Polar cod egg and larval drift patterns in the Svalbard archipelago

Abstract

Spawning of polar cod (Boreogadus saida) in the vicinity of the Svalbard archipelago has not been directly observed. From the distribution pattern of polar cod 0-group observed during annual monitoring of the Barents Sea, it has, however, been inferred that spawning occurs in Svalbard waters most years. We wanted to investigate the possibility of back-tracking the larvae from these observed distribution areas to the spawning areas from which they originated and applied a coupled ocean-sea ice and particle tracking model to simulate the drift of particles released at suggested spawning sites. The model was run for 1 year (December 2006-September 2007), and the results were compared to observations of polar cod larvae in the autumns of 2007 and 2004-2010. The particles released in the western fjords were mostly retained in the fjords. For the rest of the suggested spawning grounds, the released particles drifted mostly clockwise around the archipelago. Model runs mainly indicated a drift pattern with end points that qualitatively match the main features of the August-September distribution of the polar cod 0-group observed. We conclude that the suggested spawning sites on the southern, northern and eastern sides of Svalbard could have caused a distribution of 0-group polar cod similar to that observed during August-September 2007. From the environmental factors experienced during drift of eggs and larvae and assumptions about habitat suitability for survival and growth, we conclude that spawning in the Svalbard area probably occurs on the southern and eastern sides and later than the area in the southeastern Barents Sea.

Key processes regulating the early life history of Barents Sea polar cod

“…While the polar cod is found over large areas in the Barents Sea during the feeding season, spawning is apparently restricted to two separate regions; one in the Pechora Sea in the southeastern Barents Sea (Ponomarenko 1968) and one in the vicinity of Svalbard (Gjøsaeter 1973;Boitsov et al 2013). Recent particle drift studies, (Eriksen et al 2019;Huserbråten et al 2019) have corroborated the existence of two separate spawning areas in the region (Fig. 2).…”

“…Our recent particle drift studies have shown that polar cod offspring observed in the northwestern Barents Sea could not come from the southeastern spawning areas (Huserbråten et al 2019). Furthermore, eggs spawned east of the Svalbard archipelago may drift clockwise around the archipelago and thus could end up in almost all the areas where polar cod juveniles have been observed around the archipelago (Eriksen et al 2019). This supports earlier findings of prespawners and polar cod juveniles around Svalbard (Ponomarenko 1968;Gjøsaeter 1973;Korshunova 2012;Boitsov et al 2013;Eriksen et al 2015).…”

Arctic gadids in a rapidly changing environment

“…The genetic population structure in the Northeast Atlantic remains unclear, as Nelson et al (2020) did not have samples from the Barents Sea. There is evidence of two distinct spawning populations in the southeastern Barents Sea (Pechora Sea) and in the northwestern Barents Sea east of Svalbard, respectively, supported by distinct distributions of eggs and larvae (Boitsov et al 2013) and by biophysical modeling studies (Huserbråten et al 2019;Eriksen et al 2020). Hypothesized spawning sites to the south, east, and north of the Svalbard Archipelago are consistent with the observed distribution of age-0 polar cod in the northwest Barents Sea (Eriksen et al 2020).…”

“…There is evidence of two distinct spawning populations in the southeastern Barents Sea (Pechora Sea) and in the northwestern Barents Sea east of Svalbard, respectively, supported by distinct distributions of eggs and larvae (Boitsov et al 2013) and by biophysical modeling studies (Huserbråten et al 2019;Eriksen et al 2020). Hypothesized spawning sites to the south, east, and north of the Svalbard Archipelago are consistent with the observed distribution of age-0 polar cod in the northwest Barents Sea (Eriksen et al 2020). In contrast, particles released in the western fjords were largely retained in the fjords, consistent with previously reported fine-scale genetic structure differentiating fjord populations in western Svalbard and eastern Greenland from open ocean populations (Madsen et al 2016).…”

Combined effects of crude oil exposure and warming on eggs and larvae of an arctic forage fish

“…With heightened activity comes increased risk of petroleum pollution 10 . Shipping routes (i.e., the Northern Sea Route and Northwest passage route) traverse important nursery grounds for Arctic fish species [11][12][13] .Early life stages (ELSs) of many fish face greater vulnerability to environmental stressors, owing to physical and biological factors 14,15 . To ensure survival and a strong year class, pelagic eggs and larvae must maintain their position in the water column through buoyancy control and swim bladder inflation, forage when yolk reserves are exhausted, grow quickly, and build up energy reserves for overwintering while avoiding predation 16 .…”