Linking Scales of Life-History Variation With Population Structure in Atlantic Cod

Peter J Wright,Alice Doyle,Andrew Davie,John B Taggart

doi:10.3389/fmars.2021.630515

Abstract

It is increasingly recognised that sustainable exploitation of marine fish requires the consideration of population diversity and associated productivity. This study used a combination of genotypic screening and phenotypic traits to define the scale of population structuring in Atlantic cod inhabiting the northern North Sea (ICES Sub-division 4a) and Scottish west coast (ICES Division 6a). The genetic analysis indicated an isolation by distance pattern with an even finer scale structuring than previously reported, that persisted over a decade and between feeding and spawning seasons. Spatial variation in phenotypic traits reflected genetic variation with cod maturing later and at a larger size near the Viking Bank in 4a. The identified population structuring provides an explanation for differences in historic changes in maturation schedules and the temperature exposure recorded in previous electronic tagging studies. The study also highlights how the mismatch between stock divisions and population units is leading to a misunderstanding about stock recovery.

Highlights

Conserving population diversity is a key part of the UN Convention on Biological Diversity as it promotes persistence and adaptability in taxa (Balmford et al, 2005)
We examine how variation in growth and maturity relates to population scale in Atlantic cod across two stock areas; the North Sea (ICES 4) and Scottish west coast (ICES 6a)
Through the combination of phenotypic and genetic evidence this study demonstrates that spatial variation in life history traits linked to productivity reflect population structure

Summary

Introduction

Conserving population diversity is a key part of the UN Convention on Biological Diversity as it promotes persistence and adaptability in taxa (Balmford et al, 2005). The need to account for intraspecific genetic diversity has been widely acknowledged (Hilborn et al, 2003; Ruzzante et al, 2006) and overfishing has been related to a decline in genetic diversity across a wide range of marine fishes (Pinsky and Palumbi, 2014), it is still rarely considered in marine fisheries management. This is because the stock units upon which management advice is based often do not match the scale of population structuring (Stephenson, 2002; Barth et al, 2017). In order to provide advice on conserving population diversity and sustainable exploitation in marine fish, there is a need for studies that characterise both population distribution and productivity

Methods

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Conclusion