A bigger picture: factors and traits that contribute to vitality and survival of discards in fisheries

ICES WKMEDS4 report (2015)

A conceptual model for discard survival in fisheries is developed in the ICES WKMEDS4 report (2015). In this concept, survival is linked to species sensitivity, injury, and predation, through fishing factors, environment, and size. The expanded view shows potential factors and traits in more detail.

ICES WKMEDS4 report (2015) Click on images.

Importance of context for RAMP curves used to predict mortality and survival of stressed animals

Relationships between reflex/buoyancy impairment and post-capture mortality for Atlantic cod (Humborstad et al. 2016).

Humborstad et al. (2016) looked at the relationship between reflex/buoyancy impairment and post-capture mortality for Atlantic cod exposed to fishing stressors. RAMP curves were generated for (a) fish exposed to laboratory simulated forced swimming, air exposure, and net abrasion, (b) field longline capture, and (c) field pot capture. The authors concluded that:

“It appears that specific RAMP curves may be needed for gears that involve different stressors, including consideration of any additional stress associated with captive observation of delayed mortality. Differences in stressors and holding conditions certainly reduce the general applicability of RAMP across different stressors and fisheries. However, once a RAMP curve has been established for a specific set of stressors or gears, the strong relationship between reflex impairment and mortality shows the potential for predicting mortality outcomes, especially at high and low levels of impairment.”

“Reflex impairment could predict mortality among fish caught by pot and longline. However, different RAMP curves were observed between laboratory and field conditions, indicating that careful consideration must be given to the types of stressors present and captive-observation conditions for delayed mortality when comparing RAMP curves for different fisheries. The inclusion of buoyancy status in modelling greatly improved mortality predictability.”

Science and medicine generally do not know proximate and ultimate causes for why fish and other animals die. This lack of mechanistic knowledge precludes us from direct understanding and prediction of death. However, we can observe correlates with death; animal size, stressors, vitality impairment, and physiological impairment. These correlates can be used to identify risk factors and predict immediate and delayed mortality. 

Successful mortality and survival prediction requires that the context of animal exposure to stressor risk and recovery be included in any experimental analysis of this problem.  We cannot simply identify stressors, impairment, or physiological numbers and say that they will result in a particular mortality (Davis 2002). RAMP curves clearly show the importance of context for exposure to stressors and potential mortality or survival (Davis 2010). The question of interactions among stressors and their context has recently been elaborated for freshwater and marine systems (Jackson et al. in press).

Human delayed mortality can be predicted using olfactory impairment

Olfactory impairment in humans was measured by error rate in olfaction tests. Increasing number of errors in olfaction tests were related to increasing 5-year mortality rates in a logistic regression (PLoS ONE). 

The human logistic relationship between olfactory impairment and 5-year delayed mortality is a powerful method for predicting delayed mortality and is similar to other animal RAMP relationships between reflex impairment, injury, and delayed mortality. Olfactory impairment can be easily measured in human and animal clinical settings and can easily and automatically be measured in aquaculture contexts by analysis of animal distributions and activity in rearing facilities. Given the fundamental nature of olfaction, one would expect the relationship between olfactory impairment and delayed mortality to be generally present among animal phyla and this can be tested in clinical and field settings.

Pinto et al. 2014 state, “We are the first to show that olfactory dysfunction is a strong predictor of 5-year mortality in a nationally representative sample of older adults. Olfactory dysfunction was an independent risk factor for death, stronger than several common causes of death, such as heart failure, lung disease and cancer, indicating that this evolutionarily ancient special sense may signal a key mechanism that affects human longevity. This effect is large enough to identify those at a higher risk of death even after taking account of other factors, yielding a 2.4 fold increase in the average probability of death among those already at high risk (Figure 3B). Even among those near the median risk, anosmia increases the average probability of death from 0.09 (for normal smellers) to 0.25. Thus, from a clinical point of view, assessment of olfactory function would enhance existing tools and strategies to identify those patients at high risk of mortality.”

