Unique perspectives on the influence of size and age on consumer 15N from a rainbow smelt complex
Analysis of covariance indicated size had a greater influence than age on 15N in three rainbow smelt Osmerus mordax morphotypes of Lake Utopia, New Brunswick, Canada. The distinction in size between the three forms allowed a unique analysis and separation of size and age effects, which is not commonly possible because of the strong correlation between size and age. These results provide support for the continued use of 15N as a trophic level indicator in food web studies. While a slight increase in 15N with age (P≤ 0·05) in intermediate-sized smelt raises questions about a potential accumulation of 15N with age, the effect of size was far stronger in governing 15N values. The possible confounding influence of age when interpreting trophodynamics of short-lived consumers appears to be small.