Using the most recent data (2019–2021), advice published today on mitigation measures to reduce bycatch of common dolphin in the Bay of Biscay stands in contrast to similar advice released in 2020.
The newly published advice reflects greater bycatch estimates in the recent period. This is partly due to improvements in the knowledge base (including métiers covered by at-sea sampling and more accurate assignment of effort to different métiers), and changes in the distribution of common dolphin within the Bay of Biscay.
Emergency measures in 2020
In 2020, following an increase in the number of common dolphins caught in the Bay of Biscay in the preceding years, the EU made a special request, asking ICES to provide additional advice on emergency measures for North East Atlantic common dolphin in the Bay of Biscay . At the time, Virginijus Sinkevičius, the European Commissioner for Environment, Oceans and Fisheries, urged the EU to take action on bycatch of dolphins and other marine animals, stating that, “The levels of bycatch we are facing are not acceptable. It can result in the extinction of local populations of protected species".
At the time, ICES advised a combination of temporal closures of all fisheries of concern during peaks of mortality (concentrated in December–March and July–August) and the use of pingers on pair trawlers to mitigate bycatch outside of the period of closure.
The advice in 2020 highlighted that protection measures could only be effective when applied over a longer period of time. As the EU could only implement emergency measures for a period of six months (with a possible six month extension), ICES advised that these short-term emergency measures can only be considered as a first step toward longer term measures for small cetaceans.
Mitigation measures
Today's advice release addresses only the implementation of mitigation scenarios in the Bay of Biscay to enable a direct comparison with the 2020 advice. The advice recognizes that while there were several mitigation measures that facilitated several management objectives in 2020, there are now very few that work anymore and none for the most conservative management objectives.
ICES again advises a comniationation of temporal closures of all métiers of concern and the application of pingers on pair trawlers to mitigate bycatch outside of the periods of closure.
Enhanced monitoring to assess the effectiveness of management measures (including pinger use) and to augment precision in bycatch mortality estimates of common dolphin is also recommended.
What has changed?
There are now less mitigation measures to reduce bycatch levels to the tested management objectives and none that meet the most conservative objectives. This is due to higher bycatch estimates in the recent period, which is partly due to improvements in the knowledge base (including métiers covered by at-sea sampling and more accurate assignment of effort to different métiers), and changes in the distribution of common dolphin within the Bay of Biscay.
When bycatch mortality estimates based on strandings data is considered, none of the fifteen proposed mitigation measures can reduce bycatch of the common dolphin in the Bay of Biscay below the potential biological removal limit, and only six mitigation measures When considering bycatch mortality estimates based on strandings data.
Implementing measures to reduce dolphin bycatch
The use of pingers has been mandatory for French pelagic pair trawl, bottom otter trawl and bottom pair trawl vessels > 12 m in the first four months of the year since 2020 and year-round for all French pelagic pair trawl, bottom otter trawl, and bottom pair trawl vessels since 2021. Since 2020, the use of pingers has been mandatory for all Spanish trawlers operating in the Bay of Biscay and the northern part of the Iberian Coast.
2023 advice
ICES was requested to evaluate whether the scenarios described in the 2020 advice are still valid - as such, exactly the same methodology was applied. To assess the effectiveness of management measures (and to augment precision in bycatch mortality estimates), enhanced monitoring is required. Regional-scale (Bay of Biscay) abundance surveys should also be carried out on a seasonal basis to monitor short-term changes in distribution and density of common dolphins, which will also help assess the continued appropriateness of the proposed management measures in time.
ICES reiterates that temporary closures in Bay of Biscay in métiers of concern are likely to be the most effective management measures for reducing bycatch mortality in the short term. Availability of bycatch estimates for the species’ entire distribution range, and evaluation of mitigation measures at the same scale, would increase confidence in the evaluation of the mitigation measures performance. ICES also recommends enhanced monitoring to assess the effectiveness of management measures (including pinger use) and to augment precision in bycatch mortality estimates.
View and download ICES advice on EU request on mitigation measures to reduce bycatches of common dolphin (Delphinus delphis) in the Bay of Biscay (ICES Subarea 8).
