Use of water flow direction to provide spatial information in a small-scale orientation task V. A. B RAITHWAITE * AND J. R. G IRVAN Institute of Cell, Animal and Population Biology, School of Biological Sciences, Edinburgh University, Edinburgh EH9 3JT, U.K. Experiments were designed to investigate whether three-spined sticklebacks Gasterosteus acu- leatus can use direction of water flow as an orientation cue. The fish had to learn the location of a food patch in a channel where water flow direction was the only reliable indicator of the food patch position. Fish from two ponds and two rivers were trained and tested in the spatial task to determine whether river three-spined sticklebacks are more adept at using water flow as a spatial cue than fish from ponds. All fish were able to use water flow to locate the food patch but one of the two river groups was significantly faster at learning the patch location. When the task was reversed so that fish that had formerly been trained to swim downstream now had to learn to swim upstream and vice versa both river groups learned the reversed task faster than the two pond groups. In a second experiment, to investigate whether fish from ponds or rivers vary in the type of spatial cue that they prefer to use, fish from one pond and one river were given a choice between two different types of spatial cue: flow direction or visual landmarks. A test trial in which these two cues were put into conflict revealed that the river population showed a strong preference for flow direction whilst the pond population preferred to use visual landmarks. # 2003 The Fisheries Society of the British Isles Key words: spatial learning; flow direction; stickleback. INTRODUCTION Animals living in complex and changeable habitats use learning to help them adapt their behaviour to their local environment. Learning and memory there- fore provide a way for animals to make appropriate responses when faced with different types of decision (Giraldeau, 1997). This enables animals to modify their behavioural output to take into account changing requirements within a heterogeneous environment. One area of learning and memory research that has received considerable attention is that of spatial behaviour (Healy, 1998). Here, the goal is to determine how animals learn to move and navigate around an environment to better understand how animals, for example, efficiently locate food and effectively avoid predation. Many fish species occupy complex and changeable environments and are therefore expected to show a reasonable capacity for learning and memory. *Author to whom correspondence should be addressed. Tel.: þ44 (0) 131 650 5448; fax: þ44 (0) 131 650 6564; email: v.braithwaite@ed.ac.uk Journal of Fish Biology (2003) 63 (Supplement A), 74–83 doi:10.1046/j.1095-8649.2003.00218.x, available online at http://www.blackwell-synergy.com 74 # 2003 The Fisheries Society of the British Isles