Ommastrephid squid spawning in the North Sea: oceanography, climate change and species range expansion

Abstract

The lesser flying squid (Todaropsis eblanae) and the shortfin squid (Illex coindetii) are two abundant ommastrephids of the northeast Atlantic. Spawning ground existence was inferred from the captures of mature, mated females in summer 2016–2019 and their occurrences were compared with respective oceanographic data from international surveys to gain insight into environmental predictors of their presence throughout the North Sea. Spawning T. eblanae were found in relatively cooler and more saline waters (6–8°C, 34.2–35.1 psu) in the northern North Sea linked to the Fair Isle Current and East Shetland Atlantic Inflow, whilst spawning I. coindetii occurred across the entire North Sea (mostly at 9–10.5°C, 34.1–34.8 psu). We hypothesize that a combination of water salinity and water temperature are key factors in the spatiotemporal distribution of spawning ommastrephid squids as they define water density that is crucial for pelagic egg mass to attain neutral buoyancy.

Climate change-related changes in cephalopod biodiversity on the North East Atlantic Shelf

“…IPCC 2014). While in the twentieth century the temperatures in the northern North Sea might have been too cold for some cephalopods, the increased temperatures seem to be more adequate now and it seems that at least the newcomers T. eblanae and I. coindetii are linked to the Atlantic inflow from the north (Barrett et al 2021).…”

“…In winter, most I. coindetii were immature or maturing, while in summer almost exclusively larger individuals were fished; mostly mature and spent . Furthermore, mated females with spermatangia bundles, were observed in summer and Illex eggs were identified in the Greater North Sea and adjacent waters (Barrett et al 2021;Ringvold et al 2021). Consequently, it is very likely that the species started to reproduce in the area with a hatching period at least from June to December Barrett et al 2021).…”

Stock discrimination of two European squids (Illex coindetii, Loligo forbesii) by statolith shape analysis

“…Previously, single adult individuals without any evidence of reproduction occurred in the North Sea, which were thought to have migrated into the North Sea from adjacent waters (Oesterwind et al, 2020). The current reproductive success in the North Sea (first observed in 2016) probably results from rising temperatures and prevailing currents (Barrett et al, 2021;Oesterwind et al, 2022) and has led to an independent stock. The S4).…”

“…Mean statolith shapes of Illex coindetii and Loligo forbesii (all maturity stages and sexes) from the Balearic Sea (blue), Celtic Sea (grey), North Sea (Q1 & Q3 combined; black), Sea East of Sardinia (red), Sea West of Sardinia (orange), Sea West of Scotland (green), South Adriatic Sea (yellow), Western Ionian Sea (purple) of the North East Atlantic and Northern Mediterranean Sea during 2021-2022. Intersection of coordinate lines corresponds to the statolith centroid.North Sea appears to be the northernmost breeding area, with main spawning grounds in the Central and Northern North Sea(Barrett et al, 2021), while floating egg masses have been observed in the Norwegian Channel(Ringvold et al, 2021). The bathymetry and hydrology of the North Sea, as a shelf sea with an average depth of 90 m and a relatively narrow connection to the Atlantic Ocean(ESaTDOR, 2013), could prevent emigration from this area by passive drifting egg spheres and hatchlings of I. coindetii.…”

Cephalopods, a gap in the European Marine Strategy Framework Directive and their future integration

“…Last but not least, many knowledge gaps exist regarding habitat requirements in cephalopods, although studies are beginning to be performed to fill this gap (recently e.g. Barrett et al 2021;Laptikhovsky et al 2022). All-in-all, cephalopods can be integrated in D1, at least for some of the criteria, as described above.…”