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.”

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.

Making and Using RAMP in Fisheries

A video is available that explains making and using RAMP in fisheries.

Why is vitality impairment related to mortality?

By definition, healthy animals have full vitality. Vitality becomes impaired as animals become stressed by capture and handling. Severe vitality impairment can result from the effects of physical injury or other stressors, e.g., fatigue, temperature, light, sea state, and air exposure. Maladaptive stress responses or critical injury associated with severe vitality impairment can result in immediate and delayed mortality.

Why score reflex actions and injury?

Reflex actions are fixed behavior patterns that are directly related to vitality impairment, without control by volitional behavior factors, e.g., motivation, hunger, fear, shelter seeking, migration, and reproduction. Reflex actions reflect the state of neural, muscle, and organ functions.

Injuries are directly related to vitality impairment because they can control neural, muscle, and organ functions.

Scoring vitality impairment in general

Any type of reflex action or injury that is related to vitality can be summed to score vitality impairment. The important point is that a sum of presence/ absence scores for vitality characteristics produces an index of vitality impairment. This vitality index can then be used as a measure of variability for sublethal stressor effects in fisheries, as well as a validated indicator and predictor of mortality and survival.

Steps for making and using RAMP in fisheries.

Ecological significance of cold shock: reflex action impairment in bonefish

Bonefish, Florida Sportsman

Fast moving weather fronts or upwelling events can rapidly drop water temperature in sub-tropical areas. Effects of cold shock were studied in bonefish by Szekeres et al. 2014. Fish at 25^oC were exposed to either 18^oC or 11^oC for 2 hours. Ventilation rate and reflex actions were monitored throughout the cold shock. Five reflex actions were tested before and after cold shock, including equilibrium, body flex, vestibular-ocular response, tail grab, and head complex (Brownscombe et al. 2013). Given that the focus of this study was on sub-lethal effects, cold shock exposure was terminated if the fish lost equilibrium. Blood plasma and swimming ability, defined as line crossings and time to loss of equilibrium associated with chasing were also sampled during the experiments.

The authors found that “Behavioral responses of bonefish to cold shock were generally characterized by decreased ventilation rates for the 7°C below ambient treatment with little reflex impairment, and extreme behavioral and reflex impairment in the 14°C below ambient treatment. Fish in the latter treatment exhibited varying periods of hyperactivity followed by impaired or no swimming ability, reduced responsiveness, and the loss of equilibrium, which are all common traits of cold shock exposures.” Experiments with bonefish exposed to the 14°C below ambient temperature were terminated after 30 minutes, as fish lost equilibrium.

Importantly, the authors found “Despite the fact that bonefish in the 14°C below ambient treatment had almost complete reflex impairment during the exposure and sustained high blood lactate concentrations than other treatments, post-exposure swimming abilities were similar to handled control fish. This suggests that although fish become highly behaviorally impaired at colder temperatures, if they are able to escape to more suitable conditions, swimming abilities quickly return and they are unlikely to experience further fitness consequences due to behavioral impairment (e.g. higher predation risk).” 

There “are many facets that have yet to be explored as this research was the first attempt to understand the sub-lethal consequences of cold shock on these sub-tropical fish species. Our research only considered swimming ability as a proxy to understand predation risk in the wild. Future research may focus on determining whether the fish experience compromised disease resistance, poor foraging decisions, changes to fecundity or altered developmental stages. The combination of a changing climate and the economic importance of bonefish throughout the Caribbean warrant more research to be conducted on this species and their responses to an array of changes to ambient conditions.”

Methods for estimating discard survival in fisheries: an integrated approach

Discarding Pacific halibut, FAO

ICES has published a report on methods for estimating discard survival in fisheries. The report details the results of the February, 2014 ICES WKMEDS workshop on discard survival.

“This report will:

-  describe the concepts behind assessing discard survival (Sections 2 and 3);

-  describe three different approaches for estimating survival (vitality assessment, captive observation and tagging) (Sections 4, 5 and 6); and 

-  provide guidance on the selection of the most appropriate approaches and experimental designs, as well as how to integrate and utilize information from them, with respect to specific discard survival objectives (Sections 3, 7, 8 and 9). 

Later versions of this report will cover in more detail: 

-  techniques for assessing survival using tagging and biotelemetry; and 

-  the most appropriate methods for analyzing and reporting survival data. 

It is assumed that the user of these guidance notes has sufficient scientific training, or at least access to suitable scientific support, to be able to conduct the techniques described in these notes in an appropriately systematic and disciplined manner. However, these guidance notes are intended also to be informative for other stakeholders associated with fishing (primarily fishers and managers) who wish to support and understand discard survival estimates.”

