Sampling
The study will analyse MTL of pelagic and demersal food webs collected at coastal and neritic habitats in the northern (Cantabrian Sea) and northwestern (Galicia) Iberian shelf. Samples of selected organisms will be obtained during sampling campaigns already implemented by IEO-CSIC, covering a large range of habitat and productivity conditions, from coastal and eutrophic environments in the Galician rias to neritic zones of the shelf and slope with oligotrophic conditions in the eastern Cantabrian Sea. Some of the campaigns will allow to examine seasonal effects on MTL at one habitat type while others will provide specific samples from the main habitat types along the continental shelf.
Four types of cruises and sampling campaigns will be used:
• RADIALES sampling near A Coruña is based on monthly sampling of a fixed transect of stations since 1990. MTL-FISH will use RADIALES plankton samples collected over one year at the reference station E2CO (80 m depth) for a detailed seasonal study (Objectives O1.1, O2.1, O3.1, O3.2). Besides, RADIALES will provide hydrographical observations and plankton biomass estimates.
• PELACUS is a shelfwide survey cruise carried out every spring sampling pelagic fish and plankton over the whole Iberian shelf covering Spanish national waters providing
data for fisheries and environmental policies. MTL-FISH will use fish and plankton samples collected during one PELACUS cruise to analyse the effects of spatial habitat variability (Objectives O1.1, O2.2, O3.1, O3.2). Besides, PELACUS will provide hydrographic observations and plankton and fish biomass estimates.
• DEMERSALES is a shelfwide cruise carried out every year in autumn as part of the International Bottom Trawl Survey (IBTS) sampling demersal fish over the whole Iberian shelf covering Spanish national waters, and providing data for fisheries and environmental policies. Samples of demersal fish species for MTL-FISH will be collected during one DEMERSALES cruise to analyse the effects of spatial habitat variability (Objectives O1.2, O2.2, O3.1, O3.2). Besides, DEMERSALES will provide estimates of demersal species biomass and gut-content analysis of the main species, as well as habitat characteristics including sediments.
• BIGA (BIodiversidad del Golfo Ártabro) is a seasonal survey of megafaunal assemblages sampling every 3-4 months the most characteristic habitats near A Coruña since 2017. This survey is supported by funds of the IEO Centre in A Coruña. MTL-FISH will use fish samples collected by BIGA over one year for a detailed seasonal study (Objectives O1.2, O2.1, O3.1, O3.2). Besides, BIGA will provide estimates of demersal species biomass, as well as habitat characteristics including sediments.
• Commercial catch samples. Samples of fish targeted by local fishing fleets are regularly sampled by IEO-CSIC to obtain complementary data required for fisheries advice. MTL-FISH will be able to collect additional samples to complete the MTL characterization using this survey (Objectives O1.1, O1.2, O2.1, O2.2, O3.1, O3.2).