Stock Assessment Form Demersal species. Red mullet - GSA7. Reference year: 1998-2016. Reporting year: 2017
|Other titles||Rapport d'évaluation de stock des espèces démersales. Rouget de vase- GSA7. Année de référence: 1998-2016|
|Ref.||CGPM/AssessmentFormMUT07_2016 , 27p|
|Author(s)||Jadaud Angelique1, Guijarro Beatriz2, Massuti Enric2|
|Sponsor||CGPM/GFCM - General Fisheries Commission for the Mediterranean|
In the Gulf of Lions (GSA 7), red mullet is exploited by both French and Spanish trawlers. Information on French gillnetters is only available for 2011 and 2013-2016, but although it is suspected that they have been fishing red mullet in the past, no data is available to quantify their catches. According to official statistics, during the first part of this period (2004-2012), the total annual landings have oscillated around an average value of 190 tons; since 2012, landings have shown a clear increasing trend. French trawlers dominate the fishery, as they represent 88% of the catches (average 201 tons) for the entire period. After 2009, because of the large decline of small pelagic fish species in the area, the trawlers fishing small pelagic have diverted their effort on demersal species, which may partially explain the high levels of catches since 2010. Between 2004 and 2014, the number of French trawlers operating in the GSA 07 has decreased by 50%: From a maximum number of 121 trawlers in 2004, the French fleet catching red mullet is nowadays composed by 57 units. This follows management measures to reduce the number of boats. The mean modal lengths in the catches of the French and Spanish trawlers are 14 and 15 cm, respectively and the length at first capture is about 5 cm. Catch is mainly composed by individuals of age 0, 1 and 2 (Figure 6.1.3-2), while the oldest age class (3+ group) is poorly represented. In GSA 07, the trawl fishery is a multi-specific fishery. In addition to M. barbatus, the following species can represent important catches: Merluccius merluccius, Lophius sp., Pagellus sp., Trachurus sp., Mullus surmuletus, Octopus vulgaris, Eledone sp., Scyliorhinus canicula, G. melastomus, Trachinus sp., Triglidae, Scorpaena sp. and Raja sp.
The assessment was carried out by means of Extended Survivor Analysis (XSA) over the period 2004-2016, calibrated with fishery independent survey abundance index (MEDITS). In addition, a yield-per-recruit (Y/R) analysis was carried out, over age classes ranging from 0 to 3+. These methods were applied using the FLR libraries in the statistical software R. The residuals, retrospective analyses and other sensitivity analysis performed confirm the stability of the assessment using XSA model.
The stock is in a High overfishing status with a relative high biomass and an increasing trend in the recruitment. The exploitation level is currently above the level estimated to be sustainable since the referent point F0.1 is equal to 0.35 and current fishing mortality (Fcurrent) to 1.18 (average 2014-2016). The current fishing mortality follows fluctuations without clear trend and the spawning stock biomass currently follows an upward trend. The exploitation is mainly concentrated on young individuals (age 0-2). Moreover 75% of the recruitment is mature. The current biomass is above the 66th percentile, however computed over a relatively short time-period (2004-2016).