Why observe several reflex actions together to measure animal vitality?

Philipchircop 2012

Why observe several reflex actions together to measure animal vitality? The short answer is that animals are whole beings; a summary collection of component parts and their interactions in response to stimuli.

Animals are constructed of biochemical and behavioral components that interact to form a whole; capable of responding to stressors. The interactions of stressors and behavior are also important for prediction of vitality impairment and survival. Reflex actions are fixed behavior patterns that include biochemical, muscle, organ, and nerve functions.

Efforts to identify factors that can control vitality and predict post-release survival and mortality of captured animals generally strive to identify single important variables. For example, temperature changes, injury, exhaustion, and hypoxia can control vitality and survival. For simplicity, single factors are statistically modeled as predictors for survival. Factor interactions are rarely considered because of their complexity.

Patterns of vitality impairment vary with species and contexts. Observing impairment of several reflex actions and possible injury in a defined context integrates the effects of multiple stressors, contexts, and their interactions on animal impairment and survival. Measurement of single reflex action impairment can miss the range of vitality that spans from excellent to moribund. 

Stoner 2012 (crabs)

Below are several examples of the cascading nature of impairment observed as individual reflex actions cease to function in a spectrum of stressor intensities. Reflex actions with higher proportion of impairment are impaired before those with lower percentage. Note that patterns of impairment vary with taxa and context.

Davis 2010 (walleye pollock, coho salmon, northern rock sole, Pacific halibut)

Stoot et al. 2013 (turtles)

Uhlmann et al. 2016 (plaice, sole)

Forrestal 2016 (triggerfish)

Forrestal 2016 (yellowtail snapper)

Danylchuk et al. 2014 (lemon shark)

McArley and Herbert 2014 (snapper)

Sampson et al. 2014 (mottled mojarra)

Stoner 2009 (Tanner crab, snow crab)

Stoner 2012 (spot prawn)

Belly up: Righting reflex action time to recovery correlated with delayed mortality?

Upside down fish in market tank (Hong Kong)

RAMP incorporates presence/absence of several reflex actions and injuries to measure vitality impairment and potential delayed mortality. A simpler method may be possible by measuring time for recovery of orientation when fish are placed upside down in water. This method can be tested.

Place a fish upside down in water and observe the time until the fish returns to normal orientation. This duration is a measure of vitality impairment. Longer recovery times indicate greater vitality impairment and data can be included in statistical models for relationships among fishery stressors, injury, righting time, and delayed mortality. We can test the relationship between righting impairment and delayed mortality. 

Righting reflex action is a central behavior that is the nexus of neural, muscle, and organ actions and is intimately linked with loss of physiological regulation associated with stressor exposure.  Olfactory impairment is another example of a central function that is correlated with delayed mortality (in humans, Pinto 2014).

Body orientation is a sensitive measure of fish consciousness. Presence or absence of righting can be included in the RAMP score. Loss and recovery of orientation is a well known symptom for induction of and recovery from fish anesthesia and is used as an indicator of morbidity and delayed mortality in stress experiments (Davis and Ottmar 2006, Szekeres et al. 2014, Raby et al. 2015).  

Measuring replicate animals for the time to righting recovery and delayed mortality after a stressor experiment can test the correlation between righting impairment and delayed mortality. If the correlation between righting and delayed mortality is valid and strong, then we have a rapid method for predicting discard mortality on board fishing vessels without need for holding or tagging fish to confirm their survival. Research groups on fishing vessels can observe fish during catching, landing, sorting, and discarding under differing stressors; seasons, water temperatures, tow durations, catch quantities, species mixes, and sorting times.

Measuring and scoring vitality impairment

Associations between vitality impairment and mortality in Tanner and snow crab; Stoner et al. 2008.

At the risk of repetition and irrelevance, I will repeat my short history with vitality impairment and mortality.  I began by trying to find out what kills fish. The word fish applies to all animal types in a fishery. We chose to do this in the lab for control reasons, given the common confounding of stressors in fisheries (Davis 2002). All sorts of objections were made by field people that the work was irrelevant because it did not include field conditions. Well we focused on the fish and their capabilities, in an effort to formulate hypotheses that could be tested in the field. We found that each species and size of fish has different sensitivities to stressors and that stressors of importance were different for species.  We also found that some stressors (temperature and hypoxia) could kill fish without apparent macro-injury. After killing many fish, we endeavored to identify characteristics (traits) of fish and fisheries that could be correlated with mortality as predictors, given the difficulty of holding fish and measuring delayed mortality in the field. We tried many traits; muscle and plasma physiology, stressors, volitional behavior, injury, and reflex actions.

