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Mark R. Vinson

Publications and source records attributed to Mark R. Vinson.

At least 19 recordsLinked to original sources
USGS2026

A genomic tool to tackle cryptic diversity demonstrates the potential for off-target use of GT-seq panels

A comprehensive understanding of life history is vital to successful species conservation and management. When different life history stages are accompanied by considerable morphological or cryptic variation, such as the egg and larval phases exhibited by most fishes, genomic tools are essential for identifying species so that early-life ecology questions can be studied. Genotyping-in-thousands by sequencing (GT-seq) has recently emerged as a targeted and efficient approach for species identification. We leveraged existing genomic and transcriptomic data to develop a GT-seq panel capable of differentiating the members of the Coregonus artedi complex, a radiation of salmonids in the Laurentian Great Lakes whose members are indistinguishable with mitochondrial DNA barcoding loci and are the focus of bi-national conservation initiatives. Our panel of 494 loci was able to assign fishes in the C. artedi complex to species and lake. We examined cross-amplification in other coregonines with overlapping distributions and found that congeneric Lake Whitefish ( C. clupeaformis ) cross-amplified at 94% of loci and confamilial Round and Pygmy Whitefish ( Prosopium spp.) cross-amplified at 42% and 38% of loci, respectively. We adapted bioinformatic probes to account for Prosopium -specific variants including 22 new SNPs and developed a whitelist of 428 SNPs capable of distinguishing these whitefishes. Finally, we demonstrated performance by identifying 3066 coregonine larvae and juveniles collected in spring 2019–2021 from Lake Superior. These results hold promise for future insights into the species-specific ecology of early life coregonines and demonstrate the flexibility of GT-seq panels, which may cross-amplify hundreds of informative genome-wide loci in related taxa.

Great Lakes↗
USGS2026

Competition between invasive round goby and native slimy sculpin in a coldwater laboratory setting

Slimy sculpin ( Cottus cognatus ) abundance has substantially declined in many regions of the Laurentian Great Lakes coincident with the arrival and range expansions of invasive round goby ( Neogobius melanostomus ). Previous studies have shown that round goby can outcompete native mottled sculpin ( C. bairdii ) for shelter and negatively affect native spoonhead sculpin ( C. ricei ) growth, but direct behavioral interactions of slimy sculpin and round goby have not been observed. We conducted a laboratory experiment in which a pair of slimy sculpin were placed in an aquarium that contained an artificial spawning shelter and one round goby (treatment, n = 10) or no other fish (control, n = 10) for at least 30 days at temperatures reflective of their potential offshore overlap. We measured slimy sculpin egg deposition, aggressive interactions, artificial shelter occupancy, growth, and survival. Slimy sculpin were less likely to occupy shelters and experienced increased intraspecific competition when a round goby was present. In contrast, round goby rarely chased slimy sculpin, slimy sculpin were more likely to chase round goby, and slimy sculpin growth, egg deposition, and survival were not significantly different between groups. Differences in density between treatments and the relative size of fish could confound our observations. However, the dominant slimy sculpin occupied the shelter at similar rates between experimental groups if the round goby was smaller. Our results indicate that larger round goby overlapping with slimy sculpin could affect slimy sculpin shelter and space use, but the Great Lakes environment may create more stress for slimy sculpin than we observed.

Lake Michigan, Lake Superior↗
USGS2026

A genomic tool to tackle cryptic diversity demonstrates the potential for off-target use of GT-seq panels