(PLoS ONE)

The human study controlled for the mortality effects of age, gender, socioeconomic status, and race. Additionally, “We excluded several possibilities that might have explained these striking results. Adjusting for nutrition had little impact on the relationship between olfactory dysfunction and death. Similarly, accounting for cognition and neurodegenerative disease and frailty also failed to mediate the observed effects. Mental health, smoking, and alcohol abuse also did not explain our findings. Risk factors for olfactory loss (male gender, lower socioeconomic status, BMI) were included in our analyses, and though they replicated prior work [41], did not affect our results.” Note that the study did not control for effects of possible episodic exposure to toxins or injury that may result in temporary or permanent olfactory impairment not related to death.

Olfactory response is an involuntary response to a stimulus, and may be considered a reflex action. In the human study, presence or absence of smell detection for rose, leather, orange, fish, and peppermint were summed and related to delayed mortality. Olfactory responses to various substances can be scored as present or absent and summed to predict delayed mortality. In the same way, the RAMP method is an example of presence-absence scoring with summation of reflex impairment and injury scores to predict delayed mortality.  Measuring and summing whole animal responses, i.e., olfaction, reflex actions, and injury to stimuli is a powerful method for observing the effects of stressors and aging on delayed mortality.   

“We believe olfaction is the canary in the coal mine of human health, not that its decline directly causes death. Olfactory dysfunction is a harbinger of either fundamental mechanisms of aging, environmental exposure, or interactions between the two. Unique among the senses, the olfactory system depends on stem cell turnover, and thus may serve as an indicator of deterioration in age-related regenerative capacity more broadly or as a marker of physiologic repair function [13].”

Clearly, measurement and summation of presence-absence for whole animal involuntary characteristics (olfaction, reflex actions, and injury) is a powerful way to predict delayed mortality in humans and other animals.

Cautionary tale of rockfish barotrauma and survival: looks can be deceiving

 Yelloweye rockfish, ADFG

Canary rockfish, WDFW

Canary and yelloweye rockfish were captured by Hannah et al. 2014 at 46-174 m depth, retrieved to the surface, and then submerged to depth in specialized sea cages for evaluation of survival.

The authors state, “The external physical signs associated with extreme expansion and retention of swimbladder gas (pronounced barotrauma), including esophageal eversion, exophthalmia and ocular emphysema, were common for both species at these capture depths and were more frequent than in prior studies conducted at shallower depths. Despite similar frequencies of most external barotrauma signs, 48-h post-recompression survival of the two species diverged markedly as capture depth increased. Survival of yelloweye rockfish was above 80% across all capture depths, while survival of canary rockfish was lower, declining sharply to just 25% at capture depths greater than 135 m. Fish of both species that were alive after 48 h of caging displayed very few of the external signs of pronounced barotrauma and had a high submergence success rate when released at the surface.”

Survival and submergence success of canary and yelloweye rockfish, Hannah et al. 2014

Difficulty for evaluating vitality and potential survival by observing barotrauma symptoms and reflex actions is outlined by the authors. “The divergence of 48-h post-recompression survival of canary and yelloweye rockfish as depth of capture increased beyond 135 m shows how difficult it can be to evaluate the survival potential of rockfish with barotrauma based on their appearance at the surface. Most specimens of both species captured at these depths showed some signs of pronounced barotrauma, yet nearly all of the yelloweye rockfish survived following recompression while many of the canary rockfish perished as capture depth increased beyond about 75 m. Studies of post-recompression release behavior also support the notion that surface observations are not indicative of survival, at least for rockfish that tend to retain most of their expanded swimbladder gas (Hannah and Matteson, 2007; Hannah et al., 2008a). The retained gas can make it very difficult or impossible for rockfish to submerge (Hannah et al., 2008b; Hochhalter, 2012) and interferes with the evaluation of reflex behaviors, which have been shown to be useful predictors of survival in other captured and discarded fishes (Davis, 2007; Davis and Ottmar, 2006).”

With regards to stock management, the authors state, “The estimates developed in this study can be very useful for informing the management of hook-and-line fisheries that encounter these two overfished species, especially in combination with data on submergence success as a function of capture depth, like that provided by Hochhalter (2012) for yelloweye rockfish. For example, a primary recommendation from prior studies of post-recompression survival and submergence success for these two species was that hook-and-line fishers should use a variety of “descending” devices to help released fish overcome surface buoyancy (Theberge and Parker, 2005; Hochhalter and Reed, 2011; Hannah et al., 2012; Hochhalter, 2012). The data from this study suggest that descending devices may have a positive effect on survival of yelloweye rockfish across a wide depth range (Fig. 6, lower panel). However, for canary rockfish captured at depths greater than 135 m, survival may be so low that it might be better to either allow retention of these fish or to simply not allow a fishery to operate at these deeper depths (Fig. 6, upper panel).”

