Fishing - multispecies management approaches: evaluation

Introduction

To ensure long-term food supplies from marine waters, fisheries must be managed responsibly whilst maintaining economic security for the fishing industry. The Fisheries Act 2020 provides the legal framework for fisheries management in the UK (following EU exit) and provides a commitment to sustainability as committed to at the World Summit on Sustainable Development in Johannesburg, South Africa in 2002.

Scotland is one of many nations exploiting fish stocks in the North Sea. In this region fisheries management is primarily based on controlling fishing mortality through total allowable catches (TACs). The TACs are agreed through several rounds of negotiations that occur between the UK, EU and Norway and result from a combination of scientific advice and political pressures. The International Council for the Exploration of the Sea (ICES) is the scientific advisory body that supplies advice for North Sea stocks. In addition to TACs, other fisheries management measures, including gear regulations and effort management, are also used in the North Sea to control fishing mortality. These are designed to protect juvenile fish, reduce by-catch and minimise the effect of fishing activities on the wider ecosystem.

For stocks shared between the UK, EU and Norway, and in the absence of internationally agreed management plans, ICES provides Advised Catches under the maximum sustainable yield (MSY) approach. Under this approach the advised catches for healthy stocks are derived from a target fishing mortality (F) of F_MSY - the fishing mortality that generates the highest sustainable long-term yield under the current environmental conditions and fishing patterns. For stocks with a spawning stock biomass (SSB) that falls below a ‘trigger’ reference point (known as MSY B_trigger), the target F is reduced below F_MSY in proportion to the ratio between SSB and MSY B_trigger. For each individual stock, the advised catch derived from the target F is typically used as the basis for the TAC for the next year.

Despite the extensive management of demersal fisheries in the North Sea and recent improvements in the status of many stocks, there are still some stocks for which fishing mortality exceeds F_MSY (ICES, 2024). A major cause of this is because the North Sea is a mixed fishery where multiple species are caught simultaneously due to the high degree of overlap in the spatial distribution of demersal species. Therefore, reconciling the composition of a fisher’s catch to their quota composition is a difficult task and often results in significant amounts of unwanted catch. Historically, this unwanted catch was discarded, giving rise to additional fishing mortality not directly controlled by the setting of TACs. The 2010-2012 average total weight of discarded demersal species in the North Sea was estimated at 148,765 tonnes, equating to approximately 40% of the total catch (Quirijns et al. 2014).

More recently, a landing obligation was introduced as part of the Common Fisheries Policy (CFP) reforms in 2014 (EU, 2013) in an effort to reduce the levels of discarding. The full implementation of the landing obligation was phased in over time starting in 2016, and by 2019 discarding of any species managed by a TAC became illegal. The landing obligation was retained in UK Fisheries Act 2020 following the EU exit in 2021.

Under these landing obligations all fish caught must be retained onboard and brought back to land to be counted against a fisher’s quota; although certain exemptions such as de minimis, high survivability species and protected, endangered and threatened (PET) species do exist. Overall, the aim of the landing obligation is to gain greater control over fishing mortality by eliminating discards and incentivising more responsible fishing through selective targeting and avoidance of specific species. However, eliminating the practice of discarding also exacerbates the mismatch between single species quota and catch compositions. The ICES Working Group on Mixed Fisheries Advice (WGMIXFISH-ADVICE; ICES, 2022) produces fleet-based model scenarios each year to explore the implications of attaining single-stock advised catches in a mixed fishery in terms of under- or overshooting the ICES catch advice. WGMIXFISH-ADVICE also identifies the most limiting stock or ‘choke stock’- the stock for which quota is fully utilised first across the largest number of fleets. The choke stock limits fishing activity and leaves quota of other stocks underutilised thereby affecting fleet profitability.

A single species approach to management combined with landing obligations in a mixed fishery appears to be increasingly challenging. In recent years, the Marine Directorate has been focussed on developing plans to address the issue. This project was initiated to help inform these plans as well as discussions during consultations with a variety of stakeholders. Several proposals for managing multispecies fisheries have been suggested in the literature and by stakeholder groups (Shetland Fishermen’s Association, 2014. EU, 2013, Woods et al. 2015, Christensen et al. 2009, Needle 2012, Kraak et al. 2012, Rijnsdorp et al. 2007). These alternative approaches either consist of adjustments to the current system or comprise an entirely new management system. The primary aim of this report is to evaluate the viability of a number of these alternative multispecies management options and identify those schemes worthy of further investigation in conjunction with stakeholders and fisheries managers.

Proposed multispecies management approaches

The multispecies management approaches that are tested in this report are described below (see Materials and Methods for details on how these were chosen). However, other approaches from the literature may be of future interest. These include the Real Time Incentives (RTI) scheme (Kraak et al., 2012) as an option for managing cod mortality in the Celtic and Irish Seas, an approach using Total Allowable Effort (TAE) to control fishing (Rijnsdorp et al. 2007) and the Icelandic catch-quota balancing system designed to account for unavoidable over-quota catch (Christensen et al., 2009; Woods et al., 2015).

The Shetland Fisherman’s Association (SFA) has proposed a scheme that introduces a new quota pool called ‘Others’ (Shetland Fishermen’s Association, 2014). This new Others quota pool is created by transferring unused quota from non-target species to account for over-quota catches of target species. The example given by the SFA (2014) recommended that the quota for all species except cod (Gadus morhua), haddock (Melanogrammus aeglefinus), whiting (Merlangius merlangus) and saithe (Pollachius virens) be grouped together to form the Others quota pool. Catches of cod, haddock, whiting and saithe in excess of quota would then be counted against the Others quota.

Interspecies flexibility is where quota is converted from one species to another to cover either over-quota catches or to obtain quota for a species not currently held. Similar to the SFA Others pool, this scheme aims to conserve the amount of biomass taken from the sea, while allowing more flexibility in the quota system. Provision is made for such a system under the landing obligation in the CFP (Regulation (EU) 1380/2013 Article 15 (8)), which was retained in UK legislation following EU exit. This provision states that up to 9% of the quota for the target species can be transferred to non-target species to cover over-quota catches providing the non-target species stock is within safe biological limits.

A quota points system was proposed by Needle (2012). This system works by converting single species quota, measured in tonnes, to a multispecies quota measured in points. Each fisher then gets a share of these points and points are deducted based on the composition of their catch. Points can be "spent" on any species but each species costs a different number of points as stipulated through a tariff. This aims to encourage catch-avoidance of specific species by setting higher point values on the tariff.