Alternative migratory strategies related to life history differences in the Walleye (Sander vitreus)

Abstract

Background While Pace of Life Syndrome predicts behavioural differences between individuals with differential growth and survival, testing these predictions in nature is challenging due to difficulties with measuring individual behaviour in the field. However, recent advances in acoustic telemetry technology have facilitated measurements of individual behaviour at scales not previously possible in aquatic ecosystems. Methods Using a Walleye (Sander vitreus) population inhabiting Black Bay, Lake Superior, we examine whether life history characteristics differ between more and less mobile individuals as predicted by Pace of Life Syndrome. We tracked the movement of 192 individuals from 2016 to 2019 using an acoustic telemetry study, relating patterns in annual migratory behaviour to individual growth, and seasonal changes in optimal thermal-optical habitat. Results We observed two consistent movement patterns in our study population—migratory individuals left Black Bay during late summer to early fall before returning to the bay, whereas residents remained within the bay year-round. The average maximum length of migrant Walleye was 5.5 cm longer than residents, and the sex ratios of Walleye caught during fall surveys was increasingly female-biased towards the mouth of Black Bay, suggesting that a majority of migrants were females. Further, Walleye occupancy outside of Black Bay was positively associated with increasing thermal-optical habitat. Conclusions Walleye in Black Bay appear to conform to Pace of Life Syndrome, with migrant individuals gaining increased fitness through increased maximum size, which, given size-dependent fecundity in this species, likely results in greater reproductive success (via greater egg deposition vs. non-migrants). Further, apparent environmental (thermal) controls on migration suggest that migratory Walleye (more so than residents) may be more sensitive to changing environmental conditions (e.g., warming climate) than residents.

The Ecological Consequences of Hypoxia in a Temperate, Freshwater Ecosystem.

“…Superior walleye (McKee et al, 2022). Their study found migratory walleye were slightly larger than residents and predominantly female; however, size was not a significant predictor of variability in displacement distances in our study and sex was not obtained for our tagged fish.…”

Estimating internal transmitter and external tag retention by Walleye in the Laurentian Great Lakes over multiple years

“…Further, Hayden et al (2014) tagged adult Walleye that were included in this study and reported that 95% of the fish were detected moving from the river release site into Saginaw Bay of Lake Huron within 21 days, supporting low postrelease mortality or tag shedding and suggesting that recently tagged fish are capable of rapid movement. These results were expected due to the number of years spent developing and evaluating surgical procedures for implanting transmitters (Cooke et al 2011;Schoonyan et al 2017) and the widespread use of these transmitters in the Great Lakes (Hayden et al 2014;Brooks et al 2019;Faust et al 2019;McKee et al 2022). Additionally, premature failure of transmitters occurred at an overall rate (2%) that seems unlikely to compromise inferences that are made from many telemetry-based studies that use similar transmitters.…”

“…2019; McKee et al. 2022). Additionally, premature failure of transmitters occurred at an overall rate (2%) that seems unlikely to compromise inferences that are made from many telemetry‐based studies that use similar transmitters.…”