From polar night to midnight sun: photoperiod, seal predation, and the diel vertical migrations of polar cod (Boreogadus saida) under landfast ice in the Arctic Ocean

By Delphine Benoit, Y. Simard, J. Gagné, M. Geoffroy, L. Fortier. Polar Biology, 2010

128 citations recorded by the source corpus.

The winter/spring vertical distributions of polar cod, copepods, and ringed seal were monitored at a 230-m station in ice-covered Franklin Bay. In daytime, polar cod of all sizes (7–95 g) formed a dense aggregation in the deep inverse thermocline (160–230 m, −1.0 to 0°C). From December (polar night) to April (18-h daylight), small polar cod <25 g migrated into the isothermal cold intermediate layer (90–150 m, −1.4°C) at night to avoid visual predation by shallow-diving immature seals. By contrast, large polar cod (25–95 g), with large livers, remained below 180 m at all times, presumably to minimize predation by deep-diving mature seals. The diel vertical migration (DVM) of small polar cod was precisely synchronized with the light/dark cycle and its duration tracked the seasonal lengthening of the photoperiod. The DVM stopped in May coincident with the midnight sun and increased schooling and feeding. We propose that foraging interference and a limited prey supply in the deep aggregation drove the upward re-distribution of small polar cod at night. The bioluminescent copepod Metridia longa could have provided the light needed by polar cod to feed on copepods in the deep aphotic layers.

Subfields: Ecology, Global and Planetary Change, Oceanography

View Paper: https://www.semanticscholar.org/paper/0ff42503bddc81dbd4bb2cf371a476f2d8925786

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In Ecology

1. Ø. Varpe
2. Malin Daase
3. S. Falk‐Petersen
4. Jørgen Berge
5. Janne E. Søreide
6. E. Leu
7. L. Fortier
8. Paul E. Renaud

In Global and Planetary Change

1. Malin Daase
2. S. Falk‐Petersen
3. Ø. Varpe
4. Janne E. Søreide
5. Jørgen Berge
6. L. Fortier
7. E. Leu
8. O. Lønne

In Oceanography

1. Ø. Varpe
2. S. Falk‐Petersen
3. Malin Daase
4. Jørgen Berge
5. Janne E. Søreide
6. E. Leu
7. A. Wold
8. L. Fortier

Citations in the corpus

• Timing of reproductive events in the marine copepod Calanus glacialis: a pan-Arctic perspective (2013, methodology): “Sampling procedures are described in detail in Benoit et al. (2010).”
• Is the poleward expansion by Atlantic cod and haddock threatening native polar cod, Boreogadus saida? (2011, background): “Vertical migration and mass schooling have been observed and presumed to be predator avoidance mechanisms (Welch et al. 1993; Hop et al. 1997a, b; Benoit et al. 2010).”
• The aggregation of polar cod (Boreogadus saida) in the deep Atlantic layer of ice-covered Amundsen Gulf (Beaufort Sea) in winter (2011, background): “The vertical distribution of polar cod in relation to zooplankton prey and temperature Polar cod in southeastern Beaufort Sea prey primarily on the copepods Calanus hyperboreus, Metridia longa and C. glacialis (Benoit et al. 2010).”
• Vertical segregation of age-0 and age-1+ polar cod (Boreogadus saida) over the annual cycle in the Canadian Beaufort Sea (2016, background): “Polar cod are cannibalistic, the adult stages feeding occasionally on the younger stages (e.g. Benoit et al. 2010; Rand et al. 2013).”