Diet and feeding strategy of Northeast Atlantic mackerel (Scombrus scomber) in Icelandic waters.

Cecilia Kvaavik,Anna Kristín Daníelsdóttir,Gudrún Marteinsdóttir,Gudmundur J Óskarsson,Geir Ottersen

doi:10.1371/journal.pone.0225552

Cecilia Kvaavik, Anna Kristín Daníelsdóttir + Show 3 more

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https://doi.org/10.1371/journal.pone.0225552

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Abstract

Predator-prey relations, as well as the trophic ecology of highly migratory marine species, is important to understand their impact on the ecosystem. Conventional methods were used to study the diet composition and feeding strategy of the Northeast Atlantic mackerel (Scombrus scomber), during their summer feeding migration to Icelandic waters in 2009–2014. In addition, generalised additive modelling (GAM) was used to determine which biological and environmental factors contribute to the variation of their stomach weight in the years 2011–2014. From the dietary analysis, we found that calanoid copepods (especially Calanus finmarchicus) were the most important contributor to the overall diet of mackerel in the years studied. Although in some years and areas, they also preyed heavily on larger prey items such as euphausiids, amphipods and megalopa larvae of crab and shrimp. The GAM showed that temperature and the time the day of sampling were significant explanatory variables for the stomach weight, while zooplankton biomass did not seem to have much influence. The Northeast Atlantic mackerel are ferocious feeders upon copepods, as well as exhibiting an overall opportunistic feeding strategy. During their feeding migration in Icelandic waters, they were found to feed on the most dominant species available to them.

Highlights

Marine ecosystems are under an increasing threat from climate changes on top of environmental variability
The overall prey specific index of relative importance (PSIRI) showed that the most common prey group that occurred in all mackerel stomachs for all the years was the copepod group (Fig 2), constituting a PreySpecific Index of Relative Importance (PSIRI) between 48.7% to 86.6% in the years studied
The results showed that mackerel’s main food source while feeding in Icelandic waters, were calanoid copepods, which constituted >60% of the total content weight of the stomachs

Summary

Introduction

Marine ecosystems are under an increasing threat from climate changes on top of environmental variability. Migratory pelagic fish species occupying large and different marine ecosystems might respond to such changes by altering migration patterns, distribution and feeding habits. These responses will impact the ecosystems inhabited through predator-prey interactions, which can be difficult to predict and observe [1,2]. Understanding these impacts requires studying fish diets and feeding habits (i.e. prey selection and specialisation). Such studies provide the basis for understanding trophic interactions in marine food webs and the effect the predator has on the ecosystem as a whole [3,4] and are crucial for more ecosystem-based fishery management.

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