Effects of fishing gear, temperature, and fish size on sablefish mortality, NOAA.

Muscle and plasma physiology were not correlated with mortality because these are alarm responses that can be adaptive or maladaptive responses to stressors. In specific contexts, lactate and CO2 may be useful where hypoxia or fatigue are a concern.  

Stressors are an approach that has garnered enthusiasm. However their effects can be confounded and difficult to model given the relatively unlimited combinations of factors that are possible in a fishery; seasonal effects, gear type and deployment times, catch type and amount, sorting and discarding.  

Volitional behavior is not correlated with mortality because it is subject to variation that is not directly linked to mortality, such as changes in perception, motivation, fear, and attraction; all which confound the relationship of behavior and mortality.  

Injury is often correlated with mortality, especially in accidental death.  However not all mortality is correlated with injury, as in the effects of temperature and hypoxia, for which micro-injury may be evident (apoptosis) but difficult to measure in the field. Often the effects of injury, temperature, and hypoxia are confounded making interpretations of their effects on mortality difficult.

Single reflex actions are often not correlated with mortality when they are part of systems not central to body function and regulation directly related to mortality. They may be important for complex behaviors; predator avoidance, feeding, habitat choice, migration and these can have indirect effects on mortality. 

We reasoned that fish had a quality called vitality and that vitality was correlated with mortality. However, for an individual fish this relationship is binomial. The fish is alive or dead. So decreasing vitality results in sublethal effects on behavior until a threshold is reached and the probability for death increases rapidly. In statistical groups of fish, decreasing vitality is log-linearly related to mortality.

At this point we chose to not measure the strength of reflex actions (because of confounded size effects); instead to score the presence or absence of several reflex actions as an expression of reflex action impairment and loss of vitality. Reflex actions are fixed behavior patterns based on neural, muscle, and organ functions which do not vary with changes in perception, motivation, fear, and attraction.  We chose to focus on several types of reflex actions to increase the probability that reflex actions key to body regulation were included. Later work has shown that the orientation reflex is such a key reflex, often correlated with morbidity and mortality associated with hypoxia and fatigue. 

Previous work with vitality scoring in fisheries had developed the semi-quantitative analysis method (SQA) of scoring fish activity and injury, which was used in tagging studies and in Pacific halibut discard mortality estimation (ICES 2014). The method observes the sequential loss of operculum clamping and startle to touch and increased injuries from minor to major and bleeding; with ordinal scoring (1-4) for severity of impairment. The vitality score is readily incorporated in multivariate models that may identify stressors of importance to mortality and model mortality based on those stressors. RAMP can be scored in a similar manner as SQA and included in multivariate models. RAMP scores severity of impairment by noting the sequential loss of several types of reflex action and inclusion of injury types. Scores range from 0 to a maximum which is the number of trait types observed for presence/absence. Strength of action and extent of injury are not included because of the confounding effects of size. The effect of size is included in the model explicitly as fish length or weight. Smaller fish will have more vitality impairment than larger fish, when exposed to equivalent stressors.

RAMP is a simple extension of the SQA concept that includes more testing for reflex actions. SQA and RAMP are similar scoring systems that differ by emphasis. SQA and RAMP score activity, responsiveness, and injury to quantify levels of vitality impairment. RAMP simply includes more information about types of reflex actions in an effort to include reflex actions that are central to body regulation over a range of stressor conditions.

The primary reason for inclusion of more reflex action information in RAMP is the observation that some reflex actions are central expressions for status of body regulation. Given the binomial nature of mortality observations, we need to know why fish die. They die for many reasons which all seem to point to the loss of physiological regulation; either homeostatic or allostatic regulation. How do we measure regulation?  Allostasis shows us that consideration of homeostatic set points is not sufficient to predict mortality. My view is that vitality is correlated with physiological regulation and that impairment of vitality and regulation leads to mortality when physiological bounds of the species are exceeded. Until we can directly measure the causes for mortality, we rely on measures for vitality based on activity, responsiveness, and injury.

