The documentation for each IMMA includes a list of the primary marine mammal species that occur and that are fundamental to satisfying each criterion used in the IMMA identification. Secondary species are marine mammal species that occur within the IMMA but which are not fundamental to satisfying the criteria. Figure 2 shows the number of primary species listed for each IMMA. The majority were identified on the basis of one or two primary species.
Thirty-nine different marine mammal species have been used as the primary species for an IMMA. As shown on Figure 3, humpback whales (Megaptera novaeangliae), spinner dolphins (Stenella longirostris) and dugongs (Dugon dugon) were the most commonly represented species.