Migratory Variation in Mackenzie River System Broad Whitefish: Insights from Otolith Strontium Distributions

Abstract

There is growing recognition of the global importance of preserving biodiversity. While many organisms show immense variation in intraspecific biodiversity, for example in life history variation and migratory strategies among conspecific populations, accurate descriptions of such variation are lacking for the majority of contemporary species. One such example is the broad whitefish Coregonus nasus of the lower Mackenzie River system in Canada's Northwest Territories, where anadromous, lacustrine, and putative riverine populations are thought to exist. In this study we resolve migratory variation exhibited by lower Mackenzie River broad whitefish by employing otolith microchemistry and find that (1) anadromous, lacustrine, and riverine populations exist in this system, (2) a high degree of variability exists within anadromous broad whitefish (e.g., varying degrees of marine and estuarine use), and (3) lacustrine populations are not composed solely of resident fish as anadromous broad whitefish occasionally migrate to, and stay in, lacustrine habitat. Overall, our results are consistent with the suggestion that there may be a higher level of migratory complexity in this system than previously reported and these results will be important in guiding the conservation of intraspecific biodiversity in Mackenzie River system broad whitefish.

Brackish-water residency and semi-anadromy in Arctic lake trout (Salvelinus namaycush) inferred from otolith microchemistry

“…Concentrations of strontium, Sr, in water are positively correlated with increasing salinity (Elsdon et al, 2008;Secor and Rooker, 2000;Secor et al, 1995;Zimmerman, 2005) and Sr has been documented to deposit in calcified structures such as the otolith of fish (Walther and Thorrold, 2006) proportionally reflecting Sr in the ambient water (Zimmerman, 2005). Due to this relationship, Sr in the otoliths of wild-caught fish is frequently used to determine fresh or marine water residency and movement (Babaluk et al, 1997;Harris et al, 2012) and has been successfully used to differentiate freshwater resident and semi-anadromous life history types in lake trout populations (Swanson et al, 2010).…”

“…Inference of fish movement and life history through analysis of otolith microchemistry has become common for fishes inhabiting fresh and marine water environments (Limburg, 1995;Zimmerman, 2005;Swanson et al, 2010;Harris et al, 2012). Concentrations of strontium, Sr, in water are positively correlated with increasing salinity (Elsdon et al, 2008;Secor and Rooker, 2000;Secor et al, 1995;Zimmerman, 2005) and Sr has been documented to deposit in calcified structures such as the otolith of fish (Walther and Thorrold, 2006) proportionally reflecting Sr in the ambient water (Zimmerman, 2005).…”

The importance of continuous dialogue in community-based wildlife monitoring: case studies of dzan and łuk dagaii in the Gwich’in Settlement Area

“…Broad whitefish is a highly mobile species and may occupy rivers, lakes, and the ocean. Although variation exists in the extent of migrations, a single individual may use multiple of these habitats in a lifetime (Thompson and Millar 2007;VanGerwen-Toyne et al 2008;Harris et al 2012). As a result, this species could encounter changing conditions throughout the Mackenzie River watershed, including changes to river habitats through thawing permafrost and altered hydrology (St. Pierre et al 2018), the potential for Pacific salmon colonization (Dunmall et al 2016), and shifts in ocean productivity (Ardyna et al 2014).…”

“…Currently, broad whitefish populations remain abundant, and within the GRRB's 2013 priorities framework they are included under the "climate change" Research and Management Priority, they are listed on the Research and Management Interests list, and they fit within the goals of establishing standardized monitoring programs. The Department of Fisheries and Oceans has conducted some work on broad whitefish prior to 2005 (VanGerwen-Toyne et al 2008;Harris et al 2012;Millar et al 2013), but relatively few efforts have focused consistently on this species and the GRRB has therefore highlighted an outstanding need for baseline data.…”

Migration, Dispersal, and Gene Flow of Harvested Aquatic Species in the Canadian Arctic

“…They range from latitude 105 W westward to 50 E. They are harvested throughout their range for subsistence and commercial purposes in the lower Mackenzie River system of Canada's NWT. Broad whitefish exhibit three presumed life history strategies including anadromous, riverine, and lacustrine (complete their life cycles entirely within a lake) forms [26,27]. One anadromous population of Broad whitefish is known to spawn in the Arctic Red River at Weldon Creek, about 160 miles upriver from the mouth [28].…”