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Research about Canada, United States

Source-linked reports with geographic coverage including Canada, United States.

At least 523 records · Page 29Linked to original sources
USGS2020

Lake sturgeon (Acipenser fulvescens) spawn in the St. Marys River Rapids, Michigan

The St. Marys River connects Lake Superior to Lake Huron, comprising the international border between Michigan, United States, and Ontario, Canada. This Great Lakes connecting channel naturally encompasses various habitats including lakes, wetlands, islands, tributaries, side channels, and main channels. The St. Marys River Rapids are shallow rock areas with high flow velocities (>1 m/s) in the upper river adjacent to the navigation locks and electric power generating stations, while the Little Rapids are shallow, recently restored rocky areas with lower velocities located about 7 km downstream. The St. Marys River Rapids provide important spawning habitat for several native and introduced fishes, but spawning by lake sturgeon ( Acipenser fulvescens ) was not previously documented. We sampled for lake sturgeon eggs and larvae in both locations during June and July 2018–2019 using weekly benthic egg mat lifts and overnight D-frame larval fish drift nets. Viable lake sturgeon eggs (11 in 2018, 45 in 2019) were collected in the tailrace of a hydroelectric power facility adjacent to the St. Marys River Rapids. Larval lake sturgeon (21 in 2018, 1 in 2019) were collected in the same area as the eggs. Neither lake sturgeon eggs nor larvae were collected at Little Rapids in either year. Our results are the first documentation of successful lake sturgeon spawning and larval drift in the upper St. Marys River. While our observations showed spawning in a human-made tailrace area, the fate of larvae produced here is unknown and warrants further research.

Michigan, Ontario↗
USGS2020

Spatial and vertical bias in down-looking ship-based acoustic estimates of fish density in Lake Superior: Lessons learned from multi-directional acoustics

Hydroacoustic surveys using hull-mounted down-looking transducers are useful for estimating pelagic fish densities; however, this method may miss shallow fish owing to the acoustic surface dead zone and vessel avoidance. Our objective was to compare pelagic fish density estimates acquired by a traditional down-looking acoustic survey to estimates obtained by a new multi-directional-towed sled capable of sampling the entire water column using upward-, sideways-, and downward-aimed transducers simultaneously. We deployed both systems concurrently in the western arm of Lake Superior during a period of stable stratification. We found the two survey approaches provided significantly different estimates of fish density in the upper water column layer (~4–9 m below the lake surface) with the sled up-looking transducer providing 56 times higher densities compared to the traditional ship down-looking method. Densities also varied significantly in the 9–14 m layer where densities were 6.2 times higher in the sled survey. Midwater trawl sampling indicated that cisco ( Coregonus artedi ) and rainbow smelt ( Osmerus mordax ) were the predominant species occupying the uppermost 14 m of the water column. The two acoustic approaches provided similar results at water column depths >14 m where rainbow smelt and kiyi ( Coregonus kiyi ) were predominant . Overall, the sled-based method estimates were, on average, 2.5 times higher for the whole water column. Our findings show that the new sled can reduce bias by better sampling the surface dead zone leading to more accurate estimation of pelagic fish densities for both management and research.

Lake Superior↗
USGS2020

Mineral deposits of the Mesoproterozoic Midcontinent Rift system in the Lake Superior region – A space and time classification

The Mesoproterozoic Midcontinent Rift System (MRS) of North America hosts a diverse suite of magmatic and hydrothermal mineral deposits in the Lake Superior region where rift rocks are exposed at or near the surface. Historically, hydrothermal deposits, such as Michigan’s native copper deposits and the White Pine sediment-hosted stratiform copper deposit, were major MRS metal producers. On-going exploration for and potential development of copper-nickel sulfide deposits hosted by the Duluth Complex of Minnesota and the opening of the Eagle nickel mine in Michigan indicate an expanding interest in MRS magmatic deposits. MRS hydrothermal and magmatic mineral deposits, many of which are significant past, present, and likely future providers of critical minerals, here are placed into a space and time metallogenic framework. To construct this framework, regional MRS mineral deposits extracted from the U.S. Geological Survey Mineral Resources Data System (MRDS) and the Ontario Ministry of Energy, Northern Development and Mines Mineral Deposit Inventory (MDI) were supplemented by other known and recently recognized mineral deposits described in the literature. All mineral deposits were classified by deposit type, host rock age and type, and estimated timing of mineralization. Deposits were then put into a tectonic evolutionary framework (stages) for the MRS, which shows that deposits formed within discrete spatial and temporal stages of rift evolution.

