Ecological segregation within and among Arctic char morphotypesin Gander Lake, Newfoundland

Abstract

Stable isotopes of carbon and nitrogen were used to examine differences in the feeding ecology of sympatric morphotypes of Arctic char, Salvelinus alpinus, from Gander Lake, Newfoundland. Morphotypes were differentiated on the basis of colour (pale and dark) and meristic characteristics. Significant differences in length, age and habitat depth were also noted, with the pale-form being smaller, younger and caught at greater average depths than the dark-form. Pale and dark morphotypes possessed significantly different carbon and nitrogen stable isotope signatures, with the dark-form being more δ13C enriched than the pale-form. Within each morphotype grouping distinctive isotopic signature differences related to diet (dark-form) and capture depth (pale-form) were also observed. Differences in the isotopic signatures within and among habitat groupings were induced by differences in feeding opportunities arising from differences in habitat use and feeding strategies and generally corroborated by stomach content analysis and an index of dietary overlap. Study results provide evidence for the contention that sympatric forms of Arctic char in Gander Lake occupy significantly different foraging niches within the lake. Results further suggest ecologically relevant separations within morphotype groupings result in lower resource competition.