Abstract
Predation pressure and energy requirements present particularly salient opposing selective pressures on young fish. Thus, fry are expected to possess sophisticated means of detecting predators and resources. Here we tested the hypotheses that fry of the swordtail fish Xiphophorus birchmanni use chemical and visual cues in detection of predators and conspecifics. To test these hypotheses we presented young (<7 day-old) fry with combinations of visual and chemical stimuli from adult conspecifics and predators. We found that exposure to predator odors resulted in shoal tightening similar to that observed when fry were presented with visual cues alone. In trials with conspecific stimuli, fry were particularly attracted to adult conspecifics when presented simultaneous visual and chemical stimuli compared to the visual stimulus alone. These results show that fry attend to the odors of adult conspecifics, whose presence in a particular area may signal the location of resources as well as an absence of predators. This is one of the first studies to show that such young fish use chemical and visual cues in predator detection and in interactions with conspecifics. Previous research in X. birchmanni has shown that anthropogenic alteration of the chemical environment disrupts intraspecific chemical communication among adults; we suggest that because fry use the same chemosensory pathways to detect predators and conspecifics, alteration of the chemical environment may critically disrupt predator and resource detection.
Highlights
Predation pressure is a primary force driving morphological, physiological, and behavioral evolution in many fishes [1,2,3,4,5,6]
We suggest that one way they may do this is to attend to the odors of adult conspecifics, whose presence in a particular area may signal the location of resources as well as an absence of predators
Individuals in prey species are expected to attend closely to predator cues, and respond to these cues with predator avoidance tactics. This hypothesis has received much support among studies of adult fish [7, 8, 21; reviewed in refs. 22, 23], and in a handful of studies investigating the use of predator chemical cues by juvenile fish
Summary
Predation pressure is a primary force driving morphological, physiological, and behavioral evolution in many fishes [1,2,3,4,5,6]. Vulnerability to predators may be high for young fish due to their small size and lack of experience with predators. In two-spotted gobies (Gobiusculus flavescens), for instance, whether juveniles respond to predator chemical stimuli depends on prior visual experience with the predator [7; see ref. Young fish may experience constant and conflicting pressure imposed by the high metabolic demands of growth and development countered by foraging-associated predation risk. Young fish are expected to attend closely to cues associated with predation risk while foraging [e.g. ref. Young fish are expected to attend closely to cues associated with predation risk while foraging [e.g. ref. 9], and to modify their behavior appropriately when these cues are encountered
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