Lake Superior region↗
USGS2020

2,200-Year tree-ring and lake-sediment based snowpack reconstruction for the northern Rocky Mountains highlights the historic magnitude of recent snow drought

In recent decades, Rocky Mountain accumulated snowpack levels have experienced rapid declines, yet long-term records of snowpack prior to the installation of snowpack observation stations in the early and mid 20th century are limited. To date, a small number of tree-ring based reconstructions of April 1 Snow Water Equivalent (SWE) in the northern Rocky Mountains have extended modern records of snowpack variability to ∼1200 C.E. Carbonate isotope lake sediment records, provide an opportunity to further extend tree-ring based reconstructions through the Holocene, providing a millennial-scale temporal record that allows for an evaluation of multi-scale drivers of snowpack variability, from internal climate dynamics to orbital-scale forcings. Here we present a ∼2200 year preliminary reconstruction of northern Rockies snowpack based on δ 18 O measurements of sediment carbonates collected from Foy Lake, Montana. We explore the statistical calibration of lake sediment δ 18 O to an annually resolved snowpack reconstruction from tree rings, and develop an approach to assess and quantify potential sources of error in this reconstruction approach. The sediment-based snowpack reconstruction shows strong low-frequency variability in snowpack over the last two millennia with few snow droughts approaching the magnitude of recent snowpack declines. Given the growing availability of high-resolution, carbonate-rich lake sediment records, such reconstructions could help improve our understanding of how snowpack conditions varied under previous climatic events (mid-Holocene climate optimum ca. 9−6 ka), providing critical insights for anticipating future snowpack conditions.

Alberta, British Columbia, Idaho, Montana, Nevada,↗
USGS2020

Brown Bear (Ursus arctos; North America)

This chapter comprises the following sections: names, taxonomy, subspecies and distribution, descriptive notes, habitat, movements and home range, activity patterns, feeding ecology, reproduction and growth, behavior, parasites and diseases, status in the wild, and status in captivity.

Book chapter↗
USGS2020

Comparing discharge computation methods in the Great Lakes connecting channels

Records of discharge for the connecting channels within the Great Lakes Basin are important to national governments of Canada and the United States and the various water management agencies and users in the basin. For more than 100 years, the official discharge records for the St. Clair and Detroit Rivers, two connecting channels within the Great Lakes Basin, have been computed using various stage-fall-discharge (SFQ) methods. However, as a result of technological advancements, newer methods have recently been considered for discharge computations. In this study, three discharge computation methods were compared: two SFQ methods and the index-velocity discharge (IVQ) method. Although the two SFQ methods have significantly different assumptions and use different data from the index-velocity method, the differences between the computed discharges derived from the methods are small, especially as the time step approaches monthly discharge values. Statistical analyses of discharge measurements and discharges computed using each of these methods indicate that there is no substantive difference in the discharges computed using the three methods. However, the IVQ method provides distinct advantages over the SFQ methods, including increased temporal resolution of computed discharge (minutes versus daily) and the ability to account for changes caused by aquatic vegetation and ice. Based on the results of the comparisons described herein, the IVQ discharge computation method is the most appropriate method for discharge computation in the St. Clair and Detroit Rivers. Updated SFQ equations for the St. Clair and Detroit Rivers, also presented herein, can be used to compute discharge during periods of missing or invalid IVQ record.

Indiana, Michigan, Minnesota, New York, Ohio, Onta↗
USGS2020

Rapid early development and feeding benefits an invasive population of lake trout

Lake trout ( Salvelinus namaycush ) were discovered in Yellowstone Lake in 1994 and their population expanded dramatically despite intensive suppression. The lake is species-depauperate, with no major lake trout embryo predators. We hypothesized that without this predation threat, lake trout free embryo feeding and growth may be greater than in their native range, leading to increased survival of age-0 individuals and rapid population growth. We compared length, developmental rate, and feeding patterns of lake trout free embryos captured at a spawning site in Yellowstone Lake with free embryos captured in their native range in Lake Champlain, Vermont. More embryos were feeding, contained more food, and were significantly longer at the same developmental stages in Yellowstone Lake. With an abundance of available food and minimal threat of predation, free embryos remained on the spawning site in Yellowstone Lake later into the summer than in Lake Champlain and achieved a greater maximum length before they dispersed. Greater food consumption and associated growth likely leads to high survival of lake trout free embryos in Yellowstone Lake, contributing to rapid population growth.

