Winter Flounder Habitat Model
go to: USFWS Gulf of Maine Watershed Habitat Analysis
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Draft Date:
June 2001

Species:
Winter flounder, Pleuronectes americanus

Use of Study Area Resources:
Winter flounder occur year around in the Gulf of Maine (Jury et al. 1994). They range from southern Labrador to Georgia, and are most abundant from the Gulf of St. Lawrence to Chesapeake Bay (Ross 1991).

Habitat Requirements:
Winter flounder have been collected from the tideline to depths of 143 m (McCracken 1963 in Armstrong 1995). Within their range, three stocks have been defined: an offshore stock on Georges Bank, and two in nearshore waters, dividing north and south of Cape Cod (Pereira et al. 1998, Howell et al. 1992). For the inshore stocks, bays and estuaries provide critical spawning and nursery habitat, and spawning areas have been found to “play a crucial role in the productivity of these stocks” (Howell et al. 1992).

This species is demersal, spending most of its time on or close to the bottom. In the Gulf of Maine, coastal stocks move to comparatively warmer offshore depths in winter and inshore to the warmer shallows in summer (Scott and Scott 1988). Generally, most movement is associated with seasonal warming, and winter flounder are known to prefer temperatures of 12-15 degrees. C (Pereira et al. 1998). Studies In Newfoundland found winter flounder “remained in shallow water during the summer as long as food was available and water temperatures did not exceed 15 degrees. C” (VanGuelpen and Davis 1979 in Buckley 1989). They were observed to cease feeding and bury in cooler bottom sediments when temperatures reached 23 degrees. C, (Olla et al.1969, in Pereira et al. 1998).

Coastal stocks spawn in the mouths of estuaries from from late winter to early spring.  Spawning is at its height during March and April along the coast of Maine (Perlmutter 1947). Spawned eggs become strongly adhesive after fertilization, settling to the bottom “singly or in clumps” to stick to vegetation or the substrate (Scott and Scott 1988; Pereira et al 1998). Spawning occurs over sandy or muddy bottom, “often in water as shoal as 1-3 fathoms, but as deep as 25-40 fathoms on Georges Bank" (Perlmutter 1947). Eggs hatch 15-18 days after being released, and “by the time the larvae are 9 mm long, they have undergone complete metamorphosis, the left eye having migrated to the right side of the body” (Ross 1991). By that time juveniles are bottom-dwelling, and they remain in the estuaries for the first 2-3 years (Ross 1991, Scott and Scott 1988).

Juveniles prefer sandy shallows (Armstrong 1995), and adults occur over sandy and muddy substrates inshore and nearshore. Bigelow and Schroeder (1953) described suitable bottom habitats as ranging from muddy sand, cleaner sand, clay, “and even pebbly and gravelly ground.. the populations on the offshore banks are on hard bottom of one type or another. When they are on soft bottom they usually lie buried, all but the eyes, working themselves down into the mud almost instantly when they settle from swimming.”

Adult flounder feed opportunistically on polychaete worms, molluscs, crustaceans, other invertebrates, fish eggs, small fish and vegetation (Ross 1991, Scott and Scott 1988, Bigelow and Schroeder 1953). Juveniles feed mostly on worms, amphipods and copepods; larvae take planktonic crustaceans, worms and protozoans (Ross 1991). Most feeding is done during daylight hours, and flounder feed more heavily in summer than in winter (Scott and Scott 1988).

Winter flounder are preyed upon by seals, by other fishes such as monkfish, dogfish and sea raven, and by birds such as herons, cormorants, and ospreys (Scott and Scott 1988). Nearshore bottom habitats can be degraded by toxic contamination of sediments, or overheating by thermal discharges (Pereira et al. 1998). Winter flounder have declined in the Gulf of Maine due to overfishing.

Habitat Suitability
Habitat information was compiled from summaries by Buckley (1989), and by Brown et al. (2000), and by examination of conditions associated with collection sites in Great Bay and the Seabrook/Hampton estuary, New Hampshire. Banner and Hayes (1996) and Brown et al. (2000) developed winter flounder habitat suitability models operating on four environmental parameters: substrate, salinity, temperature, and depth. Since winter flounder are known to occur throughout the study area we are confident that temperature is suitable, seasonally, and so dropped it as a parameter.

