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Diet and Morphological Variation in Snipefishes, Presently Recognized as Macrorhamphosus scolopax, from Southeast Australia: Evidence for Two Sexually Dimorphic Species
Thomas A. Clarke
Vol. 1984, No. 3 (Aug. 1, 1984), pp. 595-608
Stable URL: http://www.jstor.org/stable/1445140
Page Count: 14
You can always find the topics here!Topics: Fish, Freshwater fishes, Discriminants, Specimens, Discriminant analysis, Species, Body length, Female animals, Diet, Animal morphology
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Diet analyses of snipefishes from the edge of the continental shelf off southeast Australia indicated that very few specimens had eaten substantial amounts of both planktonic and benthic prey; most contained only one or the other type of prey. The planktivorous individuals tended to have relatively longer snouts, shorter second dorsal spines, slenderer bodies and smaller eyes than the benthos feeders. Diet could be predicted with a high degree of accuracy by a discriminant function based on the four morphological characters and individual size. The discriminant analysis also indicated that females of both diet types differed from males in the same manner that planktivorous individuals differed from benthoseating types. Both types fed by day; the planktivorous types apparently feed on vertically-migrating zooplankton trapped on the shelf edge. The two types differed in depth distribution, and planktivorous types showed marked diel changes in abundance. The results indicate that previous lumping of all nominal species of Macrorhamphosus under M. scolopax is wrong, both because there appear to be at least two scolopax-like forms and because evidence that M. gracilis is the juvenile of M. scolopax is weak. Additional analyses of diet and sexual dimorphism from other geographical areas are necessary to determine if geographical differences warrant recognition of more than two species of M. scolopax-like snipefishes and to resolve the appropriate names for the two types from Australia.