Offshore Prey Densities Facilitate Similar Life History and Behavioral Patterns in Two Distinct Aquatic Apex Predators, Northern Pike and Lake Trout

Abstract

Northern Pike Esox lucius are important aquatic apex predators in freshwater ecosystems across the Canadian Boreal Shield. Although Northern Pike have historically been described as nearshore ambush predators, larger individuals have been anecdotally observed foraging in offshore habitats. We used two province‐wide data sets from Ontario, Canada, to investigate the degree to which Northern Pike are generalist predators by examining the influence of offshore prey fish densities on their life histories. To better understand whether the life history patterns observed were unique to Northern Pike or representative of aquatic apex predators generally, we compared Northern Pike life history and catch results to those of the Lake Trout Salvelinus namaycush, a well‐known pelagic apex predator. We found that the asymptotic lengths of both Northern Pike and Lake Trout were positively related to Cisco Coregonus artedi CPUE. Furthermore, both Northern Pike and Lake Trout occupied offshore habitat more frequently in lakes with greater Cisco CPUEs. Northern Pike early growth and mortality rates were negatively related to Cisco CPUE but positively related to Yellow Perch Perca flavescens CPUE, suggesting that Northern Pike undergo ontogenetic shifts to foraging on Ciscoes later in life. Although the growth and mortality of these predators were related to prey availability, variation in the CPUEs of Northern Pike and Lake Trout was best explained by physical lake characteristics. Our study suggests that Northern Pike and Lake Trout respond similarly to Cisco CPUE across the Canadian Boreal Shield, consistent with research reported for other aquatic apex predators. Results of this work collectively suggest that generalist behavior and large‐bodied life history strategies of Northern Pike are facilitated by the availability of Ciscoes.

Life at the top: Lake ecotype influences the foraging pattern, metabolic costs and life history of an apex fish predator

“…Many studies of marine and freshwater fish species have revealed correlations that are consistent with this theory: size of preferred prey increases with predator size (Fuji, Kasai, Ueno, & Yamashita, ; Graeb, Mangan, Jolley, Wahl, & Dettmers, ); predator growth rate and/or condition increase when accessibility of larger prey increases (Golet et al., ; Kaufman, Morgan, & Gunn, ); size at maturity and maximum adult size change in concert with changes in typical prey size (Kennedy, Bartley, Gillis, McCann, & Rennie, ; Shuter, Giacomini, de Kerckhove, & Vascotto, ). In addition, physiological measures of activity on top predators (e.g., respiratory enzyme concentrations—Sherwood, Pazzia, Moeser, Hontela, & Rasmussen, ; Kaufman, Gunn, Morgan, & Couture, ; indices based on bioenergetic models of contaminant accumulation—Henderson, Morgan, & Vaillancourt, ; Pazzia, Trudel, Ridgway, & Rasmussen, ) are also consistent with this theory.…”

Thermal preference influences depth use but not biomass of predatory fishes in response to lake morphometry

“…One possibility is that predators respond to changes in resource abundance by shifting towards locations with abundant resources (i.e., the birdfeeder effect, see Eveleigh et al 2007). This phenomenon has been documented in the freshwater top predator northern pike ( Esox lucius ) (Kennedy et al 2018). However, the ability of predators to respond to resource abundances may be limited by accessibility, especially temperature (Tunney et al 2012, 2014, Guzzo et al 2017a).…”

“…In contrast, and consistent with their physiology, smallmouth bass appear to have no limitations to nearshore accessibility; however, it remains unclear whether warmwater species experience limited accessibility to the offshore. Offshore resources can be significant for some nearshore-associated predators like northern pike ( Esox lucius ) (Kennedy et al 2018). Overall, our results are also consistent with a growing body of theory that suggests that increasing ecosystem area may impact the behaviour of predators in ways that and structure food webs in space (Eloranta et al 2015).…”

A synthesis of senescence predictions for indeterminate growth, and support from multiple tests in wild lake trout

“…Variation in maximum body size across populations (variable realization of indeterminate growth) within the same species may be useful for testing predictions of negligible and negative senescence [20]. Lake trout are among the largest members of the Salmonidae family, but maximum body size varies greatly as a function of prey availability [52,53] and populations vary in life-history traits that influence their fitness [54]. Inter-population comparisons of senescence could exploit environmental variation (sensu [15,16,26,28,33]) in variables such as growing season, prey resources and juvenile predators.…”