Scientists suspect decline of herring is result of bycatch in other fisheries
Published: July 12, 2010
Chesapeake Bay Journal
By Karl Blankenship
Herring were so common in the Potomac River in the spring of 1832 that a single seine net captured a few more than 950,000 "accurately counted," according to a report at the time. A few decades later, Spencer Baird, head of the U.S. Fish Commission, estimated that during the 1830s, the herring in the river must have numbered 3 billion fish.
Today, their numbers are only a "faint shadow" of what they were, said Jim Cummins, a biologist with the Interstate Commission on the Potomac River Basin. Like their cousin, the larger American shad, river herring numbers are thought to be at near-record lows along the East Coast.
"I'm worried that their populations are down so low that they can't recover," Cummins said. Herring, an important food source for other fish, rely on mass spawning to produce enough offspring to overwhelm predators. Without enough fish, he said, "they have a tough time getting past that gantlet."
Herring numbers have been falling for more than a century, but their numbers plummeted in the 1970s and early 1980s when foreign fleets working off the coast targeted them.
The foreign ships, which once fished as close as 3 miles to the coast, are now banished. Still, herring numbers haven't come back. Many, including Cummins, believe they are still being caught in the ocean, but this time by ships targeting species such as Atlantic herring, squid and mackerel.
River herring-alewives and blueback herring-have become the focal point of a growing fishing debate as some surveys indicate that more river herring may be caught as bycatch in ocean fisheries than the 1 million pounds caught annually in the few remaining fisheries in coastal rivers.
Last year, the Atlantic States Marine Fisheries Commission requested the U.S. Commerce secretary, who oversees the National Oceanic and Atmospheric Administration and its National Marine Fisheries Service, to take emergency action to step up monitoring and reduce the ocean bycatch of river herring. Department officials rejected the request. They said the data indicating a high bycatch was poor and the problem did not rise to "emergency" status, and thus relegated its management to the regional councils responsible for managing fisheries in federal waters-those more than 3 miles offshore.
This year, the New England and mid-Atlantic councils are considering an array of actions that could include stepped-up monitoring, potentially closing areas when trawls encounter large numbers of nontarget fish or even setting limits on the amount of bycatch. Each council includes a representative from the federal government, representatives from state fishery agencies and citizens appointed by governors.
At issue are small-mesh trawl fisheries, in which large boats deploy nets that can be the size of a football field. As they sweep through the water, their small-mesh nets scoop up large numbers of fish, both target-and nontarget-species.
Critics say the number of boats with trawl nets has sharply increased catches in some fisheries. In the mackerel fishery, landings increased from 12,000 metric tons in 2001 to 54,000 metric tons in 2004. They think that the bycatch increased, too.
"It is entirely possible that in one tow of a large trawl net you can catch more river herring than run through an entire river system," said Ken Stump, policy director of the Marine Fish Conservation Network.
River herring are an anadromous fish: They live most of their lives in the ocean but when they mature, return to their native rivers to spawn.
Stump held out the possibility that endangered species status could be sought for river herring-or at least some river-specific populations-if they are not sufficiently protected. "If no significant action is taken to address these issues, that option is going to become even more important in people's minds," he said.
But no one really knows how severe the problem is-or whether river herring bycatch is actually a problem at all. Only a fraction of the fishing boats have federally funded observers to examine their catches. And even in those cases, the array of herring-like fish has not always been broken out by species.
Available data show that the majority of trawl ships do not catch river herring or shad. But limited data suggest that when river herring are encountered, large numbers may be caught.
"It's hard to extrapolate that to the entire fishery, which is what we would like to do," said Bob Sadzinski, a Maryland Department of Natural Resources fisheries biologist who once chaired the ASMFC technical committee responsible for river herring. "We don't know what happens out there, and it's time that we actually start getting useful data that can be used to estimate the annual ocean bycatch of river herring."
But observers are funded by the National Marine Fisheries Service, and the program has never had adequate funding. Available observers have typically been assigned to higher priority fisheries.
Environmental groups say the lack of observers has resulted in the threat to river herring being "out of sight and out of mind." Even if the councils approve new restrictions, their effectiveness could be undercut if there are not enough observers on fishing vessels, they say.
Another issue hampering action is the lack of a current assessment of the river herring stock.
Many consider the species to be at an all-time low, and the ASMFC last year required that remaining state river herring fisheries be closed by 2012 unless they can be shown to be "sustainable."
But the ASMFC won't complete a stock assessment until sometime next year, and without that information, no one knows how significant bycatch is to the overall population.
Pam Gromen, executive director of the National Coalition for Marine Conservation, said many would like an absolute limit set on the amount of river herring that could be caught as ocean bycatch, after which areas could be closed to harvest. But, she added, "it's been a challenge to reach a consensus on the number to use until the stock assessment is complete. At the very least, the fishery councils could cap bycatch at recent levels."
The river herring issue feeds into a larger debate over forage fish-those that serve as food for larger fish, marine mammals, birds and other species. Many of the species targeted in the trawl fisheries, such as Atlantic herring and squid, are important sources of food for other species, but are caught in large numbers to create fish food for aquaculture, pet food and bait for other fish, such as lobster.
Environmental groups contend that the populations of some forage fish are already too small to support predator species, potentially limiting the recovery of some fisheries. It is the same argument that environmentalists make about the menhaden fishery in the Chesapeake, but played out in a coastal context.
River herring themselves are forage fish, but their importance is greatly diminished. In the Bay, the low numbers of blueback herring and alewives "multiplies the affect of the lack of menhaden, and then exacerbates the pressure that predators like striped bass put on blue crabs and other alternative prey species," said Bill Goldsborough, a fisheries scientist with the Chesapeake Bay Foundation.
Because their populations have been low for so long, Goldsborough said, many people have forgotten the importance of shad and herring to the Bay food web, especially during the fall when vast numbers of juveniles would migrate out of the rivers to the ocean. "Today, they are severely diminished from what they once were, so that is a key missing element of the food web."