Reflex impairment in largemouth bass shows interactions of gear type, fight time, and air exposure

Largemouth bass, Bemep/Flicker

Cooke et al. 2016 examined reflex impairment in largemouth bass captured during the summer (25-27^oC). Excerpts from their paper detail study findings: 

“…little is known about how gear strength and fight time interact with air exposure duration to ultimately influence the level of exhaustion experienced by fish at time of release. Here we systematically varied fishing gear strength (ultralight versus medium-heavy) and air exposure duration (0 versus 120 s) when targeting Largemouth Bass Micropterus salmoides. We relied on reflex impairment (using five different reflexes) as a real-time indicator of fish condition.”

“One of the more interesting observations from this study was that fish that were landed rapidly and thus in better condition were more difficult to handle, which led to longer air exposure. We are aware of anglers and scientists that have mused about the trade-offs between fight time and ease of handling, but to our knowledge this is the first study to formally assess this idea.”

“In this study we used two extremes in gear type and suggest that moderate strength gear likely represents the best compromise in terms of achieving an appropriate level of exhaustion that would facilitate handling and hook removal without leading to complete exhaustion.”

Reflex impairment in captured largemouth bass, Cooke et al. 2016.

“Using reflex indicators, we showed clearly that there was a gradient in reflex impairment with Largemouth Bass; fish captured on UL gear had significantly higher reflex impairment than those captured with MH gear with no air exposure, while fish captured with both gear types had similarly high reflex impairment when exposed to the air.”

Yelloweye rockfish barotrauma and reflex impairment after capture in shallow and deep water

Yelloweye rockfish, Neil McDaniel

Rankin et al. 2016 report on barotrauma and reflex impairment observed for recompressed yelloweye rockfish in situ. They evaluated orientation, reaction to noise and motion stimuli, and visual and swimming capability. 

Behavior of recompressed fish. Top fish, presence of orientation and vision-dependent movement. Bottom fish, absence of vertical orientation in live fish. Rankin et al. 2016

The authors conclude, “Recompression is a valuable treatment for discarded rockfish that would otherwise be too buoyant to return to depth without assistance. However, the loss of reflex actions as basic as vertical orientation, along with the evidence we found of visual compromise in deep-dwelling recompressed yelloweye rockfish, is concerning, as are the long-lasting physical injuries and lack of neutral buoyancy observed in the weeks after capture and recompression. At a minimum, these effects indicate limits to a rockfish’s ability to move effectively, find refuge, and avoid predators upon release.

The findings from these two studies, which reveal severe and lasting injuries, as well as behavioral compromise of recompressed deep-water yelloweye rockfish, reinforce the importance of avoiding fishing contact with deep-dwelling yelloweye rockfish and maintaining spatially-managed rockfish conservation areas closed to fishing.”

Stressors, vitality impairment, and survival of fishes

Developing rapid visual in situ trait assessment (reflex actions, injury) associated with vitality impairment.

Video slideshow (2:06) discussing stressors, vitality impairment, and survival of fishes in fisheries contexts.

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

White sturgeon, NEEF 2016

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

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

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

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

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.

Sport catch and release (C&R) fishing: assessing captured fish condition (vitality) with injury and reflex impairment

Fix.com (2015)

A review and synthesis of tools and tactics for best practices in sport C&R fishing is made by Brownscombe et al. (2017). A key factor for conservation of species fished with C&R is the assessment of fish condition (vitality) and associated survival after release. This assessment is conducted primarily with observation of injury and reflex impairment that results from fishing practices. Fishers can then make educated adjustments to their fishing practices (capture gear, playing time, handling, release, recovery, or harvest) to enhance future species recruitment in sport fisheries.

Reflex tests for C&R fishing, Brownscombe et al. (2017).

