Changing fish distributions challenge the effective management of European fisheries

Abstract

Changes in fish distribution are being observed across the globe. In Europe's Common Fisheries Policy, the share of the catch of each fish stock is split among management areas using a fixed allocation key known as ‘Relative Stability’: in each management area, member states get the same proportion of the total catch each year. That proportion is largely based on catches made by those member states in the 1970s. Changes in distribution can, therefore, result in a mismatch between quota shares and regional abundances within management areas, with potential repercussions for the status of fish stocks and the fisheries that depend on them. Assessing distribution changes is crucial to ensure adequate management and sustainable exploitation of our fish resources. We analysed scientific survey data using a three‐tiered analytical approach to provide, for the first time, an overview of changes in distribution for 19 northeast Atlantic fish species encompassing 73 commercial stocks over 30 yr. All species have experienced changes in distribution, five of which did so across management areas. A cross‐species analysis suggested that shifts in areas of suitable thermal habitat, and density‐dependent use of these areas, are at least partly responsible for the observed changes. These findings challenge the current use of relative stability to allocate quotas.

Climate risk to European fisheries and coastal communities

“…Diversification of catches and landings can take place autonomously as fishers respond to changes in the abundance and distribution of the fish they depend on 32,37 . For example, changes in the distribution of fish species in surrounding waters [42][43][44] have led to the development of new fisheries in the UK for squid, seabass and red mullet, amongst others 45 . There are, however, barriers to diversification 31,41 , most notably in the form of the variety of resources available: the limited catch diversity and therefore high exposure of fleets and regions adjoining the Black Sea, for example, arises at least in part from the relatively low biodiversity of this region.…”

Can we project changes in fish abundance and distribution in response to climate?

“…Fits tend to improve in later years in the time series for several species, perhaps reflecting the reduction in fishing mortality (Simpson et al, 2011) and its effect on survey data distributions in later years (Figure 3). However, this could also be the result of a more representative area being covered by the surveys since their geographical extend has increased over time (Baudron et al, 2020).…”

“…The reported shifts are sparse such as the increase in horse mackerel, sprat and reduction of cod in abundance (Alheit et al, 2005; Reid, de Fatima Borges, & Svendsen, 2001) despite the occurrence of other species shifts. However, a recent publication shows species distribution shifts for 17 main widely distributed species in the North‐East Atlantic (Baudron et al, 2020). The comparison of the performance of the models at different resolutions shows, in general, that outputs are more reliable when aggregated at larger time‐ and space‐ scales.…”

The Celtic Sea Through Time and Space: Ecosystem Modeling to Unravel Fishing and Climate Change Impacts on Food-Web Structure and Dynamics

“…The European IBTS survey data employed in this study encompassed a large range of environmental values, hence providing insights into the potential response of species groups to the warmer conditions that could become the norm in the Celtic Sea by the end of the century. The European IBTS survey dataset recently proved to be highly valuable to study species distributions (Baudron et al, 2020;Moriarty et al, 2020) and characterize ecosystem functioning (Maureaud et al, 2019). The methodology developed by Grüss et al (2018Grüss et al ( , 2020 can integrate as many variables as desired (e.g., variables measured at different locations of the water column, percentages of different substrate types) and can be applied to any particular representation of functional groups, including multistanza groups.…”