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Chapter 7 - Demersal Fishsubstrates, and rarely occur on any other bottom type(Cargnelli et al. 1999b; Stevenson 2008). Adult yellowtailprefer sand or sand/mud sediments where they find theirdemersal prey, and appear to avoid rocks, stony ground,and very soft mud (Collette and MacPhee 2002).Flounders in the group spawn throughout much of theyear. Spawning season varies with species, but tendsto occur later in the year along a south-north gradient.Spawning for American plaice occurs from February toJune with a peak in April and May. Plaice generally spawnin shoaler waters less than 90 m over benthic habitatscomprised of sand and muds. Highest spawning concentrationsoccur in the western Gulf of Maine on JeffreysLedge and Stellwagen Bank and along the Great SouthChannel and southern flank of Georges Bank (Johnson2004; Stevenson 2008). Winter flounder spawning occursduring the winter and spring, peaking in Februaryand March, in shoaler waters less than 72 m over benthichabitats. Coastal bays and estuaries are particularly importantspawning sites (Periera et al. 1999; Stevenson2008). Witch flounder spawn from March to November,with a peak occurring in the summer months, in deeperwaters over benthic habitats comprised of sand and muds.The most active spawning sites are found in the westernand northern portions of the Gulf of Maine (Cargnelli atal. 1999b; Stevenson 2008). Yellowtail flounder spawnfrom March to August, with a peak between April andJune (Johnson et al. 1999; Stevenson 2008).Most of the flounders reach sexual maturity by age 4;winter flounder reaches sexual maturity slightly earlier(Periera et al. 1999). Fertilized eggs of plaice, witch, andyellowtail flounder are pelagic and buoyant while winterflounder eggs are demersal, forming clusters that adhereto benthic substrates comprised mostly of sands, but alsomuds and gravel. The larval phase for plaice and yellowtailflounder occurs in the water column and persists fortwo to four months before settlement to the ocean floor(Johnson 2004; Johnson et al. 1999). Witch flounderdemonstrate one of the longest pelagic larval developmentphases of all flounders, lasting more than 12 months(Cargnelli et al. 1999b). Larval development for winterflounder occurs in the water column and lasts about eightweeks before settling to the ocean floor (Periera et al.1999). Juvenile life stages of all of these flounders arefound predominantly on sandy substrates. Juvenile winterflounders are especially dependent on nearshore coastalbays and estuaries, spending more than a year in theseshallow zones before moving off to deeper water as theymature (Periera et al. 1999, Stevenson 2008). Juvenileplaice are also known to utilize bays and estuarine riversystems as nursery areas, though they do occur in the Gulfof Maine, along the Great South Channel, and along thenorthern edge of Georges Bank (Johnson 2004).Primary prey items include crustaceans, mollusks, amphipods,and polychaete worms. Winter and yellowtailflounder are also known to eat a variety of fishes. Principalpredators include fish, skates, dogfish, sharks, and seals.ElasmobranchsElasmobranchs, the sharks, skates, and rays, are representedin this assessment by five skate species from the familyRajidae: barndoor skate (Dipturus laevis), clearnose skate(Raja eglanteria), little skate (Raja erinacea), rosette skate(Leucoraja garmani), and thorny skate (Amblyraja radiata).The spiny dogfish (Squalus acanthias) represents the familySqualidae. All six species are characterized by their relativelyslow growth rates, late age at maturation, and internalegg fertilization and development. Given their uniquelife history, these species are particularly vulnerable toexploitation due to longer mean generation times and therelatively small number of offspring.Species included in the elasmobranch group are distributedacross much of the Northwest Atlantic, with thornyskate occurring in both the Northeast and NorthwestAtlantic; barndoor, little, clearnose, and rosette skateslimited to the Northwest Atlantic; and spiny dogfish distributedcircumglobally. Within the Northwest Atlantic,barndoor, thorny and little skate generally occur from theGulf of St. Lawrence to Cape Hatteras, while distributionsof clearnose and rosette skates occur further south,from Southern New England to Florida. Highest densitiesare found on the Continental Shelf in the Gulf of Maine,Northwest Atlantic Marine Ecoregional Assessment • Phase 1 Report 7-77