Brownscombe et al. (2017) concluded that “As catch-and-release grows in popularity, so must angler education and implementation of best angling practices to ensure the sustainability of this practice and conservation of fish and aquatic environments. Sustainable catch-and-release angling is a joint venture where it is the responsibility of management agencies and scientists to communicate and evaluate the best angling practices, while anglers need to be educated and use the correct tools and tactics to maximize the likelihood that released fish survive. In this regard, catch-and-release angling is perhaps among the most successful and rewarding conservation partnerships.”

C&R practices, Thousand Islands Life (2014).

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).

Triage for captured and released fisheries species: research and survival

Will they survive? (The Guardian, 2013)

Vitality impairment can be linked to post-capture mortality in fisheries bycatch. Vitality impairment can be estimated by direct observation of animal activity, responsiveness, and injury. For each critical fisheries species in crabs, fishes, sharks, and turtles, reflex actions that are consistently present in healthy, uninjured individuals are listed as control levels. Impairment is signified by loss of reflex action types and addition of injury types after capture.  

Reflex actions are fixed, consistent animal behavior patterns that can be triggered by perception of external stimuli (light, sound, smell, gravity, touch). Stimulation of reflex actions is not controlled by body size, motivation, strength of stimulus, or fear. Reflex action traits summed as a whole animal can be an expression of vitality (Davis 2010). In contrast, volitional behavior can be altered by body size, motivation, strength of stimulus, fear, cognition, and as such is not a controlled measure of vitality.

With the species reflexes and potential injury lists, observations of captured animals can be made in commercial and sport fisheries. Patterns of significant impairment can be determined and related to fishing context and species (Raby et al. 2015). These patterns help identify the relative effects of fishing gears, handling, and physical factors (air, temperature, light, pressure) on impairment and potential survival and mortality.

Figure shows overlap between information on animal physiology and fisheries biology, adapted from Horodysky et al. 2015 and modified to show vitality information. Measures of vitality include reflex impairment and injury, which are whole animal measures that are ecologically relevant, linking physiological and population level research and hypothesis testing. Volitional behavior is coordinated whole animal movements beginning with perception and motivation, followed by attraction and aversion to various stimuli (injury, threat, food, shelter, species mates, migration).

Patterns of vitality impairment can guide research questions and priorities to triage fisheries for treatment of bycatch mortality and enhancement of survival. Vitality impairment can measure the efficacy of engineering fishing gears to increase bycatch survival. 

Snow crab discard mortality

Snow crab in Bering Sea pot fishery (ASMI).

Over 19,000 snow crab were evaluated in Bering Sea pot fisheries 2010-2012 for impairment using the RAMP method (Urban 2015). The estimated discard mortality rate was 4.5% (s.d. = 0.812), significantly below the rate used in stock assessment models. The author concludes: “ In this study, the results of RAMP observations showed that at the range of winter temperatures typically encountered by the Bering Sea snow crab fishery, nearly all discarded crab experienced no reflex impairments. Therefore, we estimate that they should have only a 4.8% chance of short-term mortality. Injuries caused by the fishery occurred at very low levels and so should also have a minimal effect on discard mortality rates. However, because long-term survival rates and the effects of reduced crab vitality are difficult to predict, an estimate of the total impact of discard practices on snow crab stocks is not possible. Even with these uncertainties, the current empirical evidence indicates that the assumed discard mortality rate of 50% is conservative.”

Figure 1. The upper panel shows the relationship between the temperature at the snow crab sorting table and the predicted mortality of snow crab based on reflex impairments. Error bars indicate the 95% CI. The lower panel shows the proportions of the temperatures recorded, while the observations were being made during the 2010–2012 fisheries (Urban 2015).

Elements of vitality testing and delayed mortality in fisheries

Conceptual diagram outlining elements for vitality testing and delayed mortality in fisheries. Fish are captured and environment sampled. Fish become stressed which is measured as impairment from control health by observing reflex actions and injury types. Stressed fish are held for captive observation to determine delayed mortality. Bias and error can be introduced by initial impressions of vitality before testing reflex actions and injury, by differing observer scoring opinions, and by holding conditions that are stressful for the fish. 

