EPA's Vessel General Permit and Small Vessel General

36 weeks from 1850 to 1995, but in the last ten years (from 1985 to 1995), ANS were introduced
once every 12 weeks (http://anstaskforce.gov/more_impacts.php). Invasion rates also differ by
location. In the Lower Columbia River Basin, the ANS invasion rate is one every 20 weeks
(Sytsma, 2004); in the Great Lakes the rate was one new invasion every 28 weeks, although no
new invasions have been documented in the Great Lakes since 2006 (US EPA 2012b).
For the vectors described below, we estimate the number of vessels authorized by the VGPs and
overall discharge volumes. We also attempt to provide a broad estimate of the number of ANS
released to waters of the U.S., as authorized under the VGPs. We describe EPA’s proposed
actions that are likely to minimize the exposure of listed resources to ANS. Finally, we
summarize the likelihood that ESA-listed resources would be exposed to ANS as a result of
vessel discharges. When possible, we provide quantitative estimates, but in most instances, these
data are not available. We therefore review the best available scientific data to provide a
qualitative analysis of the risk of ANS invasion and the exposure of listed resources (NAS 2011;
G. Ruiz, J. Carlton, pers. comm.).
Hull Fouling
Biofouling of hulls is a significant, if not the single greatest, source of ANS invasions. For
example, 90 percent of the 343 marine aquatic invasive species in Hawai’i are thought to have
arrived via hull fouling (Carlton 2001), while 36 percent of the nonnative coastal marine species
established in continental North America are attributed to hull fouling (Bax et al. 2003).
Approximately 800 million square meters of hull area arrives in the U.S. annually (Miller et al.
2007). As described in the BE, Miller et al. (2007) investigated the extent of biofouling on
21commercial vessels and found that even the best-maintained commercial vessels had
biofouling on up to 5% of their wetted surface, while 10 drydocked ships were covered over 5 to
>90% of their wetted surface. Container ships are expected to have the lowest levels of
biofouling due to their fast speeds and short port durations. In a study of 22 in-service container
ships at the Port of Oakland, Davidson et al. (2009) found low levels of biofouling on 21 hulls;
however, biofouling covered 90% of one hull. Taxonomic richness was high among all
container ships. A study of underwater video and scrapings taken from 20 vessels shortly after
their arrival to the Great Lakes estimated that total abundance averaged >170,000 invertebrates
per vessel, belonging to 109 species (Sylvester and MacIsaac 2010). A study of 40 transoceanic
vessels arriving in Vancouver and Halifax estimated that total abundance averaged up to 600,000
invertebrates per ship belonging to 156 species (Sylvester et al. 2011).
Hull fouling ANS are generally bottom-associated sessile and sedentary organisms
(http://www.serc.si.edu/labs/marine_invasions/vector_ecology/fouling.aspx). They attach in
succession: a slime layer of bacteria and algae colonizes first; barnacles, bryozoans, and tube
worms follow; and with this base established, mollusks, sponges, sea squirts, and seedweed are
able to colonize (US EPA 2012b). Highly developed fouling communities may provide
microhabitats for mobile organisms, such as fish, crabs, and sea stars (EPA 2011). These
organisms are able to release themselves, gametes, or fragments into aquatic environments
encountered by the vessel, including novel harbors and waterways.
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