Doctor of Philosophy (PhD)
Oceanography and Coastal Sciences
The Louisiana-Texas coast is one of the largest areas of seasonal, coastal hypoxia. The hypoxic zone has increased in size since the 1900s and has significantly increased in thickness since 1985. Hypoxia can negatively affect fish through direct mortality, reduced fecundity, and reduced preyavailability. Movement algorithms were used to model fish movement and avoidance of hypoxia in 2-D and 3-D with static and dynamic environmental fields. Output from a 3-D, coupled, hydrodynamic-water quality model was used for the environmental conditions of the model. A particle tracking module for the hydrodynamic model was used to track fish movement. Movement algorithms were added to the tracking module to allow for active movement. Three movement algorithms for use outside of hypoxic conditions were compared in static 2-D scenarios. There was not a large difference in hypoxia exposure for the three algorithms, but there was a difference in sinuosity (amount of wiggle in the fish track). Comparing static and dynamic environmental fields in 2-D resulted in higher exposures for dynamic conditions. There was also an unexpected effect from a narrow region of normoxic water surrounded by hypoxic water. The presence of this thin area resulted in more outliers in hypoxia exposure. Three algorithms for hypoxia avoidance were compared in dynamic conditions. Two of the algorithms were found to be similar, but a third that used both dissolved oxygen and temperature as inputs had much higher exposures. Balancing the two environmental cues resulted in poor hypoxia avoidance. Comparing 2-D and 3-D scenarios resulted in lower exposure for fish in 3-D scenarios. Two different methods of perception ranges were used and found to result in similar hypoxia exposures. The research highlighted the need to include 3-D movement in fish models for the Gulf of Mexico hypoxia region. Also, high-resolution field data need to be collected to calibrate and validate such models and facilitate selection of appropriate movement algorithms.
Document Availability at the Time of Submission
Student has submitted appropriate documentation to restrict access to LSU for 365 days after which the document will be released for worldwide access.
LaBone, Elizabeth Dawn, "Modeling the Effects of Hypoxia on Fish Movement in the Gulf of Mexico Hypoxic Zone" (2016). LSU Doctoral Dissertations. 4441.