Ecophysiological impacts of hypoxia on nursery habitat quality for juvenile estuary-dependent fishes: A comparison of laboratory and field growth rates

In this study, I examined the effects of hypoxia on feeding and growth rates of several important estuary-dependent fishes in the Middle Atlantic Bight to better understand its impact on nursery habitat quality.; Chapter 1 is an introduction to the concept of estuaries as nursery habitats, the current state of hypoxia in estuarine systems, and the known effects of hypoxia on the behavior and physiology of estuary-dependent fishes.; Chapter 2. In the laboratory, I investigated the interaction of temperature (20--30°C) and constant (2.0, 3.5, 5.0, and 7.0 mg O 2 l-1 (saturated control)) and dielcycling DO (2-11 mg O2 l-1) on feeding and growth rates of juvenile summer flounder (Paralichthys dentatus) and winter flounder (Pseudopleuronectes americanus), two estuary-dependent flatfishes. In addition, growth data from the summer flounder growth experiments were used to model growth over a nursery season to illustrate the potential long-term effects of hypoxia on size-at-age, and to examine whether wild summer flounder in a hypoxic nursery were growth limited.; Chapter 3. In a similar set of laboratory experiments, I examined the interaction of temperature (20, 25, and 30°C) and constant (2.0, 3.5, 5.0, and 7.0 mg O2 l-1 (saturated control)) and diel-cycling DO (2-11 mg O2 l-1 on growth rates of juvenile weakfish (Cynoscion regalis), an estuary-dependent bentho-pelagic fish.; Chapter 4. From these and other laboratory studies, it was clear that some fishes were more likely to be impacted by hypoxia than others. Further, previous laboratory and field studies indicated that numerous estuarine fishes could detect and avoid hypoxia, thus minimizing its effects on growth. Therefore, I was interested in the extent to which growth rates of such fishes are impacted by hypoxia in the wild. In this chapter, I examined temporal and spatial differences in growth rates of juvenile summer flounder and weakfish relative to continuously measured DO conditions in Pepper Creek, a shallow tributary of Indian River Bay, DE, during two nursery seasons (2002 and 2003).; Chapter 5. I examined the contribution of behavioral adaptations (aquatic surface respiration, ASR) and changes in hematocrit to the hypoxia tolerance of mummichog (Fundulus heteroclitus). Growth rate and hematocrit was measured in fish exposed to constant and diet-cycling hypoxia. (Abstract shortened by UMI.)...