Near-bottom aggregations of Calanus spp. copepods in the southern Gulf of St. Lawrence in summer: significance for North Atlantic right whale foraging

Abstract Copepods of the genus Calanus are a critical source of food for the North Atlantic right whale (NARW), Eubalaena glacialis. We quantified variations in depth-integrated abundance and vertical distribution of Calanus spp. in the southern Gulf of St. Lawrence (sGSL) in August 2019. While Cala...

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Bibliographic Details
Published in:ICES Journal of Marine Science
Main Authors: Sorochan, K A, Plourde, S, Johnson, C L
Other Authors: Fields, David, Fisheries and Oceans Canada
Format: Article in Journal/Newspaper
Language:English
Published: Oxford University Press (OUP) 2023
Subjects:
Ecology
Aquatic Science
Ecology, Evolution, Behavior and Systematics
Oceanography
Calanus finmarchicus
Eubalaena glacialis
North Atlantic
North Atlantic right whale
Copepods
Online Access:http://dx.doi.org/10.1093/icesjms/fsad003
https://academic.oup.com/icesjms/article-pdf/80/4/787/50385032/fsad003.pdf
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Summary:Abstract Copepods of the genus Calanus are a critical source of food for the North Atlantic right whale (NARW), Eubalaena glacialis. We quantified variations in depth-integrated abundance and vertical distribution of Calanus spp. in the southern Gulf of St. Lawrence (sGSL) in August 2019. While Calanus finmarchicus was the most abundant species of Calanus, the larger C. hyperboreus was prominent in the Shediac Valley, a NARW high-use area, contributing a median of 55% estimated depth-integrated biomass of Calanus spp. during the first leg of the field mission. Near-bottom aggregations of Calanus spp. with concentrations exceeding 1000 ind m−3 occurred primarily at depths ranging from 70 to 90 m. Ontogenetic and diel vertical migrations likely contributed to development of these subsurface aggregations. During the day, Calanus spp. and euphausiids occurred in a compact near-bottom layer, indicating enhanced foraging conditions for NARW. We observed considerable variation in abundance and vertical distribution of Calanus spp., highlighting the dynamic nature of NARW prey distribution at scales of weeks and tens of kilometers in the sGSL.

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