For some populations, a single-habitat approach as in project 1 above may not be the most 
appropriate model. In particular, many economically valuable fishes are mobile, migrating from 
habitat to habitat. The scale which affects these populations most is that of an entire aquatic 
shoreline or even an entire lake or estuary, all of which are composed of many interconnected 
habitats. The shoreline approach, which considers the entire nearshore mosaic of habitats from 
intertidal through shallow subtidal and into deeper habitats, may be the smallest scale that can be 
applied meaningfully to mobile, economically valuable finfishes. Many of these species recruit 
into nearshore habitats (marshes, seagrass beds, and mud and sand shallows) for their Juvenile 
development, then move into deeper habitats as they grow. Shallow waters, whether vegetated or 
not, provide juveniles with a significant refuge from predation by larger aquatic predators (Ruiz 
et al. 1993). Shallow waters are also very susceptible to habitat destruction. The general life 
history pattern of "shallow-to-deeper" is true for many finfishes and mobile shellfish. Research 
at the scale of a shoreline, estuary, or lake is appropriate for species with these life history 
patterns. Thus the two projects will work together to deliver habitat alteration-population 
response models for high priority species. 
Researchers also will need to consider temporal variability in constructing these models. Given 
the short time frame for results (~ 8 years) relative to the time frame for cyclical fluctuations of 
some aquatic populations, researchers will need to consult historical long-term data sets for the 
species of primary concern. Fortunately, the focus on commercially and recreationally important 
aquatic species increases the likelihood that long term abundance data will be available. 
In order to achieve larger goals, continuing collaboration and coordination among Divisions will 
strive towards the goal of establishing comparable and quantitative methodologies. These efforts ■ 
will also link closely to different Aquatic Stressors research implementation plans that are 
delivering habitat alteration as stressor-response endpoints. Examples are the Nutrients plan 
(Section 5) and collaboration with other EPA laboratories, and other Federal and State agencies 
also will be required to develop the best possible products. Another important aspect of model 
development will involve determination of the data quality required to produce models with 
adequate predictive power. Models will be designed to provide valid information EPA needs to 
meet its regulatory requirements. 
3. Develop comprehensive multi-species models to quantify population responses to habitat 
alteration at the shoreline, lake, or estuary scale. 
A series of validated habitat alteration-population response relationships for the individual high 
priority species at the shoreline-, lake-, or estuary-scale (as described above) is the first-order 
goal of these efforts. Development of these single-species models would be a valuable and 
sufficient contribution of this project. However, where feasible, this work will be taken a step 
ftirther. A subsequent goal of this work is, for each region, to develop comprehensive multi¬ 
species models that can quantify the effects of habitat alteration on the entire suite of 
economically valuable and charismatic populations within a shoreline, lake, or estuary. These 
comprehensive multi-species models will be constructed initially by combining the species 
models described above, taking care to ensure that the sum of these models represents the 
complete set of major species. 
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