Contemporary spatial extent and environmental drivers of larval coregonine distributions across Lake Ontario

Larval cisco and lake whitefish exhibit high distributional overlap within nursery areas

“…The 554 larvae that genotyped successfully were assigned with high confidence, exhibiting an average assignment score of 0.95 (range = 0.85-0.98) and an average Q-score of 0.99 (range = 0.88-1). The genetic species composition was consistent with the existing 2018 catch data where only 1% of larvae in Chaumont Bay and less than 6% of larvae lake-wide were identified as lake whitefish (Brown et al, 2022). Correcting for subsampling, we observed cisco (n = 1821) and lake whitefish (n = 41) at mean densities of 313 (max.…”

“…We also leveraged the spatially and temporally extensive survey datasets to characterise larval cisco and lake whitefish stage development and contemporary growth dynamics across space and time (Figure 4; Table 2). This work directly builds upon our recent study of Lake Ontario larval coregonines (Brown et al, 2022) by describing the larval habitat use of cisco and lake whitefish within nursery areas, including explicit statistical distributional comparisons between species and across ontogeny.…”

“…Ontogenetic habitat shifts have also been described for both species, where newly‐hatched larvae of both species are first found in the water column near spawning shoals before moving into shallow littoral habitats (Clady, 1976; Faber, 1970; Hart, 1931; Pritchard, 1931). In our recent paper (Brown et al, 2022), we used larval presence and relative abundance to infer the contemporary spatial extent of cisco and lake whitefish spawning habitat across Lake Ontario, with a broad focus on identifying which regions are currently used for spawning by each species at a lake‐wide scale. Larval distributional dynamics at finer resolutions were not investigated, such as the spatial distribution of larvae within individual nursery areas, how those distributions changed over time throughout the season or how they differed between species.…”

“…Assessments of coregonine spawning habitat in New York waters during the same time period predominantly encountered cisco eggs and larvae and found little evidence of successful lake whitefish production (George et al, 2017(George et al, , 2021Paufve et al, 2022), a stark contrast to the mid-2000s when lake whitefish were the primary coregonine species encountered . Most recently, in 2018, a lake-wide larval survey found that cisco was 37 times more abundant than lake whitefish among multiple spawning populations, providing further evidence of large-scale differences in recent recruitment success between species (Brown et al, 2022). Lake Ontario fish community objectives seek to conserve and increase populations of both cisco and lake whitefish (Stewart et al, 2017) but increased understanding of which processes are regulating the populations of these two species may be needed to effectively meet those joint objectives (Bronte et al, 2017;.…”

Diversity in spawning habitat use among Great Lakes Cisco populations

“…Assuming areas with shorter fetch are exposed to weaker wind and wave energy, this may indicate Great Lakes Cisco prefer spawning areas with lower physical disturbance regimes. Furthermore, ice duration over the winter period has been associated with larval Cisco presence in Lake Ontario, indicating regions with higher ice coverage that could decrease wave and current energy may provide good spawning locations (Brown et al, 2021). Within spawning areas, habitats differ in exposure to physical disturbance, whereby depositing eggs in deeper habitats may confer protection from wave and current disturbances during ice free periods (e.g.…”