Habitats were mapped for adults and juveniles by comparing salinity, substrate types and depths occurring in the study area with the relative suitabilities of those conditions (see tables, below) for these stages. The tables were based on the literature and sampling in Maine (Tort 1993) and New Hampshire (Nelson et al. 1981, 1982).  Habitat was mapped by combining maps developed for adults and for juveniles, using the highest score for either stage.

Substrate Preferences
Sources: Armstrong (1995), Bigelow and Schroeder (1953), Buckley (1989), Brown et al. (2000), Tort (1993), MacDonald et al. (1984). Substrate data was obtained from Banner and Hayes (1996) Barnhardt et al. (1996), Knebel and Circe (1995), and Butman and Lindsay (1999).

Substrate Suitability  (0 - 1 scale)
Substrate type Adults Juveniles
mud dominant

0.3

0.5

mud with sand

0.5

0.8

sand, sand/mud

1.0

1.0

sand/gravel, sand/rock  

0.8

0.5

gravel dominant

0.1

0.1

rock dominant

0

0

Depth Preferences
Sources: Brown et al. (2000), Buckley (1989), McCracken (1963), Van Guelpen and Davis (1979), MacDonald et al. (1984).

Depth Suitability  (0 - 1 scale)
Depth (feet, mlw)

Adults

Juveniles
+8 to 6

0

0

6 to 0

0

0.5

0 to -60

1.0

1.0

-60 to -150

1.0

0.5

-150 to -300

0.5

0.1

-300 to -600

0.1

0

Salinity Preferences
Sources: Brown et al. (2000), Buckley (1989), Rogers (1976), Tort (1993), Targett and McCleave (1974), MacDonald et al. (1984).

Salinity Suitability  (0 - 1 scale)
Salinity  (ppt)  

Adults

Juveniles
0 to 5

0

.1

5 to 25

0.6

1.0

25 to 35

1.0

0.5

Habitat Suitability = geometric mean of: (depth suitability x substrate suitability x salinity suitability)

Model Testing: Flounder occurrence data in the Gulf of Maine were used to test the habitat map. Data included point files representing Massachusetts inshore trawl surveys, (Massachusetts Division of Marine Fisheries groundfish surveys, 1978 - 1997, spring & fall, and NMFS Northeast Fisheries Science Center (NEFSC) groundfish surveys,1978 - 1997, spring & fall, both from USGS 1999). Occurrences also were obtained from Brown et al. (2000). We compared the distribution of habitat around a random set of 382 points in the Gulf to that for sites at which flounder were observed. Of the 1283 sites with flounder, 1279 had mapped habitat, while only 260 of the randomly distributed sites had habitat.  A chi-square test of these proportions showed a highly significant difference. When just the habitats scored 0.5 and higher were compared, 1011 of 1283 had habitat, but only 98 of the 382 random sites did. This greater proportion indicates that the higher scored habitats are, in fact, more heavily used by winter flounder.

Sources:
Armstrong, M.P. 1995. A comparative study of the ecology of smooth flounder, Pleuronectes putnami, and winter flounder, Pleuronectes americanus, from Great Bay estuary, New Hampshire. Dissertation, Univ. of New Hampshire. 130 pp.

Banner, A. and G. Hayes. 1996. Important Habitats of Coastal New Hampshire. USFWS Gulf of Maine Project, Falmouth, ME. 77pp.

Barnhardt, W.A., D.F. Belknap, A.R. Kelley, J.T. Kelley,and S.M. Dickson. 1996. Surficial Geology of the Maine Inner Continental Shelf. Digital Data provided through Maine Office of GIS.

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.

Brown, S.K., K.R. Buja S.H. Jury, M.E. Monaco, and A. Banner. 2000. Habitat Suitability Index Models for eight fish and invertebrate species in Casco and Sheepscot Bays, Maine. N. Am. J. Fish. Manage. 20:408-435.

