Cannibalism and trophic structure in a high Arctic lake: insights from stable-isotope analysis

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Hobson, Keith A., Welch, Harold E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1995
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Arctic; Arctic Lake; Northwest Territories; Salvelinus alpinus; Zooplankton
• Online Access: http://dx.doi.org/10.1139/f95-116; http://www.nrcresearchpress.com/doi/pdf/10.1139/f95-116

Stable-nitrogen ( 15 N/ 14 N) isotope ratios (from 2.1‰ in moss to 14.5‰ in Arctic char, Salvelinus alpinus), showed enrichment with trophic level in the food web of Char Lake, Northwest Territories, and may be used to infer trophic position. The average 15 N enrichment of 1.5‰ between moss or algae and invertebrates suggests input to the food web of isotopically lighter nitrogen than that measured for these sources of primary production. Stable-carbon ( 13 C/ 12 C) isotope ratios differed between moss and algae by almost 10‰ and indicate that carbon in the Char Lake food web is derived from a blend of these sources of primary production. Arctic char δ 15 N values for muscle tissue were positively correlated with fork length and clustered into three distinct groups: small fish (1–3 cm, mean δ 15 N = 5.7‰), which possibly consumed more benthic particles than previously assumed; intermediate-size fish (10–35 cm, mean δ 15 N = 10‰), which likely depended on larval char as well as their primary zooplankton and chironomid prey; and larger Arctic char, which showed a mean stepwise increase in δ 15 N of 3.7‰. This suggests that complete cannibalism in this population generally occurs abruptly and is exercised by a relatively small number of large individuals.