EU-UK request on ecosystem considerations in the provision of single stock advice for forage fish species

The current ICES advice for forage fish species does include ecosystem effects on the assessed stocks through both variable predation mortality and qualitative ecosystem considerations.

ICES stock annexes clearly recognize the ecological significance of forage fish species such as sandeel, Norway pout, herring, and sprat as important food sources for seabirds, other fish species, and marine mammals. All the stock annexes document the implementation of natural mortality (M) and nearly all include predation mortality estimated from a multispecies model. The North Sea is one of very few regions worldwide where quantitatively based and often time-varying predation mortality is routinely included in forage species assessments. This is the primary way that predator–prey interactions are handled in assessments supporting advice. Other ecosystem considerations outlined for the studied stocks include description of conservation of spawning habitat (herring), potential habitat shifts (sprat), ecosystem drivers of larval survival (herring, sandeel), and the importance of maintaining diverse stock structure to promote population resilience (herring, sandeel). All of these are important to stock sustainability and therefore to sustaining the ecosystem services provided by forage stocks. Additional information is included on the bycatch of other fish species and protected species in forage fisheries for Norway pout and herring.

What is not conducted in the assessments is specific analysis of whether the forage fish biomass is kept high enough for specific predator requirements. Such an analysis would depend on the specifics of individual predator populations, and overall stock levels of forage fish are only part of the issue. Minke whales, for example, can move large distances to find food and are not limited by any local abundance, while nesting seabirds have a restricted feeding range. ICES advice on fishing opportunities is given at stock level and cannot function at the level of individual feeding grounds, which goes beyond the detail level of the stock assessment models. Therefore, a large part of the question of whether management is supporting ecosystem functions should occur at the level of national regulations, which is outside the scope of this technical service.

ICES advice framework distinguishes between stocks with relatively stable biomass for which advice is based on a target fishing mortality (herring) and those with variable biomass for which advice is based on an escapement strategy (sandeel, Norway pout, sprat). In both cases, the advice is consistent with the maximum sustainable yield approach, the aim of which is to have high stock sizes producing pretty good yields. It is possible that exploitation levels consistent with this framework would result in a high enough biomass required to sustain ecosystem services. However, it is also possible that the resulting biomasses may be too low. Although the ICES advice framework includes a provision to keep the stocks above a given precautionary level, there is no analysis of whether this precautionary level is sufficient to provide adequate food levels for individual predator populations. Such an analysis would need to take account of the interplay between ICES advice, national management measures, and the dynamics of a given predator population.

It is stressed that sandeel is currently undergoing a harvest control rule (HCR) evaluation process and that North Sea herring will undergo the same in 2024. Some of the conclusions of ICES advice could change once the new assessments and HCRs have been adopted. However, no big changes are expected in the underlying concepts (e.g. predation mortality and reference points rationale), in which case the conclusions would remain valid.

This request is responded to as a review of the ecosystem considerations in the provision of single-species advice for forage fish species. The response is based on two independent reviews based on the ICES most recent advice and the stock annexes for North Sea herring, Norway pout, sandeel (seven stocks), and sprat (two stocks) as well as supplementary scientific papers and reports.