|Ref.||Working Document for the Working Group on Widely Distributed Stocks (WGWIDE). 26 August – 1 September 2020, Copenhagen (Denmark)|
|Author(s)||Caill-Milly Nathalie1, Lissardy Muriel1, Bru Noëlle2|
|Affiliation(s)||1 : Ifremer, LITTORAL, LERAR, 1 allée du Parc Montaury, F-64600 Anglet, France
2 : Université de Pau et des Pays de l'Adour, E2S UPPA, CNRS, LMAP, Anglet, France
The ROMELIGO project included a proposal of abundance indicators for mur-west stock using professional fishing data. The methodolgy is based on the selection of samples of representative vessels grouped in clusters with the same technical characteristics, taking into account their LPUE for specifed period and area. The analysis was conducted on an historical dataset from 2005 to 2015. To be able to update it, conditional decision trees were used to find rules to assign any new vessels to one of the predefined OTB or GNS clusters. Then, the trends of LPUE on the overall period were considered.
For OTB, the number of uses shows little variation during the period. In recent years, the LPUEs calculated for the Bay of Biscay show low levels compared to the whole series. The end of the series seems to be marked by an upward recovery which will remain to be confirmed in the following years.
For GNS and over the whole period, a downward trend is observed in three out of four cases for the number of fishing sequences and in two out of four cases for the average LPUE.
Professionals identified one management measure likely to affect the OTB indicators. After analysis, it is estimated that it did not impact the trends of the series. No regulatory element was identified for GNS.
Currently five fleets are selected for the Bay of Biscay (one for OTB and four for GNS).
For the GNS indicators, the number of uses decreases in three out of four cases, that concerning the mesh class 50 - 59 mm in the 2nd quarter reaching a very low level (around 40 sequences in 2018). It is proposed to no longer use this last indicator because we consider that it is no longer representative. For the others, more in-depth work should be able to be carried out in the project ACOST. At the same time, the interest of considering the Danish seine gear could be posed because the length of the series is now sufficient.
Caill-Milly Nathalie, Lissardy Muriel, Bru Noëlle (2020). Update of striped red mullet abundance indices from professional fishing data (2016-2018). Working Document for the Working Group on Widely Distributed Stocks (WGWIDE). 26 August – 1 September 2020, Copenhagen (Denmark). https://archimer.ifremer.fr/doc/00683/79516/