New York, Quebec, Vermont, Wyoming↗
USGS2020

Can nutrient additions facilitate recovery of Pacific salmon?

Multiple restoration actions have been implemented in response to declining salmon populations. Among these is the addition of salmon carcasses or artificial nutrients to mimic marine-derived nutrients historically provided by large spawning runs of salmon. A key assumption in this approach is that increased nutrients will catalyze salmon population growth. Although effects on aquatic ecosystems have been observed during treatments, it is unclear whether permanent population increases for salmon will occur. To test this assumption and address associated uncertainties, we linked a food web model with a salmon life cycle model to examine whether carcass additions in a river reach would improve conditions for salmon in the long term. Model results confirmed immediate increases in the biomass of periphyton, macroinvertebrates, and fish during carcass additions. In turn, juvenile salmon grew larger and experienced improved freshwater and smolt survival, which translated to a greater number of adults returning to spawn. However, once additions ceased, salmon abundance returned to pretreatment levels, which, based on our model, is owing to a combination of instream and out-of-basin factors. Overall, results of this work suggest that benefits during carcass and nutrient additions may not translate into persistent productivity of salmon unless additions are sustained indefinitely or other limiting factors are addressed.

Alberta, British Columbia, Idaho, Montana, Nevada,↗
USGS2020

Integrated geophysical analysis provides an alternate interpretation of the northern margin of the North American Midcontinent Rift System, Central Lake Superior

The Midcontinent Rift System (MRS) is a 1.1 Ga sequence of voluminous basaltic eruptions and multiple intrusions followed by widespread sedimentation that extends across the Midcontinent and northern Great Lakes region of North America. Previous workers have commonly used seismic-reflection data (Great Lakes International Multidisciplinary Program on Crustal Evolution [GLIMPCE] line A) to demonstrate that the northern rift margin in central Lake Superior developed as a normal growth fault that was structurally inverted to a reverse fault during a compressional event after rifting had ended. A prominent, curvilinear aeromagnetic anomaly that extends from Isle Royale, Michigan, to Superior Shoal in central Lake Superior, Ontario (the IR-SS anomaly), is commonly presented as a manifestation of this reverse fault. We have integrated multidisciplinary geophysical analyses (seismic-reflection, seismic-refraction, aeromagnetic, and gravity), physical-property information (density, magnetic susceptibility and remanence, and compressional-wave velocity), and geologic concepts to develop an alternate interpretation of the rift margin along GLIMPCE line A, where it intersects the IR-SS anomaly. Our new model indicates that a normal fault is the dominant structure at the northern rift margin along line A, contrary to the original rift-margin paradigm, which asserts that compressional structures are the dominant features preserved today. Integral to this alternate model is a newly interpreted, prerift sedimentary basin intruded by sills in northern Lake Superior. Our alternate model of the northern rift margin has implications for interpreting the style, scale, and timing of extension, rift-related intrusion, and compression during development of the MRS.

Lake Superior↗
USGS2020

Phylogeographic analysis of Mudpuppies (Necturus maculosus)

The geology of the Pleistocene, and particularly the Last Glacial Maximum approximately 26.5 ka, is a critical driver of species’ present-day distributions and levels of genetic diversity in northern regions. Using mitochondrial DNA sequence data, we tested several predictions relating to the postglacial recolonization of the northern United States and southern Canada by Mudpuppies (Necturus maculosus). Our analyses revealed a significant split between western and eastern lineages, with the divide corresponding to the location of the Mississippi River. Our data support the presence of one or more Mississippian glacial refugia, with subsequent expansion and diversification of a western cluster into the upper Midwest, and an eastern cluster into the eastern Great Lakes and New England. As predicted in cases of postglacial colonization, each of these clusters contains a single widespread and common haplotype, along with numerous low-frequency, closely related haplotypes. Given recent conservation concerns about amphibians in general, and Mudpuppies specifically, we discuss our results in light of species conservation. Knowledge of a species’ genetic diversity allows for informed management and facilitates decisions that preserve local adaptation and evolutionary potential.

