Stressors, vitality impairment, and survival of fishes

Developing rapid visual in situ trait assessment (reflex actions, injury) associated with vitality impairment.

Video slideshow (2:06) discussing stressors, vitality impairment, and survival of fishes in fisheries contexts.

Assessment of reflex impairment and mortality in discarded deep-sea giant isopods

Giant isopod, Wikipedia

Giant isopods were subjected to simulated capture and discarding by Talwar et al. (2016). Reflex impairment and mortality were induced by capture, exposure to air, and time at surface before discarding. Reflex actions tested are included in Table 1.

Talwar et al. (2016)

Six reflex actions were tested in control animals. Impairment of antennae extension and pleopod movement were not associated with mortality and were removed from the mortality analysis. Figure 1 shows the relationship between increasing reflex impairment and increasing mortality. 

Talwar et al. (2016)

Note that an impairment score of 0 was associated with 50% mortality. Clearly this score does not mean that animals were not impaired. Stressed animals were initially impaired without associated mortality, as indicated by the loss of antennae extension and pleopod movement.  Removal of these two reflex actions from scoring and the mortality analysis may have produced a tighter analysis, but fails to show the sublethal effects of the experimental stressors. 

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.

Sport catch and release (C&R) fishing: assessing captured fish condition (vitality) with injury and reflex impairment

Fix.com (2015)

A review and synthesis of tools and tactics for best practices in sport C&R fishing is made by Brownscombe et al. (2017). A key factor for conservation of species fished with C&R is the assessment of fish condition (vitality) and associated survival after release. This assessment is conducted primarily with observation of injury and reflex impairment that results from fishing practices. Fishers can then make educated adjustments to their fishing practices (capture gear, playing time, handling, release, recovery, or harvest) to enhance future species recruitment in sport fisheries.

Reflex tests for C&R fishing, Brownscombe et al. (2017).

Brownscombe et al. (2017) concluded that “As catch-and-release grows in popularity, so must angler education and implementation of best angling practices to ensure the sustainability of this practice and conservation of fish and aquatic environments. Sustainable catch-and-release angling is a joint venture where it is the responsibility of management agencies and scientists to communicate and evaluate the best angling practices, while anglers need to be educated and use the correct tools and tactics to maximize the likelihood that released fish survive. In this regard, catch-and-release angling is perhaps among the most successful and rewarding conservation partnerships.”

C&R practices, Thousand Islands Life (2014).

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)

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).

What is RAMP: reflex action mortality predictor?

Reflex actions and injury traits in crab scored for impairment (Stoner 2012, Yochum et al. 2015).

Reflex actions and injury traits in sharks scored for impairment (Danylchuk et al. 2014).

Reflex actions and injury traits in fish scored for impairment (Davis 2010, McArley and Herbert 2014).

Reflex actions and injury traits in turtles scored for impairment (LeDain et al. 2013, Stoot et al. 2013).
Photos; crab - Farm to Market, shark -  Swell Brains, fish - DEEP, turtle - Aquatica.

Any animal has reflex actions and potential injury traits; see diamonds in figures. These fixed traits can be observed, scored present or absent, and summed to form an animal vitality impairment score. Animal vitality is a gestalt of reflex and injury traits that we can observe as a whole animal, active and responding to stimuli. Vitality impairment and mortality are correlated and this relationship is expressed as RAMP, reflex action mortality predictor.

Impairment of well-defined reflex actions and injury types may differ for each species, dependent upon their natural history and phylum.  These species traits of reflex actions and injury types can be scored and combined to express the percentage of whole animal impairment. No impairment represents a healthy animal with all actions present and all injury absent. Increasing absence of reflex actions and presence of injury types is increasing impairment and is correlated with mortality.

Sublethal and lethal zones associated with reflex action impairment scores (RAMP) in walleye pollock, rock sole, sablefish, and Pacific halibut (Davis and Ottmar 2006). For these species at specific transition impairment values, a rapid rise in mortality is observed after a small increase in reflex impairment. 

