The transition from day to night in coral reef systems provides a fascinating window of time to see the indirect effects of parasites on the behavior of fish.
Can parasites limit fish migratory behaviors? Using in situ studies, I determined that French grunt infected with Anilocra haemuli do not leave the reef at night to forage with uninfected conspecifics. As a consequence the exchange of nutrients between reef and seagrass systems is altered, and the diet and fitness of infected fish is also affected.
Can parasites drive fish migratory behaviors? By tracking the infection rate of French grunt from their daytime resting grounds to their nocturnal foraging grounds, I determined that their foraging ground not only provide prey resources but are habitat to fewer parasites. In fact, the diel and nocturnal homes of these fish are similar in prey density, such that their true reason for migrating nightly may be to seek refuge from parasitism!