A bioenergetic framework is developed to predict optimal life history responses to environmentally driven changes in the rate of energy production by a predator. This framework is used to predict the responses of age at maturation, size at maturation, and asymptotic size to changes in the predator–prey size ratio. Predators feeding on relatively smaller prey (i.e., having larger predator–prey size ratios) have lower growth efficiency and are predicted as a consequence to mature earlier, at smaller sizes, and reach smaller asymptotic sizes. This prediction was tested using a 78-year time series (1936–2013) of data from a natural population of lake trout (Salvelinus namaycush) in Lake Opeongo, Algonquin Park, Ontario, Canada. A large decrease in the predator–prey size ratio for this population occurred over the period 1950–1965 when a preferred prey (cisco, Coregonus artedii) was introduced to the lake. This decrease was followed by ∼20 years of constancy in the size ratio and then 25 years of progressive increase. Lake trout life history responded plastically during both periods and consistently with our predictions. Extensive analysis of available data provided little empirical support for alternative explanations for the observed changes in lake trout size and maturity (e.g., changes in cisco and (or) lake trout density and harvest rates). The framework developed here derives plastic life history changes from fixed developmental thresholds that are based on the scaling of net production with body size and can be used to predict the shape of maturation reaction norms for the major shifts in community structure that are compactly summarized by changes in size spectrum parameters.
There are ~250,000 lakes in Ontario that support important cultural, recreational, and economic fisheries. In 2005, the Ontario Ministry of Natural Resources and Forestry adopted the Ecological Framework for Recreational Fisheries Management to tackle the heterogeneity of lake resources and angler mobility across the landscape, increase public participation in fisheries management, and streamline an ever‐growing list of regulations. The Broad‐Scale Monitoring Program for Inland Lakes began in 2008 to meet these goals. Essential elements of the program are: clear objectives, standardized sampling methods, operational implementation, diagnostic indicators, standardized reporting, a multidisciplinary team, and adaptive monitoring. Fishes, zooplankton, habitat, and angling activity are measured at each lake and provide the data needed to make evidence‐based fisheries management decisions. The data have benefited other provincial initiatives and provided significant contributions to the science of freshwater ecology. Recommendations are provided for other jurisdictions considering the implementation of a standardized broad‐scale monitoring program.
The expanding human global footprint and growing demand for freshwater have placed tremendous stress on inland aquatic ecosystems. Aichi Target 10 of the Convention on Biological Diversity aims to minimize anthropogenic pressures affecting vulnerable ecosystems, and pressure interactions are increasingly being incorporated into environmental management and climate change adaptation strategies. In this study, we explore how climate change, overfishing, forest disturbance, and invasive species pressures interact to affect inland lake walleye (Sander vitreus) populations. Walleye support subsistence, recreational, and commercial fisheries and are one of most sought‐after freshwater fish species in North America. Using data from 444 lakes situated across an area of 475 000 km2 in Ontario, Canada, we apply a novel statistical tool, R‐INLA, to determine how walleye biomass deficit (carrying capacity—observed biomass) is impacted by multiple pressures. Individually, angling activity and the presence of invasive zebra mussels (Dreissena polymorpha) were positively related to biomass deficits. In combination, zebra mussel presence interacted negatively and antagonistically with angling activity and percentage decrease in watershed mature forest cover. Velocity of climate change in growing degree days above 5°C and decrease in mature forest cover interacted to negatively affect walleye populations. Our study demonstrates how multiple pressure evaluations can be conducted for hundreds of populations to identify influential pressures and vulnerable ecosystems. Understanding pressure interactions is necessary to guide management and climate change adaptation strategies, and achieve global biodiversity targets.
Freshwater protected areas are rare even though freshwater ecosystems are among the most imperiled in the world. Conservation actions within terrestrial protected areas (TPAs) such as development or resource extraction regulations may spill over to benefit freshwater ecosystems within their boundaries. Using data from 175 lakes across Ontario, Canada, we compared common indicators of fish-assemblage status (i.e., species richness, Shannon diversity index, catch per unit effort, and normalized-length size spectrum slopes) to evaluate whether TPAs benefit lake fish assemblages. Nearest neighbor cluster analysis was used to generate pairs of lakes: inside versus outside, inside versus bordering, and bordering versus outside TPAs based on lake characteristics. The diversity and abundance indicators did not differ significantly across comparisons, but normalized-length size spectrum slopes (NLSS) were significantly steeper in lakes outside parks. The latter indicated assemblage differences (greater abundances of small-bodied species) and less-efficient energy transfer through the trophic levels of assemblages outside parks. Although not significantly different, pollution- and turbidity-tolerant species were more abundant outside parks, whereas 3 of the 4 pollution-intolerant species were more abundant within parks. Twenty-one percent of the difference in slopes was related to higher total dissolved solids concentrations and angling pressure. Our results support the hypothesis that TPAs benefit lake fish assemblages and suggest that NLSS slopes are informative indicators for aquatic protected area evaluations because they represent compositional and functional aspects of communities.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.