These curves illustrate the expression “you are alive until you are not”. Animals live in various states of vitality impairment that are correlated with stress. Above a quantifiable level of vitality impairment, animals begin to show mortality, correlated with continued increase for impairment. The distribution of reflex impairment and injury in a group of animals is a measure of population vitality. 

For fish species (Davis 2010, McArley and Herbert 2014), animals have several types of reflex actions which can be secondary or primary. One action group contains secondary peripheral actions that are part of swimming and defensive behavior (fin erection and startle). Impairment of these reflex actions generally indicates sublethal stress effects and is associated with increasing stressor intensity (duration or strength). A second action group contains primary body functions (orientation and coordinated breathing). Impairment of primary body functions generally indicates delayed mortality after stress induction. In the same way, for crustacean species (Stoner 2012, Yochum et al. 2015), loss of leg reflex actions are associated with sublethal stress effects. Loss of eyestalk and mouth actions are associated with delayed mortality after stress induction.

Snow crab discard mortality

Snow crab in Bering Sea pot fishery (ASMI).

Over 19,000 snow crab were evaluated in Bering Sea pot fisheries 2010-2012 for impairment using the RAMP method (Urban 2015). The estimated discard mortality rate was 4.5% (s.d. = 0.812), significantly below the rate used in stock assessment models. The author concludes: “ In this study, the results of RAMP observations showed that at the range of winter temperatures typically encountered by the Bering Sea snow crab fishery, nearly all discarded crab experienced no reflex impairments. Therefore, we estimate that they should have only a 4.8% chance of short-term mortality. Injuries caused by the fishery occurred at very low levels and so should also have a minimal effect on discard mortality rates. However, because long-term survival rates and the effects of reduced crab vitality are difficult to predict, an estimate of the total impact of discard practices on snow crab stocks is not possible. Even with these uncertainties, the current empirical evidence indicates that the assumed discard mortality rate of 50% is conservative.”

Figure 1. The upper panel shows the relationship between the temperature at the snow crab sorting table and the predicted mortality of snow crab based on reflex impairments. Error bars indicate the 95% CI. The lower panel shows the proportions of the temperatures recorded, while the observations were being made during the 2010–2012 fisheries (Urban 2015).

Elements of vitality testing and delayed mortality in fisheries

Conceptual diagram outlining elements for vitality testing and delayed mortality in fisheries. Fish are captured and environment sampled. Fish become stressed which is measured as impairment from control health by observing reflex actions and injury types. Stressed fish are held for captive observation to determine delayed mortality. Bias and error can be introduced by initial impressions of vitality before testing reflex actions and injury, by differing observer scoring opinions, and by holding conditions that are stressful for the fish. 

Scoring vitality impairment is most difficult when observer decision is used. Training observers is a key part of RAMP development. Reflex actions (RA) are clearly present in control animals, and observers do not need decisions to score present. As impairment increases, scoring RA requires increasing observer decisions about whether sampled RA are present. The decision can be based on how control RA appear to trained observers. Each observer will have different opinions that can be influenced by their initial impressions of the animal and of the stressor treatments the animal has been exposed to.

Initially after stress induction, RA impairment increases and mirrors stress levels, while mortality is not evident. When animals reach a critical impairment level, replicates begin to show mortality, which increases rapidly over small changes in RA score. At highest levels of impairment decisions are less frequent as the animal ceases general movement and responsiveness.

Observer bias and RAMP

Cognitive bias (The Daily Omnivore, 2012)

Subjective scores for animal behavior can be biased by observer opinions about experimental treatment differences and resulting outcomes (Tuyttens et al. 2014). The research paper title expresses a fundamental bias of human perception and belief: “Observer bias in animal behaviour research: can we believe what we score, if we score what we believe?” The problem is to separate belief from observation. This may be accomplished by clearly defining and adhering to consistent protocols for behavior observation and analysis.

