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Habitat heterogeneity is thought to be an important
feature of aquatic ecosystems, but specific metrics for designing
habitat heterogeneity in restoration and assessing it from observations
or simulations are lacking. With this on-going research we are exploring
the incorporation of habitat heterogeneity into spawning habitat rehabilitation
designs with (SHIRA).
Although optimal spawning habitat as defined by habitat suitability
models is generally found in riffles, proximity of habitat to structural
cover (pools, large woody debris, boulder clusters and overhanging
vegetation) and hydrodynamic shear zones provide equally important
refuge from predation and resting zones for energy conservation.
Increased heterogeneity at enhancement sites on the Mokelumne River
appeared highly effective in terms of redd utilization with 70 redds
located in close proximity to 93% of the available structural cover,
and 42 redds located in close proximity to 90% of the available shear
zone refugia. Partial results emphasizing habitat heterogeneity availability
and utilization metrics were presented at the Ecohydraulics
Symposium (see paper)
to illustrate their potential in rehabilitation design and assessment.
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| Distribution of observed chinook redds at an spawning
bed enhancement site on the Mokelumne River, overlaid on a 2D hydrodynamic
model depth solution. ©2002 Wheaton (See Figure Copyright
Disclaimer before downloading). |
FUTURE PLANS:
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There are two strands I would like to pursue to continue this research:
- First, I would like to expand the empirical data collection
effort (i.e. redd surveys) to a mix of dynamic and regulated rivers
to see if similar trends to what was found on the Mokelumne emerge.
- Secondly, using this empirical backbone, I would like to incorporate
the habitat heterogenity proximity measrurements into an ecohydraulic
model I am developing.
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CASE STUDIES: |
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RELEVENT REFERENCE(S):
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Wheaton, J.M., Pasternack,
G.B. and Merz, J.E., 2004.