River Herring Habitat Model
go to: USFWS Gulf of Maine Watershed Habitat Analysis
go to: Species Table
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Draft Date:
July 2001

Alewives (Alosa pseudoharengus) and blueback herring (Alosa aestivalis) are closely related anadromous fishes, similar in appearance, and commonly termed "river herring".  They are managed as a single fishery due to similarities in morphology, biological requirements, and ecological role (Ross 1991, Mullen et al. 1986). Both species are in the family Clupeidae; they have compressed streamlined bodies, a single soft-rayed dorsal fin, and rough protruding scales on their ventral surface (Bigelow and Schroeder 1953, Allaby 1991). Bigelow and Schroeder (1953) describe alewife: “much more heavily built forward than the herring, and the serrations on the midline of its belly are much stronger and sharper (hence the local name ‘sawbelly’).  

Use of Study Area Resources:
Reproduction, growth, migration. Blueback herring range from Nova Scotia to Florida, while alewives range from Labrador to South Carolina (NMFS 1994). Both species are marine inhabitants after their first year, except for spawning migrations up freshwater rivers and tributaries (Ross 1991). Larval and early juvenile stages occur primarily in lakes (alewives) and streams (blueback herring); juveniles pass out to coastal waters in late summer and fall.  Adult blueback herring occur throughout the Gulf of Maine (NMFS trawl data, 1982 through 1999, provided by Holly Yachmetz, NOAA, Woods Hole MA). Alewives mature in two to four years (Gray 1991) and may live to 10 years (NMFS 1994).  

Habitat Requirements:
Adult alewives and blueback herring migrate from ocean waters to spawn in freshwater rivers and streams when water temperatures reach 10.5 degrees C and 14 degrees C (50.9 and 57.2 degrees F) respectively (Pardue 1983). Although they use many of the same routes, spawning differs temporally and spatially (Mullen et al. 1986). Alewives spawn from mid-April to mid-May in Massachusetts, and from early May to early June in Maine, with peak blueback spawning occurring 2-3 weeks later (Cole et al.1980, Flagg 1977, Libby 1981, Jones et al. 1978; all in Mullen et al. 1986). Bluebacks favor warmer water and do not migrate as far upstream as alewives (Bigelow and Schroeder 1953). Alewives spawn above the head of tide in freshwater ponds, lakes, and slow-flowing segments of rivers and streams (Bigelow and Schroeder 1953, Scott and Scott 1988). Blueback herring spawn over hard substrates in fast-flowing water of rivers and streams and over organic material in slower-flowing rivers and streams (Pardue 1983). Bluebacks use deeper waters, while alewives spawn in water depths of 15 cm - 3 m (5.9" - 9.8'). Most fishes spawn in their natal watersheds, but some mixing of stocks does occur (Ross 1991). Adults return seaward within days of spawning (Bigelow and Schroeder 1953).  Landlocked populations of alewives have developed in some managed lakes in the watershed.

The eggs of both species are adhesive until water hardened, drifting thereafter in the water column until they hatch in 2-3 days. Fry remain in freshwater; as juveniles river herring drop downstream to tidal freshwater and estuarine areas in spring and early summer, moving upstream as more saline (< 5 ppt) waters encroach (Warinner et al. 1969, Pardue 1983). Seaward migration is triggered by a combination of heavy rainfall, high water levels and sudden drops in water temperature (Mullen et al. 1986), which occurs in Maine anytime from mid-July into December (Flagg 1977 in Mullen et al. 1986, Warinner et al. 1969, Burbridge 1974, Loesch 1987, Gray 1991).

Food: River herring feed on zooplankton, eggs and larvae of fish, insects, and crustaceans, small fish and insects (Mullen et al. 1986, Ross 1991).

Limiting Factors: River herring suffer high rates of mortality throughout their life cycles; fewer than 1% of eggs survive to produce young that reach the ocean, and annual mortality of all adults is believed to be 70% (Ross 1991). Both species are fished commercially for bait and recreationally as food fish. Pollution and damming of rivers and streams have both contributed to population declines (Ross 1991). Predators include other fishes, especially on eggs and young, as well as gulls and terns (Mullen et al. 1986).

Depth: In ocean waters between Cape Hatteras and Nova Scotia, Fay et al. (1983) found alewives to be most abundant at depths between 56 and 110 m; the NMFS trawl data found alewives as deep as 360 m.  Fay et al. found blueback herring most abundant at depths between 27 and 55 m; the NMFS trawl data found bluebacks as deep as 283 m.

