Genetic analysis redraws the management boundaries for the European sprat.

María Quintela,Kevin A Glover,Geir Dahle,John B Taggart,Dorte Bekkevold,Richard D M Nash,Eeva Jansson,Cecilie Kvamme,Anne Grete Sørvik,Øystein Skaala

doi:10.1111/eva.12942

Abstract

Sustainable fisheries management requires detailed knowledge of population genetic structure. The European sprat is an important commercial fish distributed from Morocco to the Arctic circle, Baltic, Mediterranean, and Black seas. Prior to 2018, annual catch advice on sprat from the International Council for the Exploration of the Sea (ICES) was based on five putative stocks: (a) North Sea, (b) Kattegat–Skagerrak and Norwegian fjords, (c) Baltic Sea, (d) West of Scotland—southern Celtic Seas, and (e) English Channel. However, there were concerns that the sprat advice on stock size estimates management plan inadequately reflected the underlying biological units. Here, we used ddRAD sequencing to develop 91 SNPs that were thereafter used to genotype approximately 2,500 fish from 40 locations. Three highly distinct and relatively homogenous genetic groups were identified: (a) Norwegian fjords; (b) Northeast Atlantic including the North Sea, Kattegat–Skagerrak, Celtic Sea, and Bay of Biscay; and (c) Baltic Sea. Evidence of genetic admixture and possibly physical mixing was detected in samples collected from the transition zone between the North and Baltic seas, but not between any of the other groups. These results have already been implemented by ICES with the decision to merge the North Sea and the Kattegat–Skagerrak sprat to be assessed as a single unit, thus demonstrating that genetic data can be rapidly absorbed to align harvest regimes and biological units.

Highlights

Increasing global attention is being given to sustainable production and harvest of human food from the marine environment
These results have already been implemented by ICES with the decision to merge the North Sea and the Kattegat–Skagerrak sprat to be assessed as a single unit, demonstrating that genetic data can be rapidly absorbed to align harvest regimes and biological units
There was a stated need to improve the knowledge about population genetic structure to describe the biological units in order to inform more sustainable exploitation (ICES, 2018c, 2018f, 2019). We addressed this issue by performing a genetic analysis of an extensive set of sprat sampled in the North Sea, Kattegat–Skagerrak, and Baltic Sea areas, with the aim to strengthen input to harvest advice and management

Summary

| INTRODUCTION

Increasing global attention is being given to sustainable production and harvest of human food from the marine environment. ICES provided advice on maximum total catch on five separate sprat stocks in the Northeast Atlantic: (a) North Sea, (b) Kattegat–Skagerrak and Norwegian fjords, (c) Baltic Sea, (d) West of Scotland—southern Celtic Sea, and € English Channel (ICES, 2013). This stock delineation was considered as unlikely to adequately reflect the true underlying biological units, that is, populations. In order to achieve this, we first identified single nucleotide polymorphism markers (SNPs) throughout the genome by using ddRAD sequencing, and thereafter genotyped and analyzed approximately 2,500 sprat from the geographical areas described

| MATERIALS AND METHODS

| DISCUSSION

Findings

CONFLICT OF INTEREST None declared