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

ICES WKMEDS4 report (2015)

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

ICES WKMEDS4 report (2015) Click on images.

Observing vitality impairment

Animal vitality can be measured by observing species traits associated with activity, responsiveness, and injury. For each species, a group of reflex actions can be observed that are consistently present in healthy animals. As vitality becomes impaired, reflex action traits disappear and injury traits may begin to appear. 

Activity, responsiveness, and injury for measurement of vitality impairment (Benoît et al. 2010). 

Fisheries show gradients of stressors associated with capture, handling, and release or escape. Discard mortality, survival, and vitality impairment are controlled by stressor gradients.

Gradients of mortality and simulated stressors in sablefish fisheries; water temperature and gear type including trawl (time), longline, pot. Smaller fish are more sensitive to stressors (AFSC).

Vitality impairment gradients are associated with stressors and can be used to predict survival and delayed mortality for populations of impaired animals. Vitality impairment gradients can be measured by identifying classes of health condition; excellent, good, poor, and moribund based on rapid observation and impression of animal injury and activity (Benoît et al. 2015). 

The resolution for observations of vitality impairment gradients can be increased by including more information. RAMP is an example of this approach (Davis and Ottmar 2006, Davis 2010). A list can be made of reflex actions present in control animals and possible injuries. Then presence or absence of listed traits is observed after exposure to stressors. Increasing impairment is associated with stress effects and morbidity.

Reflex actions observed in snapper by McArley and Herbert 2014.

Relationships between vitality impairment and survival or delayed mortality can be experimentally determined. Then predictions of stress effects in other settings with similar stressors can be made by measuring vitality impairment associated with stressors, without the need to hold or tag animals. Vitality impairment can be rapidly observed in sampled populations as an additional factor to evaluate stressor effects and is a useful indicator of animal health and stress status, that can be validated experimentally.

Reflex impairment and mortality for individuals (A) and groups (B) of Atlantic cod with 95% confidence intervals (Humborstad et al. 2009). 

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.

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

Blue sharks and food, WASC

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

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

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

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

Trawl bycatch reduction device, FRDC

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

Using RAMP to help automate aquaculture operations

Net pen for fish culture (NOAA).

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

Inside net pen for fish culture (NOAA).

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

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

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

Mortality sources and the limits of RAMP

Exposure of animals to stressors can result in changes to physiology, behavior, and injury that can result in stress, impaired reflex actions, morbidity, and delayed mortality.  Stressors in fishing, aquaculture, net penning, aquarium trade, research settings, and other ecosystems are present in a number of ways as departures from nominal temperature, light, oxygen, food, xenobiotics, injury, crowding, disease, social interactions, and predators.

While reflex impairments and RAMP can accurately assess vitality and stress levels and predict delayed mortality, these measures are solely dependent on the internal state of an animal at the time of observation.  When other external stressors and sources of mortality are present after an animal is assessed with RAMP, predictions of delayed mortality may not be accurate.

In open, wild ecosystems, important sources of mortality in animals can be predation, lack of food or feeding ability, and impairment of social behavior that is protective (schooling, shoaling, and shelter seeking).  The presence of any or all of these stressors can alter mortality rates predicted by RAMP.  Use of RAMP for predicting delayed mortality in open systems is probably limited to short term delayed mortality.

In closed, human managed ecosystems, external sources for delayed mortality can be controlled and eliminated after RAMP measurements and RAMP predictions of delayed mortality can be accurate over longer time periods.

Sorting wild-caught animals for high quality and live market

Many fishers are becoming aware of the value added to catch by controlling and accounting for animal vitality and food quality.  Fish and crabs that are stressed by capture and then transported to markets, either as live animals or freshly killed, have lesser value for discriminating consumers.  Vendors and educators for sea- and fresh-water food are developing programs to account for the methods and sustainability of food capture and handling.

Accounting for animal vitality and quality requires information about capture methods and associated impacts on ecosystem structure and function.  Sorting of catch is important for maintaining high market quality.  Rapid transport of catch to market can insure fresh product.  All of these aspects of fishing can benefit from the information that RAMP supplies.

Changes in the design of fishing gear and fishing methods that improve catch vitality and decrease bycatch can be tested and validated using RAMP to measure animal stress responses to the stressors of capture and handling.

Turtle escaping trawl

Fish or crabs can be captured and then transported to net pens for holding and later release onto markets.  Planned supplies of fresh product stabilize markets and increase the value of the catch.  These methods of capture and marketing require the availability of animals with best vitality and quality to reduce transport and holding costs associated with poor quality catch.  RAMP has been proposed for use in an Atlantic cod capture-based aquaculture system.

Capture-based tuna

Increasing use of combinations of wild fishing and aquaculture rearing requires information on animal quality, vitality, and fitness.  RAMP can supply this information used to test and validate the design and use of new aquatic food supply systems and sources.  Because RAMP is a cheap, easy, and immediate source of critical data on animal vitality and fitness, it can be an important component for efficient economies of operation in aquatic food production.

Capture-based aquaculture

The ornamental fish trade has a big impact on wild fish populations and is in critical need of information on fish vitality and fitness in capture, holding, transport, and marketing aspects of the industry.  RAMP can easily, effectively, and economically supply this needed information to improve the sustainability and ethics of this growing industry.

Ornamental fish trade

Handling, transporting, and processing animals often involves the use of anesthesia. Reflex impairment and RAMP can be used to assess the induction and recovery from anesthesia. 

