The dissection begins by inserting a fine scalpel blade into the anus (also called the vent) of the fish. The Blue Mackerel's anus is located just anterior to (in front of) the anal fin, on the ventral (lower) side of the fish. This is also the case for most fishes, but some, for example the pearlfishes (familiy Carapidae), the anus is located well forward on the throat.
