For decades, the Chesapeake Bay’s rivers and tributaries have been home to a troublesome guest whose presence continues to ripple through the ecosystem. The blue catfish — first introduced in the 1970s for recreational fishing — has since become an ecologically disruptive force in Virginia waters. In response, scientists at William & Mary's Batten School & VIMS are making critical discoveries about blue catfish biology, impact and commercial market potential, and playing a key role in advising how the commonwealth can address the challenge.
Through the long-running juvenile finfish trawl survey, Batten School of Coastal & Marine Sciences & VIMS Professor Mary Fabrizio, along with her students and colleagues, has documented both the spread of blue catfish and the corresponding decline of native species. “As the blue catfish population started to increase in our tributaries, we saw a decline in the native white catfish and white perch, which is likely due to predation or competition for resources,” she said. “And some of our colleagues in Maryland have evidence suggesting the blue catfish may be impacting striped bass, likely predating on the eggs and the juveniles.”
According to Fabrizio, another icon of the Chesapeake Bay may also be threatened: “The other effect is that blue catfish, especially the medium sized fish, are preying on blue crabs. And because there are so many medium sized blue catfish, that translates into a lot of removals. They’re eating a lot of blue crabs.”
To investigate that interaction, Fabrizio recently led a two-year diet study, published in Marine and Coastal Fisheries, which quantified blue catfish predation on blue crabs. “We worked with a commercial waterman who was setting gillnets out in the James River. He would bring back the catch, and we would examine the stomach contents,” she said. “We looked at predation year-round, which hadn’t been done before.”
The results were sobering: “It turns out blue catfish are eating the same things in winter as in spring and fall, so there’s blue crab predation happening year-round,” said Fabrizio. Stomach content analysis also showed that blue catfish are specifically targeting juvenile crabs. “Older, larger crabs may be too feisty and fight back, or perhaps they’re faster and able to escape. Either way,” she said, “blue catfish are eating the juvenile crabs that Virginia counts on to sustain the future blue crab population.”
At his retirement party from SERC a couple of weeks ago, I asked Mr. Crab himself, Tuck Hines, former director, if he thought Blue Catfish were part of the current problem with Blue Crabs. He told me almost assuredly yes, and that he and collaborators have a paper coming out soon to that effect.
No comments:
Post a Comment