglers have the options of 1)terminate the fish by removing the gills, cutting off the head or gutting the fish in order to transport it from its site of origin or 2) to return the live snakehead fish caught into the body of water it originally came from. Relaying the information that the snakeheads that are killed are only a small fraction of what are remaining in the river. Ending a few mating pairs could help slightly keep their population numbers down.
The lack of validation of age of the fish caught using sagittal otoliths, growth data comparison, egg count, inconsistent fishing and measurements, and gut content will hopefully be addressed in the continued observational study for 2017.
Overall, it appears that in this colonized area the Northern Snakehead fish are thriving. They are highly adaptable and a unique species added to this small ecosystem. I believe that by promoting the education of this fish to fellow anglers and community members, we can promote catch and release as well as responsible harvesting. I am advocating for this fish to not only become a game fish but table fare.
