Shoaling Decisions in Angelfish: The Roles of Social Status and Familiarity

Abstract

Past research has shown that angelfish, Pterophyllum scalare, are capable of discriminating between shoals composed of familiar dominant and subordinate companions, whereas they show no preference for shoals of unfamiliar conspecifics. In this study, the relative importance of familiarity and social status (shoal factors) on the shoaling decision of juvenile angelfish, which also differed in social status (individual factor), was investigated as very little is known about such tradeoffs in fishes. Dominant and subordinate individuals were given the choice to shoal with a group of conspecifics composed of familiar dominants vs. unfamiliar dominants and composed of familiar subordinates vs. unfamiliar subordinates. The findings demonstrate that fish with different social status differed in their shoaling preference. Subordinate test fish showed a preferential association with familiar subordinates over unfamiliar subordinates, but preferred the unfamiliar shoal over the familiar one when both shoals were constituted by dominant individuals. The shoaling behaviour shown by dominant test fish, on the other hand, indicated no significant preference for any of the shoals regardless of their composition. A replicate preference test carried out 2 h 30 min after the first one indicated that the association pattern was relatively consistent. Results suggest that angelfish are able to differentiate between the stimulus shoals and demonstrate that the pervasive influence of familiarity on the shoaling decision may be restrained or overridden by the composition of the familiar shoals and the social status of the test fish.

Social Recognition of Conspecifics

“…When given a choice between familiar and unfamiliar dominant conspecifics, the subordinate angelfish preferred to associate with the unfamiliar fish. Dominant fish exposed to the same test did not demonstrate any clear preference (Gomez-Laplaza & Fuente 2007). Similar results were reported in the humbug damselfish (Dascyllus aruanus) where subordinate individuals are choosier than dominant fish (Jordan et al 2010).…”

Shoaling preference and evidence for maintenance of sibling groups by juvenile black perch Embiotoca jacksoni

“…The precise mechanisms behind the behavioural biases observed in this study are not known. In viviparous fishes such as embiotocids, it is difficult to completely separate the role of familiarity from other factors because live‐bearing fishes can become familiar with each other before and immediately after birth, and familiarity per se has been shown to influence shoaling preferences in a variety of fishes (Van Havre & Fitzgerald, 1988; Dugatkin & Wilson, 1992; Hojesjo et al , 1998; Barber & Wright, 2001; Gomez‐Laplaza & Fuente, 2007). Magurran et al (1995) found that free‐living juvenile guppies Poecilia reticulata Peters, the only other live‐bearing fish studied to date, were more closely related than the average for the population.…”

Social familiarity and shoal formation in juvenile fishes

“…P. reticulata : Griffiths & Magurran, 1998; Godin et al , 2003). Moreover, some fish species have no preference for familiar shoalmates or there are even situations where familiar shoalmates are actively avoided (Frommen et al , 2007; Gómez‐Laplaza & Fuente, 2007). Whether familiarity occurs through individual or general group recognition, or even via a chemical cue preference for fishes occupying the same habitat or sharing a similar diet, is an important question that has been addressed in fishes only recently (Ward et al , 2004, 2005; Webster et al , 2007).…”