Are digestive characteristics important contributors to the profitability of prey? A study of diet selection in the fifteen-spined stickleback, Spinachia spinachia (L.)

Michel J. Kaiser, Andrew P. Westhead, Roger N. Hughes, Robin N. Gibson

Research output: Contribution to journalArticle

Abstract

In the field, Spinachia fed on four types of prey; copepods, isopods, mysids and amphipods. As fish size increased, mysids gradually succeeded amphipods as the most important food type in the diet. Prey dimensions and morphometry of the fish's mouth most accurately predicted capture efficiency for amphipods, whereas for mysids capture efficiency was determined by the prey's escape response and the fish's fast-start capability. Responses to model prey revealed the ability of fish to differentiate among contrasting prey characteristics, resulting in the adoption of appropriate predatory tactics. Amphipods were associated with a shorter gut evacuation time than mysids, although approximately equal proportions of energy were absorbed from each. Similar rations of mysids and amphipods were required to satiate fish. The lower energy content per unit dry mass of amphipods was off set by their lower water content. From pre-digestive behaviour, we predicted that mysids were more profitable than amphipods, and this was reflected in the fish's choice. Conversely, incorporating the net rate of energy uptake by the gut led us to predict that amphipods were more profitable. Although physiological constraints clearly influence the net rate of energy uptake, it appears that dietary preferences are based on pre-digestive predatory behaviour and hence on time minimisation.

Original languageEnglish
Pages (from-to)61-69
Number of pages9
JournalOecologia
Volume90
Issue number1
DOIs
Publication statusPublished - Apr 1992

Keywords

  • Diet selection
  • Energy maximisation
  • Gut emptying time
  • Handling time
  • Prey profitability

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

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