The assessment of the state of the stocks in the Baltic Sea

ICES advice on fisheries management

The International Council for the Exploration of the Sea (ICES) is an intergovernmental organization supported by 19 Member Countries around the border of the North Atlantic. established by international convention in 1902, its role is to promote, co-ordinate and disseminate the results of research activities associated with the sea and its living resources.

Following a number of international conventions in the 1960s-1980s, ICES has been identified as the body that provides advice on fish stocks and fisheries to three international fisheries commissions (the North east Atlantic Fisheries Commission NEAFC, the International Baltic Sea Fishery Commission IBSFC and the North Atlantic Salmon Conservation Organization NASCO). It also provides advice to the Governments of Member Countries, the European Commission and the Faroes and Greenland.

To provide advice on behalf of the Council, ICES in 1978 established its Advisory Committee on Fishery Management (ACFM) which is composed of experts from each of the ICES Member Countries. Experts from all countries thus have a say in the formulation of the advice. The role of ACFM is, for all the major fish, shellfish and, in some cases, marine mammal resources in the ICES area, to assess the historical development in terms of size and structure of the stocks and to provide advice on the expected impact of various management measures, and were appropriate to make recommendations on management actions required.

The advice given by ICES is based on stock assessment which for present purposes can be defined as the process of estimating the current size of a stock and the level of exploitation on it, relating these to historical trends, analysing the cause of any changes that have occurred and making forecasts of future changes and catch possibilities.

Advice is provided in response to requests from the Commissions, Member Governments and the EC, but ACFM is also empowered to give unsolicited advice when, in the opinion of the Committee, it is required.

The requests for advice are discussed at ICES Annual Statutory Meeting, which is held in late September, normally one week after the annual meeting of IBSFC. A umber of Working and Study Groups are set up to provide the necessary scientific input for the response to the requests.

The terms of reference and work plan for the Groups are decided by the ICES delegates at the Statutory Meeting. for 1997 the following groups have items on their agenda which refer to requests for advice received from IBSFC:

the Baltic Salmon and Trout Assessment Working Group, the Herring Assessment Working group for the Area South of 62^o N, the Baltic Fisheries Assessment Working Group, the Baltic International Fish Survey Working Group, Study Group on Baltic Acoustic Data and Baltic Herring Age-reading Study Group. The Working Groups are open for scientific experts nominated by the Delegates.

The Groups meet in advance of the May meeting of ACFM. The reports of the Working and Study Groups are reviewed by ACFM and used scientific basis for formulating the answers to the requests received from IBSFC. The report of ACFM is send to IBSFC, all ICES member countries and the European Commission in late May or early June.

Data required for Fisheries Management

In preparing advice on the state and management of fish stocks ICES uses all relevant information provided by the scientific experts nominated by the Delegates. All data and information are collected by ICES member countries. ICES may co-ordinate the data collection, but is as such not involved in sampling.

The types of data and information available are basically of two types: fishery dependent and fishery independent.

Fishery-dependent data

Fishery-dependent data include catch and fishing effort data and those obtained by sampling the catch and landings to record the biological information on the composition of the catch required to determine growth, maturation, mortality and other population parameters. The sources of these data are as follows:

• Nominal catches (the weight of fish landed converted to their whole round weight at capture) are reported by the national statistical offices. The statistics provided are in most cases annual landings desegregated into the ICES subdivisions.

• Quantities of fish discarded. An international programme on sampling discards data has been running in the Baltic since 1996. The programme is financed by EU and involves all ICES member countries.

• Fishing effort data. These data (e.g. days or hours fishing) are provided by national statistical offices. As a result of incomplete submissions ICES decided to discontinue the official reporting of effort data and the data are now in most cases provided to ICES on an unofficial basis.

• Sampling of commercial Catches. The provision of data on the species composition of the catch is, in most ICES Member Countries, the responsibility of the national statistical offices. Additional data on the size, age and maturity composition of the catch are normally provided by Governmental fisheries institutes.

In recent years ICES has become aware of a deterioration in the basic data made available for stock assessment. In some cases there is evidence of misreporting of catches (both non-reporting and mis-reporting by area) on a large scale however the situation has improved in the most recent years..

Fishery independent data

The fisheries direct their effort to fish concentrations and avoid small ''pre-recruit'' fish and the fisheries may therefore not be representative of the stock's size and age compositions. Therefore, some form of survey is needed either to provide an index of abundance of the youngest age groups or to provide an estimate or index of abundance of the adult component of the population. An estimate of the relative abundance of age groups that will recruit to the fishery in the next one or two years is essential if catch and stock forecasts are to be made.

Fishery-independent data are those obtained on surveys and in other forms of research investigations

• Research Vessel Surveys. The most important data for stock assessment are abundance indices from trawl surveys (including data on small fish that have not yet recruited to the fishery) and estimates of spawning stock abundance from acoustic surveys and bottom trawl surveys. Both surveys are co-ordinated by ICES.
• Tagging data. Is used in evaluating stock identity, distribution and mortality.

• Stomach content data. Used as important input for the Multi Species Model.

• Other types of data. While the above represent the main types of data currently used in stock assessments, a number of other types of data may be used in specific instances. These include environmental data which may be used in developing predictive models and data on mortality caused by diseases, parasites and contaminants.