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

Abstract

Production and outmigration of young-of-year (YOY) northern pike from natal sites in Lower Green Bay, WI, USA, were documented over three consecutive years (2013)(2014)(2015). We tested the hypothesis that spawning success and outmigration characteristics of YOY northern pike would vary among natural and anthropogenically modified habitats. Sixteen focal study locations were surveyed, including a restored natural wetland, agricultural drainage ditches, a flooded forested wetland and several unimpounded tributaries. We collected 1469 YOY northern pike with most individuals (N = 1163) originating from a flooded forested wetland on the east shore. Most sites produced YOY in all years (range N = 2-1145 individuals among study years). Outmigration ranged between 1 and 40 days during 2013-2015.Greater production and extended outmigration times occurred at most sites in 2014 (range 17-40 days) when the region experienced a late spring with heavy precipitation. In contrast, the lowest production and shortest outmigration period occurred at most sites in 2015 (range 14-23 days) when environmental conditions reflected regional averages. Outmigration began nearly 3 weeks earlier in 2015 (5/8) than in other study years (8 June 2013 and 25 May 2014). Total length (TL) of outmigrating northern pike ranged between 17 and 138 mm. Total length of YOY was significantly different among sites in 2013 and 2014, with the smallest fish (17 mm TL) outmigrating from agricultural ditches in both years. There were no significant variations in size among sites in 2015 (range 21-95 mm TL). Our results indicate significant variation in YOY northern pike outmigration characteristics within Lower Green Bay that may reflect the interplay between adult spawning site selection and annual weather patterns. Our findings highlight the importance of quantifying overlooked habitats in regions of mixed development.

Influence of water‐level variability on fish assemblage and natural reproduction following connectivity enhancement in a Typha‐dominated coastal wetland, USA

“…If ΔWL declines after the spawning period, as was the case in 2012 and 2016, water connections between spawning and nursery areas may be reduced or lost, potentially stranding eggs or newly hatched larvae in upslope habitats, leading to poor natural reproduction (Mingelbier et al, 2008;Neveldine et al, 2019;Massa & Farrell, 2020). When WLSpring and ΔWL were both high, fish could access inundated spawning habitats and YOY could exploit resources within an expanding habitat afforded by rising water levels which maintain reliable emigration routes (Casselman & Lewis, 1996;Cottrell et al, 2021;Farrell et al, 2006;Foubert et al, 2019;Mingelbier et al, 2008). However, during peak ΔWL years, the benefits of sustained hydrological connectivity may be offset by hydrologically induced hypoxia.…”

“…The connectivity channels and unmodified channels, in contrast, maintained a shallower depth gradient relative to spawning pool complexes as flood waters inundated the riparian sedge‐meadow habitat. The channelized habitats, which provided connectivity to sedge‐meadow habitats, likely maintained sufficiently shallow habitat used by both nest building (largemouth bass; Garvey et al ., 2000; Havens et al ., 2005) and broadcast spawning species (northern pike; Cottrell et al ., 2021; Foubert et al ., 2020; Neveldine et al ., 2019; Oele et al ., 2018) during high and low water level years.…”

Vertical Patterns in Lake Sturgeon (Acipenser fulvescens) Larval Drift within Two Rivers Directly Connected to Green Bay, Lake Michigan

“…Te larval stage of migratory riverine spawning fshes is further characterized by a brief period of posthatch larval retention in the substrates, active downstream outmigration or "drift and dispersal" from spawning areas often induced by internal/external cues (e.g., depletion of the yolk sac; water temperature), and subsequent settlement in downstream nursery habitats [2]. Patterns in the outmigration behavior of larvae have been described for many migratory fsh species [3][4][5], providing insights into adult spawning behavior and quantifcation of adult reproductive success, which can play an important role in species conservation and river management [6].…”

Estimating population size and survival of adult northern pike (Esox lucius) in Lower Green Bay

“…These spawning factors may include high water temperatures (Mingelbier et al, 2008) and size of spawning adults (Haugen & Vøllestad, 2018). Thus, a dedicated long-term monitoring approach deployed at frequently used spawning locations, which are uniquely concentrated and accessible throughout Lower Green Bay (see Cottrell et al, 2021), may provide the backdrop for a dedicated sampling effort, establishing an alternative set of data to generate population estimates while accounting for variables influencing spawning migrations and unveiling a great deal about northern pike ecology in this system.…”