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# Mole Crab Distribution

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## Sungmee Park

on 7 June 2013

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#### Transcript of Mole Crab Distribution

Mole Crab Distribution in Intertidal Zone Methods 1. X by Y transect system (X=from ocean to where wave hits shore, 15 cm; Y=along shoreline, 30 cm
2. After wave receded, sand collected to first ridge of plastic container for each plot
3. No crabs = "o", Results p-value 0.0323 < 0.05
Refute null hypothesis that there is no difference in distribution of mole crabs at different shore heights
Mole Crabs live further from water Discussion Heights 1&2 are statistically different from Height 4
30-45 cm is distance that makes significant difference in mole crab distribution PROBLEMS: Torrey Pines State Reserve Beach
San Diego, CA
5/13/13 -Sungmee Park Histogram of Mean # of Mole Crabs based on Intertidal Zone Heights 4. 4 total X plots + 4 Y plots, 4 heights from water
5. 71 total crabs collected (41 females, 30 males)
6. Tested for normality + analyzed through one-way ANOVA (JMP) orange eggs Female Mole Crab X Y One-way ANOVA:
p-value: 0.0323 Null Hypothesis: The null hypothesis is that there will be no significant difference in distribution of E. analoga at different shore heights Hypothesis: The hypothesis is that E. analoga will aggregate further from the shore Why?: Main predator = fish, so avoid them by living further up to protect themselves and their clutch (if female) Important part of beach ecosystem (fish, birds, sea otters rely on them as food) & intermediate host for parasites + indicator for toxins like DDT and domoic acid Compared Means of Each Height:
B: 1, 2, 3 (not statistically different)
A: 3, 4 (not statistically different) -Harder to get mole crabs at height 1 (closest to water) due to wave activity
-For more accurate results, should study over different wave activity, water temperature, etc.
-Should scoop up sand at once vs. using hands to scoop up multiple times (crabs could have escaped)
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