As of February 2025, 323 IMMAs have been identified following the hosting of eleven expert workshops in the regions represented in Table 1 below. There are an additional 196 Areas of Interest (AoI). Details of all these are in the searchable database and displayed on the e-Atlas. Table 1 shows the number of IMMAs by region.
Table 1 – Summary of the number of IMMAs and AoI by Workshop
IMMA size
There is a huge range in size among different IMMAs, the largest is 11,818,614 km2 encompassing an area North Atlantic Humpback Whale Migratory Corridor in the North West Atlantic Ocean, and the smallest is 1 km2, the São Pedro and São Paulo Archipelago IMMA which hosts a very small population of common bottlenose dolphins (Tursiops truncatus).
Criteria used to identify IMMAs
Table 2 provides a summary of the criteria that have been used to identify IMMAs: Criteria C, Key Life Cycle Attributes, which includes migration routes, reproductive areas and feeding areas has been the most frequently used criterion, and Criterion D, Special Attributes has been the least frequently used.
Table 2 – Summary of the criteria used to identify the 323 IMMAs identified as of February 2025 (note that one IMMA can meet multiple criteria, so the totals in the table are greater than 323).
Figure 1 shows the number of IMMAs broken down by the sub-criterion applied. After Criterion A (Species or Population Vulnerability (21.5%), the most frequently used sub-criteria were C2 (Feeding Areas) (16.2%) and C1 (Reproductive Areas) (15.5%).
Figure 1 – Number of IMMAs broken by subcriteria
Qualifying Species in each IMMA
The documentation for each IMMA includes a list of the qualifying marine mammal species that occur and that are fundamental to satisfying each criterion used in the IMMA identification. Supporting 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 qualifying species listed for each IMMA. The majority were identified on the basis of one or two qualifying species.
One hundred and nineteen different marine mammal species (subspecies included) have been used as the qualifying species for an IMMA. As shown on Figure 3, Humpback whales (Megaptera novaeangliae), Common Bottlenose dolphins (Tursiops truncatus), Sperm whales (Physeter macrocephalus), Blue whale (Balaenoptera musculus), Common dolphins (Delphinus delphis) and Fin whale (Balaenoptera physalus) were the most commonly represented species.
Figure 2 – Number of qualifying marine mammal species listed for each IMMA
Figure 3 – Qualifying marine mammal species used to satisfy the IMMA criteria
