The National Oceanic and Atmospheric Administration has determined that an environmental group's petition to list river herring under the Endangered Species Act contains enough information to merit a full review.

The Natural Resources Defense Council petitioned NOAA's National Marine Fisheries Service in August, contending that populations of blueback herring and alewife - collectively known as river herring - have declined so dramatically that they warrant listing as a threatened species under the act. A threatened species is one that could become endangered in the foreseeable future.

The petition triggered an initial 90-day review by the service to determine whether a full, yearlong review of the species' status was justified. In November, the service determined it was.

Information being developed by the Atlantic States Marine Fisheries Commission as part of a new river herring stock assessment will be used as part of the review. The commission regulates migratory fish along the East Coast.

NOAA will also consider information contained in the petition, published literature and other details about the historic and current range of river herring, their physical and biological habitat requirements, population status and trends, and threats.

If NOAA determines that a listing as a threatened species is appropriate, the agency will publish its recommendation in about a year and take public comments before publishing a final decision. If NOAA determines that listing these species is not appropriate, the process ends.

Alewife and blueback herring, smaller cousins of the American shad, were once the most numerous anadromous fish to migrate up rivers in the Bay watershed, where they swim farther upstream and into smaller creeks than do the larger American shad. But their population today is a small fraction of what it was a few decades ago and appears to have continued to decline in recent years.