Importance of context for RAMP curves used to predict mortality and survival of stressed animals

Relationships between reflex/buoyancy impairment and post-capture mortality for Atlantic cod (Humborstad et al. 2016).

Humborstad et al. (2016) looked at the relationship between reflex/buoyancy impairment and post-capture mortality for Atlantic cod exposed to fishing stressors. RAMP curves were generated for (a) fish exposed to laboratory simulated forced swimming, air exposure, and net abrasion, (b) field longline capture, and (c) field pot capture. The authors concluded that:

“It appears that specific RAMP curves may be needed for gears that involve different stressors, including consideration of any additional stress associated with captive observation of delayed mortality. Differences in stressors and holding conditions certainly reduce the general applicability of RAMP across different stressors and fisheries. However, once a RAMP curve has been established for a specific set of stressors or gears, the strong relationship between reflex impairment and mortality shows the potential for predicting mortality outcomes, especially at high and low levels of impairment.”

“Reflex impairment could predict mortality among fish caught by pot and longline. However, different RAMP curves were observed between laboratory and field conditions, indicating that careful consideration must be given to the types of stressors present and captive-observation conditions for delayed mortality when comparing RAMP curves for different fisheries. The inclusion of buoyancy status in modelling greatly improved mortality predictability.”

Science and medicine generally do not know proximate and ultimate causes for why fish and other animals die. This lack of mechanistic knowledge precludes us from direct understanding and prediction of death. However, we can observe correlates with death; animal size, stressors, vitality impairment, and physiological impairment. These correlates can be used to identify risk factors and predict immediate and delayed mortality. 

Successful mortality and survival prediction requires that the context of animal exposure to stressor risk and recovery be included in any experimental analysis of this problem.  We cannot simply identify stressors, impairment, or physiological numbers and say that they will result in a particular mortality (Davis 2002). RAMP curves clearly show the importance of context for exposure to stressors and potential mortality or survival (Davis 2010). The question of interactions among stressors and their context has recently been elaborated for freshwater and marine systems (Jackson et al. in press).

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.

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.”

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.

Assumptions for use of RAMP

Loggerhead sea turtle escaping trawl, NOAA

Here is a list of key assumptions for the use of RAMP. The list is probably not exhaustive and can be added to as new perspectives and research warrant. These assumptions have been experimentally tested and validated to various degrees by peer-reviewed published research. Further validation is useful and helps to better define possible error terms in RAMP curves. Healthy, control animals are assumed to have a full complement of reflex actions present. See choices for reflex action testing. 

Vitality is inversely related to reflex impairment. Animal vitality is an abstract concept for which we have strong intuitive notions related to observing absence of injury and presence of behavior, including activity and responsiveness. Reflex actions are fixed response patterns to stimuli that clearly reflect internal state without confounding factors. By using reflex actions to quantitatively measure vitality, the confounding effects of volitional behavior and motivation that are often more related to external conditions can be eliminated. Also animals may not be injured, yet show reflex impairment and reduced vitality associated with other factors (e.g., temperature, exhaustion, hypoxia, and xenobiotics).

Reflex impairment is directly related to stressor types and intensities.  Stressors have been shown to induce reflex impairment, interpreted as symptoms of stress. Therefore reflex impairment is a useful measure of stress. Reflex impairment integrates the effects of stress in whole animal responses that are ecologically meaningful for vitality and fitness outcomes. An impaired animal can have morbidity or decreased predator avoidance, feeding, sheltering, migrating, and reproducing.

Reflex impairment occurs immediately after exposure to stressors. Time course studies for several species have shown immediate impairment after exposure to stressors.  Animals with lower levels of stress can then recover full reflex actions hours to days after exposure to stressors. Reflex actions are sensitive measures of sublethal acute and chronic stress as well as predictors of delayed mortality.    

RAMP curve is different for each species and related to stressor sensitivity. Each species has reflex responses that are evolved for habitat types in which they occur. Differences in reflex types and responsiveness among species are apparent in body types, predator avoidance, habitat choices, and feeding strategies. Some species are easily injured and reflex impaired, while others resist injury or are relatively insensitive to environmental insults (e.g., temperature, hypoxia, and hydrostatic pressure).