For predicting mortality, I chose to measure vitality over modeling stressors because of the direct relationship between vitality impairment and mortality. Stressor interactions in fisheries can make interpretation of stressor effects on mortality difficult to interpret. Information about stressors in multivariate models for mortality can be used to identify changes in the design of fishing gears that reduce bycatch mortality. Then vitality impairment can be used to evaluate reduction in discard mortality associated with new gears.

Sublethal effects of simulated angling capture (fatigue and air exposure) in snapper: reflex impairment and physiological stress.

Snapper, Pagrus auratus. Floor Anthoni 2006.

A study of reflex impairment and physiological stress was conducted with captured snapper and published in JEMBE 2014 by McArley, T.J & Herbert, N.A.  Fish were exposed to simulated angling by chasing to fatigue, followed by air exposure.  The authors' text is quoted below.

Reflex impairment (RI) was measured for seven reflex actions (Table 1). “If the presence of a positive reflex response was ambiguous it was scored as absent. The entire RI assessment was completed in less than 50 s, of which the fish was exposed to air for approximately 30 s. Reflexes were scored present (1) or absent (0) for individual fish and the RI score (proportion of reflexes impaired) was calculated by dividing the number of reflexes absent by the total number of possible reflexes (Davis, 2010). For example if four out of the seven possible reflexes were absent a fish would be given an RI score of 0.57.”

Reflex impairment is a potential measure of vitality loss after exposure of snapper to angling stressors: 

“A primary aim of this study was to assess the potential use of RI as a simple tool for measurement of fish vitality following angling and our lab-based trials indicate RI has the potential to be used in this way. RI was significantly related to the duration of strenuous exercise and air exposure (Fig. 1) and therefore provided a good index of fish condition. Importantly, fish exposed to more severe stress treatments exhibited greater RI than those exposed to more mild stress treatments, a finding that agrees with several other studies of RI in fish (Barkley and Cadrin, 2012; Brownscombe et al., 2013; Campbell et al., 2010b; Davis, 2007; Humborstad et al., 2009; Raby et al., 2012, 2013). Furthermore, greater RI was associated with significantly higher plasma lactate concentration and reduced muscle pH suggesting that RI can indicate (predict) an alteration in physiological condition.” 

Anaerobic respiration is associated with lactate production and reflex impairment:

“Burst swimming is powered by anaerobic respiration fueled by stored energy in white muscle (Milligan, 1996) and the lactic acid produced accumulates rapidly in muscle tissue and then “spills over” into circulation after a 5–10 min delay (Wood, 1991). Plasma lactate therefore serves as a useful indicator of anaerobic respiration in fish (Gale et al., 2011; Lowe and Wells, 1996; Meka and McCormick, 2005) and, as fish performed burst swimming during chasing, it is unsurprising that plasma lactate correlated positively with the duration of chasing stress and that both muscle pH and blood pH were lower in fish chased for longer periods. Physiological alterations appeared to be more pronounced in summer than in winter suggesting that when water temperature is warmer a more severe stress response appears to occur in snapper.”

Physiological basis for reflex impairment: 

“RI is thought to have a physiological basis (Davis, 2010) and a significant relationship between RI and increased plasma lactate concentration has been observed in salmonids (Raby et al., 2013). As RI is measured directly after stressor exposure physiological disturbances that manifest quickly during stress are likely causes of RI. Physiological alterations such as cortisol concentration that can plateau 30 min - 1 h after the initial stressor exposure (Milligan, 1996; Wendelaar Bonga, 1997) are therefore unlikely to be directly responsible for the RI measured in this study. In this study most RI occurred as a result of an inability to perform reflexes involving powerful muscular contractions, such as the gag reflex, body flexing and the startle response. Powerful muscular contraction is fueled by anaerobic metabolism in white muscle fibres and can only be maintained for short periods (Milligan, 1996). As higher RI scores were correlated with lower muscle pH and higher concentrations of plasma lactate it is hypothesized that muscle fatigue resulting from anaerobic metabolism performed during strenuous exercise caused the majority of the observed RI. The muscle pH and plasma lactate concentrations associated with the same RI scores, however, were different in summer and winter (Fig. 4) and there was no difference between the summer and winter measures of fish vitality (RI) and mortality. This suggests that rather than being causes of RI, plasma lactate concentration and muscle pH may have been indicators of an unmeasured physiological process that impaired some of the reflexes quantified in the current study. Other reflexes we measured that were not as commonly impaired, such as the righting response and vestibular ocular, are essentially neurological and their impairment likely results from alternative pathways to those measured in this study.”

