Influence of habitat complexity on route learning among different populations of climbing perch (Anabas testudineus Bloch, 1792)

Animals use different behavioral strategies to maximize their fitness in the natural environment. Learning and memory are critical in this context, allowing organisms to flexibly and rapidly respond to environmental changes. We studied how the physical characteristics of the native habitat influence the spatial learning capacity of Anabas testudineus belonging to four different populations collected from two streams and two ponds, in a linear maze. Stream fish were able to learn the route faster than pond fish irrespective of the presence or absence of landmarks in the maze. However, climbing perch collected from ponds learned the route faster in the maze provided with landmarks than in Plain maze. The results indicate that fish inhabiting a lotic ecosystem use egocentric cues in route learning rather than visual cues like landmarks. A local landmark may be a more reliable cue in route learning in a relatively stable habitat like a pond. In flowing aquatic systems, water flow may continually disrupt the visual landscape and thus landmarks as visual cues become unreliable. Spatial learning is thus a fine-tuned response to the complexity of the habitat and early rearing conditions may influence the spatial learning ability in fish.