INTRODUCED MARINE SPECIES IN PAGO ... - Bishop Museum

the total biota in these two embayments. Although they do support corals and coral reefs, both
Kane‘ohe Bay and Waikiki are highly disturbed environments with histories of marine species
introductions and plentiful artificial surfaces, and Kane‘ohe Bay especially has many harbor
characteristics such as low flushing rates, relatively high organic, nutrient, and turbidity content,
and non-reef biotopes that may support a variety of introduced organisms. More typical coral reef
environments supporting coral dominated biota occurred at Kaho‘olawe, Midway, French Frigate
Shoals and Johnston Atoll, where NIS were only a minor (0.3-1.5%) component of the total biota.
All of these reef areas are remote from large harbors and therefore presumably relatively isolated
from major sources of marine introductions. Proximity to harbors or docking areas has been
indicated to be a major contributing factor in the occurrence of NIS on coral reefs determined on
rapid assessment surveys underway in the main Hawaiian Islands (Coles et al. in prep). The
overall values of 3-4% NIS shown in Table 7 for surveys completed on Kaua‘i, Moloka‘i and Maui
are averages of values which ranged from as high as 8-9% on small reefs in the vicinity of
Nawiliwili and Port Allen harbors on Kaua‘i to zero on remote reefs on Moloka‘i and Maui, with
most reefs that are distant from harbors showing NIS percentages of 1-3%, similar to the values
found for American Samoa reefs (Table 5) or around the island of Guam (Table 7).
VI. MANAGEMENT CONSIDERATIONS
The results of this survey indicate that introduced marine species are a minor component of the
total biota of Pago Pago Harbor and an even less frequent and smaller percentage of the total
biota in coral reef areas both in and outside of the harbor. Nonindigenous and cryptogenic
species are mostly confined to the docking areas of the innermost harbor, where they are fewer in
number and a smaller component of the total identified taxa than has been determined for
harbors in Hawai‘i. None of the 28 nonindigenous or cryptogenic species found in this study have
been reported to be invasive in other areas where they have been reported, and no native
species appear to be threatened by these introductions. Therefore, no intervention or mitigation
measures are apparently necessary or advisable at this time. However, managers should
maintain vigilance concerning the prospect of new introductions or the possibility that cryptic
introduced species already present in American Samoa may be favored by temporary
environmental conditions that promote their irreversible proliferation. Observations in Hawai‘i
have indicated that it may require 10-20 years for an introduced organism to propagate to the
point that it is considered invasive, such has occurred for the algae Gracilaria salicornia (Smith et
al. 2002), the octocoral Carijoa riisei (Coles and Eldredge 2002a), and the barnacle Chthamalus
proteus (Southward et al. 1998). Periodic rapid assessments and monitoring by trained
observers should be undertaken to assure that introductions have not occurred or proliferated, in
order to be able implement control measures in the early stages of the introduced organism’s
growth and spread. As indicated in the successful intervention against the bivalve mussel
Mytilopsis sallei (Récluz) in Darwin, Australia harbors (Willan et al. 2000, Bax et al. 2002)
eradication of an invasive introduced species is likely to be possible only if the introduction is
caught in its early stages, thus requiring periodic evaluation of existing conditions. Wherever
possible, inspections of barges and other slow moving craft which is moving from Pago Pago
Harbor to other areas in American Samoa should also be undertaken to limit the spread of
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