In the absence of suitable scientific campaign identified to provide one or more abundance indices for the mur-west stock, abundance indices based on commercial fishing data are of interest. They can be constructed using two approaches: a "design-based" approach (already initiated during the ROMELIGO zone 8 project) and a "model-based" approach.

The present document refers to the first approach. For this ICES zone 8, an update of the data for the 5 fleets already identified (trawlers and gillnetters) has been carried out and completed by an analysis for the vessels using Danish seine. In addition, the methodology was applied to ICES zone 7, and the relevance of developing a global indicator for the combination of zones 7 + 8 was discussed in order to take into account the entire geographical area delimiting the mur-west stock.

For Danish seine in zone 8, the fleet identified corresponds to vessels with an average size of 22.0 m (between 18.0 and 24.9 m), average tonnage of 149 GRT (between 88 and 227 GRT) and average power of 459 kW (between 331 and 626 kW) using 70-80 mm mesh with activity in quarter 2. We do not propose a Danish seine reference fleet for zone 7.

For bottom otter trawls in zone 7, we do not propose an indicator of red mullet abundance due to the spatial distribution of catches that could be attributed to the mur.27.3a47d stock (not included in the study).

For gillnetts, catches in zone 7 are very close to those in zone 8, which led us to propose an overall indicator for zones 7 + 8. Among the fleets identified, it is proposed to retain vessels with an average size of 10.8 m (between 7.5 and 14.8 m), an average tonnage of 11.4 GRT (between 2.0 and 31.0 GRT) and an average power of 151 kW (between 70 and 525 kW) using mesh sizes 50-59 mm in quarter 3 even if if attention must be paid to its use and are detailled in the document.

The second approach (model-based ») is currently under development and will be communicated to the WGWIDE at a later date.