Greenland cod movements in a semi-enclosed channel in the western Canadian Arctic and in reference to a literature synthesis on nearshore Arctic gadids

Background/Question/Methods

Coastal Arctic marine ecosystems are data deficient and facing increasing stressors as a result of climate change, including the ongoing northern range expansion of Boreal fauna and contraction of the distribution of Arctic fauna. As such, there is both a need for studies on species movements and synthesis of current literature to identify knowledge gaps and research direction. Here we present telemetry data on the movements of Greenland cod (Gadus ogac) in a semi-enclosed channel in the western Canadian Arctic. Through working closely with an Indigenous community (Ulukhaktok, NT), we tracked the fine scale movements of Greenland cod (n = 91) using acoustic telemetry over multiple years (2018-2020). We assessed the relative importance of oceanographic variables, bathymetry, substrate, body size and condition as drivers of variation in observed time series movements, with a cod ID random component to investigate inter-individual variation. Findings were then examined in relation to a literature synthesis on the movements of nearshore gadids; Greenland cod, Saffron cod (Eleginus gracilis), and Navaga (Eleginus navaga), in context of climate change effects on species distributions. Movement literature was synthesised from original data papers in online databases identified based on pre-determined search terms present in the title and abstract.

Results/Conclusions

Telemetry revealed high intraspecific and low population-level variation in Greenland cod space use, residency and distance travelled indicating flexibility through dynamic movements within coastal waters. The random component explained by far the most variation, followed by ice concentration and salinity with significant negative relationships suggesting this species may cover a wider area in the future. However, strong intraspecific variation and comparatively little response to oceanographic variables challenges predictions at the population level. With the exception of one individual, Greenland cod remained within the semi-enclosed channel for the duration of the study with evidence of spawning occurring in spring. The literature synthesis revealed a rarity of studies directly relevant for understanding the movements of nearshore gadids (19 Greenland cod, 13 Saffron, 3 Navaga), although indirectly relevant studies provide some context (e.g., trophic ecology, distribution; 35, 35, 13, respectively). Previous spatial and temporal telemetry coverage is often insufficient to confirm the extent of seasonal and multi-year variation of movements to feeding and spawning grounds. Findings of the case study highlight the importance of examining behavioural variation within and among individuals, which is lacking in the current literature and can be an important indicator of flexibility to ecosystem change and potential species interactions.