INTRODUCED MARINE SPECIES IN PAGO ... - Bishop Museum

8 transposed on the graphs to correspond to their location in Pago Pago Harbor. All of these
groups showed decreasing occurrence with proximity to the inner harbor, with their minimum
numbers of taxa occurring at Stations 4 or 5. Interestingly, although maximum numbers of taxa
for reef corals and fishes occurred in bays outside the harbor, numbers of non-coral taxa were
greatest at Stations 6 and 7 in the outer harbor, resulting in numbers of total taxa at Station 6
about equal to the maximum values in Fagetele and Vatia Bays, where the highest numbers of
algae, coral and fish taxa occurred. This suggests that the relatively turbid and eutrophic
conditions at these outer harbor sites near the entrance support biota that occur both on coral
reefs and in harbors, but that the coral reef associated organisms decline with further movement
into the harbor. This transition is quite rapid, since the Utulei Station 3, less than 2 km southwest
of the main dock and drydock stations, had high numbers of algae, fishes and non-coral
invertebrates, resulting in number of total taxa nearly as high or higher that at reef sites outside of
the harbor.
D. Nonindigenous and Cryptogenic Species
As indicated for the previous reports summary in Table 3 and the list of organisms in Appendix B,
most available information for the marine biota of American Samoa is limited to algae, reef corals
and fishes, and little has been reported about non-coral invertebrates. This largely precludes an
evaluation of introduction status based on new species occurrences, since the present study is
the first to sample and analyze a full complement of organisms in Pago Pago Harbor or the four
bays that were surveyed. Therefore, species were categorized as native, nonindigenous or
cryptogenic (i.e. of uncertain origin but with indications of being introduced per Chapman and
Carlton 1991) based upon studies and evaluations that have been made in Hawai‘i (Carlton and
Eldredge In prep.), Guam (Paulay et al. 2002) or for port surveys in North Queensland, Australia
(Hewitt et al. 1998, Hoedt et al. 2000, 2001), or were based on recognized geographic
distributions of the species that may suggest an anthropomorphic introduction. We consider this
to be a conservative approach that may overstate, rather than underestimate the likelihood of the
species being assigned nonindigenous or cryptogenic status. Nonindigenous and cryptogenic
species are hereinafter referred to collectively as NIS.
Using these criteria, a total of 28 species occurred on these surveys that may be considered
nonindigenous or cryptogenic in American Samoa (Table 5) representing a total of 2.2% of the
total taxa identified. These consist of two algae, one sponge, six hydroids, one polychaete, two
barnacles, four amphipods, one isopod, two bivalves, six bryozoans, one ophiuroid and two
tunicates. In addition, one amphipod (Leucothoe micronesiae Barnard) and one crab (Panopeus
pacificus Edmondson) were found that are considered introduced in Hawai‘i but not in Samoa,
based on their geographic distributions (R. C. DeFelice, pers. comm.). A single dead shell of
Trochus niloticus Linnaeus, 1758 was found at Onesosopo. T. niloticus was transported from Fiji
to American Samoa in 1958, but no specimens had been observed as of April 1992 on several
invertebrate surveys (Eldredge 1994). The two algae Caulerpa serrulata (Forsskål)
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