European Member States must collect a wide array of technical, biological, economic and ecosystem data on their national fisheries, as required by the so-called Data Collection Regulations (EU Council Regulation 1543/2000 and Commission Regulations 1639/2001, 1581/2004 and 199/2008). Due to the fleet's wide action radius, multiple species and areas need monitoring.The following data must be collected:estimates of the species, size and age composition of the landings and the discards, fishery-independent estimates of stock size and recruitment strength derived from surveys at sea, and regular updates of biological parameters of several key species, such as growth, sexual maturity and fecundity We use two methods to collect these data: market sampling in the main Belgian fishing harbours and fishery-dependent surveys. We obtain data on the species, size and age composition of the landings. During the fishery-dependent surveys, data are collected during the onboard sampling of the retained and discarded catch fractions. We focus on the beam trawl fleet, the most important fleet segment in the Belgian sea fisheries.In the southern North Sea, the RV "Belgica" (BTS) conducts annual surveys. These surveys give fishery-independent estimates of the distribution, abundance and movements of adult flatfish. Also annually, we conduct young fish and brown shrimp surveys (DYFS), in the nursery areas along the Belgian coast. These surveys give recruitment indices of juvenile flatfish and estimates of the abundance of brown shrimp. The survey data are used to study the biotic and abiotic factors that affect the population dynamics of commercial species. These data are also incorporated in the annual stock assessments.Supportive research activities include the following:evaluation and improvement of market and at sea sampling protocols particular methods of analysis (e.g., for maturity staging and age reading) and the development of data storage systems and quality assessment techniques As fisheries are usually international, international co ordination in the field of data gathering is also needed. This co-operation is organised regionally, through annual Regional Co-ordination Meetings (RCMs). These also include the national co ordinators of the Member States' data collection programmes and experts in the fields of fisheries biology.Examples of agreements made at the RCMs are:sampling of foreign flag vessels, task and cost sharing of age and maturity sampling, development of regional databases, etc. ILVO-Fisheries attends two of the RCMs: the North Sea and East Arctic, and the North-East Atlantic. In addition, ILVO-Fisheries also participates in several expert groups of the International Council for the Exploration of the Sea (ICES) [link naar ICES] to plan sea surveys, harmonise maturity staging and age reading techniques, etc.