Estimating the proportion of a beluga population using specific areas from connectivity patterns and abundance indices

Abstract

An understanding of habitat use and connectivity is key to preserving wildlife habitat integrity. In this study, we present an innovative approach to habitat connectivity and quantitative assessment of their use that is applicable to any terrestrial or aquatic species. Specifically, we aimed at estimating the proportion of the St. Lawrence Estuary beluga population (Canada) likely to use specific habitats within their summer range from habitat connectivity. To achieve this goal, we used a long-term (~30 yr) observational database of beluga herd movements to derive transit corridor and an index of connectivity among habitats. These were then coupled with relative abundance estimates from aerial surveys for each of these habitats. Specifically, our objectives were to (1) verify the existence and location of transit corridors, (2) examine the effect of environmental factors on movement patterns and corridor routes, (3) describe their use by different age classes, and (4) based on connectivity patterns, determine the proportion of the population likely to transit along these corridors and to be present in each habitat. Our results highlighted the existence of a network of transit corridors among habitats that are connected to a central confluence zone, and expanding with three main branches into the three main regions of their summer range (Upper and Lower Estuary, and Saguenay River). They also highlighted the existence of a spatial segregation of sex and age classes in the population. Previously published aerial survey data indicate that on average, <6% of the population can be found within the limits of each habitat at any given time. Using this information within the framework of habitat connectivity provided a minimum estimate of the proportion of the population likely to visit each habitat, with minimum proportions reaching 45% in habitats of the central confluence zone (Île Rouge area). While we detected no evidence of an influence of bottom depth on corridor routes, we identified a tendency of beluga for moving with surface and ebb tide currents. The application of this approach to beluga and other wildlife populations will contribute to better assessing their potential exposure to natural or human-related stressors.

Extracting spatial networks from capture–recapture data reveals individual site fidelity patterns within a marine mammal’s spatial range

“…The CTN sector for instance appeared as a potential high mixing zone for the population, whereas the AME sector seemed to be used by a specific subset of the population. These findings align well with a recent study on habitat connectivity in this population exploiting a different dataset, and suggesting that the CTN sector interconnects strongly with other sectors (Ouellet et al, 2021).…”

“…As this population is endangered and occupies a busy marine traffic Applied ecology; Behavioural ecology; Conservation ecology; Movement ecology; Spatial ecology area in the summer, there has been considerable effort to understand their distribution and habitat use among other things. In particular, a lot of work has been done to identify hot spots of use and how habitat use varies by age and sex to better mitigate threats to this population (Gosselin et al, 2017;Lefebvre et al, 2012;Lemieux Lefebvre et al, 2018;Michaud, 2005;Ouellet et al, 2021). These studies focused largely on population-level patterns, such as identifying which areas are used the most.…”

Protection, energetic assistance, or social perks: How do beluga offspring benefit from allocare?

“…These findings are consistent with the hypothesis that Sainte‐Marguerite Bay is a particular important site for females with offspring and may function as a nursery or rearing ground (Lemieux Lefebvre et al, 2012; Ménard et al, 2018; Michaud et al, 1990; Pippard & Malcolm, 1978). Similar to Ouellet et al (2021), we also found support for the idea that the Saguenay Fjord primarily represents a transit corridor between Sainte‐Marguerite Bay and the St. Lawrence Estuary. We found that traveling was the predominant behavior in the fjord: 53.6% of focal observations in the fjord occurred in groups that were traveling, compared to only 5.9% in the bay.…”

“…In contrast, the Saguenay Fjord appears to serve as a transit corridor connecting the St. Lawrence Estuary to Sainte-Marguerite Bay (Ouellet et al, 2021). We obtained a total of 1,846 focal observations of beluga calves and juveniles from the two sites, and identified a series of variables that, if related to maternal care and allocare, may allow us to infer the benefits of allocare to offspring and whether they are similar to the benefits of maternal care.…”

“…Similar patterns of habitat use are observed in Arctic populations, where belugas congregate in shallow bays and estuaries in the summer to molt, rest, feed, care for young, and socialize (Anderson et al, 2017; O'Corry‐Crowe et al, 2009; Smith et al, 2017). In contrast, the Saguenay Fjord appears to serve as a transit corridor connecting the St. Lawrence Estuary to Sainte‐Marguerite Bay (Ouellet et al, 2021). We obtained a total of 1,846 focal observations of beluga calves and juveniles from the two sites, and identified a series of variables that, if related to maternal care and allocare, may allow us to infer the benefits of allocare to offspring and whether they are similar to the benefits of maternal care.…”