EPA's Vessel General Permit and Small Vessel General

oxygen levels in an ecosystem. Oxygen depletion can result in “dead zones,” murky water,
seagrass and coral habitat degradation, and large-scale fish kills (Deegan and Buchsbaum 2005).
Therefore, successful ANS invasions are likely to adversely affect the critical habitat of listed
species, especially when ANS threaten the prey that has been designated as a primary constituent
element, i.e., physical or biological features that are essential to the conservation of a given
species, including: space for individual and population growth and for normal behavior; food,
water, air, light, minerals, or other nutritional or physiological requirements; cover or shelter;
sites for breeding, reproduction, and rearing of offspring; and habitats that are protected from
disturbance or are representative of the historical geographical and ecological distribution of a
species (50 CFR 424.12(b)).
Salmon critical habitat primary constituent elements include areas that contain prey, including
“aquatic invertebrates and fishes” (e.g. 70 FR 52630). The primary constituent elements of
Pacific eulachon critical habitat includes “prey resources to support larval eulachon
survival…[and] prey items, in a concentration that supports foraging leading to adequate growth
and reproductive development for juveniles and adults in the marine environment” (76 FR
65324). Sturgeon critical habitat primary constituent elements include: “abundant food items,
such as detritus, aquatic insects, worms, and/or molluscs, within riverine habitats for larval and
juvenile life stages; and abundant prey items, such as amphipods, lancelets, polychaetes,
gastropods, ghost shrimp, isopods, molluscs and/or crustaceans, within estuarine and marine
habitats and substrates for subadult and adult life stages” (68 FR 13370). As described above,
ANS invasions are likely to reduce the availability of prey and thus adversely affect critical
habitat for these fish species. In addition, invasive plant species are likely to adversely affect the
critical habitat of endangered salmonids. Two introduced plants, purple loosestrife (Lythrum
salicaria) and Eurasian water milfoil (Myriophyllum spicatum), have displaced native wetlands
vegetation in the Pacific Northwest. The rapidly decomposing purple loosestrife produces a
seasonal shift in local nutrient availability. Eurasian water milfoil forms dense mats of
vegetation that can depress dissolved oxygen concentrations (Unmuth et al. 2000, Cronin et al.
2006). These invasive plants, which were likely introduced via shipping, are likely to change the
structure and function of the ecosystem (Sanderson et al. 2009) and destroy native salmonid.
The primary constituent elements of critical habitat for the southern resident killer whale include
“prey species of sufficient quantity, quality, and availability to support individual growth,
reproduction, and development, as well as overall population growth” (71 FR 69054). Cook
Inlet beluga whale critical habitat includes the primary constituent element of “primary prey
species consisting of four species of Pacific salmon (Chinook, sockeye, chum, and coho), Pacific
eulachon, Pacific cod, walleye pollock, saffron cod, and yellowfin sole” (76 FR 20180). As
described above, ANS invasions are likely to reduce the availability of prey and thus adversely
affect critical habitat for these cetacean species.
Black abalone critical habitat includes a primary constituent element of “abundant food resources
including bacterial and diatom films, crustose coralline algae, and a source of detrital
macroalgae, required for growth and survival of all stages of black abalone” (76 FR 66806).
Elkhorn and staghorn coral critical habitat includes the primary constituent element of “substrate
of suitable quality and availability” means natural consolidated hard substrate or dead coral
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