Journal of Herpetology↗
USGS2020

Postmortem evaluation of reintroduced migratory whooping cranes (Grus americana) in eastern North America

We reviewed necropsy records of 124 Whooping Cranes ( Grus americana ) recovered following reintroduction of 268 individuals from 2001 to 2016 in the eastern US. Causes of death were determined in 62% (77/124) of cases facilitated by active monitoring that limited decomposition and scavenging artifact. The greatest proportions of mortality were caused by predation (0.468; 95% confidence interval 0.356–0.580; 36/77), collision with power lines or vehicles (0.260; 0.162–0.358; 20/77), and gunshot (0.169; 0.085–0.253; 13/77). Six deaths were attributed to infection (0.078; 0.018–0.138; 6/77), including bacterial and fungal etiologies. Lead analysis of 50 liver samples yielded two results with elevated concentrations (3.65 and 10.97 ppm wet weight), and 10 bone samples from partial carcasses lacking suitable liver tissue resulted in one elevated result (48.82 ppm dry weight). These data indicate that underlying subclinical or clinical lead toxicosis may be a factor in up to 5% of deaths attributed to predation or impact trauma. Brain cholinesterase activity testing indicated no exposure to organophosphate or carbamate pesticides (mean±SD=17.32±2.90 µmol/min/g, 31/71). The causes of death and potential underlying factors summarized in this study constitute the first definitive mortality survey of migratory Whooping Cranes based on a high carcass recovery rate. Causes of death by infectious etiologies remained comparatively rare in this study, and occurred as single cases with no evidence of sustained transmission among reintroduced Whooping Cranes.

Eastern North America↗
USGS2020

Drivers of landscape change in the northwest boreal region

The northwest boreal region (NWB) of North America is a land of extremes. Extending more than 1.3 million square kilometers (330 million acres), it encompasses the entire spectrum between inundated wetlands below sea level to the tallest peak in North America. Permafrost gradients span from nearly continuous to absent. Boreal ecosystems are inherently dynamic and continually change over decades to millennia. The braided rivers that shape the valleys and wetlands continually change course, creating and removing vast wetlands and peatlands. Glacial melt, erosion, fires, permafrost dynamics, and wind-blown loess are among the shaping forces of the landscape. As a result, species interactions and ecosystem processes are shifting across time. The NWB is a data-poor region, and the intention of the NWB Landscape Conservation Cooperative is to determine what data are not available and what data are available. For instance, historical baseline data describing the economic and social relationships in association with the ecological condition of the NWB landscape are often lacking. Likewise, the size and remoteness of this region make it challenging to measure basic biological information, such as species population sizes or trends. The paucity of weather and climate monitoring stations also compound the ability to model future climate trends and impacts, which is part of the nature of working in the north. The purpose of this volume is to create a resource for regional land and resource managers and researchers by synthesizing the latest research on the historical and current status of landscape-scale drivers (including anthropogenic activities) and ecosystem processes, future projected changes of each, and the effects of changes on important resources. Generally, each chapter is coauthored by researchers and land and natural resource managers from the United States and Canada.

Northwest Boreal Region↗
USGS2020

Bottom trawl assessment of Lake Ontario prey fishes, 2019

Multi-agency, collaborative Lake Ontario bottom trawl surveys provide information for decision making related to Fish Community Objectives including predator-prey balance and understanding prey fish community diversity. In 2019, bottom trawl surveys in April (n = 252 tows) and October (n = 160 tows) sampled main lake and embayments at depths from 5–226 m. Combined, the surveys captured 283,383 fish from 39 species. Alewife were 67% of the total catch by number while round goby, deepwater sculpin, and rainbow smelt comprised 13, 10, and 4% of the catch, respectively. In 2019, the lake-wide adult alewife biomass index declined from 2018 and age-1 biomass, a measure of reproductive success the previous year, was low. Year-class catch curve models identified years where estimates from surveys conducted only in U.S. waters were biased, potentially due to a greater portion of the alewife population inhabiting unsampled Canadian waters. Accounting for spatial survey bias, these model estimates indicated the 2019 adult alewife biomass was the lowest value in the 42-year time series. Models also identified the extent to which age-1 alewife biomass was historically underestimated, however lake-wide results from 2016-2019 appear less biased. If below-average year-class estimates from 2017 and 2018 are accurate, adult alewife biomass will continue to decline in 2020. Abundance indices for other pelagic prey fishes such as rainbow smelt, threespine stickleback, emerald shiner, and cisco were low and similar to 2018 values. Pelagic prey fish diversity is low because a single species, alewife, dominates the community. Deepwater sculpin and round goby were the most abundant demersal (bottom-oriented) prey fishes in 2019. Despite declines in slimy sculpin and other nearshore prey fishes, demersal prey fish community diversity has increased as deepwater sculpin and round goby comprise more even portions of the community. New experimental trawl sites in embayment habitats generally captured more species, a higher proportion of native species, and higher densities relative to main lake habitats. In 2019, a western tubenose goby (Proterorhinus semilunaris) was captured for the first time in the trawl surveys.

