population. Wherever possible, existing models and data will be used to develop these habitat 
alteration-population response models. When this is not possible, researchers will plan the 
research needed to develop the models. 
This work will be done from the aquatic shoreline scale (including intertidal and shallow habitats 
through deep water habitats) to the whole-lake/whole-estuary scale, as appropriate for the 
populations in question. The majority of lake research will probably take place in the U.S. Great 
Lakes, but smaller lakes are not excluded from consideration. In addition to developing these 
habitat alteration-population response models, targeted community-level and process-level work 
may be required to achieve the desired results. For example, it may be necessary to quantify key 
functions of certain habitats, or to examine how species in habitats of interest are linked to 
adjacent habitats. In each situation, proposed research will be designed to support habitat 
alteration-f)opulation response models. 
An important point is that these models need not consider the full life history of each population. 
The goal of this work is to provide the scientific basis for resolving enviroiunental protection 
policy and regulatory questions, not for policies to enhance fishable biomass, and so models may 
focus on specific stages of valuable species (e.g., juveniles). These "population models" may 
then actually model a sub-population, a single life history stage, or a specific "bottleneck" in a 
population. Otherwise, full-life-history models would need to consider harvest and over fishing, 
which is only going to be of incidental policy interest to EPA regulatory staff. The models we 
propose are designed to provide the necessary scientific basis to protect habitats by relating 
habitat characteristics to population or sub-population endpoints for fish, shellfish, and wildlife. 
Spatial habitat mapping also will be a component of this work. The consequences of habitat loss 
need to be considered in the context of how much of each key habitat is available in the area of 
interest Habitat mapping a shoreline, lake, estuary, or subestuary will be a vital tool in 
application of models. For this reason, spatial habitat mapping also should be a part of the 
quantitative research involved in creating these models. 
In some cases when developing these models, it will be possible to link the status of a certain 
population to alteration of a single (often vegetated) habitat This is most realistic for species 
that are very tightly tied at key life stages to single habitats that act as population "bottlenecks". 
This may apply to penaeid shrimp and vegetated marsh and seagrass habitats in the Gulf of 
Mexico, to bay scallops and seagrass habitat in the Mid-Atlantic and Northeast, and to other 
species and habitats. In these situations, project 1 will be a more appropriate means of 
determining population response. Project 1 evaluates in better detail at the single-habitat scale. 
Project 2 is intended to be fairly crude at the scale of the individual habitat, looking primarily at 
the effects of areal habitat loss on populations within a larger setting; the shoreline, lake, or 
estuary. Alternatively, project 2 analyses may look at how habitat mosaics and landscape 
patterns affect the identified populations. In order to best meet the goals of the Aquatic Stressors 
Framework, projects 1 and 2 will need to work closely together. Approaches, data, and results 
will be shared between the two groups to produce the best product and to eliminate duplication of 
effort. In most cases, results of the more detailed habitat alteration work conducted under project 
1 will be directly incorporated into the larger scale habitat alteration-population response models 
described here. 
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