About Aquatic Organism Passage (AOP)
Transportation network alignments and facilities such as Culverts, Bridges and Pipelines can pose barriers to Aquatic Organism Passage (AOP). This section describes some types of aquatic species and stocks that can be impacted by those barriers. It also describes transportation alignments and facilities that may pose barriers to AOP . Finally, it describes how AOP projects can improve the movement of aquatic organisms within and between habitats.
What is AOP?
AOP is the ability of aquatic organisms to move freely upstream and downstream to access riverine, lacustrine, estuarine, and marine habitats they require to complete their life-cycle under their own power and at multiple life stages, without delay (also known as “volitional passage”). Migratory fish can travel significant distances to reach these habitats. Aquatic organisms rely on such habitats for food, growth, reproduction, shelter, predator avoidance, and other needs.
What species need AOP?
For most transportation projects, the AOP emphasis is on fish species and stocks. The following terms distinguish fish species by their migration patterns, though some species can adapt their patterns for different circumstances:
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Anadromous: Fish born in freshwater who spend most of their lives in saltwater and return/migrate to freshwater to spawn in fresh waters. Salmon are the widely known examples of anadromous fish. Other species of anadromous fish include steelhead trout, shad, river herring, lamprey, and sturgeon . These species may also be referred to as sea-run. Of note, reducing barriers to the AOP of anadromous fish species is the focus of the FHWA Culvert AOP Program.
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Catadromous: Fish that spawn at sea and move to and spend most of their lives in fresh water. American eels are one catadromous species found in North America.
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Potamodromous (resident): Fish that live and migrate wholly within fresh water. Brook trout are one such resident species. Resident fish can be subdivided into (A) fishes residing entirely in natal (birth) streams; (B) fishes that out-migrate from natal streams as juveniles to larger rivers (fluvial), growing to maturity before returning to spawn; and (C) fishes that out-migrate from natal streams as juveniles to lake environments (adfluvial), growing to maturity before returning to spawn. An example of potamodromous species are salmon species in the Great Lakes that out migrate from freshwater natal streams to the lakes and return to spawn; never encountering the marine environment experienced by their anadromous cousins.
While the emphasis on AOP is often on fish species and stocks, it is important to note that not all waterways are fish bearing and that some may provide habitat for other aquatic species that require AOP, such salamanders and freshwater invertebrates such as insects, crustaceans, mollusks, mites, nematodes, and rotifers.
What Types of Transportation Systems pose AOP barriers?
Coming soon!
What are Some Goals for AOP Projects?
Coming soon!
Some Ideas for Planning & Delivering AOP Projects
Coming soon!