A comprehensive understanding of life history is vital to successful species conservation and management. When different life history stages are accompanied by considerable morphological or cryptic variation, such as the egg and larval phases exhibited by most fishes, genomic tools are essential for identifying species so that early-life ecology questions can be studied. Genotyping-in-thousands by sequencing (GT-seq) has recently emerged as a targeted and efficient approach for species identification. We leveraged existing genomic and transcriptomic data to develop a GT-seq panel capable of differentiating the members of the Coregonus artedi complex, a radiation of salmonids in the Laurentian Great Lakes whose members are indistinguishable with mitochondrial DNA barcoding loci and are the focus of bi-national conservation initiatives. Our panel of 494 loci was able to assign fishes in the C. artedi complex to species and lake. We examined cross-amplification in other coregonines with overlapping distributions and found that congeneric Lake Whitefish ( C. clupeaformis ) cross-amplified at 94% of loci and confamilial Round and Pygmy Whitefish ( Prosopium spp.) cross-amplified at 42% and 38% of loci, respectively. We adapted bioinformatic probes to account for Prosopium -specific variants including 22 new SNPs and developed a whitelist of 428 SNPs capable of distinguishing these whitefishes. Finally, we demonstrated performance by identifying 3,066 coregonine larvae and juveniles collected in spring 2019-2021 from Lake Superior. These results hold promise for future insights into the species-specific ecology of early life coregonines and demonstrate the flexibility of GT-seq panels, which may cross-amplify hundreds of informative genome-wide loci in related taxa.

BioRxiv↗
USGS2025

Lake Superior fish community and fisheries, 2001–2022: An era of stability

Lake Superior is the least anthropogenically impacted of the Laurentian Great Lakes ecosystems, yet dramatic changes to the fish community are evident. Previous published works chronicled those changes and the efforts to rehabilitate the fish community through the year 2000. Here, we review through the year 2022, where post-rehabilitation stability was driven by lean lake trout ( Salvelinus namaycush namaycush) as the most abundant piscivore in nearshore waters, siscowet lake trout ( Salvelinus namaycush siscowet) as the most abundant piscivore in offshore waters, and a healthy, intact assemblage of native prey species, which created ecological redundancies and helped stabilize the food web. Stocking of non-native salmonines was reduced 74%, and populations of Chinook salmon ( Oncorhynchus tshawytscha) and coho salmon ( Oncorhynchus kisutch) were maintained through natural reproduction. Despite reduced stocking, yield from recreational fisheries was stable. Likewise, developments in population modeling led to evaluations and refinement of management strategies that helped create stability for lake trout, lake whitefish ( Coregonus clupeaformis ), and cisco ( Coregonus artedi ) fisheries. With lake trout rehabilitation achieved, focus shifted toward rehabilitation of native brook trout ( Salvelinus fontinalis ), lake sturgeon ( Acipenser fulvescens ), and walleye ( Sander vitreus ). Despite continued control efforts, sea lamprey ( Petromyzon marinus ) abundance increased considerably, and estimates of fish killed by lampreys averaged 2.65 million kg annually. Environmental changes have benefited sea lampreys and fostered thermal habitats more suitable to non-native organisms, posing new challenges for managers and researchers. Nevertheless, the post-rehabilitation stability in the contemporary fish community will help provide resilience to future perturbations in the ecosystem.

Lake Superior↗
USGS2025

Status and trends in the Lake Superior fish community, 2024

The U.S. Geological Survey has conducted annual fishery surveys across Lake Superior since 1978 that describe trends in fish species occurrence and relative abundance to inform fisheries management and ecosystem health. In 2024, the Lake Superior fish community was sampled with daytime bottom and surface trawls at 72 nearshore locations in June and 36 offshore locations in July. Nearshore bottom trawls collected 22,190 fish represented by 27 species or morphotypes. The number of species collected at each location ranged from 1 to 12, with a median of 5.5 species. Estimated fish biomass at individual locations ranged from <0.1 to 62.9 kg per ha with a lakewide mean of 3.7 kg per ha. Offshore bottom trawls collected 33,634 fish represented by 12 species or morphotypes. Estimated fish biomass at individual locations ranged from 0.6 to 25.8 kg per ha with a lakewide mean of 8.3 kg per ha, which was the second highest for the period-of-record. Lakewide average densities (fish per ha) of age-1 fish were 1 per ha for Bloater, 5 per ha for Cisco, 1 per ha for Lake Whitefish, 60 per ha for Rainbow Smelt, and 19 per ha for Kiyi. Surface trawling collected 5,177 larval Coregonus individuals which was the third fewest Coregonus larvae collected in a whole lake survey since the larval fish survey began in 2014. Nearshore mean larval Coregonus densities were 176 fish per ha in June 2024 and offshore densities were 7 fish per ha in July 2024. June and July surface water temperatures were near the warmest for the period-of-record.

