Hopkins Marine Station Student Paper

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Title: Behavioral patterns of three intertidal whelks, Nucella emarginata, Acanthanucella punctulata, and Ocenebra circumtexta, in response to tidal variation.
Student Author(s): Eldon, Jon
Faculty Advisor(s): Watanabe, Jim
Pages: 25
Location: Final Papers Biology 175H
Date: June 2004
Abstract: This study examined behavioral patterns of three intertidal whelks in response to tidal variation. Nucella emarginata, Ocenebra circumtexta, Acanthanucella punctulata have widely overlapping habitat but significantly different resource utilization strategies. All three species were found in the primary study site, a 6m by 9m region of rocky intertidal shore with a vertical range of 0 to +2.5m above MLLW. Individuals were marked and observed at low tide for a two week period to discern basic patterns of movement and aggregation. Following this, surveys of microhabitat and activity were taken of the same area at daily high and low low tides for another two weeks. Acanthanucella were highly responsive to tidal patterns with 76% feeding at high tide and only 27% feeding at low. They also fed significantly more on sun exposed patches of barnacles, often horizontal surfaces, during high tide (66% feeding in sun) than during low tide (21% feeding in sun). Ocenebra show a slight but significant tendency to feed less in the sun at low tide (27%) than at high tide (46%). However, the frequency of feeding in shaded areas does not significantly vary with the tide, possibly because these whelks are unique in utilizing undercut habitat. Nucella appear to have the most conservative behavior, feeding the least at high tide (61%) and showing insignificant response to sun exposure and the timing of the low tide.