EU request on appropriate bycatch monitoring systems at Member State level and on regional coordination

There is not one single monitoring design that is universally applicable to achieve a precise and accurate bycatch per unit effort (BPUE) estimate of endangered, threatened, and protected (ETP) species. In general, increasing the number of vessels monitored increases accuracy and precision.

Simulations applying an unstratified random sampling design show that the monitoring coverage needed to achieve a reliable and accurate BPUE is highly dependent on bycatch probabilities. Substantial increase in the current monitoring coverage is required to obtain precise and accurate BPUE for species which are caught rarely. For species with bycatch probability of 0.01, a monitoring coverage of 7% of fishing operations is needed to achieve the previous target coefficient of BPUE estimate variation (CV) of 0.3.

Based on the one case study, simulations showed that stratification of bycatch monitoring by métier yields more precise and accurate BPUE estimates for species with very low bycatch probability.

At‑sea scientific observer and electronic monitoring are the methodologies that provide the most reliable bycatch data. Self-reporting and questionnaires could also be implemented when access to vessels is very limited, however with greater uncertainty.

Days-at-sea is currently used as the common unit of fishing effort, as it is available for all reported fleets. However, higher resolution effort information (e.g. soak time for static gears) is necessary to obtain more precise and accurate BPUE estimates of ETP species, and these should be reported in a standard manner in logbooks.

ICES has previously advised on the high-risk métiers and areas for bycatch. ICES advises that the mandatory biological parameters to be recorded during the on‑board monitoring of bycatch events are species, sex, and length. It is recommended that fisheries observers document all bycatch events with photos to validate identifications.