The ICES WKMEDS report is a summary of an integrated approach for estimating discard survival. The approach uses various combinations of vitality assessment, captive observation, and tagging to achieve realistic estimates for discard survival in fisheries. The combinations of methods are determined by scientists, stakeholders, and managers using evaluation and prioritization:

“the choice of which species in which fisheries to study depends upon several criteria: existing survival information, the biological traits of the species, its population status, magnitude of discarding, fishery characteristics, environmental characteristics, socio-economic value of the fishery, available resources, and management policy. The process of prioritizing is unlikely to be simple and may involve a number of iterations, where results of preliminary studies inform the final choice.”

The ICES WKMEDS report represents a new approach for estimating discard survival. Sources of information about objectives, priorities, resource implications, and time frames are included in a decision matrix. Managers can use the matrix to make informed choices about discarding in key fisheries and management units and what methods can be used for further study of discard survival. Initial calibration of vitality assessment using delayed mortality observations of discards creates validated indicators for survival. Then use of validated vitality assessment indicators such as RAMP (Reflex Action Mortality Predictors) can provide rapid real-time assessment of potential discard mortality on-board fishing vessels.

ICES. 2014. Report of the Workshop on Methods for Estimating Discard Survival (WKMEDS), 17–21 February 2014, ICES HQ, Copenhagen, Denmark. ICES CM 2014/ACOM:51. 114 pp.

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

 Yelloweye rockfish, ADFG

Canary rockfish, WDFW

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

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

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

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

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

The importance of vitality in fishing experiments

Key fishing stressor factors, Davis, 2002

Knowledge of key factors controlling fisheries is necessary for sustainable management of fishery stocks. Scientific hypothesis testing in the form of fishing experiments is a necessary component of fisheries knowledge development and validation. Fishing experiments are performed in the field by simulating actual fishing conditions, by actual fishing, and during survey cruises. Fishing experiments can be used to identify key stressor factors that control and contribute to the survival and mortality of captured, discarded, or escaped animals as well as identifying the key factors controlling fishing gear capture efficiency and selectivity.

Trawl captured animals, Robert A. Pawlowski, NOAA Corps

While field fishing experiments represent realistic conditions, they are a matrix of confounded factors which cannot be easily separated into mechanistic hypothesis tests and explanations of factor importance. Effects of factors are often synergistic and prior animal stressor history can alter relative effects of subsequent exposure to factors, e.g., depth changes, injury, elevated temperature, air exposure, and size and species differences.

Flow chart of experimental fishing stressor factors, Davis and Olla 2001

Simulated fishing experiments with factors in controlled laboratory conditions is one way to test hypotheses about mechanistic effects of individual factors and their interactions. However these laboratory experiments are generally viewed as not realistic to field conditions and they are used to identify factors that may be important in the field. Furthermore, modern requirements of animal care laws and committees restrict the use of laboratory fishing experiments by not allowing human application of experimental stressor factors on animals and the use of mortality outcomes. These same laws and committees do not have jurisdiction over field fishing experiments. 

Laboratory trawl tow tank, NOAA RACE

Given that factors are confounded in field fishing experiments, how can we test for effects of factors in the traditional mechanistic hypothesis test? We can test for changes in animal vitality. Since vitality has been shown to be correlated with survival and mortality, it is a useful indicator of animal outcomes before and after exposure to experimental stressor factors. For example, we generally do not know the exposure of animals to stressors prior to experimental manipulation of factors. Not knowing the complete stressor profile is not an obstacle since the animal knows the complete stressor profile and presents vitality levels that have integrated the effects of that profile. Then we can expose animals to additional stressor factors and measure further changes in vitality from their initial levels. 

Important to shift mechanistic thinking from needing to know the effects of individual factors to knowing the effects of fishing variability. Manipulations of time in air and elevated temperature represent differences in fisher sorting and handling behavior on deck and are appropriate for defining the effects of fishing variability. Effects of variation in tow time and catch quantity can be manipulated and are included in the mix of animals landed. The questions of associations among individual fishing stressor factors is left for another day and are more of interest to mechanistic scientists than to managers and fishers. Fishing variability will give a picture of the fishery and its potential effects on animal vitality. By measuring animal vitality, which integrates the effects of stressor factors, you have measured a key master variable that indicates the important effects of fishing.

Vitality is the key variable that can be used to indicate and predict delayed survival and mortality outcomes for discards and escapees from fishing. The relationships between vitality and survival and mortality are defined by captive observation or tagging and biotelemetry experiments. During exposure of animals it is important to insure that all stressor types normally in the fishery in question are present for the population of tested animals (e.g., temperature, air exposure, fatigue, injury) and that a full range (0-100%) of vitality impairment and mortality are observed. Then relationships can be calculated for each species of interest that do not extrapolate beyond available data ranges and that apply to the fishery of interest. These relationships can then be used to predict survival and mortality for animals under any condition of interest in the fishery without the need for further captive observations or tagging.

