EPA's Vessel General Permit and Small Vessel General

autochthonous gross primary production (Hall Jr et al. 2003). They feed primarily on bottomdwelling
algae and detritus, competing with larval mayflies, stoneflies, and caddisflies (potential
salmon prey) for food (Kerans et al. 2005). Mud snails have been identified in the stomachs of
juvenile Chinook salmon sampled from the Columbia River estuary (Bersine et al. 2008).
Whether these snails were intentionally ingested is not clear, but because of its thick shell and
operculum, the snail is a poor nutritional source for salmon and other fish species, compared
with insect larvae, fish, or other mollusks (Vinson and Baker 2008). The Siberian freshwater
shrimp (Exopalaemon modestus), which was very likely introduced via ballast water, preys on
native amphipods, such as Corophium salmonis, and directly competes with juvenile endangered
salmon for important food resources (Emmett et al. 2002). Thus, the introduction of invertebrate
ANS is likely to reduce survival and reproduction (i.e., fitness) of individual salmonids through
reduction of their prey base and food web alteration.
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 reduce 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 ecosystems
(Sanderson et al. 2009), reducing the survival of individual salmonids.
Parasites and disease have been transmitted to native salmonids via ANS. When salmon fry
were imported to Sweden in the 1950s, a parasitic fluke worm infected native Norwegian wild
salmon stocks, resulting in 95% mortality among the naïve natives (Josefsson and Andersson
2011). Viral hemorrhagic septicemia virus was initially introduced to North America from
Western Europe via ballast water discharge in the Great Lakes. Following its introduction, it
caused extensive morbidity and mortality to both farmed and wild fish populations including
salmonids, smelts, and rockfish (McKenna 2007, Bain et al. 2010). Given EPA’s recent
clarifications to the sVGP (made in the November 16, 2013 comments on the draft Opinion),
which authorize the discharge of dead bait, salmonids are likely to be adversely affected by novel
pathogens if the bait was not obtained from the same waterbody in which it was used. As
described above, such pathogens are often lethal to salmonids. Thus, ANS are likely to reduce
the survival of individual salmonids through disease transmission.
In summary, the introduction of many vessel-related ANS species (including fish, invertebrates,
plants, and parasitic organisms) is likely to result in reductions in fitness for individual
salmonids.
Pacific Eulachon. Pacific euchalon are similar to Pacific salmon in that they are anadromous,
occupy similar freshwater habitats (including the Columbia River), and exhibit diminishing
abundance (Hay and McCarter 2000); however, they are far less studied than salmon. Their
responses to ANS invasions are likely to be the same as described above for salmonids. Aquatic
invasive species are likely to reduce the survival of individual Pacific euchalon via competition,
predation, habitat modification, and disease transmission.
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