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U.S. Fish-Trait Distribution Data

Dataset Overview

This dataset provides a distribution of fish traits by HUC across the United States.The dataset was created in 2013 using the 8-digit Watershed Boundary dataset, disributions of all North American freshwater fish species from Nature Serve (, and fish traits from Frimpong and Angermeier (2009).  

Traits are characteristics of species’ life history (e.g., maximum size, fecundity) or requirements regarding ecological needs (e.g., flowing water, temperature maxima).  Traits may be an efficient way to evaluate landscape-level patterns in fish communities since groups of fish with common traits, rather than individual species, can be considered collectively (Frimpong and Angermeier, 2009).  

The composite dataset from the above section was joined to lists of fish traits by scientific name.  Five traits or trait combinations were selected as representative of fish characteristics that could be vulnerable to hydropower development:  

1) Potadromy/Diadromy: Fish that migrate large distances to spawn or complete part of their life history requirements may be more susceptible to basin fragmentation and potential habitat modifications (i.e., lose a larger fraction of available habitat) due to new development.

2) Serial spawning behavior: Serial spawning fish species (i.e. batch spawners) spawn multiple times per spawning season, as evidence of mulitple clutches or separate distinct batches of eggs at various stages of maturation.

3) Temporally-restricted spawning season: a narrower spawning season duration may indicate more specificity in required conditions for spawning and, thus, a greater likelihood of susceptibility to altered spawning due to new development.  Some fish species are adapted to spawning within a short temporal window during specific times of the year characterized by unique daylight, temperature, and hydrologic conditions.

4) Habitat specialist: Fish that use a variety of habitats to spawn or complete their life history are typically considered to be generalist species.  Conversely, fish that require very unique habitats (e.g., substrate, flow, river size) are considered specialists.  A high proportion of specialists might identify a fish community that is more susceptible to potential habitat modifications and, therefore, would require greater mitigation due to new development.

5) Lotic specialist: Typically fish that prefer lotic habitats, or habitats with moving water, may respond negatively to impoundment.  A ratio of species that prefer habitats with moving water may provide a surrogate for potential changes in community composition that may accompany site development.

6) Geographically limited: Fish with small geographic ranges suggest one or a combination of a few plausible causal mechanisms responsible: 

  • habitat requirements fall within a narrow range and are only found in a small geographic area, 
  • speciation of fishes and geographic isolation naturally led to small, distinct species pools, or 
  • existing habitat disturbance has reduced ranges dramatically.

Regardless of the cause, a small range may cause fish to be more susceptible to potential habitat modification by elimination of habitats critical to population sustainability or reduced gene flow among isolated populations.  The presence of such species at proposed developments will likely raise a greater number of concerns for hydro development.

The number of species within each HUC08, falling into each trait category, were summarized. Potadromous/anadromous species, serial spawning species, and lotic species were identified by Frimpong and Angermeier (2009) as a binary response variable.  Species with temporally restricted spawning seasons (i.e., high spawning seasonality) were identified by species falling within the lowest tenth percentile spawning season duration (number of months) for all species.  Habitat specialist scores were calculated by summing the number of habitats and diet diversity characteristic of each species.  Species with lower values were presumed to have more specific habitat needs. Habitat specialists were identified as those species having habitat specialist scores within the lowest tenth percentile for all species.  Geographic ranges (in square kilometers) were available for all species.  Species with small ranges were identified as those with ranges falling within the lowest tenth percentile for all species.