Allostasis and it's correlate vitality; measured with reflex action impairment and injury

Figure 1. Alternative models of regulation. Homeostasis describes mechanisms that hold constant a controlled variable by sensing its deviation from a “setpoint” and feeding back to correct the error. Allostasis describes mechanisms that change the controlled variable by predicting what level will be needed and then overriding local feedback to meet anticipated demand, Sterling (2003).

Physiological regulation is considered the cornerstone of animal survival and avoidance of death. Inability to regulate is indicated by vitality impairment and causes an animal to exceed its capacity for life. To understand and predict the causes for survival and death, we must be able to measure appropriate state and rate variables involved in regulation. The generally accepted model of physiological regulation is homeostasis, based on the concept of stability through constancy. However homeostasis is unable to explain accumulating medical evidence that physiological variables do not remain constant. Clearly a more comprehensive model of physiological regulation is needed.  

Allostasis is a model of physiological regulation based on the concept of stability through change (Sterling 2003). Allostasis is able to account for evidence that physiological variables are not constant. The allostasis model connects easily with modern concepts in sensory physiology, neural computation, and optimal design, to produce anticipatory regulation. Allostasis was developed with the recognition that the goal of regulation is not constancy, but rather fitness under natural selection, that implies preventing errors and minimizing costs. Both needs are best accomplished by using prior information to predict physiological demand and then adjusting all variables to meet it. In allostasis an unusual variable value is not a failure to maintain a setpoint, but is a response to some prediction made through perception or prior knowledge. Constancy is not a fundamental condition for life. A mean value need not imply a setpoint but rather the most frequent demand.

The brain has close access to essentially every somatic cell through nerve cell connections. The broad metabolic patterns over short and long time scales, and under mild as well as emergency conditions are controlled by the brain. In other words, the brain regulates both physiology and its supporting behavior (Sterling 2003). The use of reflex action impairment to measure vitality and predict survival and mortality is consistent with the allostatic model because it is representative of key elements of physiological regulation; including perception, behavior, and neural control of somatic cell function. Injury also measures vitality impairment because of its direct effects on neural and somatic cell function, hence allostasis. 

Reflex action impairment and injury can measure vitality and predict survival and mortality in taxa ranging from invertebrates to humans. Clearly the presence of higher brain function is not a necessary condition for the allostatic model. Instead, simple interactions of neural and somatic cells can produce allostasis regulation and its correlate, vitality. It remains to elucidate the comparative details of physiological regulation as it developed in new phyla through evolutionary time.

When studying the causes for death, shifting focus from measurement of lower level plasma variables (cortisol, lactate, glucose, O2, pH) to higher level variables (vitality in its various guises) would advance the assessment of physiological regulation and its role in survival and death. Particular values for plasma variables are of secondary importance, until reaching outer limits of operation. The interactions of plasma variables are of primary importance (Ellis and Del Giudice 2014). The homeostatic model fails to capture the importance of stability through change; how animals adapt and ultimately go beyond their physiological limits. The allostatic model addresses stability through change and invites adaption and evolutionary fitness.

Reflex action impairment is probably a biomarker for impairment of physiological regulation and this is why the RAMP curve is non-linear, reflecting the inflection point where physiological regulation is lost and death results. Addition of injury to RAMP adds details of direct injury effects on physiological functioning and regulation, e.g. compromising integument gatekeeping (skin, gut, gill, lung).

On the importance of considering sublethal stress and injury effects in discard and escapee survival and fitness

Shark release, NOAA

Sublethal stress and injury are important factors to consider in discard and escapee survival and fitness (Wilson et al. 2014). Fishing gears are often designed to enhance escape of animals that might otherwise become bycatch. Captured animals are discarded from fisheries for economic, regulatory, conservation ethic, and political reasons. Observation of animal impairment (Davis 2010) and immediate mortality for discards on board fishing vessels is straightforward. For animals that are alive when discarded or that escape from fishing gear, the effects of stress and injury can alter behavior, growth, and reproduction, or result in delayed mortality. Delayed mortality of escapees (Suuronen 2005) and discards (Revill 2012) has been documented for commercially important species. However, few studies have measured potential fitness effects of sublethal stress and injury on surviving discards or escapees.

