Evaluating the Efficacy of Predicting Bycatch Mortality Using Reflex Impairment through an Assessment of Crab Discards

All animals that interact with fishing gear are not necessarily captured, and all animals that are captured are not necessarily retained. Fishing practices and gear configuration, management regulations, and markets dictate which animals ultimately are retained or discarded. The impact of a fishery and the efficacy of management regulations can depend on the mortality rate of the animals that interact with the gear or are discarded. The Reflex Action Mortality Predictor (RAMP) is a simple, non-invasive, and inexpensive approach that has been used to evaluate this component of fishing mortality. The RAMP approach relates the degree of reflex impairment in an animal to the probability the animal will die. Since its introduction in 2006, the RAMP approach has been utilized in the U.S. and abroad to evaluate mortality for a variety of species, fishing gear types, and stressors. Although there have been numerous applications of the RAMP approach in mortality estimation studies, there has been limited research to directly evaluate RAMP estimates and some skepticism remains in the fisheries science and management communities about the reliability and accuracy of the approach. The goal of this dissertation was to conduct research to assess RAMP and to synthesize findings from previously completed RAMP studies. The three research studies described in this dissertation consider: (1) the accuracy of applying an established relationship between reflex impairment and mortality probability to predict overall mortality attributed to novel stressors; (2) the development and utilization of a RAMP relationship to evaluate discard mortality in a fishery with management regulations that mandate discarding of certain categories of animals; and (3) whether the RAMP approach produces accurate estimates of mortality if survival is determined through laboratory captive holding. The first study estimated a relationship between reflex impairment and mortality probability for Tanner crab (Chionoecetes bairdi) discarded from the groundfish bottom trawl fishery in the Gulf of Alaska. This relationship was then compared to one previously established for Tanner crab in the Bering Sea bottom trawl fishery that encountered the fishing gear, but remained on the seafloor ('unobserved bycatch'). While mortality probabilities were similar between the two studies for crab with no or full reflex impairment, discarded crab with intermediate levels of reflex impairment had lower mortality probabilities than those from the unobserved bycatch study. Results from this study indicate the importance of describing all stressors to which animals are exposed and detailing the study methodology when initially creating a RAMP relationship. Failure to do so may result in inaccurate mortality estimates when the RAMP is applied to animals exposed to stressors not included in the original calibration. The second study developed a RAMP relationship using laboratory captive holding for Dungeness crab (Cancer magister) discarded in the Oregon commercial and recreational Dungeness fisheries and estimated that the discard mortality rate is lower than previously determined. This supports the goal of the '3-S' management strategy currently employed for these fisheries to protect sub-legal males (Size), females (Sex), and soft-shell (Season) crab by discarding them from the catch. For the commercial ocean Dungeness fishery, the estimated overall discard mortality rates (five days after release) varied by sex and shell-hardness, and reflex impairment was a significant predictor of mortality for both the commercial and recreational fisheries. In addition, results indicated that, when evaluating the role of discard mortality in '3-S' management with respect to fishery impact and sustainability, it is important to look not only at mortality rates, but also at the mortality- and bycatch- per retained ratios, and temporal trends relative to changes in effort, animal condition, and catch composition. This study also highlighted the (i) importance of evaluating the influence of biological, environmental, and fishing variables on mortality, (ii) complications that arise when establishing a RAMP relationship for a low impact fishery, and (iii) limitations of determining mortality through laboratory captive holding. The third study used mark-recapture methods to evaluate the reliability of results generated using the RAMP relationship established in the second study, which was based on the survival of crab held in captivity in the laboratory. Given the unnatural conditions for determining survival in captivity and the short-term duration of the experiment, mortality probability estimates may be biased. Similarities in patterns of relative survival rates between the studies lend support to the ability of the RAMP relationship to estimate discard mortality rates using captive holding. The laboratory-based RAMP approach was superior in its ability to provide direct estimates of mortality rates, whereas the mark-recapture study was limited to providing relative survival rates between reflex impairment levels that were imprecise due to low numbers of recaptured crab. This study highlighted the complications associated with tagging discarded animals and conducting a RAMP study with a fishery that has highly variable seasonal fishing effort. A synthesis of the research described in this dissertation and published work by other researchers highlights the limitations of the RAMP approach so that future researchers can avoid pitfalls in its application, and leads to suggestions on how to standardize some of the methodological steps. This analysis aims to increase the reliability of future RAMP studies and their production of high quality estimates of discard mortality rates that promote sustainable fisheries

