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Surveying the pelagic fish resources and establish an acoustic database in the Baltic Sea |
Acronym: Baltdat
Funding agency: European Union (EU CFP Study 98/085)
Project duration: 24 months (04/99-03/01)
Objectives and outline
The assessment of the pelagic resources in the Baltic is to a large extent dependent on direct stock estimates. The reason for this is that for pelagic schooling fish such as the herring and sprat, the catch-per-unit-of-effort is an inappropriate measure for the abundance of the stock. The main techniques for direct estimation of stock size of herring and sprat in the Baltic are hydroacoustic surveys. Therefore, the main purpose of the study is to intensify the study of Baltic herring and sprat under the CFP of the EU in the Baltic. More specifically, the objective is to conduct hydroacoustic surveys in the Baltic Sea 1999-2001. Results from these and earlier surveys will be stored in an acoustic database to be established for further analyses.
Hydroacoustic surveys for herring in the Baltic Sea have been conducted on an annual basis since 1978. The surveys were started by Sweden and Germany, and later joined by Russia, Denmark, Poland and Latvia. Co-ordination of the acoustic survey is done within the framework of the ICES Assessment Working Group for the Baltic Sea, and in particular within ICES Baltic International Fish Survey Working Group. Results of the catch-per-unit-of-effort tuned by the acoustics surveys have been the main basis for the assessment of the Baltic Sea stocks in recent years. Although the acoustic methodology has shown considerable improvements over the recent years, a number of technical questions still remain to be solved. It is also considered important when planning the acoustic surveys in the Baltic that the entire distribution of Baltic herring and sprat is covered annually. This has not been the case in recent years. There should also be significant overlap in space between the areas surveyed by the individual vessels.
The international acoustic surveys were until 1996 completely financed on a national basis, since 1996 it has been partly been financed by an EU-project, contract CFP 97/001. Two of the participating countries are experiencing problems in maintaining the effort for the acoustic surveys at the current level. Participating institutes outside the EU sometimes have problems in financing acquisition, replacement and maintenance especially of acoustic instrumentation from their national budgets. Problems are also experienced in co-ordinating the surveys, as insufficient national funds are available for meetings of the national co-ordinators.
Another requirement is the systematic storage of all acoustic and biological data in an international database. This will enable scientists to utilise the acoustic data for time series analyses and a number of other studies apart from direct stock estimation, therefore all historic national data must be incorporated in the database. The database should also be updated to include historic data. The database should be kept and maintained by one of the participating institutes. The database will then be available for assessment experts within ICES and the EU community. It is also open for other purposes, e.g. ecological studies and bioeconomical analyses.
The project will proceed into three steps:
Firstly, the project will support the execution of annual acoustic surveys on Baltic herring and sprat. The acoustic surveys will be designed to cover the entire distribution area and to minimise inconsistencies in the results by following the standardised methods.
Secondly, variables, data and formats should be defined and exchange formats should be elaborated. This work has already been accomplished by the BIFS WG, which used a simpler format (BAD1). Participating fishery institutes will be requested to compile and prepare historic data in agreed exchange format and submit these data to the coordinator in Lysekil. The next step will be to incorporate the data in an appropriate database structure. Software will be selected and programmes developed to fit available computer resources. This task also includes the development of software to check and load data as well as the construction of standard output reports.
The third step includes the incorporation on historic data in the database and annual updating of new results.
Participating institutions:
Data entered/updated by (Date)
Tomas Gröhsler (21-07-00)