Patrick Gibeau, 50917160, lab section A2 Essays - Otters, Fur Trade

Patrick Gibeau, 50917160, lab section A2 I believe that according to the data presented in tables 1 and 2 that sea otter predation on invertebrate abundance is in fact decreased by higher levels of rugosity up to a certain point. In table 1 we are given three different site with varying levels of rugosity. The first site having the lowest levels of rugosity, the second having the most and the third being medium, roughly in between site 1 and 2. The second table provides the abundance of snail, crab and mussel's in a radius of 100m2 in each of the three different sites; both in the absence of the Sea-Otters and after the presence of Sea Otters for three years. If our hypothesis (that the higher the rugosity, the more difficult it is for Sea-Otters to predate upon the invertebrates resulting in a higher abundance) is to be correct we should see a decline in invertebrate abundance in all three of the sites (since the presence of Sea Otters would cause a decline)but scaled so that the largest decline is in site 1 (having the lo west rugosity), the second largest decline in site 3 ( having the second lowest rugosity) and the lowest decline being in site 2 ( having the highest rugosity). Upon inspection of the table 2 we see a reduction in invertebrate population across the board in all three sites. We see a general trend that the most drastic reduction in Crab, Mussel and Snail abundance occurs in site 1 as predicted. Our hypothesis is further supported as table 2 shows that the Mussel and Snail abundance in site 3 is the second least impacted and site 2 is the least impacted. Although the Crab abundance in site 2 and site 3 is somewhat of an anomaly in our table, showing that site 3's crab population was least impacted by the predation of Sea Otters. It still is higher than that of site 1; meaning it still supports our hypothesis, but perhaps indicates that Crabs are less impacted by the Sea Otter's predation in areas with higher rugosity up until a certain point. At a certain point it is plausible that a rugosity that is too great impacts their mobility and prevents them from escaping. All in all, the data shown in both tables give concrete evidence supporting our hypothesis. In summary I believe that Sea Otter predation on invertebrate abundance is reduced by the presence of a higher rugosity, and the data in table 1 and two supports this claim.