Shad once thronged the Chesapeake every spring when they made their spawning runs up the bay's rivers from the Atlantic Ocean, but centuries of overfishing, pollution and habitat loss from construction of dams and other obstructions depleted them to the point that Maryland closed its fishery for them in 1980. Other states have taken similar measures, eliminating or sharply curtailing their commerical and even recreational catch of the fish that used to be hauled in by the millions.
Though striped bass and a few other fish have bounced back from the edge of oblivion when protected by fishing moratoria, shad have not done so, much to scientists' puzzlement and consternation. One long-time suspect has been what's known as "incidental bycatch," where fishermen going after other species hauled in some shad and their relatives, river herring, in the process.
Until lately, there hasn't been hard evidence, as no one had gathered data on numbers of shad and herring caught in the ocean. About 900 metric tons are taken annually in near-shore waters by the few remaining commercial fisheries, but how many were being caught out in the Atlantic by trawlers pursuing mackerel and other fish was a mystery. Recently, though, trips monitored by independent observers suggest roughly 300 metric tons of the fish are being taken, on average, said Jason Didden, a fisheries management specialist with the Mid-Atlantic council.
As a result, the council voted last week to set a cap on such bycatch, saying trawlers going after mackerel and other fish would have to quit if their net hauls brought in as much as 236 metric tons of river herring and shad. That comes out to roughly 2.5 million fish, Didden said.
The cap was intended mainly to protect river herrings - alewives and blueback herring - which have declined so drastically that the National Marine Fisheries Service is weighing whether to add them to the federal endangered species list. Like shad, they migrate from the ocean to fresh water in spring to spawn.
It's not clear whether the cap will be enough to help either river herring or shad, given their current low numbers and continuing problems with fish passage over dams, such as Maryland's Conowingo dam. But Didden said the council pledged to revisit the issue later.
"The council wanted to at least start addressing this bycatch issue by putting a hard cap on it," he said.