Northern Snakehead Fish in Maryland
WHAT IS AN INVASIVE SPECIES?
Invasive Species is defined as a plant, fungus, or animal species that is not native to a specific location (an introduced species). Introduction into our ecosystems, in Maryland, is believed to have occurred via two methods: 1) release by aquarium owners and; 2) the live food fish trade by individuals releasing these fish to establish a local food source. There are THREE photo documented predators of this species in the Chesapeake Bay Watershed the Green Heron, the Egret, and River Otters. Although my current observations are documenting other predatory birds (Bald Eagle, Osprey, Red Hawk, Blue Heron, Green Heron, and Kingfisher) in the research area that might be classified as predators of this non native fish.
History
Snakeheads have a native range, as a family, that includes parts of Asia and Africa. Fisheries scientists have found four species in 14 states within the United States of America and reproducing populations have been documented in New Jersey, Pennsylvania, Delaware, West Virginia, Florida, South Carolina, Louisiana, Virginia and Maryland, as of 2017.
The Northern Snakehead made its debut May of 2002 in a self-sustaining population pond located in Crofton, Maryland. Breeding populations have been established throughout the tidal Potomac River and more recently the Patuxent, Nanticoke, Wicomico, Susquehanna and Blackwater Rivers.
It has also been confirmed in Howard County at Savage Mills Park in 2012. An established population is now prospering in the Little Patuxent River south of the confluence.
Life Cycle
Description
The Northern Snakehead has an elongated body that grows to 40 inches in length. Described to have a tan, dark brown, green, gray or black coloring with a mottled, snake-like pattern and a long dorsal fin running along most of its back, they also have a large mouth with a protruding lower jaw and many teeth. They reach sexual maturity at 2-3 years of age and approximately 30-35 cm in length. Females produce eggs 1-5 times per year and release 22,000-80,000 eggs per spawn. My research is also studying how limited resources such as food, habitat and water quality may influence egg counts and spawning frequencies. As adults, they prefer to feed on fish, but will also feed on small birds, mammals, reptiles, frogs, crustaceans, and aquatic insects.
Habitat
The favored habitats are freshwater areas of ponds, lakes, streams and rivers with thick vegetation, muddy substrate, with stagnant water of somewhat shallow depths. Northern Snakehead fish have a broad temperature tolerance of 0 to 31º C, they can survive under ice. The species is an obligate air breather. They have a "primitive" lung, therefore, survival in low oxygen waters and out of water (up to 3-4 days while moist) is possible. The Northern Snakehead as been able to easily adapt to large river systems such as the Potomac and Patuxent and have had no negative impact on native species. In smaller river systems, ponds, and lakes it is still unknown.
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Juvenile Stages
Females produce eggs 1-5 times per year and release 22,000-80,000 eggs per spawn. Their eggs float and take approximately 28 hours to hatch, depending on temperature.
Parents then guard the young in a nest until yolk absorption is complete at approximately 8 mm in length. During the first few weeks of life, fry feed on zooplankton.
Migration of the Northern Snakehead fish over 10 years
Migration of the Northern Snakehead fish over 10 years