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.”

Effect of hypoxia, injury, and facilitated recovery on reflex impairment (RAMP) in migrating sockeye salmon

Sockeye salmon and Dolly Varden, J Armstrong/UW

A study on the effects of hypoxia and injury associated with gill net fisheries and facilitated recovery in sockeye salmon migrating in the Fraser River showed important results for the use of RAMP to measure sublethal effects of stressors (Nguyen et al. 2014).

The authors state:

“Here, we examined sources of delayed fisheries-related mortality in relation to three known factors influencing postrelease behavior and mortality in fish: physiological exhaustion (stress through air exposure), physical damage (via gill net entanglement), and facilitated recovery (using Fraser boxes). We used sockeye salmon (Oncorhynchus nerka) in the lower Fraser River as a model for this research, given conservation concerns regarding a number of sockeye populations (see Cooke et al. 2012). The study was designed to simulate gill net fisheries because high levels of delayed mortality may have important implications for harvest management in exploited and non-target salmon populations. Our primary objective was to distinguish the relative consequences of physical injury and air exposure stress using an experimental approach coupled with reflex assessments (Davis 2010), physiological sampling (non-lethal blood samples; see Cooke et al. 2005), and telemetry tracking of postrelease migration success (Donaldson et al. 2008). Specifically, we used assessments of reflex impairment and blood physiology to characterize the relative impacts of our experimental treatments. Our secondary objective was to test whether Fraser recovery boxes could reduce delayed mortality and improve migration speed for captured fish exposed to varying degrees of stress and injury.”

The study used experimental stressor treatments: C - Captured-only; A - captured and Air exposed; I - captured and Injured; IA - captured and Injured + Air exposed.

The authors found:

“RAMP is intended to be a rapid, simple, and inexpensive means of assessing fish vitality (Davis 2010). It has also been validated as a predictive measure for delayed mortality in coho salmon caught in beach seine fisheries (Raby et al. 2012). RAMP scores indicated sublethal effects resulting from the A treatment but not from the I treatment. Thus, either RAMP may not capture sublethal effects from injuries, even though fish were clearly stressed (elevated plasma lactate and cortisol), or the I treatment used here was not severe enough to impair reflexes. Further research investigating a large range of physical injury might be useful in resolving this issue. Until this is done, we believe it is unwise to rely solely on a RAMP score for predicting delayed mortality of injured migrating adult sockeye salmon. Previous studies show that RAMP scores are positively correlated with intensity of capture stressors (e.g., Davis 2005, 2007; Davis and Ottmar 2006; Humborstad et al. 2009; Raby et al. 2012), but none considered the potential linkage between RAMP and physical injury. Nonetheless, wounds inflicted in fish during capture, which can be highly variable, are a major source of mortality for discards and escapees (Trumble et al. 2000; Suuronen et al. 2005). In the interim, quantitative indexes for physical injuries in fishes have been developed and used in field settings such as visual assessments (e.g., Trumble et al. 2000; Davis 2005; Baker and Schindler 2009) or use of forensic techniques (e.g., fluorescein) to detect nonmacroscopic injuries (Noga and Udomkusonsri 2002; Davis and Ottmar 2006; Colotelo et al. 2009) and might be useful to include when predicting mortality.”

Clearly, further research and validation is needed to establish relationships between RAMP, injury, vitality, and mortality.  As suggested for fish that show barotrauma symptoms, it may be appropriate to consider the inclusion of scoring for presence or absence of injury types in combination with reflex impairment. The effects of injury on reflex impairment differ among species, as shown for fish (Davis and Ottmar, 2006) and crabs (Stoner et al. 2008). Also, at lower levels of stress in some species, reflex impairment may not occur, indicating that the animals are responding to stress in an adaptive manner. Consideration and inclusion of injury in RAMP is important because of it's potential relationship with delayed onset of disease associated with tissue exposure to pathogens.

Reflex impairment can measure sublethal effects of temperature, hypoxia, and injury

Epaulette shark, Aquarium

The epaulette shark is a tropical reef shark that can live in an environment with cyclical periods of low oxygen concentration and high temperature (Wise et al. 1998). After exposure to hypoxic conditions, epaulette shark reflex actions were tested, including righting, response to touch, rhythmic gill movements, rhythmic swimming, and movement of diagonally opposed fins for locomotion. Reflex actions were not impaired by hypoxia, suggesting that animals were adapted to reef conditions and would not show maladaptive responses to hypoxia. Subsequently, this species was found to have important adaptations to hypoxia (Soderstrom et al. 1999, Hickey et al. 2012).

Animal responses to stressors can be adaptive or maladaptive. When animals are exposed to stressor types or intensities for which they are not adapted, stress responses can be too much of a good thing. Adaptive responses help the animal move away from and avoid stressors to return to normal unstressed behavior and homeostatic states. Maladaptive responses cause the animal to become more stressed and eventually can result in morbidity and mortality. 

Adaptive and maladaptive responses of crustaceans to stressors and stress, Stoner 2012

Reflex impairment is an ecologically relevant measure of vitality loss, fitness, and the spectrum of adaptive and maladaptive responses to stressors. Measurement and summation of a suite of reflex actions (as in the case of RAMP or barotrauma modified RAMP) is a powerful means for testing experimental hypotheses about the effects of stressors on animals. For aquatic animals, temperature (elevated or depressed), hypoxia, and injury are important master variables associated with stress induction (Davis 2002, Suuronen 2005, Gale et al. 2013).

The key to testing for vitality, stress, and fitness using reflex actions or barotrauma symptoms is to derive an emergent index for reflex impairment by summing presence or absence of many individual actions or symptoms. The resultant emergent impairment index (RAMP) is a powerful synthesis of the many mechanistic systems (behavior, physiology, neural, muscle, organ) that have been identified in a whole animal. RAMP expresses, with quantitative data, the resultant vitality and health state of the animal.

