Why does RAMP work?

RAMP is a whole animal quantitative measure of health and vitality. It integrates several reflex actions that are combinations of neural and muscle function which are immediately responsive to the effects of stressors.  When an animal is exposed to stressors and becomes stressed, various physiological, organ, and behavioral systems respond in adaptive ways to compensate for the disturbance of stress. Initially these stress responses are beneficial, helping the animal avoid stressful situations and stimulating metabolism to support these adaptations. However if stress is prolonged, the animal begins to exhibit metabolic deficits and its health and vitality degrade.

An animal with disturbed states and degraded vitality can quickly become sick, moribund, and eventually die if stress persists at high enough levels. Prediction of animal death or recovery from stress requires measuring whole animal stress disturbances. Measuring disturbances of separate systems that make up the animal does not predict vitality and mortality because the whole animal is what dies, not the separate systems.

RAMP is a combination of several reflex actions that is an ideal predictor of whole animal vitality and mortality because it integrates the immediate effects of stress for the whole animal into involuntary fixed patterns of response that vary only with the vitality of the animal. If voluntary behavior is used as a predictor, other factors not related to animal vitality can control responses, making prediction of vitality difficult.  For example feeding and other social interactions can be controlled by motivation, resource availability, avoidance, and attraction. If component metabolic and organ systems are used as a measure, these do not reflect the whole animal vitality state because they exhibit peak responses to stressor intensities that are not related to stress levels in the whole animal.

Getting started with RAMP

How do you get started with RAMP?  Recently I sent an e-mail to a researcher with this question on bycatch in a purse seine.  My answer follows.  Good to hear from you.  Sounds like you have some bigger fish to work with.  Sample sizes depend on what you are going to accomplish and the effect size anticipated.  1) The first tasks are to get fish in good condition, lean how to hold them in good condition, and then to establish a RAMP curve.  Get as many fish as you can comfortably hold and maintain.  Then 2) establish reflex actions that can be tested consistently and that respond consistently and strongly.  Find as many testable reflex actions as you can as this makes a more refined RAMP score.  See Davis 2010 and Raby et al. 2012 papers for detailed information.  For larger salmon that are difficult to handle, Raby tested without a restraining device: 
"Each reflex was assessed categorically (0 = unimpaired, 1 = impaired) in a conservative matter – that is, if the handler had doubt as to whether the reflex was present, it was recorded as being impaired. Reflexes tested were the following: tail grab, body flex, head complex, vestibular-ocular response (VOR) and orientation. Presence of the tail grab response was assessed by the handler attempting to grab the tail of the fish with the fish submerged in water (in a fish bag or holding trough); a positive response was characterized by the fish attempting to burst-swim immediately upon contact. The body flex response was tested by holding the fish out of water using two hands wrapped around the middle of the body. The fish actively attempting to struggle free was characterized as a positive response. Head complex was noted as positive if, when held out of water, the fish exhibited a regular pattern of ventilation (for 5 s) observable by watching the opening and closing of the lower jaw. VOR was observed by turning the fish on its side (i.e. on a lengthwise axis) out of water. Positive VOR was characterized by the fish’s eye rolling to maintain level pitch, tracking the handler. Finally, upon release, each fish was placed upside-down in the river just below the surface: a positive orientation reflex was noted if the fish righted itself within 3 s. The entire reflex assessment took 20 s to complete and was always conducted on fish upon release. If a fish was too vigorous to allow researcher handling and assessment of reflexes, it was assigned an unimpaired status for all reflexes."  
Then 3) once consistent reflexes are identified and tests are finalized, a RAMP curve is constructed which establishes the relationship between reflex impairment and mortality.  This is the scoping process that establishes what stressor intensities will kill fish and what are sub-lethal and produce lesser RAMP scores.  This process involves exposing fish to a range of capture stressor intensities of interest.  For purse seine capture this may include net abrasion time (extent of injury) and air exposure time (extent of hypoxia) and temperature if there are enough fish to test.  The stressor range should induce reflex impairment and mortality that ranges from no impairment and mortality to complete impairment and mortality.  In this way, the RAMP curve covers all possible outcomes for the fish.  If possible, the most efficient use of limited fish is to expose and tag individual fish so that for each individual, a RAMP score can be assigned to a specific stressor intensity.  4) Once you have a RAMP curve, you can test fish in the field for RAMP, note their capture conditions, and predict mortality based on RAMP and also on capture conditions.  

Initially you will need at least 10 fish to construct a RAMP curve, more (20 fish) is better as it will give you a curve with tighter confidence bounds.  For a simple example lets say that fish die after 15 min in air.  So exposures might look like this: fish 1- 0 min air, fish 2 - 2 min air, fish 3 - 4 min air, fish 4 - 6 min air, fish 5 - 8 min air, fish 6 - 10 min air, fish 7 - 12 min air, fish 8 - 14 min air, fish 9 - 16 min air, fish 10 - 18 min air.  If injury is important you might do a combination of net holding and air exposure.  Expose the fish to the assigned stressor, test the fish for reflex impairment, then hold the fish and observe for delayed mortality.  Holding time vary with species and usually range from 3-11 days.

The beginning of RAMP

I was researching the effects of capture and release of non-target commercially important fish species, commonly know as bycatch. The research was aimed at understanding what happens to fish when they are captured in commercial fishing gear and then released because of fishing regulations. The question is important because fish that are stressed by capture and release often show delayed mortality and this source of mortality is difficult to measure and account for in management of fish stocks.  Results of this research were summarized in an article published in 2002.

Because delayed mortality cannot be observed directly, some kind of measure of the animal's vitality prior to release needs to be developed for prediction of delayed mortality. Our team tried to relate blood plasma variables, measures of physical injury, and complex voluntary behavior with delayed mortality. However these measures were not correlated with immediate or delayed mortality.  

One day while watching fish recover after exposure to simulated fishing capture, I began to think about the fact that the intensity of fish involuntary behavior after capture appeared to be negatively related to the intensity of the capture stressor. Fish subjected to more intense capture stressors became more lethargic and their involuntary behavior was more impaired. These involuntary activities are known as reflex actions and represent fixed involuntary actions that occur in response to external stimuli such as gravity, bright light, loud sound, or touch. The reflexes can be part of important behavior such as startle, orientation, predator avoidance, feeding, migration, and sex.

So I decided to measure and quantify reflex actions and to try to correlate impairment of these actions with delayed mortality. This idea of measuring a suite of reflex actions and correlating the measure with mortality was very successful and I called it RAMP - reflex action mortality predictor. The development and deployment of RAMP is described here, here, and here.

Since that original work, other researchers have used the RAMP approach to quantify stress and predict delayed mortality in a variety of fish and invertebrate species. I will describe their work in future posts.