RAMP relies on subjective scoring for presence or absence of reflex actions or injury types. Control fish have a suite of reflex actions that are consistently and clearly present when tested for. When an observer begins to notice the weakening or complete loss of a reflex action, that action is scored as absent (impaired). There will be variation among observers in the decisions about when reflex actions are impaired and bias will vary with experimental protocol. 

Because RAMP is an aggregate vitality impairment index summed from control reflex actions and potential injury types, a RAMP score includes the observer bias for each included reflex action and injury. Close correspondence of RAMP scores and mortality is noted at low and high scores because observers clearly know when fish are active and when fish are severely injured and impaired. Relationship of mortality and RAMP is more variable at intermediate levels of impairment and mortality in part because observer opinion about impairment is more variable. To reduce observer bias, RAMP for a species must be designed to include reflex actions and injury types that can be clearly separated into present or absent scores. Also experimental treatments can be administered without informing observers.   

Vitality of a stressed fish is readily observed. We are primarily seeing the activity, responsiveness, and injury presented by the animal. The most widely used vitality index in commercial fisheries is for the halibut fisheries of the northeast Pacific Ocean (AFSC Observer Manual 2015), based on Appendices S-X for trawl, pot, and longline fisheries.  For trawl and pot fisheries, three levels of vitality (excellent, poor, and dead) are scored by observing injury types and spontaneous activity, startle response to touch, and operculum clamping. For longline fisheries, vitality is scored by observing injury types. Mortality rates are assigned to vitality impairment scores using tagging experiments (Williams 2014).

Vitality impairment codes (Benoît et al. 2010).

Benoît et al. (2010) constructed a fishery vitality index with four levels of impairment (excellent, good, poor, moribund) that are scored by observing injury types, spontaneous body movement, startle to touch, and operculum clamping. Their vitality index and the halibut vitality index use the progressive increase of injury and impairment of activity to score vitality impairment. Benoît et al. (2010) corrected for observer bias by using a random effects term in their statistical model. 

Reflex actions scored for presence or absence in RAMP for snapper (McArley & Herbert 2014).

The RAMP vitality index alters impairment scoring to only include presence or absence of a larger number of injury and reflex actions. This shift attempts to introduce more information about activity and injury types that may be associated with mortality and to reduce decisions about degree of impairment for individual activity and injury traits. Impairment is observed as a progressive increase in the number of reflex actions that become absent and the number of injury types that become present when compared to control animals. Because observer bias can be introduced in scoring, observer protocols must be well defined with clear rules for presence or absence of traits. Observer judgements about correspondence between experimental treatments and outcomes could also be eliminated by careful experimental design.

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.

Survival of schooling small pelagic fish discarded from purse seine fisheries

Greenback horse mackerel, Trachurus declivis 

Purse seine fishing

Vitality impairment and RAMP can be used to determine survival of discarded schooling small pelagic fish in purse seine fisheries.  When catch is too large, fish are “slipped” for the net and discarded. These discarded fish are usually exposed to some level of hypoxic conditions associated with crowding in the purse seine. Elevated temperature in surface water may be a stressor. Skin abrasion and scale loss can occur in the net. Many small pelagic species (mackerel, sardine, anchovy, smelt, herring) caught in purse seines are obligate or facultative schoolers that reflexively form groups mediated by the optomotor response. Vitality impairment can be tested for individual fish or groups. See Davis and Ottmar, 2006 for testing groups of free-swimming fish. Schooling fish seek the company of species mates, so testing groups of schooling fish is probably the most informative method. How is this testing done and linked with delayed mortality in captive observation tanks?    

RAMP links vitality impairment scores with delayed mortality scores. The RAMP estimate for delayed mortality is only as good as the mortality estimates from captive observation or tagging experiments. How many replicates are needed in captive observation experiments? The purse seine schooling species need to be held in groups. A replicate group size of ten fish is good for schooling. These fish must be held in good water quality and circulation, in a circular tank size that allows schooling. For initial RAMP formulation, you will need 10 replicate groups of ten fish each. Observations of reflex action impairment and delayed mortality should be made over a range of stressor intensities that result in delayed mortality of 0 to 100%. Then replicate vitality impairment scores are linked with replicate delayed mortality scores to form the RAMP which can be validated with further experiments and replication.