Some examples of relationships between reflex impairment and temperature, hypoxia, and injury are illustrated below. In these examples reflex impairment was significantly different among stressor treatments and was related to the severity of stressors.

Reflex impairment in crabs exposed to low temperature, Stoner 2009

Reflex impairment in Atlantic cod exposed to hypoxia, Humborstad et al. 2009

Reflex impairment in coho salmon exposed to hypoxia, Raby et al. 2012

Reflex impairment in sockeye salmon exposed to injury from different gear types, Donaldson et al. 2012

Reflex impairment in blue rockfish exposed to injury from barotrauma, Hannah et al. 2008

Barotrauma, RAMP, and discard survival

Yelloweye rockfish with barotrauma, OSU

Capture of fishes with physoclist gas (swim) bladders can result in impairment by barotrauma. Symptoms of barotrauma offer additional measures of impairment that can be used as predictors for survival and mortality when combined with reflex impairment to calculate RAMP (Diamond and Campbell 2009, Campbell et al. 2010). 

Calculation of RAMP modified for barotrauma is as follows. A reflex action is scored not impaired (0) when strong or easily observed, and scored impaired (1) when not present, weak, or there is a question about being present. A barotrauma symptom is scored absent (0) when not present or there is a question about presence, and present (1) when easily observed. Barotrauma and reflex impairment scores for an individual animal are then summed and divided by the total observable impairments possible to calculate proportion impairment (RAMP score). 

  

Snapper (Lutjanus sp.) and rockfish (Sebastes sp.) often show many of the barotrauma symptoms listed above in the table. Pressure from an expanded gas bladder results in many forms of swelling, distention, and eversion. Severely impaired discarded fish have difficulty leaving the water surface and returning to depth.  These fish have low survival, which can be improved with recompression devices designed to lower fish to capture depths, where healing and recovery can occur.

NOAA

Behavioral observations of rockfish with barotrauma have shown that fish trapped on the surface have a higher incidence of reflex impairment when caged at depth for recompression. Survival during healing and recovery will be dependent on return to normal behavior, e.g. avoidance of predators, return to feeding, and appropriate habitat choice.

Blue rockfish impairment after barotrauma, Hannah et al. 2008

In a tagging study, rockfish recompressed in a cage and released were shown to recover from barotrauma and resume normal behavior in the sea (Hannah and Rankin 2011).

Copper rockfish movement recovery after barotrauma, Hannah and Rankin 2011

Gadid species such as Pacific cod and Atlantic cod do not show overt symptoms of barotrauma when captured at depth. Instead their gas bladder ruptures and relieves the potential pressure of an expanded gas bladder (Nichol and Chilton 2006, Midling et al. 2012). Discards of these species can more easily descend to depth after release, with healing and recovery occurring within short periods of time.

Pacific cod movement recovery after barotrauma, Nichol and Chilton 2006

Pearl perch is another example of a physoclist species that does not exhibit overt symptoms of barotrauma during capture (Campbell et al. 2014). As angled fish approach the surface, gas is released through rupture.  For this species, hook location and type were found to be important predictors of discard survival.

Pearl perch, Dave Harasti

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

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.

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.”

Estimating dungeness crab bycatch mortality rates

Yochum


Two approaches are used to estimate dungeness crab bycatch mortality, allowing for a field validation of the RAMP approach (Yochum et al. 2013).

Yochum et al. 2013

Preliminary results are available for using RAMP to estimate dungeness crab bycatch mortality in Oregon fisheries; including commercial crabbing, recreational crabbing, and trawling.

Yochum et al. 2013

More information on this project is available (Yochum, Stoner and Yochum 2012, and NOAA 2013).

Measuring recovery of bycatch turtles from hypoxia using RAMP

Midland painted turtle, Harding 2009

Reflex impairment was tested in recovering freshwater painted turtles (Chrysemys picta) that were exposed to hypoxia as bycatch in fyke net fisheries (LeDain et al. 2013).

"Adapting the use of RAMP from fish to gauge the severity of anoxia on painted turtles was effective. All the reflexes used in this study indicated some level of impairment following submergence, with some reflexes being more sensitive than others. The tactile responses to the limbs and head were the most insensitive to submergence: they were often the only remaining reflexes after submergence (Table 1). Thus, the absence of tactile responses could be indicative of turtles requiring assisted recovery the most. Other species of turtles may require different types of reflex responses that suit their morphology better (e.g., loggerhead turtles, Caretta caretta, are too large to use a hand holding ‘‘escape response’’). However, a tactile response is a universal reflex that can be used in all species. Employing a presence/absence scoring reduced subjectivity and will ease the training of commercial fishers, researchers, and government and nongovernment agencies on the use of the RII. In sum, we feel the RII is a very useful tool to assess turtle condition."

The authors suggest that tests for reflex impairment (RII, reflex impairment index) modeled after RAMP methodology can be useful for assessing assisted recovery and potential mortality in turtle bycatch.

"Although reduction of turtle mortality can be achieved through educating fishers on proper handling and recovery methods for turtles, the first course of action should be checking nets frequently and implementing seasonal or area restrictions. Bycatch reduction devices (turtle excluders and escape modifications) are also effective in reducing the number of turtles caught in nets while maintaining fish catch (Guillory and Prejean 1998; Lowry et al. 2005; Fratto et al. 2008; Hart and Crowder 2011; Larocque et al. 2012c). However, since turtle bycatch can still occur despite these conservation measures, albeit at reduced levels, examining reflex impairment is an effective and inexpensive way to discern whether turtles require assisted recovery after incidental capture in submerged nets."

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.