Consider how scientific peer-reviewers may see this shift from mechanistic thinking and develop thoughts that elaborate the importance of vitality from the animal’s point of view. Some resistance is expected from mechanists who believe that they can attribute cause and effect to individual factors. There is always a matrix of interactions, even under the most restrictive and controlled experimental conditions. There are always interactions and synergisms to account for. As a result, there are associations among factors, rather than cause and effect. In other words, there are causes and conditions associated with effects. 

From the fishing experiment perspective, we set up fishing conditions that are real or that simulate fishing and then measure animal vitality, which is an integrated measure of the effects of interacting factors. It is useful to identify the important stressors by experimentally changing them in fishing experiments; changes in time in air, trawl time, trap retrieval time, depth, season, temperature, catch amount, and injuries. Always remember that there is a hidden context of conditions, i.e., the animals are prestressed by other factors not being controlled. But this hidden context can be accounted for by observing and comparing vitality impairment among animals observed in all treatments, including simply captured animals without additional stressor exposures (using positive controls). This experimental approach is useful both for fishers who wish to modify fishing gear and practices, as well as managers who wish to observe animal vitality and correlate that with mortality and survival.

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).

Measuring reflex action impairment in sole and plaice; preliminary steps to making RAMP

Collection of fish with beam trawl, Jochen Depestele

The beginning steps for measuring reflex action impairment and making a RAMP are detailed in “Calibration tests for identifying reflex action mortality predictor reflexes for sole (Solea solea) and plaice (Pleuronectes platessa): preliminary results” authored by Depestele, J. et al. 2014. Experiments were designed to collect sole and plaice using short hauls of a beam trawl, to test their reflex actions, and to identify consistent reflexes for making RAMP. These experiments followed steps for making RAMP.

A short video demonstrates testing plaice for reflex actions including righting, eye roll (vestibular-ocular response), evade, operculum, mouth, and tail grab. Fish are shown in a series of increasing impairment.

Conclusions from the study included:

Preliminary investigations have been undertaken on-board the RV Belgica to assess the potential presence of a range of reflexes in sole and plaice. A wide range of potential reflexes was investigated prior and during the sea trial, leading to a final selection of seven reflexes with a good potential of being consistently present in fish in a favorably vital condition. Fish in a “perfect” condition could not be retrieved, but 22 individuals of plaice and sole were selected from short hauls and their survival potential was evaluated during 70 hours in on-board holding facilities. Only one sole died, and indicated hence that the control fish for the calibration test serve purpose.

Holding tanks for fish on board RV Belgica, Jochen Depestele

The final selected reflex actions were very similar for sole and plaice, except for one. Forced opening of sole’s operculum did not reveal much resistance of the fish, while holding plaice by its head did not induce curling of the fish. The most consistent reflex actions for sole were called “stabilize, mouth, and tail grab”, followed by the “vestibular-ocular response”. Vital individuals seemingly dig into the sand or stabilize themselves onto the floor of the water-filled box. They also keep their mouth closed when trying to open it with a probe. When fish have stabilized, they respond clearly to grabbing their tail or even tickling it. The “head” reflex was easy to assess, though not always present. However, it is clear that vital soles curled around one’s hand when they had been in holding tanks. This was not that obvious for fish that were just released from the codend. Natural righting was observed regularly, although some individuals remained at their backs for >5 sec and did not return to their natural position at all or only after stimulating them. The consistency could thus be questioned, but good candidate reflexes were proposed for sole, and should be further evaluated. The most consistent reflexes of plaice were the turning of the eyes when the fish was turned around longitudinally. The resistance of plaice to forced opening of the operculum was a clear reaction as well. Not fully consistent, but nevertheless a good indication of the reflexes was the “evade” response and the “tail grab”. When the tail is touched or grabbed in a “good” way (which might require some practice), then the fish swim away, or at least the fins stimulate propulsion. The mouth of plaice was easily opened, but mostly the individuals tried to close it or seemingly opposed to the forced movement.

Our investigations confirmed that on-board holding facilities result in high survival of plaice and sole from very short hauls (<20min). Investigated individuals were non-randomly selected and thus it was not surprising that their physical injuries were limited. These individuals were suitable for developing the reflexes, although they were limited in number (22 for plaice and 22 for sole) and they also did not range over a wide variety of fish conditions (e.g. limited length variability). The seven reflexes from these preliminary investigations are therefore proposed as candidates for the development of a RAMP score for sole and plaice.

