Abstracts of Papers from the Twenty-fifth Annual Albert L. Tester Memorial Symposium, 13-14 April 2000

The Albert L. Tester Memorial Symposium is held in honor of Professor Albert L. Tester, who, at the time of his death in 1974, was senior professor of zoology at the University of Hawai'i at Mānoa. The faculty and students of the Department of Zoology proposed an annual symposium of student research papers as a means of honoring, in a continuing and active way, Dr. Tester's lively encouragement of student research in aspects of biology. Papers reporting original research in all aspects of biology, solicited from graduate students at the university, are presented at the spring-semester symposium. Income from contributions to the Albert L. Tester Memorial Fund of the University of Hawai'i Foundation provides two prizes for the best papers. Judges include representatives of the Department of Zoology faculty, winners from the preceding symposium, and a distinguished scholar from another university, who also presents a major symposium address. In 2000 John Endler, Department of Biological Sciences, University of California, Santa Barbara, participated in the Symposium.

The Mesopelagic Community and Spinner Dolphin Foraging

Kelly J. Benoit Bird

The mesopelagic boundary community (MBC) in the Hawaiian Islands is an important food resource for many organisms, including spinner dolphins (Stenella longirostris). To understand the role of this community in the feeding ecology of spinner dolphins, spatial and temporal patterns in the density and relative abundance of these organisms were characterized using acoustic sampling. A fish-finder modified to sample directly into a laptop computer was used to survey the MBC off the leeward coasts of O'ahu, Hawai'i, Maui, and Lāna'i from dusk until dawn. Visual, passive acoustic, and sonar sightings of spinner dolphins were also recorded. Both relative abundance and density measurements suggest that the MBC undergoes a substantial horizontal migration every evening, in addition to its well-documented vertical migration. Because of this horizontal migration, the boundary community is found much closer to shore than previously reported. This movement toward shore raises questions about the accepted model of spinner dolphin foraging in Hawai'i. Observations of spinner dolphins suggest a more complex foraging pattern, compatible with patterns observed in their food resource. However, although major spatial and temporal patterns in the MBC are consistent between islands, the boundary community is spatially heterogeneous both horizontally and vertically. The parameters of patch structure vary significantly throughout a night and between islands. It is likely that spinner dolphin foraging tactics vary with these changing parameters both within and between islands. A preliminary assessment of these foraging variations indicates differences in absolute depth and vertical position of foraging animals relative to the vertical distribution of the MBC.

Environmental Impact of an Open-Ocean Aquaculture Cage on the Benthic Community

David R. Bybee

A large oceanic aquaculture cage has been placed approximately 1.5 miles offshore of 'Ewa Beach on the south shore of O'ahu, Hawai'i. It is completely submerged in 31 m of water and suspended 5 m off the bottom. Seventy-five thousand Moi (Pacific Threadfin, Polydactylus sexfilis) were placed inside the cage in April 1999. These fish are fed several hundred pounds of commercial fish feed daily. As the fish grow the amount of feed required increases, as does the amount of waste they produce. Some of the food drops through the cage onto the sand bottom below. Some of this may be utilized by the benthos. The fish waste also accumulates directly below and around the cage depending on the currents. This study examined the effects of excess nutrification on the benthic invertebrate community. Special attention has been paid to the infaunal invertebrate community (those animals living in the sand). Two of the goals of this study were to identify any potential indicator...