Mesoscale productivity fronts and local fishing opportunities in the European Seas

Jean-Noël Druon ,Cecilia Pinto,Paraskevas Vasilakopoulos,Jeroen Steenbeek,Andreas Palialexis,Natalia Serpetti,Antonella Zanzi,Jean‐Marc Fromentin,Michaël Gras,Laurent Dubroca,Didier Gascuel,Chiara Piroddi,Henning Winker,Alessandro Mannini,Marta Coll,Zeynep Hekim,Maurizio Gibin,Francesco Colloca,Pierre Hélaouët,Diego Macias-Moy ,Jordi Guillén ,François Bastardie ,Joanna K Bluemel ,Jann T Martinsohn

doi:10.1111/faf.12585

Abstract

AbstractThis study evaluates the relationship between both commercial and scientific spatial fisheries data and a new satellite‐based estimate of potential fish production (Ocean Productivity available to Fish, OPFish) in the European Seas. To construct OPFish, we used productivity frontal features derived from chlorophyll‐ahorizontal gradients, which characterize 10%–20% of the global phytoplankton production that effectively fuels higher trophic levels. OPFish is relatively consistent with the spatial distribution of both pelagic and demersal fish landings and catches per unit of effort (LPUEs and CPUEs, respectively). An index of harvest relative to ocean productivity (HPindex) is calculated by dividing these LPUEs or CPUEs with OPFish. The HPindex reflects the intensity of fishing by gear type with regard to local fish production. Low HPlevels indicate lower LPUEs or CPUEs than expected from oceanic production, suggesting over‐exploitation, while high HPlevels imply more sustainable fishing. HPallows comparing the production‐dependent suitability of local fishing intensities. Our results from bottom trawl data highlight that over‐exploitation of demersal species from the shelves is twice as high in the Mediterranean Sea than in the North‐East Atlantic. The estimate of HPindex by dominant pelagic and demersal gears suggests that midwater and bottom otter trawls are associated with the lowest and highest overfishing, respectively. The contrasts of fishing intensity at local scales captured by the HPindex suggest that accounting for the local potential fish production can promote fisheries sustainability in the context of ecosystem‐based fisheries management as required by international marine policies.

Highlights

Understanding the intertwined dynamics of marine ecosystems and fishing activities is key to implementing an effective ecosystem approach to fisheries management (Hernvann et al, 2020; Jennings et al, 2012; Tam et al, 2017)
We investigate the relationship between a new estimate of potential fish production, derived from satellite remote sensing of productivity fronts, and catch or landings per unit of effort (CPUEs and LPUEs, respectively) in European Seas
We use spatial fisheries data sets with different attributes to build a second index, the Harvest relative to ocean productivity. This HP index is defined as the ratio of gear-specific CPUEs or LPUEs over the potential fish production (OPFish)

Summary

| INTRODUCTION

Understanding the intertwined dynamics of marine ecosystems and fishing activities is key to implementing an effective ecosystem approach to fisheries management (Hernvann et al, 2020; Jennings et al, 2012; Tam et al, 2017). There is a need for analysing the spatial distribution of fishing pressure in relation to food web productivity, to better understand the impacts of fishing on the ecosystem and integrate spatial ecology into ecosystem-based management (Baudron et al, 2020; Lowerre- Barbieri et al, 2019). By assuming that a fish stock in a management unit is randomly distributed with respect to fishing effort (Quinn & Deriso, 1999), standard stock assessments may lead to local overfishing (Maury & Gascuel, 2001). This outcome is worrying for fish populations, which most often aggregate during particular life-history stages, for example, during spawning or recruitment in

INTRODUCTION

| MATERIALS AND METHODS

| DISCUSSION

Findings

| INTRODUCTION TO THE SUPPLEMENTARY INFORMATION