Tippin Boulders at Tower Beach

Whose hiding all the crabs?

Have you ever wondered whether the size of rocks on the beach have an impact on the number and size of crabs living under them? Probably not. However, as biologists we have a way of taking sometimes mundane topics and making them exciting, even for those who didn’t know they were interested. On Thursday afternoon our class travelled down to tower beach and sought out to find the answer to this question and several others. It started off very scientific, counting and taking measurements of crabs but once all of the science was out of the way it became a competition among our group of who could catch the biggest and most beautiful crabs. As we learned through our competition and later statistical analysis, the size of the rock surprisingly did not have a direct impact on the size or number of crabs living underneath. This could be explained by certain rocks having a more desirable habitat underneath. Much like how Canada is larger than the United States but the population is much lower due to an undesirable habitat (SNOW)!

Where have all the good grazers gone?

Another question was whether the density of grazers was different under rockweed versus out in the open. This proved to be a difficult task because the snails were much smaller than I had imagined and several dozen could be found amongst the rockweed. However, trying to find and accurately count all of them was like trying to find a needle in a haystack. Nevertheless we did as all good scientists do and counted our snails with considerable inaccuracy which would later be accounted for in errors section of the lab report. Within our group we found that grazers definitely had a tendency to hide out in the rockweed. However, when the group data and analyzed the results were “statistically insignificant” meaning our findings showed no preference for either. I had thought snails would prefer hiding in the rockweed but I guess there are other more important things drawing them out into the open!

What Now?

Now I don’t know about you but I can’t get enough of Tower Beach and all it has to offer. Another interesting expansion one of the topics discussed is which type of rockweed in particular grazers prefer. Although we never had a chance to test this ourselves, the following link is to an article that tests whether snails prefer native species of rock weed or invasive species. Even better, if you’re as interested in marine biology as I am just “crab” yourself a bucket and some calipers and go hunting. Ask a question, formulate a hypothesis and go find out the answer for yourself!



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