Evaluating the flexibility of a reflex action mortality predictor to determine bycatch mortality rates: A case study of Tanner crab (Chionoecetes bairdi) bycaught in Alaska bottom trawls

AbstractTo quantify total fishing mortality it is necessary to incorporate mortality rates attributed to bycatch, including animals that are discarded and that interact with the gear without being caught. The Reflex Action Mortality Predictor (RAMP) approach has been increasingly used to determine bycatch mortality rates in fisheries. This methodology creates a RAMP that relates reflex impairment to probability of mortality. As the RAMP approach becomes more prevalent it becomes important to evaluate the efficacy of its application. We evaluated the flexibility of this 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 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

Evaluating the flexibility of a reflex action mortality predictor to determine bycatch mortality rates: A case study of Tanner crab (Chionoecetes bairdi) bycaught in Alaska bottom trawls

To quantify total fishing mortality it is necessary to incorporate mortality rates attributed to bycatch, including animals that are discarded and that interact with the gear without being caught. The Reflex Action Mortality Predictor (RAMP) approach has been increasingly used to determine bycatch mortality rates in fisheries. This methodology creates a RAMP that relates reflex impairment to probability of mortality. As the RAMP approach becomes more prevalent it becomes important to evaluate the efficacy of its application. We evaluated the flexibility of this 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 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.Keywords: Trawl, Bycatch mortality, Chionoecetes, RAMP, DiscardKeywords: Trawl, Bycatch mortality, Chionoecetes, RAMP, Discar

Inter-rater reliability of categorical versus continuous scoring of fish vitality: does it affect the utility of the reflex action mortality predictor (RAMP) approach?

Scoring reflex responsiveness and injury of aquatic organisms has gained popularity as predictors of discard survival. Given this method relies upon the individual interpretation of scoring criteria, an evaluation of its robustness is done here to test whether protocol-instructed, multiple raters with diverse backgrounds (research scientist, technician, and student) are able to produce similar or the same reflex and injury score for one of the same flatfish (European plaice, Pleuronectes platessa) after experiencing commercial fishing stressors. Inter-rater reliability for three raters was assessed by using a 3-point categorical scale (‘absent’, ‘weak’, ‘strong’) and a tagged visual analogue continuous scale (tVAS, a 10 cm bar split in three labelled sections: 0 for ‘absent’, ‘weak’, ‘moderate’, and ‘strong’) for six reflex responses, and a 4-point scale for four injury types. Plaice (n = 304) were sampled from 17 research beam-trawl deployments during four trips. Fleiss kappa (categorical scores) and intra-class correlation coefficients (ICC, continuous scores) indicated variable inter-rater agreement by reflex type (ranging between 0.55 and 0.88, and 67% and 91% for Fleiss kappa and ICC, respectively), with least agreement among raters on extent of injury (Fleiss kappa between 0.08 and 0.27). Despite differences among raters, which did not significantly influence the relationship between impairment and predicted survival, combining categorical reflex and injury scores always produced a close relationship of such vitality indices and observed delayed mortality. The use of the continuous scale did not improve fit of these models compared with using the reflex impairment index based on categorical scores. Given these findings, we recommend using a 3-point categorical over a continuous scale. We also determined that training rather than experience of raters minimised inter-rater differences. Our results suggest that cost-efficient reflex impairment and injury scoring may be considered a robust technique to evaluate lethal stress and damage of this flatfish species on-board commercial beam-trawl vessels

Utilizing Fishermen Knowledge and Expertise: Keys to Success for Collaborative Fisheries Research

Collaborative fisheries research provides a mechanism for integrating the unique knowledge, experience, and skills of fishermen and scientists. It is a joint intellectual endeavor that begins with the inception of a project and continues until its final stages, with each group having mutual investment in—and ownership of— the project. Collaborative fisheries research promotes communication and trust among fishermen, scientists, and managers and can provide much-needed scientifically valid data for fisheries management. It can enhance federal and state management data collection programs, which span broad sections of coastline, by increasing the ability to detect changes in local metapopulations that may be overfished or underutilized. We describe a methodology for conducting collaborative fisheries surveys and apply it to marine protected areas along the central California coast. During a series of workshops in 2006, attended by members of the fishing, academic, environmental, and management communities, protocols were established for conducting hook-and-line surveys collaboratively with commercial passenger fishing vessel captains and volunteer recreational anglers. The protocols have been implemented annually since 2007. This case study highlights the effectiveness of—and the essential steps in—developing our collaborative fisheries research and monitoring projects

Repeatability of flatfish reflex impairment assessments based on video recordings.

