Domoic acid and fish behavior: A review

This paper provides a summary of the “state of knowledge” regarding behavioral impacts of domoic acid exposure on fish. Initial studies by authors of this paper suggested that fish are behaviorally impacted by domoic acid in the same way that birds and mammals are impacted during toxic Pseudo-nitzschia blooms. However, subsequent research and field observations have contradicted that hypothesis and provide evidence that fish are more tolerant to domoic acid under ecologically relevant exposure conditions than their piscivorous predators. This is an important distinction as more attention has been drawn to domoic acid producing algal blooms and the potential for domoic acid to cause fish kills. Currently available data indicate that domoic acid producing algal blooms do not cause fish kills or neuroexcitotoxic behaviors in fish. Neuroexcitatory behavioral effects have been documented in fish in laboratory studies when fish were intraceolomically (IC) injected with domoic acid. In fact, with IC injection as the mode of exposure all fish, bird, and mammal species tested to date show a similar neurologic sensitivity to domoic acid in terms of behavioral excitotoxicity as quantified by a 50% effective concentration (EC50) metric. However, IC injection is not an ecologically relevant mode of exposure. Dietary consumption during toxic blooms is the route of exposure for fish. Results from oral exposure experiments and observations from multiple highly toxic bloom events have provided strong evidence that fish are not behaviorally affected by domoic acid during natural bloom conditions, even though fish regularly contain high levels of the toxin and act as vectors to seabirds and marine mammals. Collectively, the data presented in this review suggest that fish are not significantly impacted by domoic acid during typical toxigenic Pseudo-nitzschia blooms.

► This review article summarizes important information that clarifies current misconceptions regarding domoic acid impacts in fish.
► It provides valuable summary tables for (1) toxin levels commonly found in fish, (2) toxicological metrics for domoic acid impacts in laboratory studies with fish, birds, and mammals, and (3) a comparative summary of oral dose studies.
► This study will move the field forward in understanding the ecological impacts of domoic acid exposure in fish populations.