Kin discrimination in juvenile brook trout (Salvelinus fontinalis): possible fitness trade-offs associated with kin-biased behaviour

Abstract

Kin discrimination abilities and possible fitness trade-offs associated with kin-biased behaviour were investigated in juvenile brook trout (Salvelinus fontinalis). Three experiments were conducted to determine: 1) if juvenile brook trout have the ability to discriminate kin based on water-borne chemosensory cues, 2) the effect cue water concentration, as an indicator of shoal size, has on kin preferences, and 3) a possible trade-off in kin-biased behaviour with respect to social status. -- In the first experiment individual kin spent a significantly greater proportion of time in water conditioned by kin and did not discriminate between familiar and unfamiliar kin. This preference indicates that juvenile brook trout have the ability to discriminate kin based on water-borne chemosensory cues. Individuals in the second experiment based cue water preferences on both concentration and kinship. When cue water concentrations were equal individual kin preferred water conditioned by kin. However, if given a choice between high and low concentrations, individual kin preferred the high concentration independent of kinship. Individuals may perceive the various cue water concentrations as an indicator of shoal size and base preferences on these differences (Chapter 2). -- The third experiment demonstrated that kin in two size class introductions 1) spent a significantly greater proportion of time nearest kin, 2) were generally less aggressive toward kin, and in the same-size introductions, 3) introduced kin had significantly greater mean weight gain than introduced non-kin (Chapter 3). -- Evidence from the present study suggests that juvenile brook trout may be able to maximize 'inclusive fitness' benefits through kin-biased behaviour under both shoaling and territorial conditions. A fitness trade-off may be associated with perceived shoal size but there was no apparent trade-off in kin-biased territorial behaviour with respect to social status in this study.