Scoring vitality impairment is most difficult when observer decision is used. Training observers is a key part of RAMP development. Reflex actions (RA) are clearly present in control animals, and observers do not need decisions to score present. As impairment increases, scoring RA requires increasing observer decisions about whether sampled RA are present. The decision can be based on how control RA appear to trained observers. Each observer will have different opinions that can be influenced by their initial impressions of the animal and of the stressor treatments the animal has been exposed to.

Initially after stress induction, RA impairment increases and mirrors stress levels, while mortality is not evident. When animals reach a critical impairment level, replicates begin to show mortality, which increases rapidly over small changes in RA score. At highest levels of impairment decisions are less frequent as the animal ceases general movement and responsiveness.

Belly up: Righting reflex action time to recovery correlated with delayed mortality?

Upside down fish in market tank (Hong Kong)

RAMP incorporates presence/absence of several reflex actions and injuries to measure vitality impairment and potential delayed mortality. A simpler method may be possible by measuring time for recovery of orientation when fish are placed upside down in water. This method can be tested.

Place a fish upside down in water and observe the time until the fish returns to normal orientation. This duration is a measure of vitality impairment. Longer recovery times indicate greater vitality impairment and data can be included in statistical models for relationships among fishery stressors, injury, righting time, and delayed mortality. We can test the relationship between righting impairment and delayed mortality. 

Righting reflex action is a central behavior that is the nexus of neural, muscle, and organ actions and is intimately linked with loss of physiological regulation associated with stressor exposure.  Olfactory impairment is another example of a central function that is correlated with delayed mortality (in humans, Pinto 2014).

Body orientation is a sensitive measure of fish consciousness. Presence or absence of righting can be included in the RAMP score. Loss and recovery of orientation is a well known symptom for induction of and recovery from fish anesthesia and is used as an indicator of morbidity and delayed mortality in stress experiments (Davis and Ottmar 2006, Szekeres et al. 2014, Raby et al. 2015).  

Measuring replicate animals for the time to righting recovery and delayed mortality after a stressor experiment can test the correlation between righting impairment and delayed mortality. If the correlation between righting and delayed mortality is valid and strong, then we have a rapid method for predicting discard mortality on board fishing vessels without need for holding or tagging fish to confirm their survival. Research groups on fishing vessels can observe fish during catching, landing, sorting, and discarding under differing stressors; seasons, water temperatures, tow durations, catch quantities, species mixes, and sorting times.

RAMP is a component of an integrated conservation approach to coho salmon bycatch mortality management

Raby et al. 2014

Results of Raby et al. 2014 demonstrate the integration of vitality impairment and coho bycatch mortality estimation and management.

“We have provided an estimate of bycatch mortality for an endangered population of coho salmon captured in an aboriginal beach seine fishery, based on three years of tracking fish released from the fishery.” 

“Among all the variables we tested as predictors of mortality, none were significant except for RAMP score, whereby fish with higher RAMP scores (more impaired) were less likely to be successful migrants (Table 3, Fig. 4).”

Distinguishing between natural mortality and bycatch mortality. 

“An alternate approach to calculating a bycatch mortality rate that attempts to distinguish bycatch from natural mortality, is to use RAMP scores and their mortality rates at each level of impairment, and assume negligible bycatch mortality for the fish that were least impacted (vigorous at release).”

“Since some in-river mortality is natural, there is a need to attempt to differentiate mortality caused by the capture itself. To do so, RAMP scores can be used whereby coho salmon released with little or no reflex impairment (vigorous) are assumed to experience no post-release bycatch mortality. Using that conservative assumption, the post-release mortality rate for those fish can then be used as a baseline within the data set. Additional mortality above that baseline that occurs at higher levels of reflex impairment can then be assigned to the fishery (see Fig. 4).”

