The particular marine mammal species found within an MPA, along with the types and intensities of human activities within an MPA, will drive questions that require the measurement of specific variables. In other words, not every ecological measure will be appropriate or require high-level priority. For example, Stellwagen Bank National Marine Sanctuary is subject to intense shipping traffic. Therefore, large whale movement patterns, as well as underwater noise, are monitored in order to seek a solution to vessel strike and acoustic impacts [3]. Where a whale-watching industry is active, such as in the Canary Islands, behavioural variables will often be recorded [4]. Where terrestrial runoff from agriculture is potentially an issue for coastal habitats, physical water parameters in the marine environment may be of high importance.

The need to monitor specific variables may also vary based on the marine mammal species of interest. While the monitoring of noise is especially relevant to some cetaceans [5], central to dugong or manatee conservation is the monitoring of seagrass abundance [6], for example.