Mortality was rarely observed when snapper were exposed to angling conditions: 

“Despite the limitations of comparing our mortality estimates to real fishing scenarios the findings provide evidence that strenuous exercise and air exposure imposed during angling, are not likely to be direct causes of discard mortality in P. auratus. During the collection of sub-legal snapper from the wild for this study, fish were landed relatively quickly (approximately 15 to 30 s), and were typically unhooked in less than 30 s. In investigations of authentic angling events for P. auratus of comparable size (< 270 mm FL) in south eastern Australia, the majority of fish were landed in less than 30 s (Broadhurst et al., 2012; Grixti et al., 2010) and had less than 30 second exposure to air (Broadhurst et al., 2012). Thus, the 5 minute strenuous exercise period and the 3 minute air exposure period in this study must be considered extreme levels for recreational angling and probably rarely occur in authentic angling events. Encouragingly, even with these high levels of stress, little mortality was seen against a backdrop of high summer water temperatures.”

Predation risk for snapper that show reflex impairment associated with angling: 

“It is often overlooked in catch and release studies but a potentially important contributor to discard mortality is post-release predation (Raby et al., 2014). While no measure of predation risk was assessed in this study, our measurements of RI indicate that snapper may not be overtly susceptible to predation upon release, at least when no barotrauma is present. This is because RI was minimal among snapper released after angling simulations most relevant to authentic recreational angling events (i.e. 0.5 min chasing with up to 1 min air exposure), and it is believed that the vigorous condition of these fish would not make them easy targets for predators. Importantly, reflexes that might be associated with reduced predator avoidance, such as the startle response and righting response, remained intact.”

Snapper captured by trawl may be at risk from increased air exposure: 

“It is likely that mortality increases significantly at some point beyond 3 min air exposure in P. auratus but this may not be relevant to recreational angling. Longer periods of air exposure, however, may be present in commercial trawl fisheries where large catches are sorted on deck so knowledge of air exposure tolerance beyond that observed in this study would be useful in this context. Therefore, the existence of a predictive relationship between RI and mortality in snapper remains a possibility but probably requires the inclusion of more extreme air exposure treatment to be clarified in future trials.”

Clearly any capture of snapper that produces barotrauma can be a source of mortality and requires further study in deep water commercial and recreational fisheries.

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.

Quest for a discard survival predictive scoring system to use on board fishing vessels

Releasing tagged Atlantic cod, John Clarke Russ

The European Union Common Fisheries Policy (CFP) ban on discarding allows for animals to be discarded if “scientific evidence demonstrates high survival rates”. Estimating discard survival for fisheries has become a priority for implementation of the CFP. Limited data on discard survival and mortality is available and methods for estimation have not been standardized. Ideally, a standardized numerical scoring system can be developed and validated, based on readily observable responses and symptoms present in animals that are candidates for discarding and survival. 

RAMP is an example of a predictive scoring system for vitality, survival, and mortality, based on animal reflex actions, barotrauma symptoms, and injury that can be observed in fishing operations where real time decisions must be made about potential discarding. See post for RAMP development and validation; also Davis (2010) and Stoner (2012) for reviews of RAMP method. Other uses for RAMP are in live fisheries, aquaculture, and pollution research and monitoring.

For inspiration and alternative perspectives, examples of validated mortality predictive scoring systems can be found in human and veterinarian intensive care unit (ICU) settings, where patients present with symptoms and disease likely to result in morbidity and mortality (Rockar et al. 1994, Bouch and Thompson 2008, Timmers et al. 2011). Measurements of blood plasma and urine variables commonly made in ICU settings are not contemplated for RAMP since they are not readily made on board fishing vessels.

