San Diego State University
Department of Biology
Fish Ecology Lab
Ecological implications of physiological condition in temperate fishes (funded by Achievement Rewards for College Scientists; Rancho Santa Fe Garden Club; SDSU Joint Doctoral Program in Ecology; USC Wrigley Institute for Environmental Studies)
Emily Floyd's dissertation project --
The supply of larvae to coastal areas and factors that affect post-settlement survivorship can be important determinants of population and community structure for reef-associated fishes. Variation in individual characteristics such as physiological condition (e.g., energy reserves) and swimming performance of recently settled fishes may also play a substantial role in determining the demography of fishes across systems. Trait variability (condition and swimming ability) and mortality may be high during the transitional period between larval and juvenile life history stages and just following metamorphosis. Consequently, examining the relative importance of these characteristics in survival of recently settled fishes is crucial to develop an understanding of the role of condition and performance on fish population dynamics. Prior laboratory studies have revealed differential survival based on differences in swimming performance and condition, but few studies have integrated laboratory and field-based research to document the ecological implications of physiological processes.
The aim of Emily's research was to determine whether individual condition in temperate fishes affects their survival in natural systems. From 2002-05, field studies were conducted at the Wrigley Marine Science Center, Santa Catalina Island, California, focusing on survival of the blackeye goby (Rhinogobiops nicholsii) based on physiological condition. Emily documented condition (manipulated by food ration) of individual gobies and placed gobies that differ in condition on experimental plots in the field. Fish fed low rations experienced higher mortality than fish fed high rations. However, refuge availability influenced this pattern, resulting in a surprising interaction between condition and refuge availability in survival of the blackeye goby. In addition, Emily tested whether fish in lower or higher condition showed differences in burst swimming speed, a possible mechanism by which gobies lessen predation risk.
Emily also conducted a study with collaborators at the University of California, Davis to determine the effects of toxicants and predation by the three-spine stickleback (Gasterosteus aculeatus) on the behavior and mortality of a freshwater fish, the fathead minnow (Pimephales promelas). Her results demonstrated a decline in individual growth and an increase in mortality with higher concentrations of a pyrethroid insecticide, esfenvalerate.
This page was last modified on May 10, 2012.
SDSU Fish Ecology Lab
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