Why do shrimps leave the water? Mechanisms and functions of parading behaviour in freshwater shrimps. (9th November 2020)

• Record Type: Journal Article
• Authors: Hongjamrassilp, W.; Maiphrom, W.; Blumstein, D. T.
• Is Part Of: Journal of zoology. Volume 313:Number 2(2021)
• Page Start: 87
• Page End: 98
• Publication Date: 2020-11-09
• Subjects: collective movement -- freshwater prawn -- Macrobrachium dienbienphuense -- migration -- Southeast Asia; Zoology -- Periodicals; Zoologie -- Périodiques; 590.5
• DOI: 10.1111/jzo.12841
• Languages: English
• ISSNs: 0952-8369

Abstract

Abstract: An understanding of the mechanisms and functions of animal migratory behaviour may provide insights into its evolution. Furthermore, knowledge about migration may be important for conservation of rare species and may help to manage species in a rapidly changing world. Upstream migration is common in riverine animals, but little is known about proximate cues and functions of the upstream migration in aquatic macroinvertebrates. In Ubon Ratchathani, Thailand, locals have observed a synchronous mass migration of freshwater shrimps on land. This so‐called 'parading behaviour' occurs annually during the rainy season and has become a large ecotourism event. Yet, we know little about the natural history, proximate causation and function of this extraordinary behaviour. Here we describe the natural history of parading behaviour and report the results from a series of experiments and observations to address its mechanisms and functions. Parading behaviour is not associated with breeding and spawning; rather, shrimps leave the water to escape strong currents. Conditions promoting shrimps to leave the water include low light, high water velocity and low air temperature. In addition, there is variation explained the specific location. River topology that creates hydrological variability and turbulence plays a role in triggering the shrimps to move out of water. Furthermore, turbidity and water chemistry were associated with shrimp activity. Finally, our results support that parading behaviour in freshwater shrimps is a mass movement upstream due to hydrological displacement. This study highlights the mechanisms that stimulate parading behaviour; a common activity in Macrobrachium and other decapod crustaceans. Abstract : We studied a synchronous mass upstream migration of freshwater shrimps Macrobrachium dienbienphuense . This migration is unique in that the shrimps climb out of a river and walk on land toward a headwater. Locals in Thailand called this 'parading behaviour', and, since 1999, it has become a popular ecotourism event. We found that parading behaviour is not associated with reproduction as believed by local lore, but rather, the shrimps parade to escape strong currents. Environmental factors stimulating the behaviour are described in this study. Results from our research could help design a shrimp ladder that facilitate shrimp movement over a dam, mitigating the impact of humans on shrimp migration.