Geoff Smith, a biologist with the Pennsylvania Fish and Boat Commission (PFBC), unfurled a weighted seine and plunged it into the water Monday at John Heinz National Wildlife Refuge. <\/p>\n
Smith and two other PFBC scientists dragged the net through the shallows of the Heinz impoundment, a sprawling wetland in Philly fed by Darby Creek. Their target: invasive Northern snakeheads. <\/p>\n
The impoundment had been drained for fall migrating shorebirds, exposing the muddy bottom to help make swift work of the hunt. Snakeheads flopped openly in the muck, demonstrating their remarkable resilience \u2014 a keen ability to survive in shallow water or open air without suffocating.<\/p>\n
\u201cThey are a prized food fish. They were brought here mainly for people to eat. And they\u2019ve been liberated into waters around the area,\u201d Smith said, with a sarcastic smile on the word liberated.<\/p>\n
Snakeheads feast on native fish, and the PFBC has labeled them \u201cvoracious predators.\u201d They <\/b>are seen as such an environmental threat that it is illegal to transport them live in the state.<\/p>\n
Smith and his team at PFBC, along with Pennsylvania State University student Matt Chotlos, are collaborating on a study of the snakehead invasion into impoundments \u2014 local lakes, ponds, and wetlands. <\/p>\n
A major goal of the team is to determine levels of contamination in snakeheads by synthetic per- and polyfluoroalkyl chemical compounds, known as PFAS. The team is also examining tissue samples for other biomarkers, and to assess the species\u2019 broader ecological impact. <\/p>\n
\u201cSince they are a popular food item,\u201d Smith said, \u201cwe want to have an idea what those contaminant levels look like.\u201d<\/p>\n
How did snakeheads get to Philly?<\/p>\n
Native to China, Russia, and Korea, Northern snakeheads (Channa argus) were first documented in Pennsylvania in 2004 at Meadow Lake in Philadelphia\u2019s FDR Park. The lake is fed by interconnected waterways that ease the spread.<\/p>\n
\u201cWe don\u2019t know who first brought them,\u201d Smith said, \u201cbut they were probably brought for live fish markets.\u201d <\/p>\n
Snakeheads grow big and have become a sport fish for anglers. Their white meat filets are tasty to some who share recipes. Anglers debate online whether they should be killed after they are caught \u2014 or cooked and savored.<\/p>\n
Snakeheads are present not only in Philly, but also in the Rancocas, Woodbury, and Raccoon Creeks in South Jersey, according to recent research by David Keller, fisheries section leader for the Academy of Natural Sciences at Drexel University. <\/p>\n
\u201cThe impact, the concern, is as high as it gets,\u201d said Keller, who hopes to publish a study soon on snakeheads in the Delaware River Basin. \u201cFrom my perspective, the concern for Northern snakeheads is how they are impacting the Delaware basin and the fish fauna and the ecology.\u201d<\/p>\n
Members of Keller\u2019s team found 46 species of fish in waterways they studied. They found 21 species in the stomachs of captured Northern snakeheads. Particularly tempting to snakeheads are killifish, sunfish, and eels. <\/p>\n
Of the <\/b>waterways Keller studied, Darby Creek had the highest concentration of Northern snakeheads in the region. <\/p>\n
\u201cIt\u2019s a top predator, and has spread very quickly,\u201d Keller said. \u201cIt was first documented in the Delaware basin in 2004, and within about 10 to 15 years, they were found basically in the entire length of the Delaware basin.\u201d<\/p>\n
Northern snakeheads have been found near the headwaters of the Delaware River in New York in areas inhabited by ironcolor shiners, which are endangered in Pennsylvania, New Jersey, and Delaware, Keller said. <\/p>\n
Keller said snakeheads are particularly adaptable to shallow water and wetlands. Unlike other freshwater fish, they have a special chamber that allows them to gulp air for periods of time out of the water. They can also survive in stagnant shallow water, or polluted waterways with low oxygen levels.<\/p>\n
The study at Heinz<\/p>\n
Smith, the PFBC biologist, chose Heinz as his location for <\/b>collecting Northern snakeheads because of its impoundment. He traveled 200 miles from Centre County with Chotlos and two other PFBC biologists, Ben Frick and Garret Kratina.<\/p>\n
\u201cWhen we take the fish, we\u2019re also archiving samples for genetics, for diet, and for other health aspects,\u201d Smith said. <\/p>\n
Snakeheads\u2019 impact<\/p>\n
Erin Lacour, a wildlife biologist for the U.S. Fish and Wildlife Service at Heinz, said the refuge has already seen the impact of snakeheads. <\/p>\n
\u201cThey out-prey other species,\u201d Lacour said. \u201cWe have some sensitive frogs and other species here. They will absolutely prey on those. Our number of frogs has gone down.\u201d<\/p>\n
Chotlos, the Penn State student pursuing a master\u2019s degree in ecology, said the five fish caught for sampling at Heinz will be taken back to a lab, sedated, and sampled for contaminants. They will then be euthanized and dissected. <\/p>\n
In the field, he extracted tissue from the gills of newly caught snakeheads with a pair of forceps. <\/p>\n
\u201cWe don\u2019t really know that much about them in general,\u201d Chotlos said while reaching into the pink gill of one. \u201cWe don\u2019t have a lot of data.\u201d<\/p>\n