Lakescape connectivity: Mobile fish consumers link Lake Michigan coastal wetland and nearshore food webs

Abstract

In large lake ecosystems, fish movement between coastal littoral habitats such as wetlands and the adjacent open-water nearshore represents an understudied but potentially important linkage supporting energy flow and fisheries production. We hypothesized that yellow perch (Perca flavescens), an ecologically and economically important sport fish in the Laurentian Great Lakes, transport energy from highly productive wetlands to nearshore food webs, but that their role changes with ontogenetic shifts in diet and habitat use. We also predicted that the relative strength of such fish-mediated habitat linkages would vary depending on physical connectivity across habitats. We collected perch and potential prey resources from seven paired coastal wetland-nearshore sites across three regions of Lake Michigan and quantified resource and habitat use with Bayesian stable isotope mixing models and otolith microchemistry. We found that juvenile perch collected in nearshore habitats showed high use of wetland resources, and that diets of wetland-collected juveniles typically contained a smaller proportion of nearshore resources than did more mobile adults from the same wetland.The least hydrologically connected sites had lower cross-habitat resource use (e.g., wetland-collected perch consumed fewer nearshore resources and vice versa) compared with sites with greater levels of hydrological connectivity. Otolith microchemistry confirmed the linkages revealed by stable isotopes, suggesting that a dual approach can increase understanding of habitat linkages in large lakes. Quantifying the importance of multiple lentic habitats (i.e., "lakescape connectivity") for fisheries production is critical for developing comprehensive large lake food web models and providing managers with information to prioritize locations for conservation and restoration.

Bidirectional energy subsidies for fish in river mouths of a large lake as revealed by stable isotopes and fatty acids

“…Ambient water isotope patterns presented herein are generally consistent with past studies in nearshore Lake Michigan (e.g., Jasechko et al 2014; Foley et al 2017, 2022; Senegal et al 2020) and with relatively few available studies that have simultaneously considered tributaries (e.g., Dufour et al 2005; Jameel et al 2018; Senegal et al 2020; O'Reilly et al 2023). Similar to δ 13 C in prey samples, δ 2 H and δ 18 O values in the ambient water followed a general trend of relatively low δ 2 H and δ 18 O values in tributaries and isotopic enrichment in nearshore Lake Michigan waters (e.g., Foley et al 2022).…”

“…Mixing model outputs showed that all three fish species, including less mobile round goby, integrate a variety of resources across Muskegon habitats. Resource exchange indicates that Muskegon habitats are likely interconnected due to the physical characteristics of this system (Essig 2016; O'Reilly et al 2023) and that fish may move between these habitats for feeding and refuge. In addition, based on isotopic variation in bivalve shells, Muskegon Channel may be an important convergence zone for fish between the productive Muskegon Lake and nearshore Lake Michigan.…”

“…Although studies of habitat utilization and resource subsidies in freshwater river mouths are rare, some studies have attempted to use stable isotope analyses to describe consumers' resource use in these transition zones (Dufour et al 2008; Senegal et al 2020; O'Reilly et al 2023). In fish, stable isotopes in soft tissues are integrative indices of resource use, reflecting food consumed and habitats occupied over the past 2–6 months, depending upon tissue turnover (Weidel et al 2011).…”

“…mussels (Barbiero et al 2019). It is plausible that due to decreased lake productivity, the relative ecological importance of tributaries and river mouths in supporting the nearshore Lake Michigan fish assemblage has increased (Höök et al 2007; O'Reilly et al 2023). However, river mouths connected to Lake Michigan differ broadly in terms of their discharge characteristics and morphology, which may influence the relative bidirectional exchange of material and resource subsidization.…”

Cryptic connectivity between hyporheic and riparian zones via winged aquatic insects revealed by DNA barcoding

“…These spatial perspectives on landscape ecological properties apply to inland aquatic systems. In lakes and ponds, coastal wetlands and littoral and offshore zones are characterized by unique biological communities and resource and animal movements across them (Schoen et al, 2016; O’Reilly et al, 2023) whereas riparian zones along the shore interact with aquatic compartments through ecosystem subsidies (Gratton et al, 2008; Francis & Schindler, 2009; Jonsson & Wardle, 2009). Similarly, in rivers, hierarchically nested habitats range from microhabitats in pools and riffles to river segments within an upstream-downstream continuum (e.g., Poole, 2002; Gurnell et al, 2016).…”