Comparative dietary analysis of a recently described fish species complex (Galaxiidae) in a New Zealand river

The diets of several populations of four recently described species of galaxiid with allopatric distributions were examined in the Taieri River, New Zealand. Comparisons of available prey items and prey consumed were carried out to examine whether the distributions of the galaxiid species might be influenced by food availability and preferences. Seventy‐three prey categories were identified. The availability of four of these (Deleatidium, Oligochaeta, Elmidae larvae and adults) differed among the streams occupied by different galaxiid species. Three differences in the frequency of prey consumption (Deleatidium, Oxyethira, and Elmidae larvae) were detected. Despite differences in diet it was concluded that all four fish species were generalist predators of invertebrates with similar diets that were influenced mainly by prey availability. Furthermore prey availability was not considered responsible for the allopatric distribution of the four species, rather, spawning habitat availability, physical nature of the streams, and prior geological history of the Taieri catchment are considered the controlling influences on galaxiid distribution.