Suuronen, 2005  Stressors in capture and escape of fisheries.

Fish can be sampled from any point on the fishing process, depending on the stressors of interest. Reflex action testing can be made on a group of fish held in a circular observation tank big enough for schooling (See Davis and Ottmar, 2006).  Possible reflex actions for testing include: orientation; schooling; rheotaxis; startle response to sound or light; swimming to bottom of tank. Injuries can also be noted; abrasion, scale loss. After testing the replicate group can then be placed in a holding tank and monitored for delayed mortality through five to ten days. 

Herring lose schooling, orientation, and tail beat frequency increases as the purse seine is drawn smaller (Morgan, 2014). Fatigue and hypoxia are possible stressors in purse seines (Tenningen 2014).

For discard species caught in purse seines that are not schooling fish, or are larger schooling fish, individual fish can be tested for vitality impairment.  Reflex actions tested can include: body flex, orientation, eye roll, operculum or mouth clamp, tail grab, righting, startle.  These fish can be tagged for identification and held together for five to ten days in tanks to determine delayed mortality.

RAMP is a component of an integrated conservation approach to coho salmon bycatch mortality management

Raby et al. 2014

Results of Raby et al. 2014 demonstrate the integration of vitality impairment and coho bycatch mortality estimation and management.

“We have provided an estimate of bycatch mortality for an endangered population of coho salmon captured in an aboriginal beach seine fishery, based on three years of tracking fish released from the fishery.” 

“Among all the variables we tested as predictors of mortality, none were significant except for RAMP score, whereby fish with higher RAMP scores (more impaired) were less likely to be successful migrants (Table 3, Fig. 4).”

Distinguishing between natural mortality and bycatch mortality. 

“An alternate approach to calculating a bycatch mortality rate that attempts to distinguish bycatch from natural mortality, is to use RAMP scores and their mortality rates at each level of impairment, and assume negligible bycatch mortality for the fish that were least impacted (vigorous at release).”

“Since some in-river mortality is natural, there is a need to attempt to differentiate mortality caused by the capture itself. To do so, RAMP scores can be used whereby coho salmon released with little or no reflex impairment (vigorous) are assumed to experience no post-release bycatch mortality. Using that conservative assumption, the post-release mortality rate for those fish can then be used as a baseline within the data set. Additional mortality above that baseline that occurs at higher levels of reflex impairment can then be assigned to the fishery (see Fig. 4).”

Using RAMP to monitor condition of bycatch and improve their survival

“The expanded validation of the RAMP approach in the present study provides confirmation that this simple technique is ready for use in this fishery if needed (Raby et al. 2012). The observers in the fishery could easily be taught how to conduct RAMP assessments to monitor the condition of bycatch in real time, provide advice to their crews on how to improve fish condition, and make decisions about whether individual fish should be revived using recovery bags.”

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.

Flexibility of using RAMP to determine bycatch mortality rates for Tanner crab caught in Alaska bottom trawls

Tanner crab (Chionoecetes bairdi), AFSC

Yochum et al. 2015 evaluated the flexibility of RAMP methodology by creating a RAMP for Tanner crab (Chionoecetes bairdi) discarded from the groundfish bottom trawl fishery in the Gulf of Alaska and comparing it to a previously established RAMP for unobserved Tanner crab bycatch (encountered gear and remained on the seafloor) from the bottom trawl fishery in the Bering Sea. The authors found that: “The two RAMPs and the overall mortality rates calculated using these predictors were comparable. However, we detected significant differences between RAMPs. While probabilities of mortality were similar between the two studies for crab with all or no reflexes missing, discarded crab with intermediate reflex impairment had lower mortality probabilities than those from the unobserved-bycatch study. Our results indicate that a RAMP may produce more accurate mortality estimates when applied to animals experiencing similar stressors as those evaluated to create the RAMP, through similar methodology.”

