Interannual variability of diet composition and prey preference of larval redfish (Sebastes spp.) in the Gulf of St. Lawrence

Abstract

Spatiotemporal overlap between fish larvae and their planktonic prey is an important source of recruitment variability. Over the past decade, one species of redfish, Sebastes mentella, from the Gulf of St. Lawrence (GSL) produced multiple strong cohorts following decades of low recruitment, which has generated strong interest in identifying potential drivers of larval survival. The present study provides the first detailed, multi-year assessment of larval redfish (Sebastes spp.) trophodynamics. Interannual variability in larval redfish diet composition and prey selectivity was assessed using high-resolution prey identification of larval gut contents and in situ prey fields. Eggs from the calanoid copepod Calanus finmarchicus represented the most frequently consumed prey in 3 of the 4 collection years, and contributed the largest proportion of carbon ingested by redfish larvae in all years. The high consumption of C. finmarchicus eggs by larvae, combined with evidence of positive selection for this taxon in some years, supports the hypothesis of a strong trophic link between larval redfish and a key calanoid copepod in the GSL ecosystem. Our results indicate that future efforts investigating GSL redfish recruitment processes should consider environment-driven variability in the reproductive phenology and abundance of C. finmarchicus.

Feeding ecology of redfish (Sebastes sp.) inferred from the integrated use of fatty acid profiles as complementary dietary tracers to stomach content analysis

“…Work by Burns et al . (2020) showed positive selection by redfish larvae on C. finmarchicus eggs, supporting the hypothesis of a strong link between larvae and a key calanoid copepod in the GSL ecosystem.…”

“…Furthermore, EPA, like DHA, is incorporated in membrane phospholipids to maintain the structural and functional integrity of biological membranes, particularly in cold conditions (Hulbert & Else, 1999). The consumption of calanoids by small redfish may be a feeding trait originating from the larval stage (Burns et al ., 2020; Burns et al ., 2021) and a good source of EPA, with mean values observed here of 12% of their total FAs. Work by Burns et al .…”

Spatiotemporal variability in diet composition of Greenland halibut (Reinhardtius hippoglossoides) from the eastern Canadian Arctic

“…In 2020, DFO surveys and fishing vessels operating on the Labrador shelf reported a very high abundance of small Sebastes sp. in the zone, which could be an indicator of a recent strong recruitment event, similar to that recently observed in the Gulf of St. Lawrence (Burns et al, 2020;DFO, 2022b). The size of Sebastes sp.…”