The MEDITS trawl survey in the Mediterranean began in 1994. Initially, it involved only four Countries: France, Greece, Italy, and Spain. Over time, the survey expanded to include other European countries and geographical sub-areas. Today the MEDITS survey covers 18 GFCM geographical sub-areas (GSAs) over an area of 543,000 km², with an average of 1,283 sampling stations annually. Collaboration with non-EU countries has been facilitated by the FAO regional projects and the General Fisheries Commission for the Mediterranean (GFCM).

The main characteristics of the survey are:

• A standard design of sampling bottom trawl gear (GOC 73) is used (codend mesh size of 20 mm stretched mesh).
• The survey uses a depth-stratified random sampling scheme, with strata defined by depth and geographical zone.
• Hauls are distributed proportionally to the surface area of depth strata, which limits are: 10-50m, 51-100m, 101-200m, 201-500m, and 501-800m.
• Haul duration is determined by depth: 30 minutes on the continental shelf (10-200m) and 60 minutes on the slope (201-800m).
• The surveys are scheduled between late spring and summer (May to July) and conducted during daytime.
• All species larger than 1 cm are identified, with total weight and number of individuals recorded. Sex and gonad maturation stage are identified on a set of target species.
• A length-stratified random sampling is applied to collect biological data, such as otoliths of bony fish and individual weight.
• The MEDITS protocol also defines common formats for data exchange, including 5 different standards:
• TA: hauls details and specifications;
• TB: aggregated data on species’ total number and weight;
• TC: length frequency distributions by length, sex, and maturity stage;
• TE: individual data of length, weight, age and sex;
• TL: marine macro-litter data

For further details refer to MEDIT Handbook (Anonymous, 2017), to Spedicato et al. (2019) and Bertrand et al. 2002.

References

Anonymous, 2017. MEDITS Handbook, Version 9. http://www.sibm.it/MEDITS%202011/principaledownload.htm

Bertrand, J, Gil de Sola, L, Papacostantinou, C, Relini, G, Souplet, A, 2002. The general specifications of the MEDITS surveys. Sci. Mar. 66, 9–17.

Spedicato, M. T., Massutí, E., Mérigot, B., Tserpes, G., Jadaud, A., & Relini, G. (2019). The MEDITS trawl survey specifications in an ecosystem approach to fishery management. Scientia Marina, 83(S1), 9-20.