Reproductive biology of the endemic goby, Lentipes concolor, from Makamaka'ole Stream, Maui and Waikolu Stream, Moloka'i |
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Authors: | Carl M Way Albert J Burky Juliana M Harding Skippy Hau William KLC Puleloa |
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Institution: | (1) Barry A. Vittor & Associates, Inc., 8060 Cottage Hill Rd., Mobile, AL, 36695, U.S.A.;(2) Department of Biology, University of Dayton, Dayton, OH, 45469-2622, U.S.A;(3) Department of Fisheries Science, Virginia Institute of Marine Science, Gloucester Point, VI, 23062-1346, U.S.A;(4) Department of Land and Natural Resources, Division of Aquatic Resources, Wailuku, Maui, HI, 96793, U.S.A;(5) Division of Aquatic Resources, Department of Land and Natural Resources, Kaulapu'u, Moloka'i, HI, 96757, U.S.A |
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Abstract: | Constant pressure in Hawai'i to use limited freshwater resources has resulted in increasing concern for the future of the
native stream fauna. Hawaiian freshwater gobies have an amphidromous life cycle with a marine larva period and require streams
which flow continuously to the ocean for the critical reproductive periods and during recruitment. As such, the stream fauna
is particularly sensitive to any anthropogenic perturbations which disrupt the continuity of stream flows. The objective of
this 2-year study was to compare the life cycles of the goby, Lentipes concolor, from a heavily diverted stream on Moloka'i
and a relatively undisturbed stream on Maui. In Makamaka'ole Stream, Maui, the population of L. concolor was reproductively
active all year with females potentially spawning 2–3 times annually. The timing of spawning did not occur consistently during
the wet or dry season but coincided with high stream flow conditions regardless of time-of-year. In Waikolu Stream, Moloka'i,
the reproductive pattern was more variable with the number of reproductively active females ranging from 0% to 100%. In general
the number of eggs was greater and egg size smaller for female L. concolor in Waikolu Stream than in Makamaka'ole Stream.
However, female reproductive condition of L. concolor from Maui was consistently higher than from fish on Moloka'i. Reproduction
of L. concolor in Makamaka'ole Stream was correlated with the seasonal pattern of flow rates with peaks in female reproductive
condition associated with periods of elevated discharge. No correlation between reproduction and discharge occurred in Waikolu
Stream. There were considerable differences between the magnitude of discharge in the two streams. Waikolu Stream experienced
prolonged periods of extremely low flows which have become common since the Moloka'i Irrigation System began diverting water
from the stream in 1960. In Makamaka'ole Stream, L. concolor was capable of reproducing throughout the year and adjusting
fecundity in response to stream flow conditions. In contrast, the population in Waikolu Stream appeared to have a ‘boom or
bust’ reproductive pattern; the population had reduced or no reproduction when stream flow conditions reached extreme low
levels, but the population succesfully reproduced during higher flow months. The diversion structure in Waikolu Stream has
dampened the natural seasonal discharge cycle, exacerbated natural low flow conditions, and increased the likelihood of prolonged
periods of extremely low flow. Stream management practices in the Hawaiian Islands must take into account the complex life
cycles and sensitivity to variable stream flow conditions of the native fauna.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | Hawai'i freshwater goby Lentipes amphidromy life cycle stream flow |
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