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The Crystal Darter (Crystallaria asprella) requires large, clear-water streams with clean sand and gravel bottoms and moderate to swift currents. It is intolerant of siltation and other forms of pollution from various land use practices. Direct habitat degradation from damming, channelization, and dredging has also reduced habitat for this species. Remaining populations have become isolated from one another by dams and impoundments. The Mississippi River most likely no longer serves as a usable corridor for the Crystal Darter because of the silt load. The isolated local populations are then vulnerable to single destructive events such as toxic chemical spills.
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Key elements of the 2015 national assessment of stream fish habitats follow the 2010 assessment, including: 1) the idea that distributions and numbers fishes reflect the quality of habitat in which they live; and 2) human landscape factors pose a risk to the condition of stream habitat, and indirectly, to fishes. The 2015 inland stream assessments for the contiguous United States, Alaska, and Hawaii all followed five broad steps (Figure 1) that are described in detail below for the inland stream assessment for Alaska. Note that analytical details for the Alaska assessment differed in southeast Alaska as compared to the remainder of the state (referred to as greater Alaska) due to differences in the resolution of...
Accounting for natural variation With the exception of differences in spatial units, assessments for greater Alaska and southeast Alaska were conducted similarly across regions. Because stream fish assemblage data were not available for the state, no steps were taken to account for natural variation in stream habitats for either southeast or greater Alaska. This represents an important need for future work.
The Bering Cisco (Coregonus laurettae) is endemic to Alaska and is present primarily along the State’s west and north coasts. It is known to spawn in only three river systems – the Yukon, Kuskokwim, and Susitna Rivers. Genetic research indicates that each of these populations is distinct. The Bering Cisco has been observed to migrate more than 1,200 miles into freshwater streams to spawn. Unlike salmon, some of these fish survive spawning runs. Since this species is slow-growing but short-lived, it is highly vulnerable to alterations in stream flow or water quality and large-scale environmental disasters.
Partnerships - Atlantic Coastal Fish Habitat Partnership, Eastern Brook Trout Joint Venture, Reservoir Fisheries Habitat Partnership, and Southeast Aquatic Resources Partnership Removed four barriers that opened access to six mile of streams and restored 21 miles of streams to improve habitat for Eastern Brook Trout and other fish species. A shoreline restoration demonstration area was constructed near the U.S. Army Corps of Engineers Visitors Center in North Carolina. Native vegetation was used to stabilize 175’ of shoreline to be used as a showcase for other lakeshore property owners. Planted 0.2 acres of tidal marsh and installed 0.1 acres of oyster reefs in Stump Sound, North Carolina. Also planted 0.15 acres...
Available data for the American Eel (Anguilla rostrata) indicate that, overall, there have been declines in recruitment, population, and escapement during three generations (36 years). A recent report indicated that barriers to migration (dams and weirs), passage through turbines at hydropower dams, habitat degradation or loss, and overharvest were likely the greatest threats by humans across the species’ range. Although eels are able to ascend many smaller barriers, recent studies have documented a tenfold reduction in eel density above each potentially passable barrier. For example, the number of juvenile eels migrating to Lake Ontario passing over hydropower dams fell from 935,000 in 1985 to approximately 8,000...
The habitats of the Southeast Atlantic states range from the mountains and uplands in the Blue Ridge and Piedmont areas in the western portion of this region to the Southeastern and Coastal Plains. Fish habitats in the higher elevation regions are typically fast-moving, clear, coldwater streams originating from seeps and springs, while warmwater rivers of the plains carry more organic material and sediment. This diversity of habitats along a very long period of stable geologic activity produces one of the most diverse assemblages of aquatic species in the nation. The Altamaha, Chattahoochee, Flint, Savannah, Catawba, Pee Dee, Broad, and Neuse are major rivers of the region. There are a large number of dams on waterways...
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