I have a set of percent data on histological abnormalities in fish gills and I need to compare the results between two sites A and B. We analyzed abnormalities in lamellae of a particular gill arch. For example for fish 1 we counted 500 lamellae and noted the number that had abnormality Y. The majority of the data is 0%. That is, in most fish, the lamellae counted had no such abnormality present. Obviously when I try different transformations the distribution does not change because of all the 0s (I have attached a graph of the distribution of the data). I do not know how to analyze this data.