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For my preliminary investigations I surveyed both Castle beach and Jetty beach to see at which height dog whelks were most abundant. At Jetty beach I noticed that the dog whelks were mainly present on the middle shore. From my research I knew that the tide at 11:30 AM was 2.07 m above chart datum. Therefore, I measured the height to the middle shore at 4 m above chart datum by using a clinometer and a meter ruler. I stood at 2.07 m above chart datum and held the clinometer perpendicular to the meter ruler and measured 1 m above chart datum. With the help of my husband I marked the point at 3.07 m above chart datum and then I measured 0.93 m the same way as mentioned up to the area where there was an abundance of dog whelks. I initially planned to lay out a 15 m transect line, however I changed this to 20 m instead so the results are more representative of the shore. At 4 m above chart datum I laid out a 20 m transect line and took my measurements. I repeated the process at Castle beach. In order to measure the length and aperture of the dog whelks I did try to use a 30 cm ruler at first but I found that the Vernier caliper provided more precision and accuracy.
The data that I collected suggests that the length to aperture ratio of the dog whelks at Castle beach is generally smaller compared to Jetty beach. This so far supports my hypothesis. I plan to continue collecting data using the same technique and I will definitely use a Vernier caliper instead of a 30 cm ruler for more precision and accuracy of the measurements.
