The WKD3C3THRESHOLDS meeting provided a platform for experts from the EU member states to meet and progress the assessment methodology on Criteria 3 of Descriptor 3 upon request by EC (DGENV). WKD3C3THRESHOLDS is the second of a series of three workshops (WKD3C3SCOPE, WKD3C3THRESHOLDS and WKD3SIMUL) to identify operational indicators for MSFD D3C3.
The workshop was organised as a series of presentations of results with intermittent group discussions.
The D3C3 indicators agreed at WKD3C3SCOPE were estimated and documented for a selection of stocks representing different life-histories (Tor a). Plots comparing indicators were investigated for stocks with all estimated indicators. The age structure indicators ABI, ASA, POS and SSB/R generally followed the temporal development of SSB and react similarly to F. A gap of up to 10 years was observed between changes in F and subsequent changes in age structure indicators for long-lived species while SSB responded quickly to changes in F. For medium-lived stocks, the four age structure indicators exhibited similar temporal patterns, with SSB divided by R tending to be more variable. Recruitment and mean weight at age documented shifts in productivity, impacting age structure indicators differently when changes occur. Plots of F, recruitment, weight at age and SSB are considered useful for understanding cases where changes in F do not impact SSB as expected (e.g. rebuilding does not occur or stock remains high in spite of high F). Higher proportions of older fish as measured by ABI/ASA/POS or SSB/R did not appear linked to an immediate increase recruitment. A comparison of length-based and age-based indicators for Mediterranean stocks was also conducted. Recruitment detection from survey time series showed uneven patterns over stocks and time series, and in some cases depended on survey timing. Length-based indicators exhibited weak consistency information from stock assessments, and confounding effects of biological variability and sampling timing on observed recruitment pulses were noted. The indicator L90R, calculated from the length-frequency distribution of fish larger than recruiting length, seemed to perform well among those inspected.
Thresholds for the D3C3 indicators for stocks representing different life-histories, data availability and MSFD (sub)regions (when possible) were discussed (ToR b and c). The suggested thresholds covered all approaches identified by WKD3C3SCOPE. Clear thresholds where the indicator signifies stock productivity declines could not be identified from the data as none of the age structure indicators showed a positive correlation with stock productivity. As a result, threshold levels cannot be determined based on levels at which stock productivity is either impaired or enhanced. In the absence of clear relationships between the indicators and stock health, the workshop used varying percentages (10th percentile, median/50th percentile) of the simulated or observed distributions of indicators to determine good status of the indicator. The analyses presented emphasized the direct influence of recruitment and growth on fisheries yield and precautionary fishing mortality limits. Finally, a decision tree to choose a threshold setting method was proposed for further testing in WKSIMULD3 on the basis of listed pros and cons discussed by WKD3C3THRESHOLD participants.
ARMELLONI Enrico;
BARTOLINO Valerio;
BELLIDO J.M.;
BOLUND Elisabeth;
BOULCOTT Philip;
CAMPON-LINARES Victoria;
CANAL Gema;
CASERMAN Helena;
COSCIA Ilaria;
FORTIBUONI Tomaso;
GARNACHO Eva;
GUIJARRO Beatriz;
GONCALVES Patricia;
GRIFFITHS Chris;
JACOBSEN Nis Sand;
KUEHN Bernhard;
MANEIRO Isabel;
MANTOPOULOU PALOUKA Danai;
PEIXOTO DA SILVA Uaelrson Iran;
PROBST Nikolaus;
ROWE Owen;
SEIXAS Sonia;
TIFOURA Amina;
VASILAKOPOULOS Paraskevas;
VILANUEVA Ching Maria;
WENNHAGE Håkan;
ZARAGOZA Nuria;
RINDORF Anna;
SCARCELLA Giuseppe;
2025-06-09
International Council for the Exploration of the Sea
JRC138587
2618-1371 (online),
https://doi.org/10.17895/ices.pub.25266580,
https://ices-library.figshare.com/articles/report/Workshop_to_apply_thresholds_for_the_preselected_indicators_for_MSFD_D3C3_WKD3C3THRESHOLDS_/25266580,
https://publications.jrc.ec.europa.eu/repository/handle/JRC138587,
10.17895/ices.pub.25266580 (online),
