U. S. Department of Commerce American Samoa Government

The number and species of fish recorded at the three historic fish transect sites at Fagatele Bay, Sita Bay and Cape Larsen are presented in Table 13.

Figure 19. Species richness of reef fishes from 1977 to 2007 at three sites around Tutuila.

In diverse ecosystems, most species are rare, and yet 94 species were common enough to be encountered within our transect areas. Obviously, in Fagatele Bay the common species are not dominating the reef community to the exclusion of less common species. The 94 species on our transects indicate a truly diverse coral community. The distribution of relative abundances matched the 2004 survey of Fagatele Bay, which indicates the system to be stable.

A total of 164 species of corals are known from Fagatele Bay from previous surveys, but this latest survey found yet another four species not previously recorded: Acropora formosa, Montipora hispida, Fungia concinna and Fungia klunzingeri, bringing the total number of species in Fagatele Bay to 168. The number of species in Fagatele Bay is not yet decreasing.

The size distribution of coral colonies in Fagatele Bay also indicates a healthy situation with a few large colonies and an abundance of smaller colonies, indicating a healthy recruitment. However, some of the smaller colonies are of species that do not usually grow large, e.g., Porites sp. 2 and Galaxea fascicularis.

The numerical pattern of relative abundance of species, the relative abundance of coral species representing the different families of corals, and the population densities of corals along the depth distribution are all fairly constant between 2004 and 2007, indicating that the population has reached a temporary equilibrium as a relatively healthy coral community. The proportion of corals in the smallest size category (< 5 cm diameter) has decreased and the proportion in the higher size classes have increased since 1995, showing that the coral community has grown in size distribution over the past decade.

This basic resilience of the coral reefs in Fagatele Bay influenced by multiple disturbance factors is in stark contrast to the coral reefs of the western Atlantic, where the rate of reef degradation has been continuous since the late 1970s (Gardner et al. 2003, Lang 2003). It is possible that the resilience of American Samoan reefs in general is in part because of the distance from continents. All the reefs in the western Atlantic are closely bordered by North and South American continents. From the north, the Mississippi River has dumped an average of 1.6 million metric tons of fixed nitrogen and 100,000 metric tons of phosphate per year into the western Atlantic and from the south the Orinoco has dumped comparable amounts. Likewise, the western Atlantic gets hundreds of tons of microbe-infected dust from North African soil (Garrison et al. 2003). Although atmospheric CO₂ concentration has increased globally, much more has been taken up in the North Atlantic and very little is being taken up in the Pacific near American Samoa because of differences in regional physical oceanography (Sabine et al. 2004).

The pipe discharging the wastewater outflow from the two main tuna canneries was constructed to extend out to the entrance of Pago Pago harbor in 1992. Since that time, the coral communities have definitely been improving at the Aua Transect and at the Rainmaker (now Sadies By the Sea) Hotel. There has been successful recruitment and growth of some colonies of Acropora hyacinthus at both sites.

The coral cover typical of a fully normal and healthy reef community has returned to wherever there are solid substrata, i.e., on the reef crest and on large coral blocks on the reef flat. The dominant species is Acropora nana because of a major massive recruitment. Pocillopora eydouxi, P. verrucosa, P. damicornis, Pavona divaricata, Porites cylindrica and some large mound Porites are fairly common on the solid substrata.

On the inner reef flat that is still blanketed by rubble, the coral cover remains small even though the few corals that are there appear in fine health. On the rubble, there are currently a few Acropora formosa colonies braced in the sand, a few coraliths of Montipora spp. and Millepora spp., occasional Stylaraea punctata attached to rubble, and a number of species growing attached to large stable rocks.

The transect was well within the protected waters of Pago Pago harbor, near the village of Aua, and was covered by branching corals, with Porites cylindrica dominant from about 15 m from shore to 160 m and with Acropora spp. dominant on the outer 100 m (Mayor 1924; Green et al. 1997). Substantial urban development began in Pago Pago after World War II. In the 1950s, two tuna canneries were constructed and began operation, a fuel dump at Aua contributed pollutants to the seawater, and the inner 90 m of Mayor’s Aua transect was dredged for road construction materials, contributing a plume of sedimentation over the transect for several years. The canneries poured large quantities of wastewater into the harbor continuously and this lower water quality was a chronic problem for about four decades. Art Dahl and Austin Lamberts (1977) resurveyed the Aua transect in 1973 and recorded that the reef flat between the solid pavement of the reef crest and the excavated pit near shore was converted from a community of branching corals to a blanket of loose rubble.

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  Could only do limited assessment because only 1/6^th of survey has been completed. A more detailed analysis will be provided when all of the surveys have been completed.
  
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  Changes in fish communities over time is partly due to changes in coral communities as a result of habitat destruction by cots, hurricanes etc. This mostly affects small specialized species that are closely associated with Acropora and Pocillopora corals (eg. Plectroglyphidon dicki – see Green 2002).
  
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  Changes in density (particularly peaks in abundance in 1985 and 2001) were primarily due to surgeonfishes (see Fig 10, Green et al 2005). These pulses are associated with mass recruitment events of C. striatus (Birkeland et al 1987; Green et al 2005).
  
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  Coral reef fish communities in FB and elsewhere around Tutuila are still showing signs of overfishing. Several large species that are characteristic of unfished reefs in the Indo-Pacific remain conspicuous by their absence or small size. They include species such as maori wrasse (Chelinus undulatus), sharks, and larger species of serranids and scarids, all of which are known to be particularly vulnerable to fishing (Green 2002).
  
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  The particularly low abundance and species richness in 1988 is believed to be due partly to a difference in methodology that year, since surveys were completed while other divers were in the vicinity (this has been avoided in other years: see Birkeland et al 2003). The apparent decline in fish abundance in Fagatele Bay and other sites around Tutuila since 2001 may be partly due to seasonal variation in abundance, since surveys were conducted in September 2004 and November 2007 rather than during the recruitment season in March, as was the case in previous surveys. The surveys were moved to late summer to avoid this recruitment season, which makes fish counting more difficult because of the large number of ephemeral juveniles at that time (particularly C. striatus). The addition of size estimates to the methods in the last few surveys will allow for the interpretation of this confounding effect using the size structure of the fish populations in future.
  
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  Surveys should be moved back to March – better weather then.
  

761 In B. Riegl and R.E. Dodge (eds.) Coral Reefs of the USA. Springer, NY. 803 pp.