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Dryad

Suction feeding by predators limits direct release of alarm cues in fishes

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Feb 08, 2022 version files 214.26 KB

Abstract

Chemical alarm cues alert aquatic prey to the presence of an actively foraging predator. There is a large literature based upon responses to alarm cues derived from skin extract, because it is anticipated that prey skin is damaged when prey are attacked by a predator. However, many predators feed by suction feeding whereby prey are quickly drawn into the buccal cavity and swallowed whole with little, if any, direct contact between the teeth of the predator and the prey. Here, we test if predation by suction feeding releases chemical information in sufficient quantity to elicit an antipredator response in conspecific prey. In tests of individual zebrafish Danio rerio, we found that odor of crushed zebrafish produced a clear antipredator behavioral response, but water collected immediately adjacent to staged predation events between a largemouth bass Micropterus salmoides (122-145 mm TL) and adult zebrafish (39 mm TL) did not elicit alarm behavior, and did not differ from behavioral responses to blank water or bass odor (on a diet of earthworms). In a second experiment, zebrafish swallowed by largemouth bass, then retrieved seconds later through gastric lavage, produced zebrafish that were alive and completely intact with minimal epidermal damage. Published relationships between bass length, gape size and the geometry of suction feeding suggest that in a hypothetical population of largemouth bass feeding on adult zebrafish, or fathead minnows, the majority of predation events by piscivorous fish probably would not release detectable levels of prey alarm cue. Accounting for the role of feeding mechanics by fish predators requires a recalibration of the literature on risk assessment by small prey fishes. Chemically-mediated antipredator behaviors against suction-feeding predators may occur primarily via post-ingestion dietary cues, or disturbance cues released near the moment of attack.