EPA's Vessel General Permit and Small Vessel General

Response Analyses
We conduct a detailed review of the literature available on the physical, physiological,
behavioral, social, and ecological responses of endangered or threatened species or constituent
elements of critical habitat given exposure to harmful discharges into waters of the U.S. or to the
effects of those discharges and the activities associated with those activities on the ecology of the
watersheds in which they occur (that is, effects resulting from changes in populations of prey,
predators, competitors, symbionts, etc.). Rather than discuss the literature for each species, we
organize the data using species groups (e.g., Pacific salmon, sturgeon, sea turtles, etc.). We
summarize the probable consequences of the identified responses for populations of endangered
and threatened species and designated critical habitat.
Treatment of Aggregate Impacts
To address the question of whether the activities that would be authorized by the proposed VGPs
have direct and indirect effects on listed resources that are sufficiently small both individually
and in aggregate, we explicitly consider the aggregate impacts of the proposed permits in the
Effects of the Action chapter of our Opinion. This usage of “aggregate impacts” is distinct from
the term “cumulative effects” which the section 7 regulations defines as “those effects of future
State or private activities, not involving Federal activities, that are reasonably certain to occur
within the action area of the Federal action subject to consultation” (50 CFR 402.02).
Aggregate impacts include: (1) time-crowded perturbations or perturbations that are so close in
time that the effects of one perturbation do not dissipate before a subsequent perturbation occurs;
(2) space-crowded perturbations or perturbations that are so close in space that their effects
overlap; (3) interactions or perturbations that have qualitatively and quantitatively different
consequences for the ecosystems, ecological communities, populations, or individuals exposed to
them because of synergism (when stressors produce fundamentally different effects in
combination than they do individually), additivity, magnification (when a combination of
stressors have effects that are more than additive), or antagonism (when two or more stressors
have less effect in combination than they do individually); and (4) nibbling or incremental and
decremental effects are often, but not always, involved in each of the preceding three categories
(NRC 1986).
Risk Analyses
We help Action Agencies determine whether or to what degree they have complied with the
requirements of section 7(a)(2) of the ESA by assessing whether and to what degree an Agency
has structured a program so that the Agency is in a position to know or reliably estimate: (a)
whether endangered or threatened species are likely to be placed at increased risk of extinction,
or (b) if those species avoid extinction, whether they are likely to experience increased risk of
failing to recover from having been endangered or threatened because of the actions the program
authorizes, funds, or carries out.
Our consideration of how well an Agency’s program manages risks to endangered and
threatened species reflects the relationship between a listed species, the populations it comprises,
and the individuals those populations comprise. The continued existence of a species is
determined by the fate of the populations it comprises and the continued existence of a
population is determined by the fate of the individuals they comprise. Populations grow or
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