We're working with the lovely garden eels: snake-like fishes that live in big colonies, attached to the sandy sea bottom. They feed on plankton and hide in their burrows whenever something big approaches. Here's a small video of them: https://www.youtube.com/watch?v=v2WEkd9qMlw

To test whether they're using social information in their evasive behaviour, we found an edge of the colony and, after satying put for 3 minutes to ensure they were not hiding at that point, one of us slowly approached until the first eel retracted. We marked that point as our zero. Then, we marked the positions where the closest and farthest eels hide. We then measured the distances between our zero and the closest (Ri), and farthest (R1) points.

Now, our null hypothesis is that if Ri and R1 are equal, the information (the evasive behaviour) is not spreading, and therefore there's no use of social information. Our H1, then, is that if information is spreading, R1 > Ri. As every pair of R1 and Ri was taken at the same time, respect to the same point of reference (zero), and our data did not pass the Shapiro normality test, we're considering a paired Wilcoxon test. Is this appropiate? Our sample size is 68.

Thank you in advance.