Science Serving Maryland's Coasts
Raleigh Hood, Ph.D.
Horn Point Laboratory
Automating the Process of Counting the Scyphomedusa, Chrysaora quinquecirrha, in Chesapeake Bay
Due to its painful sting, dense blooms that clog fishing gear and pumps, and voracious predation of mesozoplankton and ichthyoplankton, the sea nettle Chrysaora quinquecirrha, is an important species in Chesapeake Bay. Temperature and salinity influence inter-annual variability in the distribution of sea nettles, but the causes of smaller scale, intra-annual variability, remain unknown. Current efforts at understanding patchiness include visual surface and vertical net-haul counts. Here, we compare the abilities of a digital video camera to capture images of sea nettles at the water surface to those of a human observer in an attempt to automate the observing process so that visual counts could be made more frequently in time and simultaneously at multiple locations to better comprehend this patchiness. Translucent plastic disks were deployed at different depths to determine the limit of the camera's depth of view. The results showed that the camera was not able to visualize the disks as well as an observer on location, and it likely will not provide a quantitative measure of sea nettle abundance; however, we feel that it can be used as a continuous semi-quantitative data collector, and the data can be analyzed for trends in variability of sea nettle abundance.
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