Lake Superior↗
USGS2024

Winter is not coming: Evaluating impacts of changing winter conditions on coregonine reproductive phenology

Fishes in northern latitude lakes are at risk from climate-induced warming because the seasonality in water temperature is degrading, which can change ecosystem properties and the phenology of life-history events. Temperature-dependent embryo development models were developed for a group of cold, stenothermic fishes (Salmonidae Coregoninae) to assess the potential impacts of climate-induced changes in water temperature on cisco ( Coregonus artedi ) from two populations in Lake Superior (Apostle Islands [USA] and Thunder Bay [Canada]) and one in Lake Ontario (USA), vendace ( C. albula ) in Lake Southern Konnevesi (Finland), and European whitefish ( C. lavaretus ) in lakes Southern Konnevesi, Constance (Germany), Geneva (France), and Annecy (France). Water temperatures for each study group were simulated and changes in reproductive phenology across historic (1900–2006) and three future climatic-warming scenarios (2007–2099) were investigated. Models predicted that increases in water temperatures are likely to cause delayed spawning, shorter embryo incubation durations, and earlier larval hatching. Relative changes increased as warming scenarios increased in severity and were higher for littoral as compared to pelagic populations. Our simulations demonstrated that slower cooling in the autumn and (or) more rapid warming in spring can translate into substantial changes in the reproductive phenology of coregonines among our study groups. We expect that the changes in reproductive phenology predicted by our models, in the absence of thermal or behavioral adaptation, will have negative implications for population sustainability.

Apostle Islands, Chaumont Bay, Lake Annecy, Lake C↗
USGS2023

Status and trends in the Lake Superior fish community, 2022

In 2022, the Lake Superior fish community was sampled with daytime bottom and surface trawls at 71 nearshore locations in May-June and 35 offshore locations in July, and at 51 Coordinated Science and Monitoring Initiative (CSMI) locations in July-October with bottom trawls, surface trawls, mid-water trawls and acoustics that were previously sampled in 2011 and 2016. Nearshore bottom trawls collected 11,603 fish from 25 species or morphotypes. Nearshore mean biomass was 1.6 kg per ha which was one of the lowest biomass estimates over survey’s 45-year history. Offshore bottom trawls collected 13,876 fish from 11 species or morphotypes. Offshore mean biomass was 5.1 kg per ha, which was less than the annual average since 2011 of 6.5 kg per ha. Recruitment, as measured by age-1 densities, was near zero for Bloater ( Coregonus hoyi ), Cisco ( C. artedi ), and Kiyi ( C. kiyi ), 2 age-1 fish per ha for Lake Whitefish ( C. clupeaformis ) and 77 age-1 fish for Rainbow Smelt ( Osmerus mordax ). All were less than the long-term averages. Sampling at the CSMI locations collected 26 species and morphotypes. The most abundant species’ lakewide were Deepwater Sculpin (all years), young-of-year ciscoe (Bloater, Cisco, and Kiyi, 2022), and Rainbow Smelt (2011 and 2016). Cisco had the highest estimated lakewide biomass in 2011 and 2022 and siscowet Lake Trout had the highest estimated lakewide biomass in 2016. Native species were more abundant than invasive species by numbers (80, 65, and 92%) and biomass (94, 93, 96%) in 2011, 2016, and 2022, respectively. Total lakewide benthic fish biomass declined from 47 thousand metric tons in 2011 to 29 thousand metric tons in 2016 and increased to 33 thousand metric tons in 2022. Total lakewide pelagic fish biomass declined from 61 thousand metric tons in 2011 to 25 thousand metric tons in 2016 and increased to 54 thousand metric tons in 2022. The most unexpected result from our sampling in 2022 was the 2 billion age-0 ciscoe estimate from the mid-water trawl and acoustic sampling in August-October. These fish were broadly distributed across the lake, being collected at 53 of the 54 locations, and their population estimates were highest in the depths >100 m. The factors underlying the survival of these ciscoes into late summer in 2022 as compared to previous years have not been identified, but our annual population surveys of larval ciscoes suggests that lake conditions in June and July may have differed from previous years and enhanced survival. In 2022, ciscoe larval densities in May were lower than average (likely due to a cold winter and spring that delayed hatching), June densities were similar to previous years, and July density estimates were more than double that of any previous year’s estimate.

