12/4/2023 0 Comments Video playback![]() ![]() The choice is regarded “spontaneous” as no training is involved, and thus the test relies upon inherent behavioral tendencies of the studied fish species. The time spent by the test fish in each zone close to the opposite sides of the test aquarium, i.e., in the proximity of the stimulus groups (shoals), is measured and generally considered as an index of preference of the test fish for one or the other shoal. In these tests, two aquaria, each containing a different number of conspecifics, are placed at the opposite sides of a central aquarium into which a test fish is placed. But how do fish gauge group size?Ī common way to investigate numerical abilities in fish has been to employ spontaneous dichotomous choice tests. This assumption has been empirically confirmed in a variety of fish species by studies showing cognitive abilities of fish to discriminate between quantities, including number of shoal members (reviewed in Agrillo & Bisazza, 2018 Agrillo et al., 2017). Therefore, natural selection may have led to the evolution of the ability in fish to discriminate among differently sized groups. These costs and benefits may vary with group size. ![]() The disadvantages include enhanced conspicuousness to predators (Botham et al., 2005), elevated parasitism (Poulin, 1999) and resource competition within the group (Maszczyk et al., 2014). The benefits include more efficient foraging (Day et al., 2001 Hintz & Lonzarich, 2018) and swimming (Marras et al., 2015 Miller & Gerlai, 2011), as well as better protection from predators (e.g., see Ioannou, 2017). ![]() Living in groups is widespread in fish species, presumably because it can confer various fitness benefits that outweigh the costs it may incur (Krause & Ruxton, 2002). Exploring procedural and/or technological parameters will verify the suitability of video-recording-based stimulus presentation for future use in angelfish. These results imply that video-playback has disadvantages in quantity discrimination studies with angelfish. When the choice consisted of a live shoal of four conspecifics versus a video playback of a shoal of nine conspecifics no clear preference emerged. However, when we directly contrasted a live and a video recorded shoal, both having the same number of members, experimental fish preferred the live shoal. These results indicate that video-playback of live conspecifics may be appropriate in angelfish, thus allowing manipulation of specific cues that angelfish may use in quantity discrimination. We found angelfish to prefer a live shoal of conspecifics to an empty tank, and also the video playback of a shoal of conspecifics to a blank screen, although the level of preference in the latter was lower than in the former. Time spent close to one versus the other stimulus was considered an index of preference. Using binary choice tests, subjects were presented different stimuli. ![]() Here, we evaluated how angelfish ( Pterophyllum scalare) respond to a video playback of conspecifics versus a live shoal of conspecifics. However, video-recordings do not interact with the experimental subject, and thus this stimulus may be inferior in the social context. In the analysis of behavioral responses to social cues, presentation of video recordings of live conspecifics represents a consistently reproducible stimulus. Video playback is a widely used technique for presentation of visual stimuli in animal behavior research. ![]()
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