Nephrops biomass index estimation from GALNEP26_2021 Survey in FU26 (West Galicia, ICES Division 9a)

Abstract

Marin Fishing Industry (OPROMAR, Productores de Pesca Fresca del Puerto y la Ría de Marín) promoted a survey onboard a commercial vessel in order to estimate a Nephrops biomass index in FU26 with an observer onboard and the supervision of IEO since 2019. GALNEP26_2021 survey was conducted from 19th to 28th July 2021, following a systematic sampling over a 5x5 nm grid. Area survey was established on the base on the VMS analysis together the bottoms trawl logbooks in the 2009-2017 period. Additionally, sediment composition (EDMOnet) was taken account and gravel and rocky bottoms were eliminated in the area delimited by VMS. Survey was carried out by a unique commercial vessel (27.9 m Length, 109.17 TRB, 430 hp & 70 mm mesh size). The main objectives of GALNEP26_2021 survey were to estimate: the Nephrops abundance index, the discard rate and the size composition for both sexes in this FU. Nephrops total catches were 78 kg, representing lower than 1% of the total retained catch. Discard rate was very low and it was considered negligible. Survey index was 0.95 Kg/h with 95% confident of 1.31. Hauls positive in Nephrops were 18 of a total of 41 hauls carried out during the survey. Spatial analysis of the survey index shows Nephrops is concentrated in a small area on the Northwest half within the historical area distribution in FU26 although low Nephrops catches were obtained in the shallower and deeper part of the south of the area. The mean length was 35.0 mm CL for females and 41.9 mm CL for males. Sex-ratio was estimated in almost 50%.