Lake Superior↗
USGS2023

Status and trends in the Lake Superior fish community, 2023

The U.S. Geological Survey annually conducts fishery surveys across Lake Superior that describe trends in fish species occurrence and relative abundance to inform fisheries management and large lake ecology. In 2023, the Lake Superior fish community was sampled with daytime bottom and surface trawls at 51 nearshore locations in June and 31 offshore locations in July. Nearshore bottom trawls collected 157,804 fish from 25 species or morphotypes. Nearshore mean biomass was 18.3 kg per ha which was the second highest biomass estimate over the survey’s 46-year history. Offshore bottom trawls collected 15,458 fish from 10 species or morphotypes. Offshore mean biomass was 5.2 kg per ha, which was less than the annual average of 6.3 kg per ha. Recruitment, as measured by age-1 densities, was the highest recorded for Bloater, Cisco, and Rainbow Smelt in the nearshore and for Kiyi in the offshore survey’s period-of-records. Lakewide average densities (fish per ha) of age-1 fish were 140 for Bloater, 1,019 for Cisco, 616 for Rainbow Smelt, and 54 for Kiyi, which were the highest estimates for the survey’s period-of-record. Period-of-record averages for these species were 10, 67, and 9 age-1 fish per ha, respectively. Age-1 Lake Whitefish averaged 9 fish per ha which was similar to the long-term average of 8 age-1 Lake Whitefish per ha. If the future can be predicted by past large Bloater, Cisco, and Kiyi (collectively, ciscoe) year-class events, the unprecedented survival of the 2022 ciscoe yearclass will influence the Lake Superior ecosystem for the next 10 to 20-years.

Lake Superior↗
USGS2022

Lake Superior Kiyi reproductive biology

Objective The Lake Superior Kiyi Coregonus kiyi is an understudied species being considered for reintroduction into Laurentian Great Lakes where it no longer occurs. Herein, we provide descriptions of Kiyi reproductive biology with the intention of guiding potential gamete collections for propagation. Methods Data were collected on Kiyi spawning timing, spawning locations, spawning season catch rates, length at sexual maturity, sex ratios, fecundity, egg size, and larval occurrences in Lake Superior from 1996–2021. These data were compared to observations made a century prior in Lakes Michigan, Ontario, and Superior. Result Contemporary Kiyi spawning occurred between late December and late January when surface water temperatures cooled to <4°C. Spawning Kiyi were caught almost exclusively in 38.1-mm stretch mesh, as compared to larger meshes (50.8–76.2 mm). Capture depths for developing, ripe, running, and spent female Kiyi were similar and ranged from 82 to 221 m. Fifty percent of female and male Kiyi were classified as sexually mature at ~150 mm total length. Fecundity estimates ranged from 1,578 to 6,720 eggs/female. Mean diameter of unfertilized eggs was 1.7 mm. Recently hatched larval Kiyi were collected at the surface during May–July at 62 of the 113 locations sampled throughout the lake in 2019. Conclusion Our work suggests that Kiyi gamete collection efforts from mid-December through January using 38.1-mm gill-net panels set at bathymetric depths of at least 100 m would maximize the collection of spawning Kiyi and reduce the bycatch of other Coregonus species. Future research questions include the following: (1) “Do Kiyi form spawning aggregations at specific spawning areas, or do they spawn indiscriminately across the lake?”; (2) “Do Kiyi spawn near the bottom or up in the water column?”; (3) “What is the relationship between fall lake overturn and Kiyi spawn timing?”; and (4) “Could summer larval and age-0 Kiyi collections provide an opportunity for establishing a captive broodstock?”

