Modeling the effective spawning and nursery habitats of northern pike within a large spatiotemporally variable river landscape (St. Lawrence River, Canada)

Abstract

Spawning and nursery habitats are often spatially disjunct as a consequence of specific life history stage habitat requirements and spatiotemporal habitat changes. Nevertheless, free‐swimming larvae originating from spawning habitats must reach productive nurseries to maximize survival. We examined spawning and nursery habitats of northern pike (Esox lucius) over the past 50 yr to investigate how habitat connectivity and hydrological variability interact to alter the distribution of effective spawning habitat. Habitat models coupled to a least‐cost approach were developed to quantify connectivity between habitats in two contrasting regions of the St. Lawrence River (Canada): a riverine corridor lake (~ 46 km) and a large fluvial lake (~ 48 km). Our simulations demonstrate that depending on hydrological conditions, between 3% to 51% of spawning habitat used by adults in the riverine corridor, and 22% to 90% in the lake, allowed larval survival up to the fifth week of development. Although rapid dewatering of spawning habitat is responsible for most spawning losses in the fluvial lake, increasing water currents were responsible for dispersing larvae away from suitable habitats in the riverine corridor. However, stable hydrological conditions led to spatial overlapping of spawning and nursery habitats favoring larval survival and growth. In addition, downstream larval dispersal by low water currents allowed larvae to reach spatially disjunct nursery habitat, especially in the lake. Our results indicate that despite the vast areas of potentially suitable habitats provided by large vegetated floodplains of fluvial lakes, the effective spawning habitats favoring early‐life recruitment are much more heterogeneous and variable both spatially and temporally.

Acoustic telemetry detection probability and location accuracy in a freshwater wetland embayment

“…Variation in the accuracy of estimated transmitter locations was often greater in our study than previously found [37][38][39]. With our lower-powered transmitters (152 dB) located in close proximity to soft shoreline (i.e., emergent vegetation, tapered beach) where Northern Pike would likely aggregate during spawning [13,40], we had a tolerable error range (19-34 m). Taylor and Litvak [38] reported triangulation error of 18.44 ± 0.85 m when using 3-point triangulation like we used.…”

Production and outmigration of young‐of‐year northern pike Esox lucius from natural and modified waterways connected to Lower Green Bay, Wisconsin

“…Size at outmigration is correlated with rearing habitat conditions that support healthy growth rates (Crain et al ., 2004; Neveldine et al ., 2019). Not surprisingly, multiple studies stress the importance of water temperature in the duration of egg incubation, the size of larvae at hatch and early life growth rates (Foubert et al ., 2019; Nilsson et al ., 2014). YOY from less urbanized sites in some years ( e.g ., Pensaukee River and Point Comfort Creek in 2014) may therefore have a higher probability of recruiting to adults.…”

How intensive agricultural practices and flow regulation are threatening fish spawning habitats and their connectivity in the St. Lawrence River floodplain, Canada

“…As these simulations exclude anthropogenic effects, we used them to estimate the full reproductive habitat potential of northern pike in a natural environment for each year of the 1965-2013 period. Habitat quality indices (HSIs) were developed to map the maximum spawning habitat (Week0: the date varies every year according to water temperature, developed in Mingelbier et al 2008) and nursery habitat five weeks after the start of the free-swimming stage (HSI nursery at Week5, developed and described in Foubert et al 2018).…”

“…In previous work, Foubert et al (2018) examined spawning and nursery habitats of northern pike (Esox lucius) over the past 50 years to investigate how habitat connectivity and hydrological variability interact to alter the distribution of effective spawning habitat in the St. Lawrence River floodplain, Canada. The northern pike was used as a species model because it is an early-spring spawner, archetypal of the floodplain.…”

“…Pike abundance has recently declined in several major river systems (Boët et al 1999;Raat 2001), including the St. Lawrence River (Smith et al 2007). Foubert et al (2018) defined effective spawning habitats as habitats that permit survival of eggs and larvae, while affording larvae access to nursery areas that are essential for successful recruitment to the adult population. As the simulations were carried out in a reconstructed "unaltered" landscape to measure the intrinsic natural variability of the river, they provided a way to compare a simulated pristine environment with a present-day landscape altered by human activities.…”