Fig. 1. Conceptual diagram outlining the immediate and long-term effects of escape or release from commercial fishing gear and how it relates to each level of biological organization. Question marks (?) denote areas for which no primary literature exists, and present future avenues of research (Wilson et al. 2014).

Sublethal effects of capture, escaping, and discarding can occur at individual, community, and population levels of organization. For individuals, immediate sublethal effects are physiological responses, injury, and reflex impairment. Delayed sublethal effects are behavioral impairment, altered energy allocation, wound healing, immune function and disease, reproductive success, and offspring quality and performance. Few studies have been conducted for responses at community and population levels, and clearly these are important to consider.

Wilson et al. 2014 summarize:

“The obvious gap that emerges is the lack of research linking at-release measurements with latent sublethal fitness outcomes such as foraging, energetics, growth, reproduction and offspring quality. The dearth of knowledge in this area is likely based on two realities: (1) a justifiable focus on simply quantifying and reducing bycatch mortality, and (2) the difficulty of long-term monitoring of fitness outcomes in wild animals. Of the reviewed studies, several indicated that physiological disturbance, injury or behavioural impairments may have had long-term implications for growth and reproductive fitness. Further study of sublethal effects could clarify previously unaccounted-for population level consequences of fisheries and better conservation practices to mitigate the impacts of fisheries.”

Also of importance to discard survival and fitness is consideration of predation that can occur after escape or discarding of captured animals (Raby et al. in press). Controlling factors for predator-induced mortality include fishery type, stress and injury, barotrauma, predator behavior and abundance, fish size, and temperature. Summary of the Raby et al. review suggests research directions:
  “The important first step is for fishers, managers and researchers to identify systems where predation is likely to be a substantial contributor to unobserved fishing mortality. Most study of capture-and-release mortality involves quantifying the effects of factors such as temperature, capture depth or fight time. Predator type and abundance could be considered new ‘phantom’ factors that are dynamic and would be challenging to incorporate into research. A conservative approach would be to assume a constant level of predation threat for a given fishery and focus on examining the capacity of released fish to evade predators and the accompanying rates of predator-induced mortality. PRP is a unique contributor to mortality because it is probably most often characterized by a short period (minutes or hours) of risk, which could simply be overcome by using pre-release techniques that reduce the impairment of fish being released (Farrell et al. 2001; Broadhurst et al. 2009).”

Future studies that can be used to assess the presence of delayed sublethal fitness effects in fisheries escapees and discards include allostasis, biotelemetry, reproductive success of individuals, measurement of genetic material contributions to next generations, and tank or net pen holding studies to determine behavior, growth rates, and reproduction. In all these types of studies, ongoing collection of fisheries observer data on reflex impairment and injury using a vitality scoring system (RAMP) would be needed to link vitality scores of at-release discards or escapees back to fitness outcomes for individuals.

Reflex impairment can measure sublethal effects of temperature, hypoxia, and injury

Epaulette shark, Aquarium

The epaulette shark is a tropical reef shark that can live in an environment with cyclical periods of low oxygen concentration and high temperature (Wise et al. 1998). After exposure to hypoxic conditions, epaulette shark reflex actions were tested, including righting, response to touch, rhythmic gill movements, rhythmic swimming, and movement of diagonally opposed fins for locomotion. Reflex actions were not impaired by hypoxia, suggesting that animals were adapted to reef conditions and would not show maladaptive responses to hypoxia. Subsequently, this species was found to have important adaptations to hypoxia (Soderstrom et al. 1999, Hickey et al. 2012).

Animal responses to stressors can be adaptive or maladaptive. When animals are exposed to stressor types or intensities for which they are not adapted, stress responses can be too much of a good thing. Adaptive responses help the animal move away from and avoid stressors to return to normal unstressed behavior and homeostatic states. Maladaptive responses cause the animal to become more stressed and eventually can result in morbidity and mortality. 