Using RAMP to monitor condition of bycatch and improve their survival

“The expanded validation of the RAMP approach in the present study provides confirmation that this simple technique is ready for use in this fishery if needed (Raby et al. 2012). The observers in the fishery could easily be taught how to conduct RAMP assessments to monitor the condition of bycatch in real time, provide advice to their crews on how to improve fish condition, and make decisions about whether individual fish should be revived using recovery bags.”

Sublethal effects of simulated angling capture (fatigue and air exposure) in snapper: reflex impairment and physiological stress.

Snapper, Pagrus auratus. Floor Anthoni 2006.

A study of reflex impairment and physiological stress was conducted with captured snapper and published in JEMBE 2014 by McArley, T.J & Herbert, N.A.  Fish were exposed to simulated angling by chasing to fatigue, followed by air exposure.  The authors' text is quoted below.

Reflex impairment (RI) was measured for seven reflex actions (Table 1). “If the presence of a positive reflex response was ambiguous it was scored as absent. The entire RI assessment was completed in less than 50 s, of which the fish was exposed to air for approximately 30 s. Reflexes were scored present (1) or absent (0) for individual fish and the RI score (proportion of reflexes impaired) was calculated by dividing the number of reflexes absent by the total number of possible reflexes (Davis, 2010). For example if four out of the seven possible reflexes were absent a fish would be given an RI score of 0.57.”

Reflex impairment is a potential measure of vitality loss after exposure of snapper to angling stressors: 

“A primary aim of this study was to assess the potential use of RI as a simple tool for measurement of fish vitality following angling and our lab-based trials indicate RI has the potential to be used in this way. RI was significantly related to the duration of strenuous exercise and air exposure (Fig. 1) and therefore provided a good index of fish condition. Importantly, fish exposed to more severe stress treatments exhibited greater RI than those exposed to more mild stress treatments, a finding that agrees with several other studies of RI in fish (Barkley and Cadrin, 2012; Brownscombe et al., 2013; Campbell et al., 2010b; Davis, 2007; Humborstad et al., 2009; Raby et al., 2012, 2013). Furthermore, greater RI was associated with significantly higher plasma lactate concentration and reduced muscle pH suggesting that RI can indicate (predict) an alteration in physiological condition.” 

Anaerobic respiration is associated with lactate production and reflex impairment:

“Burst swimming is powered by anaerobic respiration fueled by stored energy in white muscle (Milligan, 1996) and the lactic acid produced accumulates rapidly in muscle tissue and then “spills over” into circulation after a 5–10 min delay (Wood, 1991). Plasma lactate therefore serves as a useful indicator of anaerobic respiration in fish (Gale et al., 2011; Lowe and Wells, 1996; Meka and McCormick, 2005) and, as fish performed burst swimming during chasing, it is unsurprising that plasma lactate correlated positively with the duration of chasing stress and that both muscle pH and blood pH were lower in fish chased for longer periods. Physiological alterations appeared to be more pronounced in summer than in winter suggesting that when water temperature is warmer a more severe stress response appears to occur in snapper.”

Physiological basis for reflex impairment: 

“RI is thought to have a physiological basis (Davis, 2010) and a significant relationship between RI and increased plasma lactate concentration has been observed in salmonids (Raby et al., 2013). As RI is measured directly after stressor exposure physiological disturbances that manifest quickly during stress are likely causes of RI. Physiological alterations such as cortisol concentration that can plateau 30 min - 1 h after the initial stressor exposure (Milligan, 1996; Wendelaar Bonga, 1997) are therefore unlikely to be directly responsible for the RI measured in this study. In this study most RI occurred as a result of an inability to perform reflexes involving powerful muscular contractions, such as the gag reflex, body flexing and the startle response. Powerful muscular contraction is fueled by anaerobic metabolism in white muscle fibres and can only be maintained for short periods (Milligan, 1996). As higher RI scores were correlated with lower muscle pH and higher concentrations of plasma lactate it is hypothesized that muscle fatigue resulting from anaerobic metabolism performed during strenuous exercise caused the majority of the observed RI. The muscle pH and plasma lactate concentrations associated with the same RI scores, however, were different in summer and winter (Fig. 4) and there was no difference between the summer and winter measures of fish vitality (RI) and mortality. This suggests that rather than being causes of RI, plasma lactate concentration and muscle pH may have been indicators of an unmeasured physiological process that impaired some of the reflexes quantified in the current study. Other reflexes we measured that were not as commonly impaired, such as the righting response and vestibular ocular, are essentially neurological and their impairment likely results from alternative pathways to those measured in this study.”