RAMP curve used for a species is experimentally derived by inclusion of appropriate types of stressors and animal sizes, ages, and sex. RAMP curves must be derived from reflex impairment observed in animals experimentally exposed to combinations of stressors present in systems of interest. Also animals representing size, age, and sex of interest should be included in impairment experiments. The experiments should result in animals with reflex impairment that ranges from 0 to 100%, with accompanying mortality. The curve must include the complete range of impairment and mortality to avoid extrapolation beyond available data. 

RAMP curve is stable for a species and comprehensive experimentally tested conditions. The stable RAMP curve, with defined conditions of reflex types and testing, can be used among widely different situations for measuring animal vitality, survival, and delayed mortality. Exceptions have been noted for larvae or juveniles with ontogenetically delayed development of reflex actions and spawning anadromous adults which show altered sensitivity to stressors.

Reflex actions in RAMP are given equal weighting rather than weighted differently. Reflex impairment used in a RAMP curve is the result of summing several reflex actions. This approach views the whole animal as the important entity of vitality and fitness. Different reflex actions may be affected by different stressor types. In stressor systems of interest, there are relatively unlimited sets of stressor combinations. Therefore, no a priori expectations of importance for specific reflex actions are made and all measured reflex actions can be equally important. However, the order of reflex action impairment relative to stressor intensity can give valuable information about species sensitivity and associated life history characteristics. 

Observers are assumed to objectively score presence or absence of reflex action in a replicable manner. This assumption is satisfied by using the “rule of doubt”. If any doubt exists about the presence of a reflex action, the action is scored as absent. If the reflex action is present without a doubt, it is scored as present. Further controlled comparisons of reflex scoring among observers is warranted to better define possible observer error terms.

RAMP mortality and survival predictions are dependent on the accuracy of captive holding, tagging, and biotelemetry experiments. To calculate RAMP curves, animals are observed for delayed mortality after initial exposure to experimental stressors. Mortality observed with captive holding is simply related to initial stress, assuming that holding conditions are not stressful.  Mortality observed with tagging or biotelemetry includes sources other than initial stress (e.g., additional stressors, predation, disease, and food limitation)(Thorsteinsson 2002).

Sedna, mother of all sea creatures, K. Sagiatok

High discard survival merits exemptions to European Union ban on fishery discards

Atlantic cod, NOAA

The introduction of the obligation to land all catches (eliminate discards) in the recent reform of the Common Fisheries Policy (CFP) represents a fundamental shift in the management approach to European Union fisheries from regulation of landings to regulation of catch. Research has shown that not all discards die. In some cases, the proportion of discarded fish that survive can be substantial, depending on the species, fishery and other technical, biological and environmental factors. If these surviving animals are discarded instead of landed, they can contribute to future stock recruitment.

Article 15 paragraph 4(b) of the CFP regulation allows for the possibility of exemptions from the landing obligation for species for which "scientific evidence demonstrates high survival rates". Taking the first element of this "scientific evidence"- it is important that managers have guidance on protocols and methodologies that should be followed in order to ensure the results of such experiments are scientifically robust. Presently there are no such internationally agreed guidelines. EWG 13-16 has provided guidance on best practice to undertake survival studies. In this regard EWG 13-16 has identified three methodologies for conducting survival experiments i.e. captive observation experiments, vitality/reflex assessments, and tagging/biotelemetry experiments.

Captive observation experiments involve holding animals that have been captured after exposure to fishery stressors. Holding can be in tanks or net pens while short-term survival is observed.  Holding periods typically range from 3-21 days until mortality associated with experimental fishery stressors has abated. Discard survival rates in specific fisheries conditions are then modeled using data from holding experiments. Davis (2002) reviewed an array of potential explanatory variables for discard survival, which can be classified into three broad categories: biological (e.g. species, size, age, physical condition, occurrence of injuries), environmental (e.g. changes in: temperature, depth, light conditions) and operational (e.g. fishing method, catch size & composition, handling practices on deck, time exposed to air). The complexity and interactions of explanatory variables for discard survival could present a problem to fisheries managers because instead of simply asking “Can we discard this species?” it may be necessary to ask “when, where, and under what conditions can we discard this species?” A potentially unlimited variety of fishery condition combinations would need to be modeled for determining discard survival.