Adaptive and maladaptive responses of crustaceans to stressors and stress, Stoner 2012

Reflex impairment is an ecologically relevant measure of vitality loss, fitness, and the spectrum of adaptive and maladaptive responses to stressors. Measurement and summation of a suite of reflex actions (as in the case of RAMP or barotrauma modified RAMP) is a powerful means for testing experimental hypotheses about the effects of stressors on animals. For aquatic animals, temperature (elevated or depressed), hypoxia, and injury are important master variables associated with stress induction (Davis 2002, Suuronen 2005, Gale et al. 2013).

The key to testing for vitality, stress, and fitness using reflex actions or barotrauma symptoms is to derive an emergent index for reflex impairment by summing presence or absence of many individual actions or symptoms. The resultant emergent impairment index (RAMP) is a powerful synthesis of the many mechanistic systems (behavior, physiology, neural, muscle, organ) that have been identified in a whole animal. RAMP expresses, with quantitative data, the resultant vitality and health state of the animal.

Some examples of relationships between reflex impairment and temperature, hypoxia, and injury are illustrated below. In these examples reflex impairment was significantly different among stressor treatments and was related to the severity of stressors.

Reflex impairment in crabs exposed to low temperature, Stoner 2009

Reflex impairment in Atlantic cod exposed to hypoxia, Humborstad et al. 2009

Reflex impairment in coho salmon exposed to hypoxia, Raby et al. 2012

Reflex impairment in sockeye salmon exposed to injury from different gear types, Donaldson et al. 2012

Reflex impairment in blue rockfish exposed to injury from barotrauma, Hannah et al. 2008

Using RAMP to help automate aquaculture operations

Net pen for fish culture (NOAA).

Aquaculture of animals in tanks and net pens requires monitoring and maintenance of vitality, health, and normal behavior for efficient and economic operations. Presently, health is monitored by sampling for disease outbreaks, while vitality and behavior are observed by aquaculture technicians during the course of their daily activities of feeding, cleaning, and operation of facilities.

Inside net pen for fish culture (NOAA).

In tanks and net pens, animals can swim and feed normally. They can also respond to stimuli administered inside their rearing environment, such as light flashes, sound bursts, food scent, and touch. Responses to these stimuli can be in the form of reflex actions such as startle, orientation, depth distribution, aggregation, and dispersal. These reflex responses can be observed remotely and automatically using video, infra-red, and sonar technology in light and dark conditions. Reflex responses can be recorded and summed as RAMP scores for measures of impairment and correlation with mortality.

RAMP can be a quantitive measure of animal state and be used to help automate aquaculture monitoring and maintenance. When impaired responses to stimuli are observed, alarms can be triggered and technical staff can be alerted to changes in animal vitality, health, and behavior. Then on site alteration of operations can bring rearing conditions back to nominal states and return animals and their reflex actions to vitality and health.

Future research in aquaculture can consider the use of RAMP and automated reflex testing for development of efficient operation protocols and quality assurance. RAMP can also be used as a research tool for testing and validating new designs for aquaculture operations that optimize animal vitality and health.

Pink and Chum Salmon reflex impairment at spawning grounds

A study by Raby et al. 2013 has shown remarkable resilience by Pink and Chum Salmon to simulated fisheries capture stress incurred upon arrival at spawning grounds.  These salmon species were observed to have low mortality and successful spawning after being stressed by exposure to exhaustive exercise, air, and injury.  In the authors words:

"Our study results provide evidence that, after reaching spawning areas, both Pink and Chum Salmon may be resilient to certain forms of capture-related exhaustion stress. Short of producing immediate mortality through extended anoxia, Pink and Chum Salmon are apparently able to recover from substantial physiological disturbance related to capture and ultimately spawn. Natural prespawn mortality rates for Pink Salmon (6.5%) and Chum Salmon (3.2%) in the channel during the study year (R. Stitt, Fisheries and Oceans Canada, personal communication) were nearly identical to the prespawn mortality rates for fish subjected to our capture and tagging procedures."

One of the objectives of the study was to test for possible relationships between reflex impairment (RAMP) and mortality.  However because of the general lack of mortality in these salmon species just prior to spawning, increasing reflex impairment as RAMP was related to increasing intensity of capture stressors and not to mortality or spawning success.   