The tests of the reflexes were run directly after releasing fish from the codend. When examining the survival from fish that were accommodated for some time (e.g. 48 hours), we noted that they reacted more strongly and had much clearer responses to the reflex tests. In particular the tail grab worked very nicely for sole when their status (alive or dead) was tested. Therefore we suggest that the proposed reflexes are tested once more on surviving individuals of short hauls after an accommodation period of >24hours. Consistency of the outcome of the reflex tests is expected to be improved when the impairment from the catching process is accounting for. Other recommendations for follow-up tests relate to the registration of potential environmental and biological confounding factors.

Coho salmon, RAMP, knowledge-action boundary, and stakeholder conservation actions

Coho salmon, NOAA Fisheries

A paper entitled "Bycatch mortality of endangered coho salmon: impacts, solutions, and aboriginal perspectives" by Raby et al. 2014 introduces a new model approach for bycatch conservation research. The paper identifies the use of vitality assessment in the form of RAMP to inform stakeholder and manager decisions about bycatch handling and avoidance for coho salmon in the Fraser River, Canada.

“This paper demonstrates that fisheries science, biotelemetry, and human dimensions surveys can be combined to evaluate a conservation problem for an endangered population of salmon and inform resource managers and users. We consider this a model approach for conservation research, because it can help address the persistent challenge of generating science that “bridges the knowledge-action boundary” (Cook et al. 2013). A well-known barrier to transitioning from scientific knowledge to conservation action is the scientific structure that values publications and grant income but not engagement with stakeholders (Cook et al. 2013).”

“Abstract. We used biotelemetry and human dimensions surveys to explore potential solutions to migration mortality of an endangered population of coho salmon caught as bycatch in an aboriginal beach seine fishery. From 2009 to 2011, wild coho salmon caught as bycatch in the lower Fraser River (Canada) were radio-tagged and tracked as they attempted to complete their migrations to natal spawning areas over 300 km upstream. Failure to survive to reach terminal radio receiving stations averaged 39% over three years. This mortality estimate is low compared to those obtained from telemetry studies on other salmon fisheries in the Fraser River. However, this value is markedly higher than the mortality estimate currently used to manage the fishery’s impact. It is also in contrast to the perceptions of the majority of aboriginal fishers, who did not think survival of coho salmon is affected by capture and release from their fishery. Increased probability of survival was associated with lower reflex impairment which is consistent with previous findings. Reflex impairment was positively correlated with entanglement time, suggesting that greater efforts by the fishers to release bycatch from their nets quickly would minimize post-release mortality. Survey responses by aboriginal fishers also suggested that they are receptive to employing new bycatch handling methods if they are shown to increase post-release survival. However, attempts to facilitate revival of a subset of captured fish using cylindrical in-river recovery bags did not improve migration success. Fisheries managers could use the new information from this study to better quantify impacts and evaluate different harvest options. Since aboriginal fishers were receptive to using alternate handling methods, efforts to improve knowledge on minimizing reflex impairment through reductions in handling time could help increase bycatch survival. Such a direct integration of social science and applied ecology is a novel approach to understanding conservation issues that can better inform meaningful actions to promote species recovery.”

Survival of the fittest

Bob van Marlen, IMARES

Work is in progress at ICES to define methods for estimating discard survival in reference to the new European Commission Common Fisheries Policy. The ICES newsletter states, “Under the recently reformed European Commission Common Fisheries Policy (CFP), the practice of discarding fish will be phased out, replaced instead with landing obligations. Under the landing obligation, all catches of regulated species must be landed and counted against quotas unless it has been scientifically proven that the species can survive the discarding process. Species that display a high level of discard survivability will be awarded an exemption, meaning that fishers can return these fish to the sea. Unregulated and protected species will continue to be released.”

The ICES WKMEDS focuses on developing guidelines and identifying best practice for undertaking experiments to investigate the survival of organisms discarded from the catches of commercial fisheries. 

Importantly ICES states, “Techniques for estimating survival under review include captive observation, vitality assessment, and tagging and biotelemetry, each with its own advantages and disadvantages. By using a combination of techniques, as WKMEDS suggests, clear synergies can be achieved and challenges overcome.”

"It's an exciting time", state the workshop Chairs Michael Breen and Tom Catchpole, "this group will be central to an international community that are working together to address the important issue of discard survival."

The WKMEDS group is producing a synthesis of previous discard survival and mortality research with the goal to develop an integrated approach for estimating discard survival. The integrated approach is designed to guide scientists and managers in their evaluation of potential candidate fisheries and species for discarding exceptions to the landing obligation of the CFP. The integrated approach incorporates information about the role of fishing conditions as stressors, species sensitivity to stressors, vitality impairment of captured species, estimated discard survival rates, and cost-benefit analysis of methods for survival assessment in fisheries as well as impacts of discarding on fisheries stocks.

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.