Buckley, J.L. 1989. Species Profile: Winter flounder (North Atlantic). Biol. Rep. 82(11.87):12 p.

Butman, B. and J.A. Lindsay. 1999. A Marine GIS Library for Massachusetts Bay Focusing on Disposal Sites, Contaminated Sediments, and Sea Floor Mapping. U.S. Geological Survey Open-File Report 99-439. September 1999. U.S. Geological Survey, Woods Hole, MA and NOAA Office of Response and Restoration, Seattle, WA.

Howell, P., A. Howe, M. Gibson, S. Ayvazian and J. McGurrin. 1992. Addendum 1 to the Fisheries Management Plan for Inshore Stocks of Winter Flounder. Fisheries Management Report No.23 of the Atlantic States Marine Fisheries Commission. 8 pp.

Jury, S.H. J.D. Field, S.L. Stone, D.M. Nelson and M.E. Monaco. 1994. Distribution and abundance of fishes and invertebrates in North Atlantic estuaries. ELMR Rep. No. 13. NOAA/NOS Strategic Environmental Assessments Division, Silver Spring, MD. 221 p.

Knebel, H.J. and R.D. Circe. 1995. Maps and diagrams showing acoustic and textural characteristics and distribution of bottom sedimentary environments, Boston harbor and Massachusetts Bay. Misc. Field Studies Map, USGS. Map MF-2280.

MacDonald J.S., M.J. Dadswell, R.G. Appy, G.D. Melvin and D.A. Methven. 1984. Fishes, fish assemblages and their seasonal movements in the lower Bay of Fundy and Passamaquoddy Bay, Canada. Fish. Bull., U.S. 82(1):121-139.

McCracken, F.D. 1963. Seasonal movements of the winter flounder, Pseudopleuronectes americanus on the Atlantic coast. J. Fish. Res. Bed Can. 20(2):551-586.

Nelson, J.I., J. Falicon, G. Lamb, D. Miller and S. Perry. 1981. Inventory of the Natural Resources of Great Bay Estuarine System. New Hampshire Fish and Game Department.

Nelson, J.I., J. Falicon, G. Lamb, D. Miller and S. Perry. 1982. Great Bay Estuary Monitoring Survey. New Hampshire Fish and Game Department. 199 pp.

Pereira, J.J., R.Goldberg and J.J.Ziskowski. 1998. Winter Flounder (Pleuronectes americanus (Walbaum) Life History and Habitat Requirements. Essential Fish Habitat Source Document. Northeast Fisheries Science Center, National Marine Fisheries Service, Milford Laboratory, 212 Rogers Avenue, Milford, CT 06460.

Perlmutter, A. 1947. The blackback flounder and its fishery in new England and New York. Bulletin Bingham Oceanogr. Coll. 11(2). 92 p.

Scott, W.B. and M.G. Scott. 1988 Atlantic Fishes of Canada. University of Toronto Press, Toronto, Canada. pp 541-557.

Rogers, C.A. 1976. Effects of temperature and salinity on the survival of winter flounder embryos. Fish. Bull. 74(1):52-58.

Ross, M.R. 1991. Recreational Fisheries of Coastal New England. University of Massachusetts Press, Amherst, MA. Pp. 251-255.

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

Targett, T.E. and J.D. McCleave. 1974. Summer abundance of fishes in a Maine tidal cove with special reference to temperature. Trans. Am. Fish. Soc. 103(2):325-330.

Tort, M.J. 1993. Environmental Variables Influencing Species Composition and Abundance of Intertidal Fish Assemblages in a North-temperate Estuary. M.S. Thesis, Univ. of Maine, Orono, ME. 81 pp.

USGS. 1999. A Marine GIS Library for Massachusetts Bay. U.S. Geological Survey Open File Report 99-439; cdrom copy 10/4/99.

Van Guelpen, L. and C. Davis. 1979. Seasonal movements of the winter flounder in two contrasting inshore locations in Newfoundland. Trans. Am. Fish. Soc. 108:26-37.