Below is an example of human ICU mortality prediction using the SAPS II scoring system. Note the similarity to RAMP curves for mortality prediction.

SAPS II mortality predictive scoring system, ClinCalc

Celinski and Jonas (2004) discussed scoring systems developed for the human ICU environment:

“How are scoring systems developed? All available data types and variables can potentially be used to create a scoring system. However, to make it useful, variables have to be selected to be appropriate for the predictive properties of the scoring system. The information must be unambiguous, mutually exclusive, reliable and easy to determine and collect. Ideally, the variables should be frequently recorded or measured.

The variables can be selected using clinical judgement and recognized physiological associations or by using computerized searching of data (collected from patient databases) and relating it to outcome. The variables are then assigned a weighting in relation to their importance in the predictive power of the scoring system (again by using clinical relevance or computerized databases).

Logistic regression analysis, a multivariate statistical procedure, is then used to convert a score to a predicted probability of the outcome measured (usually morbidity or mortality) against a large database of comparable patients. Lastly, the scoring system must be validated on a population of patients independent from those used to develop the scoring system.”

For discard survival prediction, groups of animals, rather than individuals, are the appropriate unit for consideration since proportion mortality is the determined outcome during index development and validation. These groups can represent various scales of resolution in fisheries of interest, i.e., single tows or traps, sets of longline, trap, or gill-net, daily catch.

Jean-Roger Le Gall (2005) discussed the appropriate use of ICU severity scoring systems:

“A good severity system provides an accurate estimate of the number of patients predicted to die among a group of similar patients; however, it does not provide a prediction of which particular patients will in fact die. Using a well-calibrated severity model, we can reasonably expect that approx. 75% of patients with a probability of mortality of 0.75 will die, but we cannot know in advance which of those patients will be among the 25% who will live. Furthermore, these 25% will not have falsified the odds but will have confirmed the validity of the probabilities. 

       The possibility that clinical decisions can be augmented by having an objective (although not always more accurate) assessment of a patient’s severity of illness is appealing. Physicians are interested in severity systems for individual patients as an adjunct to their informed but subjective opinion. Using these tools as part of the decision-making process is reasonable and prudent. Using these tools to dictate individual patient decisions is not appropriate. Decisions will and should remain the responsibility of the individual physician and should be based on a number of criteria, one of which is severity as estimated by a well calibrated scoring system.”

Stacy et al. (2013) discussed development and appropriate use of a predictive scoring system for survival in Kemp’s ridley sea turtles:

“Three mortality prediction indices (MPI) scoring systems were developed using different combinations of blood analytes, with anticipation that at least one of the three would be more accurate in predicting mortality in sea turtles within 7 days after admission. Turtles with higher scores were categorized as physiologically deranged to a degree that could result in death, and turtles that received lower scores were categorized as physiologically stable and likely to survive. Categorization of each turtle was then compared to the known outcome for that individual.

Receiver operating characteristic (ROC) analysis was used to assess the diagnostic performance of each MPI scoring system (Greiner et al., 2000; Giguere et al., 2003). The ROC analysis produces a plot that is used to estimate the area under a ROC curve, which is a summary statistic of diagnostic accuracy. A perfect test [i.e., sensitivity (SE) = 100% and specificity (SP) = 100%] will produce an area under the curve (AUC) = 1. The AUC can be used to distinguish a non-informative test (AUC = 0.5), a less accurate (0.5 < AUC ≤ 0.7), moderately accurate (0.7 < AUC ≤ 0.9), highly accurate (0.9 < AUC < 1), and perfect test (AUC = 1)."

ROC analysis of Kemp's ridley sea turtle mortality predictive scoring system, Stacy et al. 2013

"It is clear that results of mortality prediction indices (MPI) scoring systems cannot be used indiscriminately to make euthanasia decisions, because this would result in euthanasia of some turtles with a falsely positive MPI score that would otherwise survive. As with other health scoring systems in human and veterinary medicine, the MPI scores should not prevent clinicians from providing care to an individual, and euthanasia decisions should only be made in light of numerous other clinical factors, including neurological status, vision, ability to forage, ability to swim, pain and suffering, and duration of illness. Finally, MPI scores may be useful when applied retrospectively in a stranding event for comparison of various treatment outcomes within a facility or among different facilities. Thus, the MPI could provide an objective assessment tool of treatment success and contribute to the advancement of medical care in sea turtles.”

