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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 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...
A. Pervasive disturbances: The most common disturbances based on total stream length in a given region. Top five overall most pervasive disturbances to all stream reaches, regardless of stream size and across all spatial scales (ranked highest first): Total excessive (anthropogenic or man caused) sediment yield Impervious surface cover Road crossing density Population density Pasture and hay land use Top three most pervasive disturbances to creeks (<100 km 2 watersheds) across all spatial scales : Total excessive sediment yield Impervious (hard) surface cover Road crossing density Top three most pervasive disturbances to rivers (>100 km 2 watersheds) across all spatial scales: Upstream dam density...
Integrating data into a spatial framework After acquiring data, variables were attributed to a national stream coverage for use in assessment following Wang et al. (2011). The National Hydrography Dataset Version 1 (NHDV1) is a 1:100,000 scale representation of streams from throughout the conterminous United States. The NHDV1 identifies stream reaches as sections of streams occurring between confluences (Figure 2). We attributed all data to stream reaches (i.e., fish data, fragmentation metrics by dams) or to local catchments and 90m buffers draining to stream reaches (i.e., human land uses, mining activities, impervious surfaces, etc.). Local catchments (watersheds) and buffers are the land areas draining directly...
Identifying disturbances to fish habitat The approach for identifying disturbances to fish habitat was based on the assumption that greater intensities and types of human landscape disturbances would most likely lead to more disturbed stream fish habitat (e.g., Danz et al. 2007, Esselman et al. 2011). Twenty-two human landscape variables were identified for the Alaska assessment, with 21 variables used in the southeast and 19 in greater Alaska. We grouped variables into six sub-indices representing specific types of disturbances including: urban land use, agricultural land use, stream fragmentation, point source pollution, infrastructure, and active mines. Each sub-index of disturbance was represented by 2 to...
Integrating data into a spatial framework Greater Alaska For most of Alaska excluding the southeast portion of the state, watershed boundaries for individual stream reaches were unavailable, and the highest resolution spatial units available for assessment were 12-digit USGS hydrological units (HUC-12s). Greater Alaska includes 12,824 HUC-12s that partially follow watershed boundaries; however, boundaries are also intended to capture roughly similarly-sized regions vs. entire upstream landscape areas draining to streams (Figure 11). After acquiring data, variables were attributed to HUC-12s for the greater Alaska assessment. Southeast Alaska For the southeast portion of Alaska, watersheds were delineated from...
A. Pervasive disturbances: The most common disturbances based on total stream length in a given region. Top five overall most pervasive disturbances to all stream reaches, regardless of stream size and across all spatial scales (ranked highest first): Crop land use Low intensity urban land use Impervious surface cover Road crossing density Agricultural water withdrawal Top five most pervasive disturbances to , specific to spatial scale: Crop land use in network catchments Crop land use in network buffers Low intensity urban land use in network catchments Crop land use in local buffers Impervious surface cover in network catchments In the Northern Plains state group, 36.6% of streams are classified as low...
Michigan, Wisconsin, and Minnesota border four of the five Great Lakes (lakes Michigan, Superior, Huron, and Erie) and have over 150,000 miles of rivers and streams and 50,000 inland lakes within their boundaries. The upper Mississippi River flows through the Upper Midwest states, from its headwaters in Minnesota along the boundary between Minnesota and Wisconsin. Much of the region has deep glacial deposits which has a tremendous influence over the habitat types and water flow (hydrology), providing for some of the most stable river flows in the United States. An exception to the glaciated region is a unique region of deeply carved unglaciated river valleys known as “The Driftless Area” which located in southwestern...
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Tags: 2015,
RegionalSummary,
UpperMidwestRegion,
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A. Pervasive disturbances: The most common disturbances based on total stream length in a given region. Top five overall most pervasive disturbances to all stream reaches, regardless of stream size and across all spatial scales (ranked highest first): Crop land use Low intensity urban land use Pasture and hay land use Impervious surface cover Population density Top three most pervasive disturbances to creeks (watersheds <100 km 2 in area) across all spatial scales: Crop land use Low intensity urban land use Pasture and hay land use Top three most pervasive disturbances to rivers (watersheds >100 km 2 in area) across all spatial scales : Crop land use Impervious surface cover Pasture and hay land use Top...
While fish habitat was found to be generally to be at very low or low risk of degradation in this mostly arid western region of the United States, water availability (hydrology – a key fish habitat process and driver of fish habitat) could only be partly examined using the available datasets in this Assessment. The lack of information on the status of water flow in many basins has led them being overestimated in fish habitat quality, even if streams in these basins are actually dry most of year. Additionally, data availability for grazing intensity, another key landscape use, is also unavailable, and has also created situations where the Assessment overestimates habitat quality. Despite such absences, impairment...
