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Jory Jonas

Publications and source records attributed to Jory Jonas.

9 recordsLinked to original sources
USGS2025

Day versus night relations between larval lake whitefish, cisco, and zooplankton onshore in Lakes Michigan, Huron, and Superior

Lake whitefish ( Coregonus clupeaformis ) populations in the upper Great Lakes have undergone declines in the past two decades, particularly in Lakes Michigan and Huron. However, cisco ( Coregonus artedi ) are recovering in parts of the Great Lakes. Population declines are hypothesized to be due, in part, to reduced zooplankton prey in areas that serve as critical habitat for larval coregonines. Larval lake whitefish, cisco, and zooplankton are commonly sampled only during daylight hours. Habitat use, community composition, catch rates, and abundance estimates of larval fish and zooplankton can change drastically at night versus day, necessitating diel comparisons for a more comprehensive understanding of the early life history of coregonines and their prey. We collected paired day and night onshore (≤ 1 m depth) zooplankton and larval coregonine samples from Lakes Michigan, Huron, and Superior in March–June 2021 to test if there were diel differences in lake whitefish and cisco abundance and zooplankton density and biomass. We also tested if relationships exist between larval coregonine abundance and zooplankton density and biomass and environmental variables (water temperature, dissolved oxygen concentration, pH, specific conductivity, substrate type). We observed consistently higher zooplankton density and biomass and larval lake whitefish and cisco abundance at night. Larval coregonine abundance was positively related to higher zooplankton population estimates but was not related to the environmental variables measured. Our results provide insight into sampling practices for larval lake whitefish, cisco, and zooplankton onshore in the Great Lakes to better understand factors influencing larval lake whitefish and cisco recruitment.

Michigan↗
USGS2025

Stable C and N isotope analyses redefine cisco as pelagic piscivores in Lake Michigan

Lake Michigan’s cisco ( Coregonus artedi ) population is in the midst of an expansion (2011-present) recovering from near extirpation levels observed in the 1970 s. Strong evidence of piscivory derived from observed diet analyses suggests the population may occupy a unique trophic position relative to typical expectations for the species. To verify these observations, cisco and their prey were collected from 2017 to 2020 for stable C and N isotope analyses. Leveraging existing stable isotope datasets for Lake Michigan, the trophic position of cisco was assessed by quantifying the isotopic niche space occupied relative to common salmonine piscivores and prey fish species. Diet mixing models were constructed to estimate the relative importance of potential prey sources to cisco diets. Results suggested that cisco occupied an isotopic niche similar to Pacific salmonines ( Oncorhynchus spp.) and brown trout ( Salmo trutta ) that are mainly piscivorous. Conversely, there was low isotopic niche overlap with prey fish species that are mainly planktivorous. Mixing models suggest greater reliance on pelagic prey sources (including alewife Alosa pseudoharengus and Bythotrephes longimanus ) in cisco diets when compared with observations of stomach contents. Under the present ecological conditions in Lake Michigan, it appears that adult cisco in this population occupy the trophic role of a pelagic piscivore.

Lake Michigan↗
USGS2025

Drowned river mouth lakes are winter foraging habitats for the expanding Lake Michigan cisco Coregonus artedi population

Characterizing fish movements is required for understanding habitat use, energy flow, and trophic structure and can inform fisheries management. Drowned river mouth (DRM) lakes are productive inland habitats in the Laurentian Great Lakes basin used by migratory fishes. Despite recognition of their ecological connections to the Great Lakes, the value of DRM lakes as seasonal habitats is not well understood for many fishes. One such species, cisco Coregonus artedi , has recently expanded in Lake Michigan from near extirpation to higher relative abundances in the northeastern portion of the lake. Cisco are recreationally harvested in some DRM lakes during winter, but little is known about cisco movement patterns and ecology. In winter 2022 and 2023, we collected cisco from three DRM lakes along the eastern shores of Lake Michigan (Lake Charlevoix, Portage Lake, Muskegon Lake) to characterize genetics, morphometrics, and diets. We also implanted telemetry tags in 20 cisco collected in Lake Charlevoix to examine movement patterns and determine DRM lake residency (i.e., seasonal vs. year-round). We found no consistent genetic or morphometric differentiation across DRM lakes, suggesting that recolonization began from a single stock. Fish were the only diet item found in cisco guts collected during winter months. Movement patterns from Lake Charlevoix indicated strong spawning site fidelity to Grand Traverse Bay as well as non-spawning site fidelity. However, given the presence of cisco in southern DRM lakes and some site-specific differences in morphometrics, managers could benefit from further research to determine whether spawning occurs in southern Lake Michigan.

