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

2. ISUNEPCA_UWTV Survey in the Gulf of Cadiz
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.
UWTV survey was funded by IEO
4 nd to 13 June 2015 onboard RV Ramón Margalef.

3. Sledge used in the ISUNEPCA_UWTV Survey
- FullHD 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

4. - 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

5. Nephrops GROUND
Border with Portugueses waters
Results of the VMS analysis ( ) and the abundance of Nephrops obtained from the ARSA bottom trawl survey series (SpSGFS-cspr-WIBTS-Q1_ )
- 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 m) although the bottom trawl fleet activity targeting to Nephrops is not observed in the VMS.

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

7. 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

8. 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

9. 294 millions of individuals 384 millions of individuals
2014
2015
Nº burrows/m2
Nº Observations 58
Min
1er cuartil
0.027
Mediana
3er cuartil
0.1718
Max
0.4417
Mean
Standard Deviation
Coef. De sesgo
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
Standard Deviation
Coef. De sesgo
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

10. 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