Habitat Mapping:
Freshwater habitats were mapped from occurrence data obtained from several sources. Eipper et al. (1982) published upstream migratory pathways for anadromous and catadromous fishes throughout New England at a relatively small scale. We coded the corresponding stream segments as suitable habitat on 1:24,000 USGS digital maps (Maine, New Hampshire) and 1:100,000 maps (Massachusetts), supplemented by 1:24,000 for minor features absent from the 1:100,000 data. Eipper was used for the whole study area. This general information was considerably supplemented state by state with collection data. In Massachusetts we were supplied with point data from Hartel et al. (in press), and from a GIS coverage developed by Massachusetts Department of Fisheries, Wildlife and Environmental Law Enforcement (http://www.state.ma.us/dfwele/gisprog/gisanad.htm). In New Hampshire we added migratory pathways based on information from New Hampshire Fish and Game. In Maine we used Maine Department of Inland Fisheries and Wildlife unpublished stream electro-fishing and other survey information, and a state-wide fisheries survey of lakes and ponds. We coded as habitat all reaches connecting ponds having "sea run alewives" to the estuary. Maine Department of Marine Resources supplied a table from a 1982 "Statewide Fisheries Management Survey", which we  used to code lakes and migratory pathways of potential use to alewives. Comments from Lewis Flagg, Maine DMR, were particularly useful in extending and revising draft maps.

Artifacts of grid-cell mapping of riverine themes may in some cases cause habitat omissions, and in others aquatic habitat values in primarily upland areas. Fish habitats were gridded from continuous polygons/arcs derived from USGS hydrology coverages. Single line arcs were necessarily converted into strings of cells, each with a minimum width of 30 m (the cell dimensions).  Even where the dominant land cover of a cell was upland, we retained the habitat value for a stream passing through the cell.  As a result, some upland areas will display habitat value for anadromous fishes.  

The grid process left discontinuities when converting narrow (< 30 m wide) polygon features, such as small rivers, where only part of a cell was crossed by aquatic habitat. Moreover, where National Wetlands Inventory polygons representing wetlands and water bodies differed from those of USGS, the only fish habitat we retained was that which corresponded to aquatic classes in the former. Therefore, fish habitats and migratory pathways may not appear as continuous extents of habitat, or extend to the boundaries of contiguous wetlands in all cases.

Marine habitats were mapped by selecting estuarine and marine portions of the study area having depths from mid-intertidal  (suitable for juveniles) down to 55 m (180') for blueback herring, and down to 110 m (361') for alewives.  Deeper areas were mapped as lower value habitat.

Habitat Suitability:
Habitat suitability for the blueback herring and alewife models was scored on the basis of known and potential use. All freshwater areas mapped from occurrence information were scored 1.0; areas identified as potential habitat (if fishways were provided or passage otherwise restored) were scored 0.4. Marine areas within the depth zone having most apparent use were scored 0.5, and deeper areas were scored 0.2

Allaby, M. 1991. The Concise Oxford Dictionary of Zoology. Oxford University Press, NY.

Bigelow, H.B. and W.C. Schroeder. 1953. Fishes of the Gulf of Maine. U.S. Fish. Wildl. Serv. Fish. Bull. 74(53), 577 p.

Burbridge, R.G. 1974. Distribution, growth, selective feeding and energy transformations of young-of-the-year blueback herring in the James River, Virginia. Trans. Am. Fish. Soc. 103:297-311.

Edsall, T.A. 1964. Feeding by three species of fishes on the eggs of spawning alewives. Copeia 1964:226-227.

Eipper, A., W. Knapp and C. Laffin. 1982. Anadromous fish streams of New England: upstream migratory routes. Portfolio NE-1. USDI Fish and Wildlife Service.

Fay, C.W., R.J. Neves and G.B Pardue. 1983. Species Profiles: Life histories and environmental requirements of coastal fishes and invertebrates (Mid-Atlantic). FWS/OBS-82/11.9. 25 pp.

Gray, C.L. 1991. Alewife Alosa pseudoharengus species profile. Rhode Island Dept. of Env. Mgmt. 23 pp.

Hartel, K.E., D.B. Halliwell and A.E. Launer. (in press) Inland Fishes of Massachusetts. Natural Hist. New England Series. Massachusetts Audubon Society, Lincoln, MA.

Loesch, J.G. 1987. Overview of life history aspects of anadromous alewife and blueback herring in freshwater habitats. Amer. Fish. Soc. Symp. 1:89-103.

Mansueti, R.J. and J.D. Hardy, Jr. 1967. Development of fishes of the Chesapeake Bay region, an atlas of egg, larval, and juvenile stages, Part 1. Nat. Resour. Inst., University of Maryland, Baltimore, MD. 202 pp.

Mullen, D.M., C.W.Fay and J.R. Moring. 1986. Alewife/Blueback Herring. Species Profiles: Life Histories and Environmental Requirements of Coastal Fishes and Invertebrates (North Atlantic series) USDI Fish and Wildlife Service. Biological Report 82(11.58). 22pp.

Pardue, G.B. 1983. Habitat suitability index models: alewife and blueback herring. USFWS, FWS/OBS-82/10.58. 22 pp.

Ross, M.R. 1991. Recreational Fisheries of Coastal New England. University of Massachusetts Press, Amherst, MA. Pp. 185-189.

Scott, W.B. and M.G. Scott. 1988. Atlantic fishes of Canada. Can. Bull. Fish. Aquat. Sci. 219:731 p.

Warinner, J.E., J.P. Miller and J. Davis. 1969. Distribution of juvenile river herring in the Potomac River. proc. Annu. Conf. Southeast Assoc. Game Fish Comm. 23:384-388.