Fish Passage Facilities for Alosa
Anadromous Alosa symposium
Tidewater Chapter, American Fisheries Society
Dams and other instream barriers have prevented many anadromous species from ascending coastal streams to spawn in their historical habitat. The construction of many types of fishways and lifts around these barriers has succeeded in restoring some migratory populations. Four major fishway types are used in large rivers: Denil; pool; pool and weir; and lift. The Denil fishway is the most common type in the Northeast United States and will pass Alosa but not striped bass Morone saxatilis or sturgeon Acipenser spp. The most common pool fishway is the vertical slot. This high-volume fishway is effective in passing Alosa but not striped bass or sturgeon. Several pool fishways are under construction in the Lehigh River, Pennsylvania. The pool and weir fishway is dependent upon maintaining a constant depth and flow volume and may require more mechanization that either the pool fishway or the Denil. It is capable of passing large numbers of fish. The fish lift can be constructed in limited space at relatively low cost but maintenance and operation costs are high. Two fish lifts operate at the Conowingo Dam, Susquehanna River, Pennsylvania, and another operates at the Emporia Dam, Meherrin River, Virginia. Other types of fish passage facilities are navigation locks (Lake Moultrie, South Carolina) and notches in low-head dams, culverts, stream regulation weirs, and gaging stations. These are more common in southeastern streams.