level of detail for the individual habitats compared to work proposed in project 2. Where overlap 
occurs, both groups of habitat researchers will work together to convey data and findings, and to 
avoid duplication of effort. This collaboration will occur at every step of the scientific approach 
described here. Other collaborations within EPA and with different Federal agencies also will be 
necessary to accomplish these research goals. These collaborations need to be actively pursued 
and nurtured from the onset of this research. 
Scientific Approach (Research Steps) 
7. Identify suites of species and habitats that are most critical in each region, and characterize 
each habitat*s contributions towards the survival of these species. 
Species for study in each region will be prioritized and selected as described above in the 
introduction to the section on Research Projects. For each selected species, key habitats will be 
identified. These habitats might be defined on the basis of "bioengineering" species (such as 
SAV, or burrowing shrimp), or on the basis of depth and substrate. It will be necessary to 
determine how important each "critical" habitat is relative to the other habitats these populations 
utilize. To this end, an understanding of how each habitat functions to support these populations 
will greatly help the development of habitat alteration-population response models. For estuarine 
and marine fishes and shellfish, the National Marine Fisheries Service (NMFS) Essential Fish 
Habitat work has already gone through this process, and summaries of the literature are readily 
available. Other compiled resources such as the FishBase Dataset, the FWS Species and 
Community Profiles, and the NOAA/NMFS Technical Memoranda will also be very useful. In 
many cases, substantial aspects of this research step can probably be accomplished by 
synthesizing the available literature. 
2. Quantify population responses to habitat alteration at the shoreline, lake, or estuary scale for 
the identified high-priority species. 
Simple validated models will be developed to quantitatively predict changes in societally 
valuable populations due to areal loss (either partial or total) of a given habitat within the spatial 
mosaic of habitats that constitute an aquatic shoreline or an entire lake or estuarine system. This 
is the central focus of this research component. Development of single-species models to show 
changes to high-priority populations that result from areal habitat loss will be a worthwhile 
stand-alone goal for NHEERL. Once these single-species models have been developed, research 
can proceed to research step 3 (below), the development of multi-species models. 
The single-species models may be based on quantitative empirical measures of population 
density, production, or export in each habitat; or on quantitative estimates of fecundity and 
survival. As appropriate (when species life history dictates, or when broad regional coverage is 
needed), models also may be based on relative measures of population response. In each region, 
EPA researchers will ne^ to detemiine which approach is best suited to accomplishing the goals 
of this research, with an eye towards ultimate application to risk assessment models. 
As a first step in model development, researchers will consider the available literature, assemble 
existing models and data, and determine appropriate research approaches for each habitat and 
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