Mortality sources and the limits of RAMP

Exposure of animals to stressors can result in changes to physiology, behavior, and injury that can result in stress, impaired reflex actions, morbidity, and delayed mortality.  Stressors in fishing, aquaculture, net penning, aquarium trade, research settings, and other ecosystems are present in a number of ways as departures from nominal temperature, light, oxygen, food, xenobiotics, injury, crowding, disease, social interactions, and predators.

While reflex impairments and RAMP can accurately assess vitality and stress levels and predict delayed mortality, these measures are solely dependent on the internal state of an animal at the time of observation.  When other external stressors and sources of mortality are present after an animal is assessed with RAMP, predictions of delayed mortality may not be accurate.

In open, wild ecosystems, important sources of mortality in animals can be predation, lack of food or feeding ability, and impairment of social behavior that is protective (schooling, shoaling, and shelter seeking).  The presence of any or all of these stressors can alter mortality rates predicted by RAMP.  Use of RAMP for predicting delayed mortality in open systems is probably limited to short term delayed mortality.

In closed, human managed ecosystems, external sources for delayed mortality can be controlled and eliminated after RAMP measurements and RAMP predictions of delayed mortality can be accurate over longer time periods.