Pacific Science Volume 59, Number 2, 2005

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Pacific Science is a quarterly publication devoted to the biological and physical sciences of the Pacific Region.

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    Association Affairs
    (University of Hawaii Press, 2005-04)
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    The Kahana Valley Ahupua'a, a PABITRA study site on O'ahu, Hawaiian Islands
    (University of Hawaii Press, 2005-04) Mueller-Dombois, Dieter ; Wirawan, Nengah ; Jacobi, James D.
    The acronym PABITRA stands for Pacific-Asia Biodiversity Transect, a network of island sites and conservation professionals collaborating throughout the Pacific-Asia region. An ideal PABITRA site is a broad landscape transect from sea to summit. Such a landscape is Kahana Valley on Windward O'ahu. Kahana Valley served during prior centuries as an ahupua'a, a Polynesian unit of land management that integrated the three biological resource zones, the upland forests, the agriculturally used land below, and the coastal zone, into a sustainable human support system. Results of terrestrial biodiversity surveys, as begun with a vegetation/environment study and a paleoecological investigation, are presented in relation to historical land use and sea level changes. In spite of the many former human-induced modifications of the Kahana Valley landscape, the natural structure and function of its ecosystems are well preserved. The distribution patterns of vegetation can be interpreted in terms of Hawaiian ecological zones in combination with the valley's precipitation, topography, stream system, and archaeological features. Currently, efforts are under way to restore the Kahana State Park (recently renamed Ahupua'a 'O Kahana State Park) as a functional ahupua'a. In addition, focused collaborative research can yield helpful information for further restoration and integrated management of the Kahana ahupua'a as a historic Hawaiian Heritage Site.
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    Survey techniques for freshwater streams on Oceanic Islands: Important design considerations for the PABITRA Project
    (University of Hawaii Press, 2005-04) Parham, J.E.
    Fundamental differences in life history patterns of most indigenous freshwater stream species on oceanic islands and freshwater species in continental stream systems require important differences in design of appropriate aquatic survey methodologies. As an example of these issues, use of Instream Flow Incremental Methodology (IFIM) and the Index of Biotic Integrity (IBI) for describing island stream conditions are examined. Designed mainly for identifying optimal flow for salmonid fishes in the western United States, IFIM is difficult to apply to Hawaiian streams because of frequent flash floods in the Islands and because of the inherent difficulty of relating observed fish densities to total usable habitat in island streams. IBIs have been applied widely on the United States mainland as a technique for determining the health of a stream and aiding in stream fish conservation and management. Recently, there has been an attempt to establish an IBI for Hawaiian streams. Application of this technique to oceanic island streams raises a number of serious questions about the IBI's validity for use in Hawaiian streams. Potential problems are inherent in the basic assumptions of the IBI. They result in unintended consequences when applied to oceanic island streams; examples include erroneously attributing naturally occurring differences in observed fish assemblages to human-induced environmental change, not accommodating differences in closed and open system dynamics linked to life cycles of indigenous stream species, and not understanding implications of low-diversity environments typical of remote oceanic islands. Past research on Hawaiian streams supports use of appropriate survey and analysis techniques such as those developed for the Pacific-Asia Biodiversity Transect (PABITRA) for use among islands of the tropical Pacific.
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    Biological assessment of Kahana Stream, Island of O'ahu, Hawai'i: An application of PABITRA survey methods
    (University of Hawaii Press, 2005-04) Fitzsimmons, J.M. ; Parham, J.E. ; Benson, L.K. ; McRae, M.G. ; Nishimoto, R.T.
    Aquatic biologists surveyed Kahana Stream on O'ahu, Hawai'i, during December 2001 and January, March, and May 2002 to provide a background of information before restoring water diverted from the headwaters of the stream since the mid-1920s. Kahana Stream has all but one species of macrofauna common in unaltered Hawaiian streams, but abundance and distribution of amphidromous species differ conspicuously. A single specimen of 'o'opu 'alamo'o (Lentipes concolor) was found near the headwaters; until recently, this species was regarded as extinct on O'ahu. Only two individuals of the freshwater limpet (hihiwai, Neritina granosa) were found, and the brackish-water limpet (hapawai, Neritina vespertina) was not observed. Construction of the Waiahole Ditch Tunnel about 80 yr ago reduced the amount of water entering Kahana headwaters, and unimpeded growth of hau (Hibiscus tiliaceus) from the shore into the stream has slowed water movement in the middle and lower sections of the stream and estuary. Reduced flow has resulted in an extension farther inland of certain estuarine and lower-reach species (the prawn Macrobrachium grandimanus and fishes Eleotris sandwicensis and Stenogobius hawaiiensis). Alien fishes and larger invertebrates occur throughout Kahana Stream. Catches of newly hatched fish (S. hawaiiensis) and invertebrates (limited to crustaceans) moving downstream toward the ocean were meager. Recruitment of animals moving from the sea into the stream included only crustaceans and a single individual fish (S. hawaiiensis). Benthic algae were considerably more diverse than recorded for other O'ahu streams. Hau removal and extensive trimming at key locations along Kahana Stream should precede the addition of water to the basin to avoid flooding and to enhance beneficial biological effects.
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    Complementing PABITRA high-island studies by examining terrestrial plant diversity on atolls
    (University of Hawaii Press, 2005-04) Bridges, Kent W. ; McClatchey, Will C.
    The Pacific-Asia Biodiversity Transect (PABITRA) studies are based on a network of high-island biodiversity sites. These sites are structurally and historically complex. The majority of Pacific islands, in contrast, are low atolls with a common and simple flora and structure. As a result, atolls may serve as "controls" that may provide a way to assess impact of the upland high-island ecosystems on coastal regions of Pacific islands. Atoll studies can complement the PABITRA network because the gateway sites are near each other or separated from one another by one or more atolls. Such an addition will enhance interpretation of high-island ecosystems and their coastal zones because ecosystem surveys can be conducted quickly and accurately in atoll environments. We present results from quantitative studies of plant diversity from seven islets at Ailinginae Atoll in the northern Marshall Islands and discuss the value of this methodology as a way to enhance interpretation of the PABITRA data.
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