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

Tagging/biotelemetry experiments are similar to captive observation experiments in that animals are captured after exposure to fishery stressors. Then animals are tagged, released, and monitored for survival either by recapture or by biotelemetry.  Survival observations can be made over periods of weeks, months, and years. In addition to the complications of fishery stressor variable interactions, these experiments have the additional complications of including sources of mortality associated with predation and food and habitat availability that are independent of the effects of the initial capture stressors.    

Vitality/reflex assessments are real time in situ determinations of animal vitality and health.  The animal integrates the effects of fishery stressors and lives or dies according to it’s level of vitality impairment. Davis (2010) has shown that calculation of an index for reflex impairment (RAMP, reflex action mortality predictor) based on summing observations of several reflex actions is a robust, quantitative measure of animal vitality that can include the effects of fishery stressors on animal survival. When animals are exposed to fishery stressors and captured, as described above for captive observation experiments and tagging/biotelemetry experiments, they exhibit various degrees of stress and impairment of vitality which can be associated with mortality and survival.  Correlation of RAMP scores with mortality or survival levels observed in captive observation experiments or tagging/biotelemetry experiments makes RAMP a proxy for mortality or survival (Raby et al. 2012). Further RAMP validation can be made by testing with additional holding or tagging experiments in fisheries of interest.

RAMP curves for Atlantic cod, Humborstad et al. 2009

Once validated, RAMP assessments could be used to identify species in a fishery that may have the potential to survive discarding, and that merit an exemption to the Landings Obligation. Where a large majority of individuals of a particular species demonstrated consistently high RAMP scores, and there were very few examples of immediate mortality, this would indicate that species may warrant further investigation to demonstrate its potential for short & long term survival, post-discarding. Using this approach, a large number of species could be assessed (quickly & inexpensively), over a wide range of conditions and for a variety of boats (& discarding practices) throughout the fishery. 

At the same time, continued development of innovative fishing gears and fisher avoidance of high bycatch areas and times can help reduce capture of unwanted species. RAMP can be used to evaluate the survival of animals that are impacted by fishing gears and escape before landing on fishing vessels. The banning of discarding will make the evaluation of mortality rates for animals escaping from fishing gears especially important. "Out of sight and out of mind" will not be a viable strategy with regards to evaluating fishing mortality for gears engineered to enhance escape of bycatch species.

Using RAMP to reduce crab mortality associated with trawl gear encounters

Tanner crab, AMCC

Snow crab, AFSC

RAMP measures for crab mortality have been validated and used in field experiments to help reduce the effects of trawl gear encounters by crabs. Hammond et al. 2013 published the results of a study on Tanner and snow crab mortality associated with trawl gear encounters and they are quoted below:

“The study used the RAMP model to investigate whether modifications to the bottom trawl gear, specifically sweeps (cables connecting doors to trawlnet) and footrope (ground-contact gear attached to the trawlnet), reduced the unobserved mortality of snow and Tanner crab. The RAMP models for these species from Stoner et al. (2008) were augmented with additional observations that more than tripled the sample sizes. Alternative configurations of the resulting RAMP models were compared, examining the effects of sex, size, and shell condition, supplementing with injury observations, and application as a categorical or continuous variable. RAMP-estimated mortality rates were then applied to determine if alternative fishing gear reduced unobserved mortality compared with conventional fishing gear. Specifically, mortality rates for raised trawl sweeps (Rose et al., 2010) and larger diameter footropes were compared with rates for conventional configurations (Rose et al., 2013). Both modifications create larger spaces under the gear for crab escapes. These mortality rates were also compared across sex, size, and shell conditions.”

