Reflex impairment and vitality in white sturgeon exposed to simulated capture stressors

White sturgeon, NEEF 2016

A study (McLean et al. 2016) of reflex impairment in white sturgeon exposed to sustained exercise and elevated temperature showed whole-animal stress responses to simulated capture. The RAMP impairment index (a simple proportion of measured reflex actions that were impaired) was used to quantify relationships between treatment times, recovery times, and RAMP score.

The upper figure shows increasing RAMP score with increasing exercise (minutes) in summer (filled circle) and winter (filled triangle) temperatures. The lower figure shows increasing recovery time with increasing RAMP score in summer and winter temperatures. Figures adapted from McLean et al. 2016.

The authors state: “Our study demonstrates that reflex impairment (RAMP) indices are a promising tool to predict post-release vitality in white sturgeon exposed to acute fisheries encounters, such as an angling event. The reflexes used in our RAMP protocol were chosen so that multiple neurological and/or muscle pathways underlying the overall stress response were tested. What we found was that sturgeon exposed to fishing-related stressors had higher RAMP scores and took significantly longer to recover than control fish. The relationship between reflex impairment and stressor intensity (i.e. fishery-related treatment) indicates that sturgeon are undergoing whole-animal (or tertiary) responses to varying degrees of capture stress. Reflex impairment indicators were surprisingly sensitive to fisheries stressors. Control fish had all reflexes intact, whereas multiple reflexes were absent after fish were treated.

It is important to note that it was not the aim of this study to produce accurate mortality estimates for use in C&R fisheries, but rather to explore the use of RAMP on a sturgeon species frequently angled in the wild. We recognize the subjectivity of a whole-animal assessment and categorization; however, given the statistically significant difference in RAMP scores of observationally ‘recovered’ and ‘unrecovered’ sturgeon, we suggest that RAMP is an effective tool for predicting a lowered state of vitality post-release and that this suggests a continuum to an increased risk of delayed mortality.”

Using vitality scores to predict post-release survival of plaice

European plaice (Picton & Morrow, 2015)

A recent study of plaice after capture and release from a beam trawl determined that vitality scoring can be used to predict post-release survival (Uhlmann et al. 2016). Vitality scores included observation of reflex impairment and injury. 

Figure from Uhlmann et al. 2016.

The authors conclude: "Our results illustrate that a vitality score and TL were the most relevant explanatory variables to predict post-release survival probability of plaice. In agreement with other post-release survival studies (Yochum et al., 2015), 14 d of post-release monitoring was appropriate to capture almost all fishing-related mortality events. Although one fish died after 21 d, > 60% of mortalities occurred within the first 4 d. Reflexes of both plaice and sole were sensitive to capture stress, in particular air exposure, although some of the differences may have been related to an observer effect."

The authors noted reservations about scoring vitality: "As with other animal behaviour scores, reducing a continuous spectrum of responses to presence/absence observations to improve practicality (Cooke et al., 2013) require a well-defined protocol, and assessments of bias, especially when multiple observers are involved (i.e. inter-observer reliability, Tuyttens et al., 2014). Although scoring binary as opposed to ordinal or continuous responses removes some subjectivity in interpretation (Tuyttens et al., 2009), it may still persist by abstracting from a continuous scale (Tuyttens et al., 2014)."

Uhlmann et al. (2016) comments about binary scoring expose a misconception about vitality scoring using the RAMP approach. For RAMP, presence or absence of individual reflex actions and injuries are given a binary score and then summed to derive an ordinal or continuous vitality score, representing the sum total of impairment. The vitality score is then correlated with survival or mortality for samples of animals (Davis 2010, Stoner 2012).

Future research is suggested to refine the vitality method: "Further research is needed to disentangle the effects of observer, and expectation bias on reflex impairment scores, especially in studies where more than one scorer is involved. Accuracy of scores may also be improved, if researcher handling periods before reflex (and injury) assessments are kept consistently as short as possible. Finally, the utility of RAMP as a proxy to predict post-release survival will depend on both laboratory-based and field calibration studies where key technical, environmental, and biological drivers of post-release survival are included." 

Questions and answers about observer bias in RAMP

Refer to the previous post for background on observer bias in RAMP.

Q: What are the options when grappling with cognitive/expectation and sampling biases in manipulative fisheries research experiments under sometimes challenging conditions at sea?

A: Begin by training and calibrating observation. We all recognize vitality when we see animals with high vitality. This recognition is based on rapid visual assimilation of information about several traits including injury, activity, and responsiveness. We cannot separate our cognitive impression of vitality level from the act of observing individual traits and scoring their presence or absence. Presence or absence of reflex actions is scored relative to control animals which have a set of reflex actions consistently present. Reflex actions range from clearly seen through weakening stages to clearly absent. As the animal becomes more stressed and impairment increases, the interaction of impression and scoring observations contributes bias. 

If observers are trained to clearly recognize a suite of real reflex actions in the species of interest, then correctly recognizing the impairment or absence of those reflex actions should be a realistic accomplishment. An experiment to test for the effect of observer bias and variability in scoring reflex actions could be conducted in the lab or field if enough fish and observers are available. Stress some fish (air exposure) to produce replicates over a range of RAMP impairment scores and have the observers sample reflex actions. Blind the study treatments from observers. Estimates for observer bias from stress studies with different species will be useful for improving observer training by identifying protocols that need to be more defined and less subject to observer opinions. Alternatively, Benoît et al. (2010) modeled observer bias as a random factor. 

Q: How can we achieve a blinded experimental design if the experimenter who assigns or is aware of experimental treatments also scores reflex impairment on board (commercial) vessels?

A: Perform some fish experiments on observer bias outlined above and decide how important observer bias is after training with well-defined protocols for testing individual reflex actions. The bias problem may be mitigated by training using clear definitions of present or absent for reflex actions. I will assume that the vessel captain is conducting the experimental fishing treatments. So the captain could be given treatment conditions by the scientist and then could conduct fishing by assigning treatments randomly without the knowledge of the scientist observer. However tow time, soak time, or haul time and catch volume will be apparent to observers. 

Q: Is an observer influenced in his/her ability to score reflexes if, apart from knowing the treatment, also the condition of an organism is evident even before the scoring begins? Is there any option to minimise this?

A: We cannot separate the correlation between overall impression of vitality and scoring reflex actions. However, we can be trained to clearly recognize the presence of reflex actions. Any impairment through weakness, delay, or loss of action is scored absent.  The key method for minimizing observer bias for reflex actions is to clearly establish what the suite of reflex actions look like when they are consistently present in control animals. If presence of a reflex action is difficult or inconsistent to determine then it is not a good candidate for testing. Any deviation from control appearance in action strength or delayed time for action can be considered impaired and scored absent. The goal is to eliminate variability in detection of presence for reflex actions. By sharpening the decision criteria, bias and variability can be reduced. This idea can be tested using the outlined experiment design.

Q: Seeing that vitality assessments of discarded fish in Europe are now being developed in several places is there a need to also quantitatively evaluate the ability of different observers to score reflexes consistently? What would be the best setup for such a training exercise? 

A: As mentioned above, a stress experiment can be conducted to quantify observer bias and consistency.  With enough replicate fish and observers, an air stress experiment could produce fish with varying levels of reflex action impairment. These fish could be sampled by observers with defined criteria and using an experimental design for testing the effects of observer variability and bias. The effect of training could also be evaluated using this design.

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.

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.

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.

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.

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.

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.

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

Releasing tagged Atlantic cod, John Clarke Russ

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

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

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

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

SAPS II mortality predictive scoring system, ClinCalc

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

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

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

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

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

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

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

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

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

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

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

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

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