Full report - Conservation Gateway

Chapter 6 - Diadromous Fishprogram for Atlantic sturgeon, Atlantic salmon, and rainbowsmelt in the Gulf of Maine.Private conservation organizations also play an importantrole in conservation of these species. The NatureConservancy has conservation programs in all 15 coastalstates, and has identified diadromous fish as conservationpriorities coastwide. TNC programs are working ona wide variety of site-based and policy efforts, from damremoval and stormwater management projects to servingon the ASMFC Habitat Committee and Shad andRiver Herring Advisory Panel. Environmental DefenseFund serves on the Habitat Committee and AmericanEel Advisory Panel. American Rivers works coastwide onbarrier removal projects and policies to enable river restoration.Additional groups such as Trout Unlimited, CapeCod Commercial Hook Fishermen’s Association, andlocal watershed associations also play important roles inraising awareness of the conservation needs of these species,collecting data, and improving their management.Species AccountsAlewife (Alosa pseudoharengus)Alewife spawn in rivers from northeastern Newfoundlandto South Carolina, but are most abundant in the Mid-Atlantic and northeastern states. A wide range of habitatsand substrates is utilized, including large rivers, smallstreams, ponds, and lakes with substrates of gravel, sand,detritus, or submerged vegetation. The distance traveledto spawn also varies widely, from a few meters to reachback-barrier ponds to hundreds of kilometers as on theSaint John River (Collette and Klein-Macphee 2002).Most alewife are believed to return to their natal river orpond after about three or four years at sea.After the eggs hatch, the young-of-the-year spend two tosix months in freshwater nursery areas before they beginto migrate to sea. Adult and juvenile alewives are planktivorous,although they occasionally eat insects and fishlarvae, including larval alewives. Seasonal migrations inthe ocean may be related to zooplankton abundance andwater temperature (Neves 1981). Winter catches in thenorthwest Atlantic are made between 40 and 43oN latitude;in spring alewife move inshore and northward andoccur most frequently over the continental shelf betweenNova Scotia and North Carolina. During summer and fallcatches are concentrated in three areas north of 40o latitude:Nantucket Shoals, Georges Bank, and the perimeterof the Gulf of Maine. At sea, alewife congregate in schoolsof thousands of fish, sometimes mixing with other herringspecies (Collette and Klein-Macphee 2002).American eel (Anguilla rostrata)Adult eel migrate to spawning grounds located in theSargasso Sea, a large portion of the western AtlanticOcean east of The Bahamas and south of Bermuda. TheGulf Stream then transports and disperses fertilized eggsand larval eel, called leptocephali, along the entire UnitedStates East Coast and into Canadian waters. Bigelow andSchroeder (1953) described the distribution of eels in Gulfof Maine tributaries as universal — occurring in everystream, estuary, and tidal marsh and sometimes the opencoast. American eel is classified as catadromous (living infreshwater and migrating to marine waters to spawn), butit has been suggested recently that this may be a facultativetrait, that is, rather than having its growth phase restrictedto fresh water, some eels complete their life cycle in brackishor marine waters without ever entering fresh water(USFWS 2007).American eel life history is complex. The species exhibitsa multitude of life stages including leptocephalus, glass eel,elver, yellow eel, and silver eel stages. Leptocephali metamorphoseinto glass eel as they migrate toward land andfreshwater bodies. Glass eel develop into the pigmentedelver stage as they move into brackish or freshwater.Usually by age two, elvers make the transition into theyellow eel stage. Yellow eel inhabit bays, estuaries, rivers,streams, lakes, and ponds where they feed primarily oninvertebrates and smaller fishes. Sexual maturity of yelloweel can occur any time between eight and 24 years ofage according to data in the Mid-Atlantic region. Whenyellow eel reach sexual maturity they begin a downstreammigration toward the Sargasso Sea spawning grounds.During this migration yellow eel metamorphose into theadult silver eel phase, undergoing several physiologicalNorthwest Atlantic Marine Ecoregional Assessment • Phase 1 Report 6-27