Report of the Workshop on Methods for Estimating Discard Survival 5 (WKMEDS5)
The primary aim of this meeting was to complete terms of reference c) Critically review current estimates of discard mortality, with reference to the guidelines on best practice to conduct discard survival assessment (an output of ToR a); and continue ToR d) Conduct a meta-analysis, using the data detailed in c), to improve the understanding of the explanatory variables associated with discard mortality and identifying potential mitigation measures.
These terms of reference are being met as part of a “Systematic Review” (e.g. CEE, 2013; Hughes et al., 2014; Higgins and Green (eds.), 2011). The meeting was divided into two subgroups to continue on the relevant components of a SR, in context with ToRs c and d.
Group 1: Critical Review of Survival Assessments and Estimates: The precision and accuracy of discard survival estimates is likely to vary between different assessments, even on the same species in the same fisheries. This group applied the protocol for a systematic critical review process, developed in the previous meeting, using methods such as those recommended by the Collaboration for Environmental Evidence (http://www.environmentalevidence.org/), to assess different survival studies in terms of essential criteria derived from the WKMEDS Guidelines (Section 3.0).
This review process was applied to a number of case studies to establish a database of validated discard survival estimates (with appropriate measures of uncertainty):
- North Sea Flatfish, in particular Plaice (Pleuronectes platessa) and Sole (Solea solea) Norway Lobster (Nephrops norvegicus);
- Skates and Rays (regulated commercial species).
The species addressed in these case studies have attracted attention as potential candi-dates for “High survival” exemptions from EU Landing Obligation (EU Common Fisheries Policy, Art. 15, para. 2b). WKMEDS has now completed the critical review of all three case studies, this meeting focused on Skates and Rays and updated the other case studies with recently completed studies. The structure of a manuscript describing this work was agreed with a view to submit for publication.
Group 2: Meta-analysis of Survival Estimates: Meta-analysis provides a quantitative synthesis of the effect size of key explanatory variables from different but related stud-ies. At this meeting, methods for conducting a meta-analysis of discard survival data were trialled. In particular, time was dedicated to the discussion and development of methods for building on the progress made in WKMEDS 4:
- projecting non‐asymptotic survival estimates to asymptote; and
- defining quality assessment criteria and weighting methods.
The meta-analysis methods defined in WKMEDS 3 were tested at this meeting using the Nephrops data generated from Group 1 to specifically address the question: ‘what is the discard survival (and variability) of Nephrops norvegicus in European trawl fisheries?’
This being the final year of the agreed original term for WKMEDS, there was discussion on its future. There was strong support from WKMEDS members for the continuation of WKMEDS for another 3-year term and recommended ToRs included: Further development of theoretical and practical methods to assess discard survival levels; investigations into fishing practices to improve discard survival; and the application of discard survival estimates in fisheries management.
Published under the auspices of the following ICES Steering Group or Committee