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Chapter 7 - Demersal FishPredators of adults include large gadids, flounders, monkfish,sharks, seals, and dolphins.Trophic dynamics within the Gulf of Maine/GeorgesBank portion of the region have been fundamentally altered,as the depletion of gadids and flounders have coincidedwith large increases in skate and spiny dogfish populations.Spiny dogfish are now a major predator withinthis part of the region, accounting for a significant portionof the overall fish biomass in the system. Many have suggestedthat their recent population increase and associatedpredation have confounded efforts to rebuild depletedpopulations of gadids and flounders (FORDM 2009).Mid-Atlantic EstuarineThe Mid-Atlantic Estuarine species grouping includesthree species from the family Scianidae: Atlantic croaker(Micropogonias undulatus), spot (Leiostomus xanthurus), andweakfish (Cynoscion regalis). The family Labridae is representedby tautog (Tautoga onitis). The group was selectedbased upon the species’ relative dependence on estuarinehabitats to complete various stages of their life history.Specifically, a recent study on relative degree of estuarinedependence concluded that Atlantic croaker, spot, andtautog are obligate users of estuarine habitats while weakfishare facultative users of these areas (Able 2005).Global distribution of species in the mid-Atlantic estuarinegroup is limited to the western Atlantic, from NovaScotia to Florida. Distributions of croaker may extend asfar south as Brazil and Argentina. Within the NorthwestAtlantic, these species are predominantly found fromLong Island Sound to Cape Hatteras, North Carolina,with highest numbers occurring south of Delaware Bay.However, all species do occur in significant numbers alongGeorges Bank and the Great South Channel. They areoccasionally found in the Gulf of Maine in and aroundMassachusetts Bay and the Jeffreys Ledge and StellwagenBank area.Species within the mid-Atlantic estuarine group are characterizedby distinct seasonal migrations, moving inshoreand offshore in response to changes in water temperature.Spot enter bays and estuaries in the spring and remainthere until late summer or fall when they move offshoreto spawn (ASMFC 2009). Adult croaker generally spendthe spring and summer in estuaries, moving offshore andsouth along the Atlantic coast in the fall as nearshore watertemperatures decline (ASMFC 2009). When coastalwaters warm in the spring, adult weakfish form large aggregationsand undertake inshore and northward migrationsto bays, estuaries, and sounds from offshore winteringgrounds (ASMFC 2009). Adult tautog make shorterseasonal migrations in the fall when water temperaturesfall below 10 o C, moving from coastal areas to deeperwaters (25-45 m) with rugged topography. They moveback inshore to coastal and estuarine waters in the springwhen water temperatures warm above 11 o C (Steimle et al.1999c).Species included in this group are characterized by theirutilization of coastal bays and estuaries (ASMFC 2009).Spot, croaker, and tautog are recognized as obligate usersof these habitats while weakfish are considered facultativeusers of these areas. Adult spot and weakfish occur acrossa variety of substrates within nearshore bays and estuaries;habitat selection for these species is influenced by a numberof variables including sediment type, summer watertemperatures, salinity, and dissolved oxygen levels. Adultcroaker prefer muddy and sandy substrates in waters shallowenough to support submerged aquatic plant growthand are also found on oyster, coral, and sponge reefs aswell as man-made structures. Temperature and depth areimportant factors in determining distribution of adults.Distribution and abundance of adult tautog is heavilyinfluenced by the availability of cover for protection duringthe night when they are not foraging (Steimle et al.1999c).Species included in this group reach sexual maturityat relatively young ages (ASMFC 2009). Croaker andweakfish reach sexual maturity between ages 1 and 2,spot mature between ages 2 and 3, and tautog maturebetween ages 3 and 4. Croaker, tautog, and weakfish allspawn in nearshore habitats in coastal bays and estuarieswhile spot spawn in offshore waters along the ContinentalNorthwest Atlantic Marine Ecoregional Assessment • Phase 1 Report 7-79