Patterns of impairment are shown by the authors:

"The pattern of impairment of individual reflexes with successively increasing levels of overall reflex impairment (RAMP scores) was largely consistent. Tail grab and body flex were by far the two most easily impaired reflexes (Tables 2, 3). However, in Chum Salmon, tail grab impairment predominated body flex impairment at low RAMP scores (0.2, 0.4) compared with Pink Salmon. Orientation was typically the third reflex to become impaired for both species when overall RAMP score increased beyond 0.4 (Tables 2, 3). We did not commonly observe VOR impairment, which was almost always the last reflex impaired."

The authors suggest that radical shifts in metabolism during preparation for spawning may be responsible for the observed resilience to simulated capture:

"We hypothesize that Pink and Chum Salmon are resilient to capture-related exhaustion upon reaching spawning areas because of a combination of low water temperature (about 12^◦C in this study) and a physiological shift towards increased use of anaerobic pathways during their final weeks of life. The capture and release of fish arriving at the spawning ground does not appear to influence survival, in contradiction to the results of other studies, which focused on earlier components of Pacific salmon spawning migrations."

The possible shifting of metabolic pathways in prespawning Pink and Chum Salmon, associated with lack of mortality at high levels of reflex impairment is a cautionary tale for use of RAMP to predict vitality, mortality, and spawning fitness. The relationships between reflex impairment, metabolic pathways, and life history traits are important subjects for future research and validation.  

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.

Reflex impairment in dogs, birds, and turtles

Reflex impairment in animals treated by veterinarians (dogs, cats, birds, rabbits, and livestock) is widely tested as part of a neurological examination to determine the potential presence and location of neurological impairment. The neurological exam consists of tests on mentation, posture and gait, cranial nerves, proprioception, spinal reflexes, and sensory pain perception.  Detailed summaries of these test procedures can be found here and here. In the veterinarian context, results of these neurological exams are generally confined to determination of whether the nervous system is affected in a disease process and to provide an accurate anatomic diagnosis when the nervous system is affected.  Consideration of contributions to disease by neurologic, medical, and orthopedic sources are differentiated into separate testing protocols for the purpose of formulating diagnosis and treatment plans. 

 Clippinger et al. 2007

Vernau et al. 2007

The veterinarian sequence of neurological testing in dogs and cats has been applied to sea turtles.  Results of the study showed that many of the neurological methods for dogs and cats can be adapted for use in sea turtles. The authors concluded that a standardized neurologic examination resulted in an accurate assessment of neurologic function in impaired sea turtles and could help in evaluating effects of rehabilitation efforts and suitability for return to their natural environment. Another study made a detailed assessment of chelonian health that included measuring reflex impairment as part of emergency and critical care. Measured reflex actions included head lift, cloacal or tail touch, eye touch, and nose touch.

Freshwater turtles have been tested for reflex impairment in an effort to evaluate the effects of submergence and increased temperature in bycatch mortality of three species.

Stoot et al. 2013

The RAMP results from reflex impairment testing in fish and invertebrates suggest that the neurological and reflex state of an animal includes the effects of injury and infection when related to fitness outcomes such as recovery, vitality, morbidity, and potential mortality. This inclusion of fitness effects probably results from the fact that the RAMP method is a scoring system that expresses the proportion of whole animal impairment, calculated based on the presence or absence of a suite of reflex actions.  Shifting focus and perspective from individual mechanistic explanations for disease to comprehensive whole animal measures for vitality can help link reflex impairment with fitness outcomes.

Further study and reflection on human and veterinarian medicine approaches to neurological testing can probably inform selection of reflexes to be used in the RAMP approach for reflex testing.  The interaction of medical and RAMP perspectives for quantifying disease states may result in advances towards understanding how nervous system and reflex function can be a comprehensive indicator of disease and vitality states, combining the effects of injury, infection, and nerve impairment.

Examples of reflex impairment data

Here are some examples of the effects of stressors on reflex impairment and how individual reflex impairment can vary among fish species.

Atlantic cod reflex impairment and mortality occurring after exposure to air for 5 to 20 min Humborstad et al. 2009.

Coho salmon reflex impairment occurring after time in a landed seine net from 3 to 15 min Raby et al. 2012.

Proportion of coho salmon individual reflex impairment at various levels of RAMP Raby et al. 2012.

Proportion of walleye pollock, coho salmon, and northern rock sole individual reflex impairment after towing in a net for 5 min followed by exposure to air for 0 to 15 min. Pacific halibut were towed in a net for 240 min followed by exposure to air for 10 to 30 min Davis 2007.

