The International Council for the Exploration of the Seas (ICES) provides advice on fishing opportunities based on stock assessments for a range of fish stocks. This advice is instrumental not only in providing advice to fisheries management, but also in evaluating Good Environmental Status under the EU Marine Strategy Framework Directive (MSFD) and for consumer labelling by the Marine Stewardship Council (MSC).
Stock assessments are key to the management of fisheries and sustainable use of resources. The analytical stock assessment is the “gold standard” also referred to as a category 1 assessment. The analytical stock assessment utilizes both fisheries-dependent and fisheries-independent data obtained from catches and scientific surveys, respectively, and the output provides information on population demographics. The data is analyzed through mathematical models that estimate the stock status, for a given stock unit, relative to biological reference points indicating sustainable exploitation levels.
The concept of stock units is key in stock assessments. Ideally the stock unit reflects the biological entity of the stock and its geographical distribution. A well-informed stock unit is based on extensive biological data on population structure and connectivity, coming from e.g. genetics studies and tagging (learn more about “connectivity” in
Spatial population structure and connectivity among marine populations in the Skagerrak:
implications for marine biodiversity conservation:
pub.norden.org/nord2024-033). Lack of such data often results in stock units covering vast areas that are biologically inaccurate, or stocks following national or economic borders. Failure to define the stock unit correctly can lead to erroneous management, where local populations or sub-stocks can be depleted under quotas applied to large geographical areas.
However, sustainable fisheries management extends beyond mere stock assessments and outtake regulation, stock-specific reference points, and catch levels aligning with biological advice. In the Common Fisheries Policy of the EU, it is now stated that an Ecosystem-Based Approach to Fisheries Management (EAFM) must be implemented (read more about EAFM in
Fact Box 1).