Dissertation Research: Ontogenetic Ecomorphology of Escape Performance in Threespine Stickleback

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Bell 9722134 Lake populations of the threespine stickleback fish (Gasterosteus aculeatus) are believed to be derived from marine populations that migrate to fresh water to breed. Lake populations have diverged morphologically and behaviorally from the marine condition. Stickleback in some lakes feed on plankton in open water and are often exposed to predators. Stickleback in other lakes feed on bottom-living invertebrates and frequent vegetated habitats that provide refuge from predators. Adults that differ in feeding mode show body-shape variation that is probably related to the swimming styles favored by different foraging behaviors and predation risks. Little is known of foraging mode, locomotion, and body shape in larval and juvenile stickleback. The proposed study will quantify variation in (1) morphological features that affect predator evasion and foraging locomotion (using new methods involving morphological landmarks) and (2) swimming ability (by measuring steady and evasive swimming performance) in larvae, juveniles, and adults from different lake populations in Alaska. Variation in vertebral number, which may affect evasive swimming, will also be analyzed. Lake populations will be compared with a migratory population (the putative ancestral form). Field observations and stomach-content analyses will be conducted to assess variation through development and among populations in diet, foraging behavior, and microhabitat use.