A millennium of trophic stability in Atlantic cod (Gadus morhua): transition to a lower and converging trophic niche in modern times

Guðbjörg Ásta Ólafsdóttir,Ragnar Edvardsson,Sandra Timsic,Ramona Harrison,William P Patterson

doi:10.1038/s41598-021-92243-7

Guðbjörg Ásta Ólafsdóttir, Ragnar Edvardsson + Show 3 more

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https://doi.org/10.1038/s41598-021-92243-7

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Abstract

Stable isotope analyses of zooarchaeological material can be used to examine ecological variability in exploited species at centennial to millennial scales. Climate change is a notable driver of marine ecosystem change, although historical fishing is also likely to have impacted past marine systems. Fishing removes the oldest and largest individuals and may thereby result in shorter trophic pathways and reduced niche width of predatory fish species. In the current study we examine the trophic niche of Atlantic cod, haddock and Atlantic wolffish, in the last millennium using δ13C and δ15N values of bone collagen. We report a lower trophic level of Atlantic cod and haddock but higher level of wolffish in present times, following centuries at consistent and higher trophic levels of Atlantic cod. This results in a concurrent converging trophic niche of the demersal fish. We suggest that the current data set provides a valuable historical baseline facilitating interpretation of current variability in the trophic ecology of northern demersal fish.

Highlights

Stable isotope analyses of zooarchaeological material can be used to examine ecological variability in exploited species at centennial to millennial scales
All samples included in the analysis had C:N ratios between 2.9 and 3.6, indicative of well-preserved collagen (Table 1). δ13C values ranged from − 19.3 to − 10.7‰ and δ15N values from 8.2 to 15.7‰
The results provide a valuable long-term baseline of trophic ecology as they depict both remarkable long-term consistency before modern fisheries, such as the stable trophic level of Atlantic cod, and change of trophic ecology, such as the historically fluctuating trophic level of wolffish

Summary

Introduction

Stable isotope analyses of zooarchaeological material can be used to examine ecological variability in exploited species at centennial to millennial scales. In the current study we examine the trophic niche of Atlantic cod, haddock and Atlantic wolffish, in the last millennium using δ13C and δ15N values of bone collagen. We report a lower trophic level of Atlantic cod and haddock but higher level of wolffish in present times, following centuries at consistent and higher trophic levels of Atlantic cod. This results in a concurrent converging trophic niche of the demersal fish. The current level of ocean warming is unprecedented, examining marine trophic dynamics across the last millennium of climate fluctuations may reveal patterns of stability or plasticity that in turn may offer scenarios of future effects

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