The federal government is reviewing the status of a pair of river herring species to see if the little fish should be listed under the Endangered Species Act because of factors including dams and climate change.
The National Marine Fisheries Service is looking at the health of the alewife and blueback herring populations. The fish live in rivers from Maine to Florida, and conservationists have long made the case that their declining populations pose a major problem for the health of ecosystems along the East Coast.
The herring species are estimated to be at about 3 percent of their historical abundance, fisheries service biologist Tara Lake said in August. The damming of rivers and the creation of other obstructions, she said, has reduced their access to habitat to 5 percent of its historic amount.
The fish also suffer from changes in the environment, fishing pressure and pollution, Lake said.
"Dams, culverts are blocking access to spawning habitat access coastwide," she said. "Climate change is definitely impacting their distribution."
A determination about the possibility of endangered species listing could be reached by 2019, Lake said. They could potentially be listed as "threatened" or "endangered."
The Natural Resources Defense Council submitted a petition requesting listing of the river herring species in 2011. The group wrote that the fish are important because they "provide vital nutrients and carbon into riverine systems" and serve as a key food source for dozens of mammals and birds.
"River herring have been historically phenomenally important ecologically," said defense council attorney Brad Sewell. "They are a little fish that a lot of things eat."
Commercial fishermen used to catch tens of thousands of pounds of alewives, topping out at nearly 65 million pounds in 1965. They've caught more than 2 million pounds only once since 1993. Most these days are caught in Maine, though they used to be caught all along the East Coast.
The regulatory Atlantic States Marine Fisheries Commission announced this month that it had completed a review of the river herring stock and found that the fish are at historic lows along the East Coast, and their population remains depleted.
However, the commission also said there were some positive signs. Sixteen of 54 river herring stocks showed trends of increasing abundance since the last assessment, the commission said.