Proportion of walleye pollock, coho salmon, northern rock sole, and Pacific halibut individual reflex impairment in order of impairment and contribution to total impairment Davis 2010

Different patterns of individual reflex impairment among species suggest hypothesis tests that could be made about the relative development and importance of individual reflexes and how these relate to life history patterns. Walleye pollock and coho salmon are pelagic species while northern rock sole and Pacific halibut are benthic species.

RAMP: from intuition to science

Lets begin with fish, but the discussion applies to all other animals that have reflex actions.  Every fisher, commercial or recreational, intuitively knows and expresses opinions about the vitality of their fish, either in the water or caught. Excitedly proclaiming fish on and then proceeding to catch the fish, admire its size, and then release, sell, or eat the fish. These intuitive observations are grounded in our sense of vitality that is an expression of activity and responsiveness.

Intuitive notions are great for telling fish stories and are notoriously fallible when the size or fight of the fish in question is described to other bystanders. But these notions can lead to a quantitative expression of animal vitality that is grounded in solid, repeatable, and predictive science. How do we do this?

Vitality can be an expression of activity, which is diminished in stressed, lethargic fish.  Stress is an adaptive response to stressors. When fish are stressed too much or for too long, they can become diseased or die, states that do not support healthy populations and species diversity. So this loss of vitality that we intuitively observe can have profound consequences. To understand and ameliorate these consequences, we need good quantitative science.

For the purposes of describing and quantifying animal vitality and its inverse, mortality, we can start with animals in good condition and health that have a full suite of reflex actions and then study how stressors impair reflex actions until the end point of death. We use the presence or absence of reflex actions because these are fixed involuntary actions that are directly related to vitality and not subject to the effects of animal size and voluntary, complex behaviors such as feeding, social interactions, predator-prey interactions, migration, and sex, which can be modified by temperature, light, food availability, motivation, avoidance, and attraction.

We use a calculated quantitative index of reflex impairment, RAMP, that combines the presence-absence scoring of several reflex actions. RAMP is an integrative index that communicates the vitality of a whole animal. Similar reflex-based indices are used in human medicine to evaluate general health, neurological condition, and potential outcomes for coma and other non-communicating patients, as well as for triage of emergency patients.

Identifying appropriate reflex actions is where the imagination expands. We have got to figure out how to "tickle" the animal. What stimuli make it respond in the fixed involuntary patterns we call reflexes? Appropriate stimuli and testing modalities depend on the size of the animal and the logistical constraints of the situation. There are many human examples for inspiration.

Lets look at reflex actions through a continuum of animal size and activity for examples.  This list is by no means complete. Reflex actions can be tested in fish larvae by observing free swimming animal startle, orientation, and avoidance in response to light, sound, food scent, and touching with a probe.  For juveniles, fish can be restrained and tested for body flex upon restraint where fish attempt to escape when restrained, dorsal fin erection in which the fins become erect when fish are restrained, operculum and mouth closure where the operculum or mouth clamps shut when lifted or opened, the gag response where the fish opens its mouth and flexes the body when the throat is stimulated and the vestibular–ocular response (VOR) shown by eye rolls when the body is rotated around the long axis. For free swimming fish, studied reflexes included orientation where the fish should normally be upright, righting reflex where the fish returns to an upright position and the startle response in which the fish shows rapid forward motion in response to stimuli. Adult fish can present special problems because of their strength and other approaches for free swimming fish are described in another post. Sharks and other dangerous toothy or spiny animals especially need imaginative approaches to testing reflex actions.

Once a suite of reflex actions can be consistently observed and easily quantified, then building a RAMP curve can be accomplished and quantification of reflex impairment, vitality, and prediction of mortality is made possible. The RAMP method and curves developed then allow for the systematic investigation of the effects of stressors and stress in animals and systems of chosen interest. RAMP results can be compared and contrasted with concurrent results from physiological and physical injury studies in an effort to synthesize multivariate solutions to a continuum of important basic and applied questions. These questions may include understanding reflex biology, stress biology, fisheries management, bycatch reduction, animal health, population dynamics, aquaculture practices, migration biology, reproductive biology, and conservation biology to mention a few. 

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.