Concerted Action "Improvements of Tagging Methods for Stock Assessment and Research in Fisheries" (CATAG)
FINAL REPORT May 1999 (DRAFT)
Systematic tagging of fish for scientific purposes has been conducted for more than a century. When it was started, this new approach represented an exciting methodology for obtaining fundamentally new information about fish migration and movements as well as on the dynamics of exploited fish population. However, it is now clear that tagging has not developed as an extensively-used method for monitoring and management of major European commercial fish stocks in the way that might have been expected. Undoubtedly, much effort has been invested in tagging experiments, but the results have generally only been used for qualitative evaluation of distribution patterns. Instead, fisheries management has tended to focus on statistical analysis based on a variety of modelling approaches, often based on expensive sampling programmes or catch data. A major reason for the under-utilisation of tagging in the quantitative evaluation of fish stocks has been uncertainty about data quality.
Recent developments in technology have created a new situation both with respect to types of tags and the range of data that can potentially be collected. We are on the threshold of fundamental new knowledge, both with regard to the understanding of biological relationships and a full appreciation of fish-environment interactions. For the first time it is becoming possible to get detailed information about life cycle properties of individual fish. Furthermore, new and alternative population assessment methodologies are likely to emerge from these developments, as well as opportunities to validate existing modelling approaches. This new technology has arrived at a time when there is a crucial need for sustainable management of the marine environment and its resources. New approaches in tagging methodology may give us alternative solutions where traditional methodologies have failed.
Consequently, it is time to take a retrospective centennial view of tagging practice and achievements, to sum up the state of the art, and thereby establish a firm basis for identifying future possibilities and needs. Such a task can only be accomplished through the interaction of scientists with a wide scientific and geographic spread. This report represents the outcome of such an exercise, achieved through an EU concerted action programme (‘CATAG’).
The chapters in this report have been individually prepared by subgroups with special interests and competences within the fields they covered. It is also assumed that the report will often be read by chapter of interest, and not as a complete and integrated publication. The report also provides the basis of a developing, living website (http://www.hafro.is/catag) in which material is presented in discrete, accessible sections. By intention therefore, those issues covered by several of the subgroups are retained in their individual chapters even though this results in a degree of duplication.
CATAG takes advantage of the 1994 EU-supported workshop on "Electronic Tags in Fisheries Research and Management" (14-17 November 1994; Lowestoft, England [Arnold et al. 1999]). After that workshop some of its participants reunited on discussions which led to the application of another CA project which is this CATAG project.