Reflex actions that were tested for RAMP:

“A major advantage to RAMP is the simplicity of just testing reflexes which can be done in hand, thereby removing the need to retain animals for prolonged periods or to run costly and time consuming physiological lab tests. In the case of Chionoecetes spp. interacting with the trawl gear, Stoner et al. (2008) and this study have shown the reflex impairment score to be a statistically robust predictor of delayed mortality. The effect of a single additional reflex impairment multiplies the odds of mortality (p/(1- p)) by the exponentiated slope from the logistic regression (Faraway, 2006). The multipliers for snow and Tanner crab were 3.0 and 2.9, respectively. Thus, the absence of an additional reflex would roughly triple a crab’s odds of mortality.”

RAMP curves for Tanner and snow crabs:

“Logistic regression analysis of reflexes to predict mortality (RAMP model) indicated that sex, shell condition, and size did not significantly affect the relationship between reflex impairment scores and mortality. When considering the effect of the gear type, logistic regression of the RAMP-predicted mortality found that gear type, sex, shell condition, size, and the gear × shell condition interaction were significant predictor variables for snow crab mortality. Tanner crab showed gear type, shell condition, and their interaction to be significant with the footrope effect. In addition, gear type, shell condition, their interaction, and size were significant with the effect of sweeps. Although shell condition was shown to be statistically significant, the overall mortality was lower with an alternative gear than with a conventional gear, strengthening the case that alternative sweeps and footropes could be used to help reduce unobserved mortality.”

Experimental trawl gear used in study:

Results of gear modification on crab mortality:

“Previous studies have shown that reflex impairment is a sign of stress that can be correlated with mortality outcomes in fish and crab (Davis and Ottmar, 2006; Davis, 2007, 2009; Stoner et al., 2008; Humborstad et al., 2009; Stoner, 2009). One of the limitations of this approach is that we cannot account for the possible mortality that occurs as a result of predation on the crab or fish due to its potentially weakened state from its encounters with the gear. Thus, the RAMP model yields a good relative measure of mortality, if not an absolute measure of mortality. Our study took the RAMP model one step further and used it to assess whether alternative sweeps and footropes could reduce unobserved fishing mortality; the data showed this to be the case.”

“This study is one example of many possible practical applications of the RAMP model. In the context of bycatch reduction technology and modified fishing gear, the RAMP model could prove to be a very useful tool to determine if the alternative gear or modifications to the current fishing gear could reduce the many types of bycatch mortality.”

Using RAMP to estimate fisheries discard mortality in the southern New England flatfish complex

Yellowtail flounder NOAA

Winter flounder NOAA

Windowpane flounder NOAA

RAMP curves were estimated for yellowtail flounder, winter flounder, and windowpane flounder in the southern New England flatfish complex (Barkley et al. 2012).  Fish were treated with experimental trawl and air exposures and sublethal and lethal effects on reflex impairment noted.  Seven reflex actions were tested and responses were combined into RAMP scores.

RAMP curves were calculated (see also for anatomy of a RAMP curve):

RAMP was determined to be a useful method for predicting discard mortality in the flatfish complex and can be used for rapid, real time, onboard sampling of discard mortality rates:

"Implications

The utility of RAMP is the ability to test the reflexes of fish caught and use the RAMP score to predict mortality using the reflex impairment-mortality relationship. Creating reflex impairment-mortality relationships opens up the possibilities to expand RAMP sampling and to gain a more accurate representation of the total commercial discard mortality rates. These reflex methods can be applied to a subsample of fish during commercial fishing trips to allow for a more representative discard mortality estimate. The RAMP methods are also not limited to a particular gear type, so fish caught in the large-mesh otter trawl fishery as well as fish caught in the scallop fishery can be assessed using the same reflexes and can be compared to the same reflex impairment-mortality relationship. This allows for the estimation of discard mortality over a wide spectrum of gears, tow-times, and time on deck.

Summary of conclusions

- The suite of seven reflexes is a reliable indicator of survivability in yellowtail and winter flounder.