Types: Map Service,
OGC WFS Layer,
OGC WMS Layer,
OGC WMS Service;
Tags: 2015,
MountainRegion,
MountainStates,
RegionalSummary
Data on stream fishes were provided for use in the 2015 assessment by the Hawaii Division of Aquatic Resources. Data were collected from 1992 to 2010, and assemblages were sampled using standardized visual surveys (Higashi and Nishimoto 2007). Fish data indicated presence or absence of nine native taxa in stream reaches including five fluvial fish species, two shrimp species, a gastropod, and two species of native flagtails (treated as a single taxonomic group analytically) that periodically enter the stream from the nearshore coastal environment (Table 6). Fish presence-absence data were available for 403 perennial stream reaches throughout the five main Hawaiian Islands. Many different human landscape factors...
While this assessment has found that many of the inland streams were at a low or very low risk of degradation, some fish habitat disturbances, including water diversions, timber harvest practices, and intensity of livestock grazing in watersheds, could not be directly included in this assessment because national datasets of these disturbances and their component variables are unavailable. These disturbances are known to have major, negative effects on fish habitats in this region. Their absence from this assessment, along with absences of other disturbances, has likely produced an overestimation of habitat condition (quality) for some water bodies. These gaps need to be kept in mind while examining the results....
Types: Map Service,
OGC WFS Layer,
OGC WMS Layer,
OGC WMS Service;
Tags: 2015,
PacificCoastRegion,
PacificCoastStates,
RegionalSummary
The Central Mississippi River states contain the confluences of the Upper Mississippi River with the Ohio, Missouri, and Arkansas rivers. Alteration of these large rivers for transportation and flood control has substantially altered their ecological characteristics, eliminating natural floodplains, sandbars, and meanders, and impeding fish migration routes. Other major tributary rivers include the Tennessee, Cumberland, Kentucky, and Osage, all very large rivers in their own right. Large reservoirs are common in the landscape of this region and have increased recreational opportunities for sportfish as well as many other activities, but typically suffer from dissolved oxygen issues in both the reservoirs and in...
Map of the risk of current fish habitat degradation of inland streams of the Southwestern States.
Creating cumulative habitat condition scores Greater Alaska All six sub-indices of disturbance scores in each HUC-12 were summed together to yield a cumulative habitat condition index (CHCI) score for each HUC-12. The maximum value for the CHCI was 6, indicating that a HUC-12 was in the worst condition class for each sub-index of disturbance, while the minimum value of the CHCI was 0, indicating that a HUC-12 was in the best condition class for each sub-index of disturbance. We followed methods applied for the conterminous US and created condition classes using Jenk’s natural breaks. With the exception of the HUC-12s that received a CHCI score of <0.001, which were given a priory assignment of “very low” risk of...
While this assessment has found that much of the stream habitat in this region is at low or very low risk of degradation, some key fish habitat disturbances, including water withdrawals or diversions and intensity of livestock grazing in watersheds, could not be directly included in this assessment because national datasets of these disturbances and their supporting variables are unavailable. These disturbances are known to have major, negative effects on fish habitats in this region. Their absence from this assessment, along with absences of other disturbances, has likely produced an overestimation of habitat condition (quality) for some water bodies. Despite such absences, impairment to fish habitats was determined...
Creating cumulative habitat condition scores To create the cumulative habitat condition index (CHCI) for streams of the conterminous United States, associations between multiple fish metrics and multiple human landscape factors were synthesized into a single number using the following scoring process. 5a. For each significant association between a fish metric and a human landscape factor, we evaluated the shape of the relationship to identify two key points. The “ threshold point” is the level of a landscape factor associated with a decrease in abundance of a particular fish metric (change in condition class between 5 and 4 in Figure 4), and the “plateau point” is the level of a landscape factor beyond which increasing...
A. Pervasive disturbances: The most common disturbances based on total stream length in a given region. Top five overall most pervasive disturbances to all stream reaches, regardless of stream size and across all spatial scales (ranked highest first): Impervious surface cover Population density Low intensity urban land use Road length density Downstream dam density Top three most pervasive disturbances to creeks (watersheds <100 km 2 in area) across all spatial scales: Impervious surface cover Low intensity urban land use Population density Top three most pervasive disturbances to rivers (watersheds >100 km 2 in area) across all spatial scales: Upstream dam density Pasture and hay land use Population...
A. Pervasive disturbances: The most common disturbances based on total stream length in a given region. Top five overall most pervasive disturbances to all stream reaches, regardless of stream size and across all spatial scales ranked highest first): Crop land use Population density Pasture and hay land use Road crossing density Low intensity land use Top three most pervasive disturbances to creeks (watersheds <100 km 2 in area) across all spatial scales: Crop land use Population density Low intensity urban land use Top three most pervasive disturbances to rivers (watersheds >100 km 2 in area) across all spatial scales : Pasture and hay land use Population density Crop land use Top five most pervasive...
Types: Map Service,
OGC WFS Layer,
OGC WMS Layer,
OGC WMS Service;
Tags: 2015,
PervasiveSevere,
UpperMidwestRegion,
UpperMidwestStates
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