Norway lobster specimen on Gulf of Cadiz seabeds. (Photo: IEO)
Norway lobster abundance in the Gulf of Cadiz studied through underwater images
Friday, May 19, 2017, 21:40 (GMT + 9)
Researchers from the Oceanographic Centre of Cádiz and Málaga of the Spanish Institute of Oceanography (IEO) will estimate the abundance of Norway lobster in the waters of the Gulf of Cadiz through underwater videos made with a photogrammetric sledge.
The scientists, who travel aboard the oceanographic ship Ángeles Alvariño to develop the ISUNEPCA_0517 survey, will also estimate the density of Norway lobster burrows, delimit the Norway lobster distribution in the area and quantify the density of the accompanying fauna.
This study is the fourth to be carried out, after those performed in June 2016, June 2015 and ISUNEPCA_0814 exploratory survey, developed in 2014.
2014 survey was co-financed by Biodiversity Foundation and FEP funds and served to fine-tune this new methodology suggested by the International Council for the Exploration of the Sea (ICES) for estimating the abundance of Norway lobster stocks in the Northeast Atlantic. Besides, it serves as the basis of the scientific advice of such stocks.
The estimate obtained in 2017 survey will be used for the first time to offer advice on Norway lobster stock management in the Gulf of Cadiz.
So far, the assessment of Norway lobster in the Gulf of Cadiz was based on the capture trend per unit effort of the commercial fleet that is directed to this resource. However, because the Norway lobster is a sedentary species that spends most of its life inside burrows and whose behavior in and out of the burrow depends on different factors such as the time of day, the season or environmental conditions, among other variables, catch data are not always indicative of Norway lobster abundance.
This is why in the Gulf of Cadiz this methodology began to be implemented using images of underwater video: the so-called submarine TV surveys. These surveys began to be developed in the late 1990s in Scotland and are now used in the assessment of 18 stocks in the Northwest Atlantic.
During this season, which will end on May 31, the seabed will be sampled at 65 points in the Gulf of Cadiz, at depths between 200 and 700 metres, within the Norway lobster fishing ground.
In addition, this year trawling will be carried out with BeamTtrawl to validate underwater images. Once the set stations intended to meet the main objective of the survey have been completed, dives will be carried out in non-trawling areas that are interesting to know the status of the seabeds and the presence of commercial resources.