Conditions for holding crab after exposure to stressors can control delayed mortality and should be considered in experiments. “There were differential mortality rates by holding type. Higher mortality rates occurred in the on-board tanks (where the crab were held for the first few days) and in the laboratory tank. Moreover, Score-zero crab died in the holding tanks, but not in the at-sea cages. These results indicate that holding tanks contribute additional stressors, either due to transport, additional handling, or stress from being held in an unnatural setting or at temperatures greater than what was experienced in their natural environment. 

Our holding duration of two weeks was sufficient to determine mortality for all Scores. Given that it can take longer for Score-zero animals to die than those with higher Scores, our holding period allowed us to sufficiently capture Score-zero mortalities. However, the death of a Score-zero crab at day 12 may indicate that holding for more than a week confuses mortality attributed to fishing stressors with that from captivity.”

Evaluation of RAMP flexibility was made by comparing results from different studies. “To evaluate the divergence between the RAMPs we analyzed the differences between the studies. The primary difference was in experimental methods, namely the treatment of the crab before assessment. Crab from the Discard-mortality study were exposed to air for 90min on average (range from 9 to 230min) without any “recovery” in water. In contrast, crab from the Unobserved-mortality study had only brief air exposure and were held in water while awaiting assessment (generally less than 15 min), which may have allowed some recovery. 

These differences in air exposure and recovery in water probably affected the relationship between observed reflex impairments and delayed mortality and hence accounted for the discrepancy between RAMPs. Prolonged air exposure and experiencing cold temperatures was linked with increased delayed and instant mortality, number of autonomies for crab, as well as reduced vigor, juvenile growth, and feeding rates (Carls and O’Clair, 1995; Giomi et al., 2008; Grant, 2003; Stoner, 2009; Warrenchuk and Shirley, 2002). Stoner (2009) found that reflex impairment score and exposure to freezing temperatures were nearly linearly related for Tanner crab. Moreover, he found that the different RAMP reflexes had variable sensitivity to freezing temperatures, namely that the chela closure reflex was the most sensitive reflex, and mouth closure was least. Similarly, Van Tamelen (2005) found that the legs and eyes of snow crab cooled faster than the body, perhaps making them more susceptible to cold air exposure. We hypothesize that the prolonged air exposure for the Discard-mortality study likely impaired the crabs’ reflexes and resulted in higher Scores.”

Recommendations made by the authors. “Results from this study indicate that bias can be introduced in mortality rate estimates when using a RAMP created for one study to estimate mortality rates for a different study where the experimental methods differ, especially with respect to air exposure and recovery in water before assessment. However, when RAMP is used only to approximate mortality rates or to make comparisons between gear types or uses, a previously established RAMP could be used with caution, especially if animals with intermediate Scores are not predominant. For more accurate bycatch mortality rate estimates, our results indicate the importance of using a RAMP that was created by assessing animals that experienced similar stressors to those which the RAMP will be applied. Namely, the procedure for assessing the animals should be similar. We feel that the amount of time the animal spends out of water before assessment be standardized within a time range, along with whether or not the animal is allowed to recover in water before assessment, unless these variables are the treatments being studied.” 

“Our results indicate that consistency in methodology and relevance with respect to mimicking actual fishing stresses for the RAMP approach increases the flexibility of RAMP. It is therefore important, when creating a RAMP, to create repeatable methods that are well documented when publishing. RAMP reflexes should be assessed in a specified order to prevent bias from reflexes that are physiologically linked. If there is a reflex that influences the determination of other reflexes it should be assessed last or not at all. Reflexes that are difficult to determine presence or absence should not be used, and it should be clear in the methods what constitutes an “absent” reflex and how immediate mortalities are treated (are they given a Score or classified separately?). In addition, when a RAMP is being created, data should be recorded on all possible stressors, including injury, and evaluated for their contribution to mortality. Moreover, effort should be made (within the logistical constraints of field and laboratory research) to minimize additional stressors that are unrelated to the fishing stressors of interest.”