Evidence of hypoxic foraging forays by yellow perch ( Perca flavescens ) and potential consequences for prey consumption

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91146/1/FWB_2753_sm_fS1.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/91146/2/j.1365-2427.2012.02753.x.pd

Orientation of the American Eel, Anguilla rostrata

This thesis is being archived as a Digitized Shelf Copy for campus access to current students and staff only. We currently cannot provide this open access without the author's permission. If you are the author of this work and desire to provide it open access or wish access removed please contact the Wahlstrom Library to discuss permission.The use of geomagnetism as a navigational aid by American and European eels during their seaward migration has recently been and currently is an area of research. This investigation reviewed previous studies concerning the use of geomagnetism as well as light and olfaction as guidance mechanisms during various life stages of American and European eels. In this study yellow-phase and silver-phase American eels were investigated for their orientational (directional) preferences in a chambered tank. The eels were observed while the tank was rotating and while the tank was stationary. In general, the eels were found to prefer easterly directions--particularly northeast. The variability with which the eels sought their preferred directions decreased or increased depending upon whether they were examined in the tank while it was rotating or while it was stationary. It is believed that because no other orientational cues were available to the eels during testing, the orientation which was observed to occur was dependent upon geomagnetism. This supports some current theories that eels make use of directional cues derived directly from the earth*s magnetic field or from oceanic electric fields which are associated with the geomagnetic field in making their long migration across the open sea to their breeding places in the Sargasso Sea

Evaluating the effects of diel-cycling hypoxia and pH on growth and survival of juvenile summer flounder Paralichthys dentatus

Effects of diel-cycling dissolved oxygen (DO) and pH on young-of-the-year summer flounder Paralichthys dentatus were examined in laboratory experiments. Flounder were exposed to 2 cycling DO levels (extreme = 1-11 mg/O2 l; moderate = 3-9 mg/O2 l), 2 cycling pH levels (extreme = 6.8-8.1; moderate = 7.2-7.8), and static normoxia (7.5 mg/ O2 l) and pH (7.5) in a fully crossed 3*3 experimental design for 20 d. Cycling conditions reflected summertime DO and pH fluctuations in flounder nursery habitat. Experiments were conducted over 3 partial factorial trials. Growth was significantly reduced in fish exposed to the most extreme diel-cycling DO, across all pH treatments, with no consistent growth reduction in other treatments. Cycling treatments with mean daily low pH (6.87) and high pCO2 (10000 µatm) had neither an independent nor interactive effect, with hypoxia, on growth. Flounder exhibited growth rate recovery. Following initial growth reduction when exposed to extreme diel-cycling hypoxia and pH over Days 1-10, growth increased 2-fold under static DO (7.5 mg/O2 l) and pH (7.5) conditions over the following 10 d. Flounder did not exhibit growth rate acclimation, defined as increased growth during prolonged exposure, under extreme diel-cycling DO and pH for 20 d. Flounder experienced mortality (>90% of individuals) after 2-3 wk exposure to extreme diel-cycling DO and pH. These experimental results demonstrate that extreme diel-cycling DO and pH can significantly impact summer flounder growth and survival and that the growth rate reduction is driven by DO

Growth of the estuarine fish Fundulus heteroclitus in response to diel-cycling hypoxia and acidification: interaction with temperature

Growth rate of Fundulus heteroclitus was examined at 25 and 30 °C in nine treatments of diel-cycling dissolved oxygen (DO) and pH. Extreme diel-cycling DO (1–11 mg O2/L) negatively impacted growth during 10 days at 30 °C, but not at 25 °C. Moderate DO cycles (3–9 mg O2/L) had no direct growth impact at either temperature. Fish did not appear to acclimate, during days 10–30, to the initial growth-limiting effects of extreme diel DO cycles at 30 °C. Diel-cycling DO interacts synergistically with temperature to impact growth. There was no evidence of an independent growth effect of either moderate pH cycles (7.2–7.8) or extreme pH cycles (6.8–8.1) at either temperature. Mean low pCO2 levels in extreme cycles were ∼32 000 and ∼47 000 μatm at 25 and 30 °C, respectively. It is noteworthy that these high mean nightly pCO2 levels are more than an order of magnitude higher than the chronic mean oceanic pCO2 of ∼1000 μatm projected by the year 2100

Growth of the estuarine fish Fundulus heteroclitus in response to diel-cycling hypoxia and acidification: interaction with temperature

Growth rate of Fundulus heteroclitus was examined at 25 and 30 °C in nine treatments of diel-cycling dissolved oxygen (DO) and pH. Extreme diel-cycling DO (1-11 mg O2 L-1) negatively impacted growth during 10 days at 30 °C, but not at 25 °C. Moderate DO cycles (3-9 mg O2 L-1) had no direct growth impact at either temperature. Fish did not appear to acclimate, during days 10-30, to the initial growth-limiting effects of extreme diel DO cycles at 30 °C. Diel-cycling DO interacts synergistically with temperature to impact growth. There was no evidence of an independent growth effect of either moderate pH cycles (7.2-7.8) or extreme pH cycles (6.8-8.1) at either temperature. Mean low pCO2 levels in extreme cycles were ~32 000 and ~47 000 µatm, at 25 and 30 °C, respectively. It is noteworthy that these high mean nightly pCO2 levels are more than an order of magnitude higher than the chronic mean oceanic pCO2 of ~1000 μatm projected by the year 2100.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author