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Abstract

Hypothesis: Ecological specialization facilitates co-existence of Coregonus spp. in Lake Stechlin. A difference in trophic ecology is the dominant means by which the species are ecologically segregated. Background: Sympatric fish species pairs in post-glacial lakes often feed on different resources, segregating available trophic resources. Organisms: Sympatric European winter-spawning Coregonus albula and the local endemic dwarf-sized spring-spawning Coregonus fontanae. Time and place: March-December 2005, Lake Stechlin, North Germany. Methods: By combining stomach content analyses and stable isotope analyses we compared consumption patterns of the two species at different depths over a 10-month period. Results: Stable isotope analyses and stomach content analyses both showed little trophic difference between the two species, but a significant effect of capture depth and body size on individual diet. Conclusions: The sympatric species pair in Lake Stechlin does not follow the expected pattern of niche segregation. Trophic divergence is not the dominant grounds for co-existence.