Using measures of reflex impairment and injury to quantify an aquatic organism's vitality have gained popularity as survival predictors of discarded non-target fisheries catch. To evaluate the robustness of this method with respect to 'rater' subjectivity, we tested inter- and intra-rater repeatability and the role of 'expectation bias'. From video clips, multiple raters determined impairment levels of four reflexes of beam-trawled common sole (Solea solea) intended for discard. Raters had a range of technical experience, including veterinary students, practicing veterinarians, and fisheries scientists. Expectation bias was evaluated by first assessing a rater's assumption about the effect of air exposure on vitality, then comparing their reflex ratings of the same fish, once when the true air exposure duration was indicated and once when the time was exaggerated (by either 15 or 30 min). Inter-rater repeatability was assessed by having multiple raters evaluate those clips with true air exposure information; and intra- and inter-rater repeatability was determined by having individual raters evaluate a series of duplicated clips, all with true air exposure. Results indicate that inter- and intra-rater repeatability were high (intra-class correlation coefficients of 74% for both), and were not significantly affected by background type nor expectation bias related to assumed impact from prolonged air exposure. This suggests that reflex impairment as a metric for predicting fish survival is robust to involving multiple raters with diverse backgrounds. Bias is potentially more likely to be introduced through subjective reflexes than raters, given that consistency in scoring differed for some reflexes based on rater experience type. This study highlights the need to provide ample training for raters, and that no prior experience is needed to become a reliable rater. Moreover, before implementing reflexes in a vitality study, it is important to evaluate whether the determination of presence/absence is subjective

Utilizing reflex impairment to assess the role of discard mortality in ‘Size, Sex, and Season’ management for Oregon Dungeness crab (Cancer magister) fisheries

We found that crab discarded from Oregon (U.S.A.) commercial and recreational fisheries for Dungeness crab (Cancer magister) have lower post-release mortality than previously estimated. This aligns with the goals of the ‘3-S’ management strategy currently employed for these fisheries, to protect discarded sub-legal male (Size), female (Sex), and soft-shell (Season) crab. We found that, for the commercial ocean Dungeness fishery, overall discard mortality rates (five days after release) were 0.080 (95% Confidence Interval 0.061-0.100) for females; 0.012 (95% Confidence Interval 0.002-0.022) for hard-shell males; and 0.092 (95% Confidence Interval 0.026-0.157) for soft-shell males. The overall discard mortality rate for the recreational bay fishery (from a boat) was estimated to be 0.009 (95% Confidence Interval 0-0.018). A Reflex Action Mortality Predictor (RAMP) relationship, which relates reflex impairment to mortality probability, was created and utilized to estimate mortality rates. Our study highlights the importance of looking not only at discard and mortality rates to evaluate ‘3-S’ fishery management, but also the mortality- and bycatch-per-retained ratios, and temporal trends relative to changes in effort, animal condition, and catch composition.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Non-parametric Kaplan–Meier survival probability estimates over 14 days of monitoring of discarded plaice (<i>Pleuronectes platessa</i>) at 0.2 intervals of the reflex index based on scores from the continuous scale.

<p>(A) mean; (B) rater A; (C) rater B; and (D) rater C.</p

Relationship between the hazard ratio (coxph regression model for a mean rater with state of the fish as response variable and the reflex index based on continuous reflex scores; see S13 Table) and the reflex impairment index based on continuous scores for plaice (<i>Pleuronectes platessa</i>) at 17, and 24 cm in total length.

<p>Relationship between the hazard ratio (coxph regression model for a mean rater with state of the fish as response variable and the reflex index based on continuous reflex scores; see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179092#pone.0179092.s014" target="_blank">S13 Table</a>) and the reflex impairment index based on continuous scores for plaice (<i>Pleuronectes platessa</i>) at 17, and 24 cm in total length.</p