The five native species of amphidromous gobioid fishes inhabitingHawaiian streams were compared for dentition, gut length to body lengthratios, intestinal convolution, gill raker morphology, position of mouth, anddiet. Based on morphological comparisons, three manipulative modes of feedingare indicated, as follows: picking-biting, rock scraping, and sediment foraging.Comparisons indicated a surprising predominance of algae in the diet ofall species despite various degrees of morphological specialization for their use.Avoidance of competition for algae was therefore suggested as a potential factorinfluencing species interactions and community organization. Differentialpreference among native gobioids for stream invertebrates may also providemitigation for competitive interactions. Variation in food availability in thebenthic landscape of Hawaiian streams, possibly regulated by stream flow andperiodic disturbance, is hypothesized as being an important determinant of fishcommunity structure. Human-induced alteration of factors that regulate foodavailability could therefore influence stability of native fish populations throughdisturbance of their food base.
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