Why do sturgeons jump? Insights from acoustic investigations of the Gulf sturgeon in the Suwannee River, Florida, USA
| Autor: | M. T. Randall, Kenneth J. Sulak, G. W. Hill, R. E. Edwards |
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| Rok vydání: | 2002 |
| Předmět: | |
| Zdroj: | Journal of Applied Ichthyology. 18:617-620 |
| ISSN: | 1439-0426 0175-8659 |
| Popis: | Summary Gulf sturgeon (Acipenser oxyrinchus desotoi), as well as many other sturgeons, frequently jump out of the water. It is not known why they jump and expend energy during their nonfeeding residency in freshwater rivers, but many explanations have been proposed. In the present study, it is hypothesized that jumping is a form of group communication that serves to maintain group cohesion. Information was collected on seasonal and diurnal temporal patterns of jumping at a known sturgeon aggregation ‘holding’ area; jumping sounds were recorded and analyzed to test this hypothesis. Jumping was found to vary seasonally, with number of jumps every 0.5 h much higher in June than during other months in which observations were made (April, May, August, and September in 2000 and 2001). Over 1000 jumps per day were recorded in a short (0.8 km) stretch (at river kilometer 61) of the Suwannee River in northwestern Florida. Jumping activity peaked near dawn and to a lesser degree near sunset in months other than June. The June jumping rate (jumps per 0.5 h) did not show a distinct dawn peak, although it was lowest during midday. Jumping sounds were recorded on a digital video/audio recorder attached to a hydrophone. Video images of sturgeon jumps were used to register specific sounds with specific components of the jumping action. Sonograms of sturgeon jumping sounds were compared and found to be distinct and different from sounds of other fish jumping or from objects dropped into the water for comparative purposes. These results are consistent with the hypothesis (but not to the exclusion of other hypotheses) that jumping is a form of communication. |
| Databáze: | OpenAIRE |
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