• Tow-time was not as important as a stressor on flounder as air exposure. 
• The results indicate that the discard mortality of yellowtail and winter flounder may be reduced onboard fishing vessels by limiting the amount of time the fish are on a dry deck.
• Windowpane flounder are less hearty then yellowtail and winter flounder, and may not be able to survival discarding.
• The reflex impairment-mortality relationships developed from this project for yellowtail flounder and winter flounder can be used to estimate the discard mortality rate of fish, based on at-sea RAMP sampling over multiple gear types."

Realtime knowledge of discard mortality rates can be used in adjusting fishing practices to decrease and avoid discard mortality, as well as for testing new fishing gears designed to reduce bycatch capture and discarding.

Approaches for modeling and predicting bycatch mortality

Modeling and prediction of bycatch mortality can be approached in several ways. Efforts can be focused on prediction from knowledge of controlling environmental factors and fishing processes encountered by animals. Alternatively, efforts can be focused on prediction from knowledge of animal condition that integrates effects of fishing factors. A third hybrid approach combines information about animal condition and controlling fishing factors.

Fishing is conducted in freshwater and seawater, with catch retained, discarded, released, or escaped from commercial, recreational, catch and release, and subsistence fisheries. In all cases, knowledge of target and non-target fishing mortality is essential for management and conservation of fisheries stocks and ecosystems. Fishing occurs under a variety of environmental and operational conditions. Examples of fishing gears include trawls, seines, traps, dredges, hook and line, gill nets, lift nets, and falling gear. While immediate mortality is evident for non-target bycatch discards, delayed mortality is generally hidden from view for discards and escapees from fishing gears and operations.

Fishing factors include a range of types for discards and escapees. Master controlling variables include temperature, air exposure, gear injury, fatigue and exhaustion, fish size, barotrauma, and predators. Synergistic effects of combinations of factors can be significant controllers of mortality.

Davis 2002 capture and discard

Suuronen 2005 capture and escape

Bycatch mortality can be modeled by experimental determination of relationships among environmental and operational factors and mortality rates of various species, either under laboratory or field conditions. Since there are an almost infinite number of factor combinations in a fishery, it is important to prioritize the stress and mortality effects of factors and factor combinations. Primary effects are then modeled for mortality rates. 

Effects of fish size, fishing gear type, and temperature on sablefish mortality, AFSC

A second approach to modeling bycatch mortality is to shift focus from environmental and operational fishing conditions to a more limited set of predictors for mortality based on animal condition. These include wounding, physiological impairment, and reflex impairment. Reflex impairment and RAMP have been found to be the most efficient and inclusive predictors of immediate and delayed mortality.

AFSC

RAMP curves for the relationships between reflex impairment and species mortality are constructed under simulated or actual fishing conditions that are expected.

AFSC

Using constructed RAMP curves, bycatch mortality rates can be measured and predicted in fishing operations through time and space by sampling fish from fisheries.

Georges Bank scallop fishery bycatch

Hybrid combinations of the two modeling approaches can be used if data are available. Animals that are captured or escape from fishing gears can be sampled for RAMP while environmental and operational conditions are noted. Then relationships among these factors can be modeled.

Effect of air exposure on Atlantic cod reflex impairment and mortality, Humborstad et al. 2009

Banning fishery discards and using RAMP

European Union fishery ministers have agreed to phase out the practice of discarding unwanted or regulated animals (bycatch) from landed catches.  The practice of discarding bycatch can be tremendously wasteful of fishery resources including fish, elasmobranchs, invertebrates, birds, amphibians, reptiles, and mammals.

Discarding, Richard

Banning discarding from fisheries requires total retention of animals caught, which must be landed and processed.  As many of these discarded species are of low economic value, efforts are made to design fishing gears that avoid catching bycatch species in the first place.

Suuronen 2005

A key assumption in the ethical design of fishing gears that do not catch bycatch and discarded species is that animals survive gear encounters. Escaping animals must have significant survival rates after gear encounters if they are to continue contributing to recruitment and ecosystem function. If animals escape from fishing gears and do not survive, they are the same problem as discards in fisheries, except that they are hidden.

Suuronen 2005

Measurement of mortality rates for discards and for animals that escape from fishing gears is vital to the management of fisheries, as they represent a significant form of fishing mortality. Discard and escapee mortality rates have been difficult to measure and new, effective methods are needed.

