Biological data
Pan-Mediterranean Acoustic Survey (MEDIAS)
- Objectives of the survey
Evaluate the abundance and spatial distribution of small pelagic fish resources by direct methods (acoustics), independently of the data provided by commercial fisheries; Target species are anchovy and sardine.
- Description of the methods used in the survey.
Acoustic data for fish abundance estimation are collected by calibrated scientific echo sounder at 38kHz; Fish samples are collected by use of pelagic trawl net, with aim to provide information needed for echograms scrutinization, as well as for collection of fish biological data; Abiotic environmental data (measurements of temperature and salinity) collections are made by CTD vertical profiles, while additional biotic data in pelagic ecosystem are obtained by plankton sampling (acoustic at 120kHz and/or vertical hauls). Collection of navigational data ensures that all other collected data are geo-referenced (suitable for spatial analyses). Manual of the survey is available at http://www.medias-project.eu/medias/website/handbooks-menu.html, and it contains a graphical map of the surveys.
- Participating Member States/vessels and the relevant international group in charge of planning the survey
Croatia is participating in MEDIAS by conducting an acoustic survey in the eastern part of GSA17 area (Adriatic Sea), covering an area of 13,578 Nm2. International MEDIAS Steering Committee is in charge of surveys planning.
International bottom trawl survey in the Mediterranean (MEDITS)
- Objectives of the survey
The MEDITS survey programme intends to produce basic information on benthic and demersal species in term of population distribution as well as demographic structure, on the continental shelves and along the upper slopes at a global scale in the Mediterranean Sea, through systematic bottom trawl surveys.
- Description of the methods used in the survey
The MEDITS is conducted in spring – summer period from Max to July based on MEDITS protocol using specially designed bottom trawl net GOC 73. Sampling stations are randomly distributed according to the depth strata (10-50; 50-100; 100-200; 200-500; 500-800 m) and the number of stations is proportional to the surface of each stratum (Figure 1). The duration of tow in the area shallower than 200 m is 30 min, while in the area deeper than 200 m is 60 min. On board the vessel, the catches are split into the categories and sub-categories as reported in Annex V and XV of the manual. For each species the total weight and number of individuals should be collected, excluding the taxonomic category V, G, H for which only the total weight should be collected. For taxonomic categories D and E the number of individuals is not mandatory. When the catch of a given species or a fraction of a given species (e.g. juveniles) is too abundant to be measured in extenso it is reasonable to take a representative sub-sample of the catch. This sub-sample should be not less than 100 individuals.
Figure 4. Map of sampling positions during the MEDITS survey in GSA 17 (Croatian territorial waters).
- Participating Member States/vessels and the relevant international group in charge of planning the survey
Croatia is participating in MEDITS Surveys by conducting a bottom trawl survey in the eastern part of GSA17 area (Adriatic Sea), covering an area of 32000 Km2. MEDITS Working Group is in charge of survey planning.
