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Author Tyler, Robin M
Title Distribution and avoidance patterns of juvenile summer flounder (Paralichthys dentatus) and weakfish (Cynoscion regalis) in relation to hypoxia: Field studies in a temperate coastal lagoon tributary and laboratory choice experiments
book jacket
Descript 183 p
Note Source: Dissertation Abstracts International, Volume: 65-12, Section: B, page: 6155
Professor in charge: Timothy E. Targett
Thesis (Ph.D.)--University of Delaware, 2005
During summer, juveniles of numerous fishes concentrate in shallow estuarine waters where high rates of daytime photosynthesis and nighttime respiration cause wide diel (24-hour) dissolved oxygen (DO) fluctuation, the lower extreme of which can be life-threatening. This research examined the effect of diel DO fluctuation on habitat usage by juveniles of two economically important demersal fishes, summer flounder (SF) and weakfish (WF)
The field study occurred in Pepper Creek, a tributary of Indian River Bay, Delaware over the summers of 2001--2003. Bottom DO was measured continuously each summer using multi-parameter sondes. Vertical DO variability was examined in 2001 on nine dates. SF and WF were monitored at each sonde site in 2001 (3 sites, 20 dates) and 2002 (2 sites, 17 dates) using an otter trawl to examine fish abundance and distribution in relation to changes in DO. The laboratory study utilized two-way DO choice experiments at selected levels of temperature and salinity to determine the [DO] that prompts avoidance behavior
Fluctuation increased in the up-tributary direction during 2001 when severe hypoxia (<2mg O2 1-1) occurred at the upper site almost daily between mid-June and early September for periods of 1--4 hours. Severe hypoxia occurred less frequently in 2002 and 2003. Vertical DO variation, and typically concentration were lowest around sunrise. WF were abundant when DO was above 2mg O2 1-1 and were scarce or absent at lower levels. SF declined during both years around when severe hypoxia events began and their movements in response to DO remain unclear. At times of day when [DO] was above 2mg O2 l-1 at all sites, WF and SF were most abundant in the upper creek despite lower frequency of severe hypoxia events at the middle and lower sites. In the laboratory, both species avoided 1mg O2 l-1 but not 2mg O2 l-1. The sedentary nature of many SF in the laboratory, even at 1mg O2 l-1, suggests that in the natural environment this species might not initiate avoidance behavior until too late to escape a lethal condition. However, WF in the field demonstrated consistently an ability to avoid lethal DO conditions
School code: 0060
Host Item Dissertation Abstracts International 65-12B
Subject Biology, Ecology
Agriculture, Fisheries and Aquaculture
Biology, Oceanography
Biology, Zoology
Alt Author University of Delaware
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