Journal of Great Lakes Research↗
USGS2024

Reconstructing half a century of coregonine recruitment reveals species-specific dynamics and synchrony across the Laurentian Great Lakes

Understanding how multiple species and populations vary in their recruitment dynamics can elucidate the processes driving recruitment across space and time. Lake Whitefish ( Coregonus clupeaformis ) and Cisco ( C. artedi ) are socioecologically important fishes across their range; however, many Laurentian Great Lakes populations have experienced declining, poor, or sporadic recruitment in recent decades. We integrated catch and age data from 38 long-term surveys across each of the Great Lakes and Lake Simcoe, resulting in a combined time series spanning 1960–2019. We estimated Lake Whitefish and Cisco year-class strength (YCS) in each lake using longitudinal mixed-effects regressions of relative cohort abundance. We subsequently quantified interspecific, spatial, and temporal synchrony in YCS using correlation and dynamic factor analyses. Lake Whitefish YCS was positively spatially synchronous on average, and YCS in all six lakes was elevated during the 1980s–1990s. In contrast, Cisco YCS was sporadic, not spatially synchronous, and highly variable around long-term, lake-specific means. YCS was not synchronous between species in any lake. Collectively, our analyses demonstrate that these species exhibit differential recruitment dynamics that may be regulated by species-specific factors. Results from this study can be leveraged in future research on the causes and consequences of cross-species, cross-basin recruitment variability.

Laurentian Great Lakes↗
USGS2023

Updated decision analysis to inform multi-species salmonine management in Lake Michigan

The recreational fishery for salmonine species in Lake Michigan (lake trout, Chinook salmon, coho salmon, steelhead, and brown trout) is largely maintained through stocking. Decisions about how many of each species to stock require an understanding of how to maintain a sustainable balance of predators (salmonine species) to prey (alewife) in the lake. The current models used to make these decisions can estimate the ratio of Chinook salmon to alewife in the lake. However, the Lake Michigan Committee’s new stocking strategy aims to incorporate the other salmonine species into this predator-prey ratio. We used structured decision making to evaluate potential stocking strategies. We worked with fishery stakeholders and members of the Lake Michigan Committee, conducted participatory modeling to forecast outcomes of stocking scenarios using updated information on fish movement and feeding, and evaluated the risk of these stocking strategies. Most of the stocking practices we evaluated resulted in a high risk of large declines in alewife abundance, negatively affecting future salmon fisheries. The forecasts were substantially more pessimistic than those resulting from a similar analysis conducted a decade earlier, apparently due to more recent alewife assessments indicating lower alewife productivity (recruits per spawner). Alewife recruitment dynamics is an area of substantial uncertainty, with apparently large consequences for management; decision makers on Lake Michigan would benefit from greater understanding of alewife recruitment dynamics to reduce this uncertainty when accounting for risks.

Lake Michigan↗
USGS2020

2019 Lake Michigan Lake Trout Working Group Report

This report provides a review on the progression of lake trout ( Salvelinus namaycush ) rehabilitation towards meeting the Salmonine Fish Community Objectives (FCOs) for Lake Michigan (Eshenroder et. al. 1995) and the interim goal and evaluation objectives articulated in A Fisheries Management Implementation Strategy for the Rehabilitation of Lake Trout in Lake Michigan (hereafter the "Strategy"; Dexter et al. 2011).

Lake Michigan↗
USGS2017

2016 Lake Michigan Lake Trout Working Group Report

This report provides a review on the progression of lake trout rehabilitation towards meeting the Salmonine Fish Community Objectives (FCOs) for Lake Michigan (Eshenroder et. al. 1995) and the interim goal and evaluation objectives articulated in A Fisheries Management Implementation Strategy for the Rehabilitation of Lake Trout in Lake Michigan (Dexter et al. 2011); we also include data describing lake trout stocking and mortality to portray the present state of progress towards lake trout rehabilitation.

Report↗