Induction of anesthesia in fishes is described by loss of activity and responsiveness (Neiffer and Stamper 2009); “With proper dosing, induction with immersion drugs usually occurs within 5 to 10 minutes, but may take longer via other routes. Induction is marked by decreases in caudal fin strokes, swimming, respiratory rate, and reaction to stimuli; the drop in caudal fin stroke activity is usually the first sign, followed by loss of equilibrium and response to stimuli. At surgical anesthesia there is total loss of muscle tone and a further decrease in respiratory rate. A firm squeeze at the base of the tail can be an effective way to determine response to stimuli: if the animal does not respond, general anesthesia has taken effect (Harms 2003; Stetter 2001).”

Figure shows loss and recovery of swimming and equilibrium (behaviours), startle response to probe stimulation (responses), and vestibular-ocular response and rhythmic breathing (reflexes) associated with anesthesia induced in rainbow trout by MS-222 (Kestin et al. 2002). 

Reflex impairment related to pollutant concentrations

Reflex impairment can be used to test for the behavioral and fitness outcomes of exposure to possible pollutants.  A recent study tested effects of triclosan on reflex impairment in an estuarine fish, Atlantic croaker:

"The effects of triclosan on reflex responses and anti-predator behavior in an estuarine fish

Tiffany L. Hedrick-Hopper and Sandra L. Diamond, Department of Biological Sciences, Texas Tech University, Lubbock, TX Background/Question/Methods Triclosan is a common antibacterial compound found in an increasing number of personal care products including toothpastes, deodorants, and soaps. Despite partial removal by wastewater treatment plants, an increasing amount of triclosan is entering watersheds where it can have significant effects on aquatic organisms. Even at low levels, triclosan negatively impacts thyroid homeostasis in anurans and fish, and it can decrease startle responses and activity levels in anurans. The purpose of this research was to investigate the effects of triclosan on reflex responses and anti-predator behavior in juvenile Atlantic croaker (Micropogonias undulatus), an estuarine fish. Sixty Atlantic croaker were held in individual tanks and randomly assigned to be fed a diet of either normal food pellets or pellets impregnated with 50 ppm triclosan for 14 days. Both prior to and immediately following the 14 day exposure, fish were tested for a suite of reflex action mortality predictors (RAMP) and were subjected to a video-recorded 30 second simulated predator attack. Videos were then analyzed for the specific strategies (run, hide, cut across tank, turn gambit) employed by the fish before and after exposure. Results/Conclusions We found that fish exposed to triclosan were significantly more likely than control fish to exhibit reflex impairment. Specifically fish lost the dorsal spine erection response, meaning that they did not raise their dorsal fin when the fin was flattened. Reflex impairment is correlated with increases in overall fish stress and mortality outcomes. Treated fish also experienced significant shifts in their anti-predator strategies. Triclosan-exposed fish spent significantly more time in their post-exposure test hiding from the simulated predator than fish in the control group. In some cases, fish continued to stay stationary even as the simulated predator touched them. The results of this study indicate that triclosan does impair fish reflexes and creates shifts in the strategies used by croaker to escape their predators. Since these schooling fish have been shown to exhibit dominance hierarchies, triclosan may affect social patterning in Atlantic croaker. These behavioral effects may have important implications not only for croaker and similar fish species but also for croaker predators such as bottlenose dolphins as contaminated fish may be easier prey, leading to increased predator body burdens." This study used free-swimming fish and video analysis of reflex responses.  The RAMP approach can easily be adapted to pollutant research and aquaculture settings for efficient, real-time monitoring of supply waters and sediments, as well as health conditions for animal rearing.  In the basic research context, neurobiological studies of zebrafish have made use of reflex testing in pharmacology and toxicology laboratory settings.

RAMP: from intuition to science

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

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

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

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

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

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

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

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

Uses for RAMP

RAMP measures reflex impairment and predicts delayed mortality in animals. The method is a real time, cheap, effective, and easy way to monitor animal vitality, stress, disease, morbidity, and delayed mortality.  How is this useful?

In fisheries, non-target species of fish, invertebrates, birds, amphibians, reptiles, and mammals (bycatch) are captured and released for a variety of reasons, usually related to management requirements or economic factors.  The release of these animals can result in large, unquantified amounts of fishing mortality that causes uncertainty in fisheries management and wastes valuable lives and resources.  RAMP can give immediate real time data on the vitality and potential delayed mortality of captured animals.  This data can be used in real time to evaluate and adjust fishing practices to improve bycatch survival and to quantify bycatch fishing mortality.

In live fisheries, animals are captured and transported to net pens or land markets for food consumption or aquarium trade.  Sorting of animals for maximum survival can be quickly accomplished using RAMP.  This sorting saves valuable holding space, decreases shipping costs, and increases the value of catch by including only top quality animals.  RAMP also aids in perfecting capture practices that maximize animal vitality and survival.

In aquaculture, RAMP is useful for real time monitoring of animal vitality, stress, disease, and potential for morbidity and mortality.  Aquaculture depends on maintaining the highest health conditions for animals, as disease can be a major impediment to aquaculture ethics and economics.  RAMP monitoring can be automated in aquaculture settings by using computer aided reflex testing.  Stimuli such as flashing bright light, sound, and food scent can be administered randomly into holding areas and the reflex responses of free-swimming animals can be observed and analyzed by video systems.  Detection of impaired reflex responses can trigger alarms systems and bring personnel to adjust conditions for improved animal health.

In pollution research and monitoring, RAMP is a sensitive measure of animal vitality, stress, sublethal, and lethal effects of pollutants. A large body of research exists documenting effects of pollutants on volitional feeding, social behavior, and predator prey interactions. RAMP can be an even more powerful measure of pollution effects than volitional behavior, since reflex impairment is directly related to animal vitality, without the modifying effects of motivation, size, and sex.