|
|
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.
|
This shapefile contains fish habitat condition index (HCI) scores as well as specific disturbance indices for 6th level Hydrologic Unit Code (HUC12) watersheds of the Watershed Boundary Dataset. The source datasets compiled and attributed to spatial units were identified as being: (1) meaningful for assessing fluvial fish habitat; (2) consistent across the entire study area in the way that they were assembled; (3) broadly representative of conditions in the past 10 years, and (4) of sufficient spatial resolution that they could be used to make valid comparisons among HUC12 units. In this data set, variable summaries are linked to HUC12 watersheds developed for the Watershed Boundary Dataset downloaded on March 18,...
Categories: Data;
Types: ArcGIS REST Map Service,
Map Service;
Tags: 2015 National Assessment,
2015 National Assessment,
DataProduct,
Direct habitat alteration,
Environmental condition, All tags...
Habitat Characterization,
Lotic,
NFHP,
NFHP Cooperator,
Spatial Data,
USGS Science Data Catalog (SDC),
Visual,
Watershed Boundary Dataset,
drainage basins,
environmental assessment,
inlandWaters,
watershed, Fewer tags
|
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...
|
View more...
|
