Developments on the UWTV survey in the Gulf of Cadiz Y. Vila & C. Burgos WGNEPS 2015 Cadiz, 10-13 November

ISUNEPCA_UWTV Survey in the Gulf of Cadiz 2014 Spanish Oceanographic Institute (IEO) carried out an exploratory Nephrops UWTV survey on the Gulf of Cadiz fishing grounds in the framework of a project supported by Biodiversity Foundation 22nd August to 1st September 2014 onboard RV Angeles Alvariño. 2015 UWTV survey was funded by IEO 4 nd to 13 June 2015 onboard RV Ramón Margalef.

Sledge used in the ISUNEPCA_UWTV Survey - FullHD (1920x1080) @ 50 fps with an angle of 45º The field of view was confirmed using laser with a separation of 75 cm (FOV) 2014 2015 Field of view lower 75 cm on the bottom of the footage Camera with field of view wider in 2015 75 cm on the bottom of the footage

- Deploy and tow by the side of the vessel using an 11 mm diameter coaxial cable. ISUNEPCA_UWTV Survey - Speed of sledge during the tow ranged between 0.5 and 0.6 knots - Vessel position (DGPS) and HiPAP transponder on the sledge was used to obtain the ship and sledge position, respectively. - The distance over ground estimate (DOG) was calculated using the sledge position but when the HiPAP transponder failed, vessel position was used (7%) 2014: 13 good minutes were recorded . 2015: 10 good minutes were recorded This time corresponds to 180 m swept, approximately

Nephrops GROUND Border with Portugueses waters Results of the VMS analysis (2012-2013) and the abundance of Nephrops obtained from the ARSA bottom trawl survey series (SpSGFS-cspr-WIBTS-Q1_1993-2014) - The Nephrops abundance distribution from the bottom trawl survey is in concordance with the spatial distribution of the fishing activity on the ground in the Gulf of Cadiz. Nevertheless, small quantities of Nephrops occur below 200 m isobata and on the deepest area (about 600-700 m) although the bottom trawl fleet activity targeting to Nephrops is not observed in the VMS.

SURVEY DESING The UWTV designs followed a randomized isometric grid 2014 2015 Distance between stations 5nm Distance between stations 4nm 35 stations and 7 reserve stations =42 stations 60 stations and 3 reserve stations =63 stations 130-640 m depth average 410 m 98-650 m depth average 351 m Stations were extended to depth lower 100 m

SURVEY DESING HIGHER COVERAGE IN 2015 2014 2015 AREA PROSPECTED Nº STATIONS 2896 Km2 3321 Km2 58 VALID 5 NULL 2014 2015 31 VALID 3 NULL HIGHER COVERAGE IN 2015

Area is not exploited by the fleet. Where should be the border? 2014 2015 Burrows/m2 - What happen with area? The Survey in 2014 shows presence of Nephrops but surounded by stations with zero burrows according to the survey in 2015. Area is not exploited by the fleet. Where should be the border? - Better delimitation of the deeper border in 2015 with stations where burrow density were zero Shallower border is not well defined - Poor conditions of visibility - Small Nephrops burrows - Others burrowing species in high density Problems

294 millions of individuals 384 millions of individuals 2014 2015   Nº burrows/m2 Nº Observations 58 Min 1er cuartil 0.027 Mediana 0.10185 3er cuartil 0.1718 Max 0.4417 Mean 0.11577 Standard Deviation 0.10394 Coef. De sesgo 0.95695 Curtosis 3.5108 CV 0.8978   Nº burrow/m2 Nº Observations 31 Mínimo 1er cuartil 0.0325 Mediana 0.08 3er cuartil 0.1675 Máx 0.3 Mean 0.10194 Standard Deviation 0.083283 Coef. De sesgo 0.74563 Curtosis 2.7472 CV 0.8170 2014 2015 294 millions of individuals TOTAL NUMBER OF NEPHROPS IN THE GULF OF CADIZ ESTIMATED BY THE SWEPT AREA METHOD 384 millions of individuals

CONCLUSIONS 1. The boundaries of the Nephrops ground were better defined but need confirm the shallower border yet the problem is the poor visibility in depth lower than 100 m and presence of other burrowed fauna 2. How to extend the boundaries in the border with Portuguese waters? assumming stations with zero density? 3. The number of UWTV stations was increased and the distance between them was decreased obtaining better results 4. The spatial co-variance and other spatial structuring Geo-statistical analysis will be conducted using ARCGIS software. 5. The bias correction factors must be estimated (edge effect, burrow detection, etc) 6. Higher training of readers and good knowledge of the burrows of other species is needed Workshop 7. Referece footage and count for the Gulf of Cadiz should be generated