Stock Assessment Form Demersal species. Hake - GSA7. Reference year: 1998-2016. Reporting year: 2017
|Other titles||Rapport d'évaluation de stock des espèces démersales CGPM, Merlu GSA7. Années de référence 1998-2016|
|Ref.||CGPM/AssessmentFormHAKE07_2017 , 32p|
|Author(s)||Jadaud Angelique1, Guijarro Beatriz2, Massuti Enric2|
|Sponsor||CGPM/GFCM - General Fisheries Commission for the Mediterranean|
Hake is one of the most important demersal target species for the commercial fisheries in the Gulf of Lions (GSA 7). In this area, hake is exploited by French trawlers, French gillnetters, Spanish trawlers and Spanish longliners. Since 1998, an average of 241 boats are involved in this fishery and, according to official statistics, the total annual catches for the period 1998-2016 have oscillated around an average value of 1914 tons (1057 tons in 2016). In 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. Between 1998 and 2016, the number of French trawlers operating in the GSA 07 has decreased by 50%. The French trawler fleet is the largest considering catches realized. The proportion of boats and catches are respectively (38% and 74%). The length of hake in the trawler catches ranges between 3 and 92 cm total length (TL), with an average size of 21 cm TL. The second largest fleet is the French gillnetters (46 and 16% respectively. range 13-86 cm TL and average size 39 cm TL), followed by the Spanish trawlers (12 and 11%. respectively. range 5-88 cm TL. and average size 24 cm TL), and the Spanish longliners (4 and 1%. respectively. range 22-96 cm TL and average size 50 cm TL). The hake trawlers exploit a highly diversified species assemblage: Striped red mullet (Mullus surmuletus), red mullet (M. barbatus), angler fish (L. piscatorius), blackbellied angler fish (L. budegassa), european conger (Conger conger), poor-cod (Trisopterus minutus capelanus), fourspotted megrim (Lepidorhombus boscii), soles (Solea spp.), horned octopus (Eledone cirrhosa), squids (Illex coindetii), gilthead seabream (Sparus aurata), European seabass (Dicentrarchus labrax), seabreams (Pagellus spp.), blue whiting (Micromesistius poutassou), tub gurnard (Chelidonichtys lucerna).
The stock of European hake in GSA 7 was assessed over the period 1998-2016 applying an XSA analysis (using an R script developed by the Joint Research Center) 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 5+. An a4a analysis was also performed and compared to the XSA classical approach, involving sensitivity analyses on parameters to select the best run. The comparison of the a4a and XSA results displayed a good consistency as the trends for the various variables were found to be similar. Nevertheless, because of the overestimation of the last year estimated recruitment by the a4a model, the WG validated the use of the precautionary XSA approach for this assessment. These methods were applied using the FLR libraries in the statistical software R.
Diagnosis of stock status: This stock is in an overexploitation status with a relative low biomass with periodically higher recruitments in 1998, 2001-2002 and 2007. Since 2007, the recruitment has followed a decreasing trend and is currently at a very low level. Since 2010, the fishing mortality has reached the highest levels of the time series. Moreover, spawning stock biomass (SSB) displays a decreasing trend over the analysed period and is at the lowest level of the series without any sign of improvement.The exploitation level is currently above the level estimated to be sustainable. The reference point F0.1 (0.15), chosen as proxy of FMSY and as the exploitation reference point consistent with high long term yields is highly lower than current fishing mortality (Fcur=1,91). The exploitation is mainly concentrated on young individuals.