South Dakota
Aquatic Gap Analysis Project
Aquatic GAP is a fairly new
aspect of the National Gap Analysis Program.
It is currently being conducted or has been completed in about five
states. New funding has just been
appropriated for GAP to conduct a nation-wide assessment of the aquatic
component of biodiversity. With the
completion of the land cover and stewardship portions of South Dakota’s Gap
Analysis Project, we were able to begin work on the aquatic portion of our
project during the summer of 2000.
Watersheds are becoming
increasingly important as management units, and researchers are beginning to
understand how land use, water quality, and fish species occurrences are tied
together throughout watersheds. In
the same way, terrestrial ecosystems have an impact on the aquatic communities,
and land cover has effects on both terrestrial and aquatic systems and the
species using these systems. Therefore,
aquatic GAP is an extension of the terrestrial GAP that all states are currently working on, which includes aquatic
components into the analysis of protected areas. These components can be analyzed in a way similar to the land
cover types (see Gap Analysis, wfs.sdstate.edu/sdgap/gap analysis/SDgapanalysis.htm)
to determine the protection offered to individual fish species, areas of high
fish species richness, and/or watersheds.
To complete an aquatic gap
analysis, we have followed methods similar to those for terrestrial ecosystems.
However, units of measurement are different (hydrologic units versus
Environmental Protection Agency (EPA) hexagons) and land cover is evaluated as a
possible limiting factor (compared to terrestrial gap where the main focus is
the presence of suitable land cover). The
following objectives must be completed to evaluate aquatic ecosystems in South
Dakota:
1.
Define range extents for all fish species within 11-digit hydrologic
units occurring in South Dakota based on collection data.
2.
Determine species richness by 11-digit hydrologic units.
3.
Define habitat affinities for each fish species in South Dakota from
literature review and collection sites.
4.
Predict occurrence of each fish species in river reaches by similarity of
stream properties to habitat affinities and collection sites.
5.
Determine protection offered each fish species by hydrologic unit and
river reach using stewardship layer previously created for SD-GAP.
To accomplish these
objectives, we are following methods developed by Missouri GAP for a pilot
Aquatic GAP project. This prototype
focuses mainly on rivers. Lakes are
included only if they have both an inlet and outlet stream, but fish species
within a particular lake are not included.
Each stream (called a river reach) has been identified, cataloged, and
added into a digital coverage by the EPA’s BASINS program.
Each river reach contains information including, but not limited to,
segment length, location (lat-long), and watershed name (for more information,
see http://www.epa.gov/ost/basins).
To use the digital files
for predicting fish occurrence in a given river reach, they must be processed
through a series of programs using ArcView software (ESRI Inc., Redlands, CA).
Each file contains information, which can be extracted using these
processes, on habitat properties. We
will examine:
-
Temperature
– Warm vs. Cool
-
Stream
Size – Headwater, Creek, Small
River, Large River
-
Geology
– 13 values, based on parent material of soils
-
Ground
Water Potential – Amount of
percolation present
-
Relative
Gradient – Average change in
elevation (meters) from top to bottom of river reach
-
Size
Discrepancy – difference in
stream size from one reach to the next downstream, connecting reach
-
Floodplain
Reach – 250 m of a stream must flow
across the floodplain of a small or large river
Based on collection data,
each reach a species occurs in represents suitable habitat.
Therefore, fish will be predicted to occur in other reaches where similar
stream properties are found. Land
use/land cover and the presence of dams will also be used to predict fish
occurrences. Accuracy of these
predictions can be assessed by sampling in selected streams to determine whether
the species occurs there.
Range delineation maps
(using the 11-digit hydrologic units as a base unit) have been created for 130
fish species occurring in South Dakota. Presence
was determined by collection data from numerous sources.
Drafts of these maps can be viewed at wfs.sdstate.edu/sdgap/fish/fishes.htm.
All range maps are in draft form while being reviewed by experts.
Species richness by 11-digit hydrologic units will be determined by
overlaying finalized range maps.
Once these components are
compiled (predicted reaches used by a species, land use practices surrounding
those reaches, and the distribution of a particular species of fish), each
species distribution will be analyzed for “gaps” in protection.
For more information on this aspect of SD Aquatic GAP, please go to wfs.sdstate.edu/sdgap/gap
analysis/SDgapanalysis.htm.
We would like to thank MO-GAP and MoRAP for their
assistance in this project, especially Scott Sowa, Gust Annis, and Mike MoRey.
Thanks to Matthew Baker from the MI Rivers Inventory, and Brian Reger
from South Dakota State University. We
also thank Greg Wolbrink, Joanna Whittier, Eric Lindstrom, and Josh Kiesow for
researching habitat affinities from over a thousand citations.
Page updated on 03/26/01