Poleward spawning of Atlantic mackerel ( Scomber scombrus ) is facilitated by ocean warming but triggered by energetic constraints

The Northeast Atlantic mackerel is an income breeder with indeterminate fecundity, spawning in multiple batches at optimal temperatures around 11°C in the upper water column during February–July along the continental shelf from 36–62°N. Based on macroscopic staging of gonads (N ∼62000) collected in...

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Bibliographic Details
Published in:ICES Journal of Marine Science
Main Authors: Schmidt, T. C. dos Santos, Slotte, A., Olafsdottir, A. H., Nøttestad, L., Jansen, T., Jacobsen, J. A., Bjarnason, S., Lusseau, S. M., Ono, K., Holleland, S., Thorsen, A., Sando, A. B., Kjesbu, O. S.
Format: Article in Journal/Newspaper
Language:English
Published: 2024
Subjects:
Conditioning factor
Global warming
Histology
Macroscopic maturity
Northeast Atlantic mackerel
Spawning extension
Stock size
Norwegian Sea
Northeast Atlantic
Online Access:https://orbit.dtu.dk/en/publications/5a3f4381-3b5b-42da-87ec-0d3080e0f37f
https://doi.org/10.1093/icesjms/fsad098
https://backend.orbit.dtu.dk/ws/files/359164728/fsad098.pdf
Description
Summary:The Northeast Atlantic mackerel is an income breeder with indeterminate fecundity, spawning in multiple batches at optimal temperatures around 11°C in the upper water column during February–July along the continental shelf from 36–62°N. Based on macroscopic staging of gonads (N ∼62000) collected in 2004–2021, we detected an on-going extension of spawning activities into the Norwegian Sea feeding area (62–75°N), reaching stable levels around 2012 onwards. This poleward expansion increased as more fish entered the area, whilst the maximum proportions of spawners concurrently dropped from about 75 to 15% from May to July. Detailed histological examinations in 2018 confirmed the macroscopic results but clarified that 38% of the spawning-capable females in July terminated their spawning by atresia. We suggest that increased access to suitable spawning areas (≥10°C), following ocean warming from 2002 onwards, functions as a proximate cause behind the noticed expansion, whereas the ultimate trigger was the historic drop in body growth and condition about 10 years later. Driven by these energetic constraints, mackerel likely spawn in the direction of high prey concentrations to rebuild body resources and secure the future rather than current reproduction success. The ambient temperature that far north is considered suboptimal for egg and larval survival.

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