Natural geochemical markers reveal environmental history and population connectivity of common cuttlefish in the Atlantic Ocean and Mediterranean Sea

Jay R Rooker,Thomas Lacoue-Labarthe,Haritz Arrizabalaga,Ignacio Sobrino,António V Sykes,Roger Villanueva,Miguel Baptista,Jessica M Lee,Giovanni Bearzi,Persefoni Megalofonou,Igaratza Fraile,Rui Rosa,Piero Addis,R J David Wells,Michael A Dance

doi:10.1098/rsif.2020.0309

Abstract

Natural markers (δ13C and δ18O stable isotopes) in the cuttlebones of the European common cuttlefish (Sepia officinalis) were determined for individuals collected across a substantial portion of their range in the Northeast Atlantic Ocean (NEAO) and Mediterranean Sea. Cuttlebone δ13C and δ18O were quantified for core and edge material to characterize geochemical signatures associated with early (juvenile) and recent (sub-adult/adult) life-history periods, respectively. Regional shifts in cuttlebone δ13C and δ18O values were detected across the 12 sites investigated. Individuals collected from sites in the NEAO displayed more enriched δ13C and δ18O values relative to sites in the Mediterranean Sea, with the latter also showing salient differences in both markers among western, central and eastern collection areas. Classification success based on cuttlebone δ13C and δ18O values to four geographical regions (NEAO, western, central and eastern Mediterranean Sea) was relatively high, suggesting that environmental conditions in each region were distinct and produced area-specific geochemical signatures on the cuttlebones of S. officinalis. A modified δ13C and δ18O baseline was developed from sites proximal to the Strait of Gibraltar in both the NEAO and Mediterranean Sea to assess potential mixing through this corridor. Nearly, all (95%) of δ13C and δ18O signatures of S. officinalis collected in the area of the NEAO closest to the Strait of Gibraltar (Gulf of Cadiz) matched the signatures of specimens collected in the western Mediterranean, signifying potential movement and mixing of individuals through this passageway. This study extends the current application of these geochemical markers for assessing the natal origin and population connectivity of this species and potentially other taxa that inhabit this geographical area.

Highlights

The European common cuttlefish (Sepia officinalis) is an important fishery resource throughout the Mediterranean Sea and adjacent waters of the Northeast Atlantic Ocean (NEAO) [1,2]
Mean cuttlebone δ13CCORE values ranged from −2.69‰ to −5.10‰ across the 12 sites, and a distinct trend was observed for S. officinalis from sampling sites in the NEAO versus sites within the Mediterranean Sea
Univariate contrasts indicated that cuttlebone δ13CCORE values were significantly different among the four regions (ANOVA, p < 0.01), and Tukey honestly significant difference (HSD) test indicated that δ13CCORE values for S. officinalis from the NEAO region were significantly different from all three regions within the Mediterranean Sea

Summary

Introduction

The European common cuttlefish (Sepia officinalis) is an important fishery resource throughout the Mediterranean Sea and adjacent waters of the Northeast Atlantic Ocean (NEAO) [1,2]. Due to large temporal shifts in the abundance and recruitment of S. officinalis, for high-yield fisheries in certain areas (e.g. English Channel, Bay of Biscay [1]), there is renewed interest in their movement ecology and population connectivity [3]. This is primarily due to the fact that spatio-temporal shifts in distribution of marine organisms, spawning stock biomass (SSB), can have profound implications for the management of harvested fisheries [4]. While earlier studies have shed important light on the habitat use and movement of S. officinalis, expanding the geographical scope of our knowledge on population connectivity is critical to their management

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