Philosophy of using RAMP to measure vitality, survival, and mortality of animals

Blue sharks and food, WASC

Mortality can occur over varying time frames after an animal is exposed to potentially lethal stressors. The problem of mortality prediction is made more difficult by animal mobility, as animals can become hidden from observation, especially over longer time frames. Then indicator measures must be used to predict cryptic delayed mortality. What is an effective indicator for predicting mortality? Do we observe the animal immediately after stress induction and before leaving our presence, or do we observe the conditions in which the animal was stressed? 

A common approach to predicting delayed animal mortality is to observe the conditions in which stress is induced and use this information as an indicator for mortality.  Animals are experimentally exposed to important stressors and their combinations in a matrix of interactions. Then animals are sampled for mortality after holding them captive for short periods or tagging, releasing, and recapturing or using biotelemetry over longer time frames. Mortality, and its inverse, survival are then modeled from sampled combinations of risk factors. Since there are relatively unlimited sets of risk factors and their interactions, indicator models for mortality based on stressors often will not give realistic estimates or not include important conditions for stress induction.

Alternatively, animal impairment can be observed as an indicator for delayed mortality after exposure to risk factors. Reflex impairment occurs immediately in an animal when it’s neural, muscular, or organ systems are stressed. Summing presence or absence of several reflex actions calculates an index called RAMP (reflex action mortality predictor) which is a direct measure of reflex impairment and vitality. Correlation of RAMP with immediate and delayed mortality make it an indicator for mortality and survival. With RAMP, the approach of predicting mortality is based on direct observations of animal vitality. The animal continually integrates all the effects of experienced risk factors as reflex impairment and communicates it’s health state, vitality, and fitness through the language of RAMP. Other types of animal impairment that have been tested as potential indicators for mortality include physiological variables (cortisol, glucose, lactate, and electrolytes) and injury.  However these measures are not consistently correlated with delayed mortality.

In an effort to ameliorate mortality risk factors, a hybrid approach can be used for predicting cryptic delayed mortality that conserves and integrates information. Instead of asking the question “Does the animal die?” we can ask “When, where, and under what conditions does the animal die?” Animals are observed in experimentally controlled conditions of mortality risk (Davis 2002, Suuronen 2005). Then initial stressor conditions are sampled, as well as time courses for animal impairment and delayed mortality. Relationships between stressor factors, animal impairment, and delayed mortality can be identified and modeled. The resulting knowledge base can be used to test hypotheses about importance of mortality risk factors and efficacy of predicting cryptic delayed mortality using animal impairment as an indicator. Previous research has shown that reflex impairment measured as RAMP is a powerful predictor for cryptic delayed mortality (Davis 2010). After validation, RAMP can be used to test the effects of experimental or natural changes in mortality risk factors such as design of fishing gears, aquaculture rearing conditions, aquarium trade, pollution exposure, climate change, and other potentially risky situations.

Trawl bycatch reduction device, FRDC

The problem of using indicators to predict cryptic delayed mortality is simplified by shifting from modeling mortality in potentially unlimited sets of risk factors to direct, real time measurement of animal impairment and prediction of delayed mortality. This shift in focus to reflex impairment allows for real time testing of animal fitness in systems of interest and is a cheaper, more efficient use of limited research resources than using risk factor indicators for mortality prediction.

C&R fishing, physiology, RAMP, and fitness outcomes

A study by Cooke et al. 2013 reviewed the physiological consequences of C&R (catch and release) fishing. They concluded that:

"An underlying tenet of catch-and-release studies that incorporate physiological tools is that a link exists between physiological status and fitness. In reality, finding such relationships has been elusive, with further extensions of individual-level impacts to fish populations even more dubious."

