Sticklebacks use prawns to guide them to food

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Scientists from the University of Leicester and the University of Sydney have shown that Three-spined sticklebacks are capable of using common prawns as a guide to optimal foraging spots.

Mike Webster, Paul Hart, and Practical Fishkeeping contributor Ashley Ward carried out a series of experiments involving sticklebacks and prawns in a binary choice tank; their findings were published in a recent issue of the journal Proceedings of the Royal Society B: Biological Sciences.

The results from the first part of the study suggest that any aggregations of sticklebacks (Gasterosteus aculeatus) and Common prawns (Leander serratus) in nature probably arise passively as a result of shared habitat preferences.

The authors then found that both the stickleback and prawn ...showed strong preferences for joining numerically larger groups of conspecifics; however, sticklebacks exhibited no tendency to group with prawns, while the prawns actually avoided the stimulus group of sticklebacks.

This latter finding implies that prawns may experience costs by associating with sticklebacks, perhaps because sticklebacks out compete them for prey....

They also found that sticklebacks preferred to stay with stimulus groups of prawns that had been exposed to the same habitat treatment as themselves, and that focal sticklebacks made more foraging strikes against prey located next to such stimulus groups.

It is thought that the sticklebacks wee responding to chemical cues given off by the prawns.

The authors conclude that by consuming prey and assimilating water-borne cues from their habitat, aquatic animals can concentrate these cues, acting as beacons exuding chemical information to others in the vicinity.

This effect may be especially important when background levels of these chemical cues are low, or when they are dispersed by water currents, making it difficult to detect them directly from the environment.

Thus, it could be adaptive for fishes to not only choose between groups of conspecifics on the basis of such cues but also move towards groups of heterospecifics that are producing similar cues.

Doing so may enable them to gather and use chemical social information as a proxy for resource distribution, local habitat characteristics or even their location relative to different habitat components.

For more information, see the paper: Webster, MM, AJW Ward and PJB Hart (2008) Shoal and prey patch choice by co-occurring fishes and prawns: inter-taxa use of socially transmitted cues. Proceedings of the Royal Society B: Biological Sciences 275, pp. 203"208.