Viability estimates for Pacific halibut bycatch, based on vitality codes (1-4) for injury and activity have been incorporated into fisheries management for several years.  Recent research results by Benoît et al. 2012 on discard mortality have suggested methods based on fishery-scale sampling with semi-quantitative vitality codes (excellent-1, good-2, poor-3, and moribund-4) and conditional reasoning.

Benoît et al. 2012. Post-capture survival probability over time (h) for five southern Gulf of St. Lawrence marine fish taxa (panels), as a function of their pre-holding vitality class score (colours). The shaded areas represent the 95% confidence band for the Kaplan–Meier empirical survival curve for each vitality class, plotted up to the time at which the last observation was made for a given taxon and vitality level. The lines represent the fits of the selected model for each species and vitality class. For cod and plaice, the fits for models M3 and M4 are presented using solid lines and dashed lines respectively (note that these lines largely overlap). The location of the circles along the line and the size of the circles indicate respectively the times at which observations were censored and the proportion of censored observations for the taxon and vitality level at that time.

Reflex impairment measured by RAMP is a quantitative measure of vitality that gives increased resolution and accuracy to the determination of health and survival of discards and animals encountering and escaping fishing gears. Future research on this subject can benefit from the incorporation of fishery-scale sampling of RAMP for discards and for animals escaping from fishing gears.

The banning of discarding will make the evaluation of mortality rates for animals escaping from fishing gears especially important. "Out of sight and out of mind" will not be a viable strategy with regards to evaluating fishing mortality for gears engineered to enhance escape of bycatch species.

Field validation of dungeness crab RAMP underway

Crabs tell us about their vitality, using the language of reflex impairment and RAMP.

Yochum

Field validation of dungeness crab RAMP measures for discard mortality are underway off Newport, Oregon.  These field trials with combined RAMP measurements, fishery conditions, and mark and recapture experiments are a large scale field effort to develop RAMP tools for quantification of bycatch mortality (NOAA 2013).

Undersize Dungeness crab marked with a green T-bar spaghetti tag and released as part of the RAMP field validation experiment. The tag is inserted through the suture at the back of the carapace so that it can be retained through a molt. Picture and caption from Stoner and Yochum, 2013.

Scoring reflex actions

Once we have learned how to "tickle" animals to stimulate a variety of reflex actions, we can consider how to score these actions.  Individual reflex actions can be scored either as present or absent, or can be scored according to their strength of response. We might think that scoring a reflex action by its strength would be the most useful, as it gives a continuous range of values from full strength in large powerful animals through weaker in healthy smaller animals, to weak in stressed large and small animals, and absent in fully impaired large or small animals. A disadvantage of this strength scoring approach is that both animal vitality and animal size can control the strength of reflex action. We are interested in an index for vitality, not confounded by animal size, so using strength of reflex action is not going to be appropriate.

To factor out the effects of animal size, we are left with scoring a reflex action as present or absent.  This may initially be confusing, with the question remaining, is the reflex present or not? I use the "rule of doubt" which says that the reflex is present if it is strong and clearly evident. It is scored absent if there is a question about its presence, whether it is weak or not clearly evident.

Scoring an individual reflex present or absent only gives us a qualitative measure and we are looking for a quantitative measure of vitality. We then move from the perspective of scoring individual reflex actions to a whole animal perspective, which includes many reflex actions, arising from combinations of various physiological, neural, organ, and muscle systems. If we measure the presence or absence of several reflex actions, representing combinations of various metabolic systems in an animal, then we can combine these scores into an integrated measure of reflex impairment that varies continuously and reflects the integrated nature of metabolic systems included in an animal. The combined scores for reflex impairment are then used to construct a RAMP curve which models the effects of stressors on animals through a range of stress and reflex impairment, as related to potential mortality.

An advantage of using RAMP is that the animal tells its story of stress-related impairment using systems that naturally integrate function as a whole animal. The animal communicates its vitality state directly through the language of reflex actions in response to appropriate stimuli, without the confounding effects of size and motivation.