PARENT SESSION
Poster Session #22: Fish, Lakes, Streams and Wetlands.
Tuesday, August 6. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Community composition and stable isotope analysis of pond food webs in the Whooping Crane nesting area.

Sotiropoulos, Maria¹, Tonn, William^*,1, Wassenaar, Leonard², ¹ University of Alberta, Edmonton, AB, Canada² Environment Canada, Saskatoon, SK, Canada

ABSTRACT- The food webs of remote ponds in Wood Buffalo National Park have remained unstudied since their 1954 discovery as the breeding habitat for Whooping Cranes. Preliminary observations showed that cranes foraged consistently and selectively in ponds that contain small fishes, suggesting that fish play an important trophic role. Multivariate analyses of 36 ponds indicate that invertebrate communities in ponds with fish are distinct from those in fishless ponds, with the former commonly lacking invertebrate predators and cladocerans. To compare fish and fishless food webs and establish the trophic positions of fish and cranes, we sampled primary producers, invertebrates, fishes, and locally collected crane feathers from three pairs of ponds (fish and fishless) for stable isotope analysis (SIA). Benthic diatoms were the primary energy source driving higher trophic levels in both fish and fishless ponds. Although omnivory was widespread, SIA showed that fish, when present, were consistently at higher trophic positions than invertebrates. Differences in ¹³C between invertebrates in fish and fishless ponds were due to differences at the primary producer level, perhaps reflecting differences in pond pH. Values of ¹⁵N for feathers put cranes at or above the trophic position of fish, but ¹³C values suggested that the wintering-ground diet may be contributing to the signal. The identification of community patterns and feeding interactions within these nesting ponds should assist biologists in assessing suitable habitat for Whooping Crane conservation.

KEY WORDS: fish, pond food webs, stable isotopes, whooping cranes