They presented a conceptual scheme for the development of physiological stress in C&R fishes:

Cooke et al. 2013, Figure 1. "Schematic of the general stress response to fisheries capture. The thick black solid line labelled ‘general response’ provides an example of a typical response of a physiological indicator of stress, such as plasma cortisol, to a fisheries capture event. Following the initial response, a negative feedback occurs and recovery is initiated. The stressors connected by a bracket to the general response line exemplify the multiple, interactive and potentially cumulative stressors involved in a fisheries capture event, all of which contribute to the general stress response and are dependent on environmental conditions and the initial condition of the individual fish. The thick black broken line represents a disrupted recovery pattern, where recovery to routine physiological condition does not occur and there are life history consequences. The grey broken line represents an example recovery profile for individuals held in facilitated recovery gear, where the general physiological response is muted and recovery to routine condition is accelerated."

Observations of physiological stress in fishes have measured short-term changes associated with C&R angling.  However Cooke et al. 2013 conclude that:

"Beyond the problems noted previously, there is mounting evidence that, taken alone, conventional blood chemistry measures may not be definitive enough to forecast long-term survival following fisheries-related injuries and stressors (see Skomal & Bernal 2010; Pankhurst 2011; Renshaw et al. 2012), although another possible explanation is that researchers are failing to use the appropriate physiological indices (Renshaw et al. 2012; see section below on use of a limited set of metrics). Although now technically feasible to attempt to link physiological condition to fate, it has thus far failed to enhance C&R science with respect to long-term outcomes. However, with shorter-term outcomes (e.g. behavioural endpoints) and when used for conducting mechanistic laboratory studies to complement field studies, physiology has yielded valuable insight."

Prediction of delayed mortality has been successful with observations of reflex impairment (RAMP) in fishes from C&R fisheries. Cooke et al. 2013 note:

“Unlike traditional physiological tools, there has been considerable success in using a simple reflex impairment index [reflex assessment mortality predictors (RAMP) score] to predict delayed mortality for fish released from commercial fishing gears and subsequently monitored in large tanks (summarised in Davis 2010) or released into the wild with telemetry tags (Raby et al. 2012). The success of RAMP for predicting mortality is likely attributed to its holistic nature: underlying physiological impairments are integrated into whole-animal responses that can easily be assessed in a quantitative way. In the context of C&R, Campbell et al. (2010) developed a condition index for red snapper, Lutjanus campechanus Poey, that combined reflex impairment with indicators of barotrauma and was associated with immediate mortality and proxy indicators of post-release predation risk (post-release mortality was not assessed directly).

Additional research is needed to develop predictors of fate in C&R science and the logical focus should be on fisheries for which significant mortality is observed that seems to be independent of physical injury (e.g. deep hooking). Reflex assessment mortality predictors will not replace traditional physiological metrics, but it is a valid and inexpensive complement and could be incorporated into any study of C&R mortality even if the project team has little or no experience in physiological research.”

In communicating the results of C&R fishing to management and fishing communities, Cooke et al. 2013 found:

“Although physiological tools can play an important role in understanding and mitigating the sublethal consequences of C&R on fishes (Cooke et al. 2002; Wikelski & Cooke 2006; Arlinghaus et al. 2007a), it is important that the findings of physiological studies be interpreted correctly and used appropriately. It is difficult to translate the physiological results of C&R research into best practices given the limitations listed previously. Where investigators have identified physiological consequences of C&R, findings must therefore be interpreted cautiously with results not extrapolated beyond the boundaries of their study design. For instance, Wedemeyer and Wydoski (2008) examined the physiological response of some economically important salmonids to C&R fishing, and they interpreted many significant trends between angling duration and blood parameters as ‘transient’ effects, ‘generally mild’ and of ‘little physiological consequence’, without fully exploring a broader suite of metrics (e.g. cortisol) shown to be associated with angling stress in other recreational fishes. Moreover, their study was restricted to moderate water temperatures, like many C&R studies (reviewed in Gale et al. in press). The results of their study were then noticed by the angling community, which further extrapolated the findings on angling web sites, message boards and blogs, inferring that C&R in general has negligible consequences on trout and without considering how factors not explored in their study such as water temperature could alter the outcome for the fish. Consequently and likely quite unintentionally on the part of researchers, peer-to-peer communication pathways common within the recreational angling community could foster a shift of the social norm about the potential conservation value of C&R. When management implications arising from C&R physiological studies are presented in the peer reviewed literature, authors should thus provide appropriate caveats, context and draw conclusions carefully. Although the interpretation of physiological data can be subjective, it is suggested that such findings always be viewed in the context of the broader stress response and recovery probable for a given species/population (Fig. 1).”

