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Diurnal feeding and prey size selection in Atlantic salmon, Salmo salar, alevins

1986; Springer Nature (Netherlands); Linguagem: Inglês

10.1007/978-94-017-1158-6_23

0924-5316

Howard I. Browman, Brian M. Marcotte,

Marine and fisheries research

SynopsisResults of an experiment on diurnal feeding behaviour and prey size selection in Atlantic salmon, Salmo salar, alevins are reported. Peaks in total behavioural activity, ingestion rate, feeding success (# of ingestions per unit effort) and feeding error (total number of prey missed or rejected after an attack) occurred in the early morning (0600–0900 h), at mid-day (1100–1400 h) and in the evening (1900–2000 h). Variability in feeding success decreased as its mean value increased and variability in feeding error decreased as error decreased. This pattern in the behavioural indices which reflect the alevin’s ability to execute spatially-oriented activities (i.e. prey size selection, success, error) is put forward as a possible manifestation of underlying rhythms in the animal’s nervous system. In the early morning alevins fed selectively on the largest copepods (>0.8 mm). This restricted range of selectivity was associated with low light levels and high activity. Later in the day, a broader range of the larger size classes were selected (>0.7 mm). Intensity of selection was inversely associated with total activity. This evidence of diurnal pattern in alevin feeding behaviour shows that (1) fish exhibit behavioural rhythms early in their life history, and (2) prey size selection, in terms of both intensity and breadth of size class selected for, changes over the day.