Hilo Area Comprehensive Study : the biological resources of the Hilo study area, Hawaii, Hawaii : an overview

Author:

U.S. Fish and Wildlife Service,

Title:

Hilo Area Comprehensive Study : the biological resources of the Hilo study area, Hawaii, Hawaii : an overview

Year:

1978

Pages:

1 v. (various pagings)

Subject:

Biology Hawaii Island Ecology Hawaii Island

Summary:

This report supplements the U.S. Army Corps of Engineers Hilo Area Comprehensive Study, Hilo, Hawaii, and describes the environmental setting and biological resources of the study area such as the Terrestrial Biota and the Aquatic Ecosystems. The terrestrial ecosystem can be broken down into four zones: 1) alpine area; 2) high elevation (low rainfall) grassland and forest; 3) rainforest; and 4) agricultural lands. Vegetation and subsequently animal life is limited in Mauna Loa's alpine zone. But introduced feral and mouflon sheep are found on geologically older Mauna Kea. The grassland/forest area is inhabited by introduced animals including big game animals, (feral sheep, goats, and pigs), gamebirds, insects and plants and native federally declared endangered species including the nene, palila, and Newell's petrel. Introduced plants and animals have contributed to the decline of native species through habitat destruction, spread of disease, predation and overgrazing. The rainforest zone is inhabited by the five endangered forest birds found in the Hilo area. Their decline is attributed largely to habitat destruction, spread of avian malaria, competition with and predation by introduced species. High rainfall prevents much use of this area by gamebirds. The endangered hoary bat inhabits the forest zone. In the lower agricultural lands introduced pest species such as rats and mice, and introduced game and songbirds predominate. The endangered Hawaiian hawk and native owl also forage here. Because of their specific habitat requirements some native plants and invertebrates are also in danger of extinction. These species prevail in the little disturbed areas such as Kipuka. The aquatic ecosystem includes streams, wetlands, marine resources and unique resources. Approximately 54 perennial streams, (with nearly half found on the Island of Hawaii), flow through the Hamakua coast. While all of Hawaii's native and much of its introduced stream macrofauna were found in the study area, their populations may vary more in the geologically younger and more precipitous streams than on the older Hawaiian islands. Two streams are channelized and 30 diverted to varying extents. All streams drain sugarcane fields in their lower sections and are subject to siltation. The prevalence of shell disease in the native freshwater shrimp has been associated with silt abrasion. This disease was observed in atyids found above as well as below agricultural lands indicating forest areas may contribute to siltation. Erosion has been observed in pig damaged and ohia decline portions of rainforest. Four point source dischargers, including two thermal and two untreated domestic sewage, release effluent into the Wailoa and Wailuku Rivers and Kapue and Onomea Streams, respectively. Four areas, approximately 66 acres, comprise the major wetlands. Waiakea Pond and Lokowaka and Kionakapahua Pond having over 75 percent of this habitat are used by resident and migratory waterbirds, including the endangered Hawaiian coot. With the exception of Waiakea Pond, these areas are subject to potential development during residential and urban expansion or for aquaculture use. With regard to marine resources, most of the 95 miles of shoreline is inaccessible due to the precipitous cliffs that surround the Island of Hawaii. Only about 20 miles has been developed most of which is located along Hilo Bay. This area has been the most exploited, yet badly impacted, nearshore habitat. Poor circulation, point and non-point source pollution, including siltation from the Wailuku River watershed, have contributed to habitat degradation. Unproductive silt/mud areas make up half the Bay's marine habitat. The Hilo study area is fished by about 36.2 percent of the island's anglers, of which over half utilize Hilo Bay. Catch rates are low and success is associated with the limited living coral areas around the breakwater and Radio Bay. The unique resources include anchialine pool habitat, associated with areas of recent volcanic origin, is limited nationally to Hawaii. The Kapoho anchialine pools in developed areas have been disturbed significantly by filling, septic tank seepage, and introduction of predatory exotic species. Recommendations are presented which, if followed, will provide a greater understanding of the ecological parameters required by native and introduced plants and animals within the study area and contribute to the preservation of native species and the management of introductions.

Collection:

Monographs