Obstructions to anadromous fish migration

Publication Date



U.S. Fish and Wildlife Service Project No. 88-12


anadromous fish, wildlife, streams, striped bass, bass, American shad, shad, hickory shad, alewife, blueback herring, herring, Atlantic sturgeon, sturgeon, physical barriers, barriers, migration, literature review, survey, spawning, dams, canal, culverts, habitat, fish passage, structures, restoration, upstream, impoundments, bridges, cumulative impacts, design

Publication place

Raleigh, NC


U.S. Fish and Wildlife Service


Present and historical usage of rivers and streams within the Albemarle-PamlicoEstuarine Study (A/P Study) area by anadromous fish (striped bass, American shad, hickoryshad, alewife, blueback herring, Atlantic sturgeon, and shortnose sturgeon) were determined byreviewing literature and consulting with resource managers and scientists. Physical barriers toanadromous fish migrations in these tributaries were identified through literature review,consultation with resource managers and scientists, examination of maps, aerial survey, andground investigation.There is a lack of knowledge regarding historical and present migrations of Atlantic and shortnosesturgeon in the A/P study area. Shortnose sturgeon are believed to be extirpated, and Atlanticsturgeon are so uncommon that attempts to document spawning grounds in the A/P study areahave been unsuccessful.The limited data we have found regarding historical range of anadromous fish was restricted tostriped bass and the shad species in the larger rivers including the Neuse, Roanoke, Meherrin,Nottoway, and Blackwater Rivers. Present usage of tributaries within the A/P study area isrelatively well documented, especially for the large and medium sized streams. Twenty-seven obstructions known to impede anadromous fish were identified within the A/P studyarea; 18 of these are dams, 4 are storm gates on canals, 2 are highway culverts, 2 arevegetational blockages, and 1 is a navigation lock on a canal. An additional 30 impediments wereidentified on stream reaches where anadromous fish usage is suspected but has not yet beenconfirmed. Of these, 21 are highway culverts, 8 are dams and 1 is a beaver dam.Dams, the most common obstruction, have affected all anadromous species, preventing fish fromaccessing large areas of historical spawning habitat, especially in the Roanoke River Basin.Requiring future dams to install fish passage structures would help prevent the type of habitatlosses that have occurred in the past. Restoration of spawning runs by fish passagewayconstruction at existing dams may be applicable in the A/P study area, provided there issignificant spawning habitat upstream of the impoundments.Highway culverts, the second most common blockage, are low cost alternatives to bridges whenroads must cross small streams, and impact primarily alewife and blueback herring. Currenttrends in highway maintenance favour replacement of small bridges with culverts. This may resultin significant adverse cumulative impacts in the future unless appropriate culvert designs foranadromous fish passage are employed.The products of this investigation include this report and maps depicting the known historic andpresent anadromous fish utilization of streams in the A/P study area and impediments toanadromous fish migrations.

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