Spatial and seasonal variation in δ 15 N and δ 13 C values in a mesopredator shark, Squalus suckleyi , revealed through multitissue analyses

摘要: We used variance decomposition to explore the importance of body size, sex, location, and sampling period as predictors intrapopulation variation in δ15N δ13C values spiny dogfish Squalus suckleyi from Puget Sound–Strait Georgia basin. Isotopes two tissues with long (dorsal white muscle) short (liver) isotopic turnover rates (~1 year ~3–4 months, respectively) were sampled evaluate whether relative each variable differed depending on time span over which diet information was integrated. Significant spatial observed both muscle liver composition, whereby location uniquely explained 25 17 % total variance, respectively. The remaining variables considerably less tissue types. Furthermore, evidence seasonal shifts apparent, but widely direction magnitude among groups. These findings suggest that members schools may share a common feeding history, possibly by spending extended periods (weeks months) foraging spatially fixed region. Another explanation is individuals move feed aggregations exist for periods. complex group-level patterns even large-bodied, motile predators such sharks, population-level estimates derived averaging isotope ratios collected only few locations poorly reflect true population mean.