Information and data for the application of SPiCT to produce MSY advice for Nephrops Stock in FU 26-27 (Western Galicia and Northern Portugal)

Evaluación de Recursos Marinos Vivos en el Área ICESEVALICES

First steps in the estimation of harvest ratio reference points for Nephrops FU 30 (Gulf of Cadiz)

In 2014, a Benchmark Workshop on Nephrops Stocks (WKNEP) was planned for 2016 with a data evaluation meeting in June 2016 and the Benchmark meeting in October 2016. This WD shows the preliminary work carried out till the date about the Nephrops FU30-specific Harvest Ratio reference points estimation

Final report of the Working Group on Nephrops Survey (WGNEPS)

WGNEPS es un grupo de coordinación de Grupos de Expertos en campañas de arrastre y de imágenes submarinas dirigidas a la estimación de la abundancia de Neprhops en el área ICES y de forma exploratoria en el Mediterráneo

ISUNEPCA0721 UWTV Survey on the Gulf of Cadiz Nephrops Grounds and catch options for 2022 in FU30

This working document details the results of the underwater television survey on the Gulf of Cadiz Nephrops grounds (FU 30) conducted in 2021. The survey is considered multi-disciplinary in nature, collecting UW videos, CTD and dredges information. A total 65 UWTV stations were planned in a randomized 4 nm isometric grid but only 59 UWTV stations were used in the geo-statistical analysis. The mean burrow density observed in 2021, adjusted for cumulative correction factor, was 0.024 burrows/m². The final krigged abundance estimate was 73 million burrows with a CV of 11.5%. The 2021 abundance estimate was the lowest value recorded in the time series. Catch advised for 2022 in FU30 when the ICES precautionary approach is applied and according to category 3.1.4, was no more than 50 tonnes

NEW PROPOSED AREA FOR THE ISUNEPCA UWTV SURVEY IN THE GULF OF CADIZ (FU 30)

ISUNEPCA UWTV survey is carried out in the Gulf of Cadiz (UF 30) yearly in spring-summer since 2014, although the first survey is considered as exploratory. The main objective is to estimate a Nephrops abundance index to be use as base of the assessment and advice of this stock. The Nephrops area distribution and coverage of the survey was accepted by the Benchmark Workshop WKNEP in 2016 and this survey was considered as appropriated to providing scientific advice on the abundance of this stock. However, experience acquired during ISUNEPCA survey time series suggests the survey area should be smaller than the current coverage area for this UWTV survey. Therefore, the Nephrops abundance estimate and as consequence the advice of this stock could be affected. A new survey area is proposed based on the analysis of updated and available data

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

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%

A Novel Detection Refinement Technique for Accurate Identification of Nephrops norvegicus Burrows in Underwater Imagery

With the evolution of the convolutional neural network (CNN), object detection in the underwater environment has gained a lot of attention. However, due to the complex nature of the underwater environment, generic CNN-based object detectors still face challenges in underwater object detection. These challenges include image blurring, texture distortion, color shift, and scale variation, which result in low precision and recall rates. To tackle this challenge, we propose a detection refinement algorithm based on spatial–temporal analysis to improve the performance of generic detectors by suppressing the false positives and recovering the missed detections in underwater videos. In the proposed work, we use state-of-the-art deep neural networks such as Inception, ResNet50, and ResNet101 to automatically classify and detect the Norway lobster Nephrops norvegicus burrows from underwater videos. Nephrops is one of the most important commercial species in Northeast Atlantic waters, and it lives in burrow systems that it builds itself on muddy bottoms. To evaluate the performance of proposed framework, we collected the data from the Gulf of Cadiz. From experiment results, we demonstrate that the proposed framework effectively suppresses false positives and recovers missed detections obtained from generic detectors. The mean average precision (mAP) gained a 10% increase with the proposed refinement technique.Versión del edito