Related projects:

• Fena lake fish stocks
• Introduced pest species [?]

The watershed approach

On islands such as Guam, the land and the sea are intimately linked. Pollution and sediments from the land enter and damage the rivers, and the rivers carry the problems downstream to the reefs and fisheries. So, healthy reefs depend on healthy rivers, and healthy rivers depend on what is going on in the whole area around them--the watershed. [Pop-up: What is a watershed?]


In order to maintain the quality of Guam’s watershed ecosystems, we first need to identify the aquatic species residing in these ecosystems, and to determine their densities, the physical characteristics of the streams, and the quality of the water. Wise watershed management -- and ultimately the health of Guam’s coastal resources -- depends on having these baseline data.

Although various watersheds have been monitored for different parameters, in general Guam’s freshwater resources are not well studied. There are several problems with the existing data. First, the methods of monitoring have seldom been replicated, making comparisons or management as a whole unrealistic. Second, in the past ten years the island has experienced a rapid economic growth and structural development. Some existing and proposed developments, such as golf courses/resorts, occupy large tracts of land with major watersheds. Third, much of the existing watershed work has been completed by off-island consultants over short intervals using techniques developed for temperate areas and not applicable in their entirety to Guam’s tropical freshwater systems. Overall, then, few baseline data exist by which to assess potential impacts of proposed development on streams, lakes, and coastal areas. Nevertheless, it is evident that some development projects initiated within the last 10 years have significantly degraded watershed quality. The impact of this on coral reef habitat is also evident.

The freshwater monitoring project of DAWR is designed to gather long-term, reliable data for watershed management. Species composition, organism density, and habitat characteristics were collected in the rivers identified as experimental and controls were chosen in FY97, using the methods described in the annual report of FY97. The experimental rivers, located above Fena Reservoir included: Almagosa; Maulap; and Sadog. These watersheds were selected because they represent a range of watershed characteristics that may help to determine the impacts of the present and proposed land uses. The control rivers include: Maagas; Manenggon; Pago; and Ylig. [The study was originally set up to look at the effects of the dam on the fauna--especially upstream migration, thus rivers below the dam were designated as controls, and those above the lake as experimetnal.

The project has a second aim, to heighten public interest in native species found in freshwater ecosystems and to develop a recreational fishery based on native species in Guam's rivers. Knowledge of and interest in freshwater species is limited on Guam. To increase awareness of these important organisms and their habitats, educational materials, such as a field guide and posters, need to be developed. Additionally, some native species, such as the flagtail Kuhlia rupestris, are ideal candidates for a recreational fishery.
Current status

[Table 1] Species distribution in experimental and control streams determined by visual surveys.
A checkmark indicates the presence of a species and an empty cell indicates its absence.