Lake Superior↗
USGS2022

Effects of warming winter embryo incubation temperatures on larval cisco (Coregonus artedi) survival, growth, and critical thermal maximum

Freshwater whitefishes, Salmonidae Coregoninae, are cold stenothermic fishes of ecological and socio-economic importance in northern hemisphere lakes that are warming in response to climate change. To address the effect of warming waters on coregonine reproduction we experimentally evaluated different embryo incubation temperatures on post-hatching survival, growth, and critical thermal maximum of larval cisco ( Coregonus artedi ) sampled from lakes Superior and Ontario. Embryos were incubated at water temperatures of 2.0, 4.4, 6.9, and 8.9 °C to simulate present and increased winter temperatures, and hatched larvae were reared in a common environment. For the populations from both lakes, larval survival and critical thermal maximum were negatively related to incubation temperature, and larval growth was positively related to incubation temperature. The magnitude of change across incubation temperatures was greater in the population sampled from Lake Superior than Lake Ontario for all traits examined. The more rapid decrease in survival and critical thermal maximum across incubation temperatures for larval cisco in Lake Superior, compared to those from Lake Ontario, suggests that Lake Superior larvae may possess a more limited ability to acclimate to and cope with increasing winter water temperatures. However, the rapid increase in growth rates across incubation temperatures in Lake Superior larvae suggests they could recover better from hatching at a small length induced by warm winters, as compared to Lake Ontario larvae. Our results suggest propagation and restoration programs may want to consider integrating natural habitat preferences and maximizing phenotypic variability to ensure offspring are set up for success upon stocking.

Lake Ontario, Lake Superior↗
USGS2022

Quantifying status and trends from monitoring surveys: Application to Pygmy Whitefish (Prosopium coulterii) in Lake Superior

Population assessments of fish species often rely on data from surveys with different objectives, such as measuring biodiversity or community dynamics. These surveys often contain spatial–temporal dependencies that can greatly influence conclusions drawn from analyses. Pygmy whitefish (PWF, Prosopium coulterii ) populations in Lake Superior were recently assessed as Threatened by the Committee on the Status of Endangered Species in Canada, which motivated a thorough analysis of available data to improve our understanding of its population status. The US Geological Survey conducts annual bottom trawl surveys in Lake Superior that commonly capture PWF. We used these data (1989–2018) to model temporal trends in PWF biomass density and make lake-wide population projections. We used a Bayesian approach, integrated nested Laplace approximation (INLA), and compared the impact of including different random structures on model fit. Inclusion of spatial structure improved model fit and conclusions differed from models omitting random effects. PWF populations have experienced periodic fluctuations in biomass density since 1989, though 2018 may represent the lowest density in the 30-year time series. Lake-wide biomass was estimated to be 71.5 t.

Lake Superior↗
USGS2022

Status and trends in the Lake Superior fish community, 2020

The Lake Superior fish community within Management Unit WI-2 was sampled in July 2020 with daytime bottom trawls at 11 nearshore stations. The 11 locations sampled were long-term monitoring sites that had been annually sampled since 1974. In 2020, the number of species collected at each site ranged from 0 to 13, with a mean of 6.3 and median of six. All comparisons to 2020 results were limited to past collections from Management Unit WI-2. Mean total biomass was 10.5 kg/ha which was similar to the average observed over the past 10 years (10.3 kg/ha), less than averages over the past 20 and 30-years, 15.3 and 19.8 kg/ha respectively, and higher than the average observed from 1974-84 (4.7 kg/ha). Average biomass in 2020 was highest for Bloater (6.2 kg/ha), Lake Whitefish (2.3 kg/ha), and Cisco (0.9 kg/ha). Rainbow Smelt biomass averaged 0.3 kg/ha. Year-class strength, as measured by age-1 densities, was well below the 5, 10, and 25-year averages for Bloater, Cisco, Lake Whitefish and Rainbow Smelt. Bloater averaged 1 age-1 fish/ha, Cisco, 0.2 age-1 fish/ha, Lake Whitefish, 15 age-1 fish/ha, and Rainbow Smelt 6 age-1 fish/ha. Cisco survival to age-1 has been near non-existent since the 2014- and 2015-year classes and the last moderate sized year class was in 2009. This lack of survival has yet to be adequately explained and continues to be a major concern of fishery managers due to Cisco’s importance in ecosystem dynamics and value to the commercial fishery.

