WRRCTR No.147 Population Biology in Small Hawaiian Streams

Abstract

Intensive stream surveys were conducted on Maui and Kauai in Hawaiian island streams during October 1979 through 1982 to investigate whether the presence of predaceous eleotrids in terminal reaches of low-gradient streams excluded the rare goby, Lentipes concolor, from this habitat and restricted it to higher elevations. An attempt was also made to determine whether a correlation exists between seasonality of stream discharge patterns and the two life history parameters (spawning and recruitment) of the indigenous, diadromous species. Two small perennial streams, Puaaluu and Pepeiaolepo, on the island of Maui, and another small stream, Maunapuluo, on the precipitous Na Pali Coast of Kauai were selected as study areas. Although evidence indicated that Eleotris sandwicensis preys upon gobies and rarely coexists with Lentipes, many other factors influence the effectiveness of Eleotris as a predator. Factors affecting the distribution and abundance of Lentipes are complex. No sharply defined periodicity was found in the recruitment of diadromous fishes, crustaceans, or mollusks. In-stream factors, among-stream and among-island differences in physical and biotic parameters apparently make recruitment into small Hawaiian streams an event in which chance plays a dominant role. In larger streams these stochastic processes may be averaged out and populations of these indigenous animals are more stable. The importance of these physical, biotic factors in determining the disturbance of populations of native stream fauna is discussed.