Document Type

Master's Thesis

Degree Name

Master of Science (M.S.)


Moss Landing Marine Laboratories


Domoic acid (DA) is a neuroexcitatory toxin that is increasingly causing strandings and mortality of marine mammals. The hippocampus of mammalian brains; associated with learning, memory, and spatial navigation, is one of the predominant tissues affected by DA exposure. California sea lions stranding from 2003 to 2006 due to DA toxicosis were classified as having acute (n = 12) or chronic neurologic (n = 22) clinical signs. Chronic neurologic cases were examined by magnetic resonance (MR) imaging to determine the extent of brain damage related to DA exposure. Brain damage included hippocampal and parahippocampal atrophy, temporal horn enlargement, and pathological T2 hyperintensity. Post-treatment, animals were fitted with satellite transmitters and their movement and dive behaviors compared with those of a control group. There were no significant behavioral differences between acute cases and control animals. There were significant differences between chronic neurologic cases and control animals: chronic neurologic cases dove shallower with shorter durations, traveled greater distances per day and further from shore, and spent less time hauled-out and more time surface swimming than control animals. There was no relationship between severity of brain damage and behavioral patterns for chronic neurologic cases. Results indicated sea lions with chronic neurologic changes had poor prognosis for survival following release.


Thesis (M.S.) Division of Science and Environmental Policy. Moss Landing Marine Laboratories