Lake Superior↗
USGS2022

Status and trends in the Lake Superior fish community, 2021

The Lake Superior nearshore fish community was sampled in May-June 2021 with daytime bottom trawl tows at 45 stations located in USA waters. The 45 locations sampled were long-term monitoring sites that had been annually sampled since 1978. All comparisons to 2021 results were limited to past collections from USA waters, as compared to previous years, where comparisons included USA and Canadian sites. In 2021, the number of species collected at each site ranged from 0 to 15, with a median of 5 species. Average fish biomass was 6.3 kg/ha, which was higher than the average observed over the past 10 years (4.7 kg/ha), similar to the average observed from 2001-10 (6.7 kg/ha), and less than the averages observed in 1991-2000 (14.8 kg/ha), and 1981-1990 (11.9 kg/ha), but higher than the average from 1978-1980 (5.2 kg/ha). Average biomass in 2021 was highest for Lake Whitefish ( Coregonus clupeaformis , 3.2 kg/ha), Bloater ( C. hoyi , 1.4 kg/ha), Rainbow Smelt ( Osmerus mordax , 0.5 kg/ha), and Cisco ( C. artedi , 0.3 kg/ha). Coregonus spp. year-class strength, as measured by densities of age-1 fish, was 8 fish/ha for Bloater, 11 fish/ha for Cisco, and 41 fish/ha for Lake Whitefish. The age-1 Bloater estimate was in the range observed for the 2014, 2015, and 2016 year-classes (7-9 age-1 fish/ha) and greater than that observed in other years over the past decade (<1 age-1 fish/ha). The age-1 Cisco estimate was the highest estimate since the 2009 year-class. Average Lake Whitefish age-1 density was the second highest estimate observed over the past 44-years. Cisco survival to age-1 has been low since 2009 and near zero since the 2014- and 2015-year classes. This lack of survival has yet to be adequately explained and continues to be a major concern of fishery managers due to Cisco’s importance in ecosystem dynamics and value to the commercial fishery.

Lake Superior↗
USGS2021

Trophic ecology

The trophic ecology of lake charr Salvelinus namaycush morphotypes from small and large lakes within their native and introduced ranges is reviewed over the past 50 years. The lake charr is an apex predator in most habitats it occupies, where it plays a significant role in defining food webs. While often considered piscivores, lake charr feed on a range of aquatic prey throughout their life history, including zooplankton, benthic invertebrates, and fish, as well as terrestrial insects, mammals, birds, amphibians, and reptiles. Lake charr diets that vary within morphotypes among lakes and among sympatric morphotypes reflect differences in habitat use, prey availability, and individual preferences. Temporal variability in diet can result from seasonal prey pulses, thermal barriers, and long-term prey dynamics. Lake charr adapt quickly to consume invasive prey fishes, and often decimate native prey fishes and other piscivores in lakes into which they are introduced. Salient research topics in lake charr trophic ecology include: (1) how best to quantify spatial and temporal trophic niche space; and, (2) how changing environmental conditions, such as invasive species and lake warming, will influence lake charr feeding and broader lake food-web dynamics.

Book chapter↗
USGS2021

Larval Coregonus spp. diets and zooplankton community patterns in the Apostle Islands, Lake Superior

