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Ontogenetic Trophic Interactions and Benthopelagic Coupling in Lake Washington: Evidence from Stable Isotopes and Diet Analysis
Author(s) -
McIntyre J. K.,
Beauchamp D. A.,
Mazur M. M.,
Overman N. C.
Publication year - 2006
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/t05-099.1
Subject(s) - pelagic zone , benthic zone , biology , trophic level , zooplankton , predation , planktivore , trophic cascade , isotope analysis , ecology , δ15n , food web , apex predator , fishery , piscivore , perch , phytoplankton , stable isotope ratio , δ13c , predator , nutrient , fish <actinopterygii> , physics , quantum mechanics
Stable isotopes of nitrogen and carbon and stomach content analysis were used to determine the trophic position and relative importance of benthic and pelagic pathways for different life stages and species of the major fishes and invertebrate prey in Lake Washington. Significant coupling of the benthic and pelagic pathways was evident in this complex food web across seasons and fish ontogenies. Among apex predators, cutthroat trout Oncorhynchus clarkii and northern pikeminnow Ptychocheilus oregonensis shifted ontogenetically from benthic omnivory to pelagic piscivory, whereas yellow perch Perca flavescens shifted from pelagic zooplanktivory to benthic piscivory. Apex predators continued to rely on benthic prey seasonally, particularly in winter and spring. Benthic pathways were less important to the current diets of apex predators than they were during the recovery from eutrophication in the 1970s. Surprisingly, the δ 15 N values for copepods during winter and for zooplanktivorous longfin smelt Spirinchus thaleichthys and threespine sticklebacks Gasterosteus aculeatus were similar to those for top piscivores, whereas the significantly lower values for zooplanktivorous juvenile sockeye salmon O. nerka were more similar to expectations. Nitrogen and carbon isotope ratios of pelagic planktivores and invertebrates also varied seasonally. Mixing model results showed that stable isotopes and stomach contents were comparable for determining ontogenetic trends, but stable isotopes established these trends with many fewer samples and less variability and accurately portrayed ontogenetic trends when few stomach samples were available. However, stomach content analysis was critical in delineating seasonal trends in diets and for identifying specific prey species.