Catch and release largemouth bass, University of Illinois

Cooke et al. have summarized important steps to take for minimizing mortality in C&R fisheries in an effort to standardize these protocols according to scientific principles (see Arlinghaus et al. 2007, Pelletier et al. 2007):

"General guidelines for catch-and-release recreational angling to conserve fishery resources:

Minimize angling duration

The duration of the angling event increases the physiological disturbance from which the fish has to recover. Angling results in a combination of aerobic and anaerobic exercise that causes a number of physiological changes such as the depletion of energy reserves, accumulation of lactate, and alterations in acid/base status. Studies have shown that these physiological disturbances are generally more severe with increasing angling duration. In addition, the length of time required for physiological variables to return to resting levels tends to increase with angling duration.Therefore, anglers should try to land fish as quickly as possible to minimize the duration of the exercise and the related physiological disturbance.There are techniques for achieving shorter angling durations, such as choosing equipment that matches the size of fish that are expected to be encountered.

Minimize air exposure

Air exposure is harmful to fish. Air exposure occurs upon capture when a fish is removed from the hook, weighed, measured and/or held for photo opportunities. When a fish is exposed to air, the gill lamellae collapse causing the gill filaments to stick together. This has several negative physiological implications. It can cause severe anoxia. Fish that are exposed to air typically experience greater acid/base disturbance (fluctuation of pH in the blood) than those which are not. When fish are exposed to air for a significant length of time, they require a much longer time to return to their normal state. Furthermore, extended air exposure (beyond a species-specific timing threshold) can eventually result in permanent tissue damage or death. Although different fish species vary in their tolerance to air exposure, it is recommended to minimize the duration of the air exposure whenever possible.

Avoid angling in extreme water temperatures

Most fish are ectothermic (they cannot regulate their own body temperature) so the environment regulates their temperature. Any changes in the ambient water temperature can have a significant impact on their cellular function, protein structure, enzyme activity, diffusion rates and metabolism. In addition, the amount of dissolved oxygen in water is lower at higher water temperatures. Angling stressors tend to be magnified at higher water temperatures as reflected in strong relationships between water temperature and mortality for several species. On the other hand, extremely cold temperatures likely also have detrimental effects, although this has been poorly studied to date. Although individual species exhibit different thermal tolerances, catch-and-release angling has the potential to be harmful at extreme water temperatures. In some jurisdictions, there are restrictions on angling when water temperatures exceed some threshold. Since water temperature exerts control over almost all physiological processes in fish, extreme water temperatures are undoubtedly conditions in which fishes are most vulnerable and where angling should be avoided.

Use barbless hooks and artificial lures/flies

Hooks are used to capture fishes. Therefore, hook design is an important element to consider when attempting to reduce hooking related injuries and mortality. Hooks with barbs can lead to greater injury than barbless hooks and even contribute to mortality, although the literature accounts are disparate. However, barbless hooks can minimize the amount of harm caused by reducing tissue damage at the point of hook entry and by reducing the amount of time required to remove a hook. Since there is no barb, the hook can easily be removed. Some studies show that circle hook can be an effective tool in catch-and-release fisheries, when used properly under certain conditions [see section on circle hooks]. The type of bait used is another important factor in fish injuries. Live/organic baits (e.g., worms) used on hooks can be ingested and the hook becomes lodged into the viscera. This makes it hard to remove the hook and it will likely cause damage to the vital organs/tissue during the process. Artificial lures or flies do not get ingested as much so there is minimal damage to the vital organs/tissues from the hook(s). Barbless hooks and artificial lures/flies can greatly reduce handling time, hooking injuries and the likelihood of mortality.

Refrain from angling fish during reproductive period
The reproductive period is the time during which fish attept to produce off-spring and is thus critical for sustaining fish populations. Angling fish during their reproductive period canl reduce the number of off-spring that could contribute the population. Some species, like the largemouth bass, provide parental care and protection for their off-spring. If this dad is removed from the nest, even for a brief moment, its off-spring become extremely vulnerable to predators. Thus, angling immediately prior to or during the reproductive period could affect fitness and should be avoided."