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Movement of Tidal Shrimps in Isolation

Keywords: periodicities, non-parametric trend


Tidal shrimps from the Brisbane River move up and down the tidal area (harbour pylon for example) in accordance with the movement of the tides. In this experiment shrimps were removed from their natural environment and isolated from environmental stimulae which would allow them to measure time. Their vertical position on an inclined slope was recorded every half hour starting 20 hours after removal and continuing for one week. Also recorded is the actual tide height during the same period, and six other measures of the shrimps' activity.

Variable Description

Time Hours since isolation
Vertical Vertical displacement from original position
Y2 - Y7 Other activity measurements
Tide Actual tide height


Data file (tab-delimited text)


Yong Yuan, Department of Biology, University of Queensland.


The data need to be detrended non-parametrically, and then searched for periodicities. The periodic behaviour of the shrimps' movement gradually breaks up over the week.

Time series plot of vertical movements (10184 bytes)



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