Blueback Herring Overview
An overview of the biology, history and restoration efforts for Blueback Herring in Maine.
- Alosa aestivalis
- Blueback herring and alewife (Alosa pseudoharengus) have similar life histories and are collectively referred to as river herring. Adult blueback herring enter freshwater to spawn between late May and mid-June. It is thought that river herring return to their natal waters to spawn, though these two species will readily colonize new areas when given the opportunity. In the northern part of their range where both species overlap, blueback herring prefer to spawn above tidal influence in the main stem of rivers over gravel and sand substrate. In the southern part of their range, blueback herring will spawn in lakes and ponds. This habitat division is thought to reduce competition between the two species. After spawning, adults return to the ocean. Juvenile blueback herring spend 3-9 months in freshwater, then migrate downstream to the ocean. Males reach sexual maturity after 3-4 years, and females by age 5.
- Blueback herring are found from northern Florida to northeast Nova Scotia. Their populations overlap with alewife from southeast Nova Scotia to upper South Carolina. Blueback herring are most abundant where alewives are not present from Chesapeake Bay south into Florida.
History of the Fishery
- Blueback herring and alewife are managed together as river herring. River herring were once the largest commercial and recreational fishery on the Atlantic coast. In the 1800s they were fished primarily for human consumption as they kept well when salted or smoked. Currently river herring are fished mainly as bait for the spring lobster fishery. Alewives are more abundant in Maine than blueback herring, though historically both species were found in all coastal watersheds within the state.
Current Status and Management
- Both species of river herring are considered by NOAA to be a “species of concern”. Assessments of 52 river-specific stocks in 2012 showed that roughly half were depleted, while the other half needed more information to make a designation. In 2015, ASMFC and NOAA awarded funding for two research projects to help develop a coastwide river herring conservation plan. Currently, 35 municipalities have commercial harvesting rights in Maine, though only 24 are actively harvesting. Management is a cooperative effort between the Maine Department of Marine Resources and municipalities. Fishing privileges are often leased to independent fishermen, and regulations limit harvest through time and area closures as well as gear restrictions.
Current Recovery Efforts
- Threats to river herring in Maine include decreased survival in the ocean, overfishing, bycatch, and problems with freshwater passage due to the presence of dams. These have led to a drastic decline in populations across the state, especially during the 1990s. However, many efforts have been made to help populations recover. In the Kennebec River, stocking efforts have been combined with the removal of the Edwards Dam in 1999. The Skelton and Penobscot Rivers both had fish lifts installed at major dams. In the St. Croix River, fishways on the main stem were re-opened in 2013 to allow river herring access to historic spawning habitat.
Links, Useful documents
- Maine Department of Marine Resources. 2012. Maine river herring fact sheet. http://www.maine.gov/dmr/searunfish/alewife/.
- Atlantic States Marine Fisheries Commission. 2015. Shad and River Herring. http://www.asmfc.org/species/shad-river-herring.
- U.S. Fish and Wildlife Service, Central New England Fishery Resources Office. 2010. The Natural History of the River Herrings (Alosa pseudoharengus and Alosa aestivalis).
- Loesch, J.G. (1987). Overview of life history aspects of anadromous alewife and blueback herring in freshwater habitats. American Fisheries Society Symposium. 1: 89-103.
University of Maine
American Fisheries Society Student Subunit