Arctic char Salvelinus alpinus movement dynamics relative to ice breakup in a high Arctic embayment

Abstract

Arctic waters are warming rapidly due to climate change, which is altering the timing of seasonal sea ice dynamics. Summer ice breakup provides a critical productivity bloom that consumers depend on. Arctic char Salvelinus alpinus undertake seasonal migrations to marine waters presumably to exploit this prey pulse. However, specific migratory timing and residency of char relative to breakup is largely unknown. To investigate char movement, individuals were tagged with acoustic transmitters in 2017 (n = 58) and 2018 (n = 52) within Tremblay Sound, Nunavut, Canada, resulting in 625482 detections. Generalized linear models were used to relate multiple movement metrics to ice conditions as well as biological and temporal factors. Char exhibited multiple migratory patterns (chronologies), by which fish either migrated to/from rivers within Tremblay Sound (n = 67), rivers in external systems (n = 35), or a combination of both (n = 8). Fish that migrated exclusively from external systems were longer (~14 cm) than fish exhibiting other chronologies. Migration timing was related to chronology and preempted the specific ice-off date. Fish migrating from rivers within Tremblay Sound entered the marine environment ~7.5 d before the start of ice-off, while external migrants entered ~21 d after ice-off start. Differing migratory chronologies highlight the complexity of char migrations and may indicate the presence of subpopulations or potential ontogenetic shifts in migration behavior. Our study underscores the importance of the brief ice-free season, with potential implications for climate change resilience and management of this important resource in a changing Arctic.

Distinct freshwater migratory pathways in Arctic char (Salvelinus alpinus) coincide with separate patterns of marine spatial habitat-use across a large coastal landscape

“…We suggest the population-specific patterns of migratory timing of Arctic char observed here arise from a combination of differences in environmental conditions experienced along migratory routes and distance required to travel to reach optimal feeding grounds (Hammer et al 2022). While salmonid migratory behaviour is often plastic and adaptive under dynamic conditions (Crozier and Hutchings 2014;Tillotson and Quinn 2018), there is also a strong genetic component (Moore et al 2017;Lemopoulos et al 2018;Kelson et al 2019), which might be expected to evolve in response to differing conditions between MI and PAS and their associated freshwater systems.…”

“…Our observation of sympatric populations of Arctic char initiating their marine return migration at different times is likely related to migration distances (Moore et al 2016;Hammer et al 2022). Arctic char from the Kuuk River undertake a 52 km journey in their freshwater migration corridor and can perform a 200 km coastal journey to presumed foraging area in SC.…”

“…Along the Diamond Jenness Peninsula it appears that Arctic char migrate from their respective overwintering lakes and disperse within the marine environment to high productivity regions that are in close proximity to corresponding marine entry sites, maximising the energetic yield of each migratory "type" (Spares et al 2012). Were primary productivity more localised, then convergent use of marine foraging areas by Kuuk and Kuujjua river Arctic char would be expected (Moore et al 2015;Hammer et al 2022). Under this scenario, differences in migration distances likely interact with the distribution of seasonal productivity to drive the observed spatial segregation between Arctic char populations.…”

“…As such, the initiation of the marine dispersal stage of migration is likely determined by factors that influence the time required to reach optimal foraging sites, such as the total migration distance, and (or) the rate that routes become clear of sea-ice, to ensure Arctic char arrival coincides with prey presence (Gyselman 1984;Dempson and Green 1985;Gilbert et al 2016; but see Hammer et al 2021). Where Arctic char converge on shared marine foraging grounds from distinct overwintering sites (Moore et al 2016;Hammer et al 2022), those travelling a greater distance may therefore be expected to enter the marine environment and disperse towards foraging grounds earlier than conspecifics arriving from closer overwintering sites (Hammer et al 2022). Characterizing the diversity and timing of movement behaviours of anadromous Arctic char in the marine environment at regional scales is essential to evaluate their overlap with fisheries, the environmental conditions and associated stressors experienced during each movement phase, and subsequently how each may be impacted by climate change (Fenkes et al 2016).…”

“…Straying Arctic char can therefore benefit from abundant marine foraging opportunities in summer while minimising the associated costs of migration distance, thereby maximising energy gain prior to the next spawning period (Keefer and Caudill 2014). For example, marine dispersal distances for Arctic char in Tremblay Sound, Nunavut, varied from 20 to >100 km (Hammer et al 2022). In contrast, if areas of high marine productivity are less patchy, or are sufficiently large to create abundant optimal foraging habitat, Arctic char may maximise the energetic gain of migration by feeding in distinct marine regions, ostensibly those more accessible from their respective natal systems (Bluhm and Gradinger 2008).…”