With the exception of lake whitefish ( Coregonus clupeaformis ), relatively little is known about the early life history of larval coregonines in the Laurentian Great Lakes. For example, our knowledge of the feeding ecology of larval coregonines (excluding lake whitefish) is based on only 900 stomachs reported in the literature. Here, we describe the diets and demographics of larval coregonines from ice-out to late July, and the contemporaneous zooplankton community, in the Apostle Islands region of Lake Superior in 2018. Exogenous feeding was evident among the smallest larvae (down to 6 mm). Percent of larvae with food in their stomachs increased and yolk reserves decreased as larvae grew from 10 to 13 mm. A majority of the diet (58%) was copepod nauplii, with generally positive selection for adult copepods and Holopedium . The patterns in exogenous feeding and yolk sac absorption were similar to observations in Lake Superior in the 1970s. Diets were also generally similar, although Limnocalanus , Holopedium , and zooplankton eggs were more prevalent in 2018 than the 1970s. Demographic data suggested at least two distinct cohorts and/or coregonine species in 2018. Post-hoc genetic testing of larvae in a parallel study suggested our samples comprised a mix of predominantly cisco ( C. artedi ), kiyi ( C. kiyi ), and bloater ( C. hoyi ). Early life history studies, when coupled with emerging genetic techniques that can identify larval coregonines to species, will provide a powerful combination to better understand population dynamics of coregonines at a time of ongoing restoration and rehabilitation efforts throughout the Great Lakes.

Apostle Islands, Lake Superior↗
USGS2021

Trophic transfer efficiency in the Lake Superior food web: Assessing the impacts of non-native species

Ecosystem-based management relies on understanding how perturbations influence ecosystem structure and function (e.g., invasive species, exploitation, abiotic changes). However, data on unimpacted systems are scarce; therefore, we often rely on impacted systems to make inferences about ‘natural states.’ Among the Laurentian Great Lakes, Lake Superior provides a unique case study to address non-native species impacts because the food web is dominated by native species. Additionally, Lake Superior is both vertically (benthic versus pelagic) and horizontally (nearshore versus offshore) structured by depth, providing an opportunity to compare the function of these sub-food webs. We developed an updated Lake Superior EcoPath model using data from the 2005/2006 lake-wide multi-agency surveys covering multiple trophic levels. We then compared trophic transfer efficiency (TTE) to previously published EcoPath models. Finally, we compared ecosystem function of the 2005/2006 ecosystem to that with non-native linkages removed and compared native versus non-native species-specific approximations of TTE and trophic flow. Lake Superior was relatively efficient (TTE = 0.14) compared to systems reported in a global review (average TTE = 0.09), and the microbial loop was highly efficient (TTE > 0.20). Non-native species represented a very small proportion (<0.01%) of total biomass and were generally more efficient and had higher trophic flow compared to native species. Our results provide valuable insight into the importance of the microbial loop and represent a baseline estimate of non-native species impacts on Lake Superior. Finally, this work is a starting point for further model development to predict future changes in the Lake Superior ecosystem.

Lake Superior↗
USGS2021

Shining a light on Laurentian Great Lakes cisco (Coregonus artedi): How ice coverage may impact embryonic development

Changes in winter conditions, such as decreased ice coverage and duration, have been observed in the Laurentian Great Lakes for more than 20 years. Such changes have been hypothesized to be linked to low Coregonus spp. survival to age-1 as most cisco ( Coregonus artedi ) populations are autumn spawners whose embryos incubate under ice throughout the winter. The quantity of light during winter is regulated by ice coverage, and light affects embryo survival and development in some teleosts. We experimentally evaluated how cisco embryos from lakes Superior and Ontario respond to three light treatments that represented day-light intensity under 0–10, 40–60, and 90–100% ice coverage. Embryonic response measures included two developmental factors (embryo survival and incubation period) and two morphological traits (length-at-hatch and yolk-sac volume). Embryo survival was highest at the medium light treatment and decreased at high and low treatments for both populations, suggesting cisco may be adapted to withstand some light exposure from inter-annual variability in ice coverage. Light intensity had no overall effect on length of incubation. Increasing light intensity decreased length-at-hatch in Lake Superior but had no effect in Lake Ontario. Yolk-sac volume was positively correlated with increasing light in Lake Superior and negatively correlated in Lake Ontario. Contrasting responses in embryo development between lakes suggests differences in populations’ response to light is flexible. Our results provide a step towards better understanding the high variability observed in coregonine recruitment and may help predict what the future of this species may look like under current climate trends.

Journal of Great Lakes Research↗