In 2006 scientists were mapping the bottom of the York River, one of the Chesapeake Bay's many tributaries, when they came across something odd. “We started to see these little squares all over the place,” says Donna Bilkovic, a biologist at the Virginia Institute of Marine Science. “They were clearly man-made.”
The squares turned out to be hundreds of loose crab traps, escapees from the bay's large blue crab fishery. Every year crabbers around the world set millions of these cagelike traps, known as pots, and sometimes a high percentage go missing. In Maryland and Virginia alone, crabbers set out around 800,000 pots annually, and as many as 30 percent break free of their lines and drift away only to stick in the mud, sometimes for years. But just because the pots are derelict does not mean they no longer work: each one can catch more than 50 crabs a year, as well as several other species, including the diamondback terrapin, a threatened species.
The task of recovering so many pots spread over so large an area is impractical, so Bilkovic and her colleague Kirk Havens devised a simple way of disarming a wayward trap: a biodegradable panel. If a pot is lost, the panel, which is made of plant-based materials and incorporated into the pot's side, dissolves over a period of eight to 12 months. Once the panel is gone, anything that swims in can swim out.
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Bilkovic was concerned, however, that if the panel also affected the blue crab catch in working pots, then crabbers would be reluctant to use it. That does not appear to be an issue, however. In a study last December in Conservation Biology, Bilkovic and Havens had crabbers in the Chesapeake Bay test the pots with biodegradable panels against the traditional variety. They found no difference between the number or the size of crabs caught.
“It's an ingenious solution,” says John Bull, a spokesperson for the Virginia Marine Resources Commission. Yet even though each panel costs only around $1, that may still be too much: “It would add another $750,000 to $1.5 million to an industry that doesn't have the money right now.”
COMMENT ATScientificAmerican.com/jan2013