Mortality was rarely observed when snapper were exposed to angling conditions: 

“Despite the limitations of comparing our mortality estimates to real fishing scenarios the findings provide evidence that strenuous exercise and air exposure imposed during angling, are not likely to be direct causes of discard mortality in P. auratus. During the collection of sub-legal snapper from the wild for this study, fish were landed relatively quickly (approximately 15 to 30 s), and were typically unhooked in less than 30 s. In investigations of authentic angling events for P. auratus of comparable size (< 270 mm FL) in south eastern Australia, the majority of fish were landed in less than 30 s (Broadhurst et al., 2012; Grixti et al., 2010) and had less than 30 second exposure to air (Broadhurst et al., 2012). Thus, the 5 minute strenuous exercise period and the 3 minute air exposure period in this study must be considered extreme levels for recreational angling and probably rarely occur in authentic angling events. Encouragingly, even with these high levels of stress, little mortality was seen against a backdrop of high summer water temperatures.”

Predation risk for snapper that show reflex impairment associated with angling: 

“It is often overlooked in catch and release studies but a potentially important contributor to discard mortality is post-release predation (Raby et al., 2014). While no measure of predation risk was assessed in this study, our measurements of RI indicate that snapper may not be overtly susceptible to predation upon release, at least when no barotrauma is present. This is because RI was minimal among snapper released after angling simulations most relevant to authentic recreational angling events (i.e. 0.5 min chasing with up to 1 min air exposure), and it is believed that the vigorous condition of these fish would not make them easy targets for predators. Importantly, reflexes that might be associated with reduced predator avoidance, such as the startle response and righting response, remained intact.”

Snapper captured by trawl may be at risk from increased air exposure: 

“It is likely that mortality increases significantly at some point beyond 3 min air exposure in P. auratus but this may not be relevant to recreational angling. Longer periods of air exposure, however, may be present in commercial trawl fisheries where large catches are sorted on deck so knowledge of air exposure tolerance beyond that observed in this study would be useful in this context. Therefore, the existence of a predictive relationship between RI and mortality in snapper remains a possibility but probably requires the inclusion of more extreme air exposure treatment to be clarified in future trials.”

Clearly any capture of snapper that produces barotrauma can be a source of mortality and requires further study in deep water commercial and recreational fisheries.

Making and Using RAMP in Fisheries

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

Why is vitality impairment related to mortality?

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

Why score reflex actions and injury?

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

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

Scoring vitality impairment in general

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

Steps for making and using RAMP in fisheries.

Ecological significance of cold shock: reflex action impairment in bonefish

Bonefish, Florida Sportsman

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

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

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

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

Methods for estimating discard survival in fisheries: an integrated approach

Discarding Pacific halibut, FAO

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

“This report will:

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

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

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

Later versions of this report will cover in more detail: 

-  techniques for assessing survival using tagging and biotelemetry; and 

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

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

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

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

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

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

The importance of vitality in fishing experiments

Key fishing stressor factors, Davis, 2002

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

Trawl captured animals, Robert A. Pawlowski, NOAA Corps

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

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

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

Laboratory trawl tow tank, NOAA RACE

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

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

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

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

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

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

Coho salmon, NOAA Fisheries

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

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

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

Survival of the fittest

Bob van Marlen, IMARES

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

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

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

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

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