Lake Ontario↗
USGS2020

2019 Status of the Lake Ontario Lower Trophic Levels

Spring total phosphorus (TP) in 2019 was 3.2 µg/L (offshore) and 4.7 µg/L (nearshore), both all-time lows; however, there is no significant time trend in our data series (1995-2019 for nearshore; 2002-2019 for offshore). Apr/May – Oct mean TP concentrations were low at both nearshore and offshore locations (range, 3.7 – 6.5 µg/L). TP and SRP concentrations were not significantly different between nearshore and offshore habitats. Chlorophyll- a and Secchi depth values are indicative of oligotrophic conditions in nearshore and offshore habitats. Offshore summer chlorophyll-a declined significantly 1995 – 2019. Nearshore chlorophyll- a increased 1995 – 2004 and then stabilized 2005 – 2019. In 2019, epilimnetic chlorophyll-a averaged between 1.3 and 2.9 μg/L across sites, and Apr/May – Oct concentrations were not significantly different between nearshore and offshore sites. Summer Secchi depth increased significantly in the offshore 1995 – 2019 from ~6 m to ~8 m. In the nearshore Secchi depth increased 1995 – 2004 but has remained around 6 m since 1999. Apr/May – Oct Secchi depth ranged from 3.8 m to 9.1 m (12 ft to 30 ft) at individual sites and was significantly higher offshore (7.6 m; 25 ft) than nearshore (5.7 m; 19 ft). In 2019, nearshore summer zooplankton biomass increased to 16.7 mg/m 3 after an all-time low (10.3 mg/m 3 ) in 2017. Offshore biomass (12.0 mg/m 3 ) was near the all-time low (8.1 mg/m 3 , 2006). Apr/May – Oct epilimnetic zooplankton density and biomass were not different between nearshore and offshore sites. However, zooplankton average size was significantly higher in the offshore (0.72 mm) than the nearshore (0.61 mm). Peak (July) epilimnetic biomass of Cercopagis was 2.4 mg/m 3 in the nearshore and 1.4 mg/m 3 in the offshore. Peak (September) epilimnetic biomass of Bythotrephes was 2.0 mg/m 3 in the nearshore and 2.9 mg/m 3 in the offshore. Summer nearshore zooplankton density and biomass declined significantly 1995 – 2004 and then remained stable 2005 – 2019. The decline was due mainly to reductions in cyclopoids copepods. Summer epilimnetic daytime offshore zooplankton density decreased significantly 1995 – 2004, but biomass did not. Density and biomass declined significantly 1995 – 2019. Density was 3885/m 3 in 2019, about one-fourth the level observed the previous year. Offshore summer epilimnetic zooplankton biomass in 2019 was 12 mg/m 3 —well below the mean from 2005 – 2018 (20 mg/m 3 ). Most offshore zooplankton biomass was found in the metalimnion in July and early-October, and in the hypolimnion in September. Limnocalanus dominated the metalimnion in July while daphnids comprised most of the biomass in October. In September, Limnocalanus dominated the hypolimnion.

New York, Ontario↗
USGS2020

How and why is the timing and occurrence of seasonal migrants in the Gulf of Maine changing due to climate?

Plants and animals undergo certain recurring life-cycle events, such as migrations between summer and winter habitats or the annual blooming of plants. Known as phenology, the timing of these events is very sensitive to changes in climate (and changes in one species’ phenology can impact entire food webs and ecosystems). Shifts in phenology have been described as a “fingerprint” of the temporal and spatial responses of wildlife to climate change impacts. Thus, phenology provides one of the strongest indicators of the adaptive capacity of organisms (or the ability of organisms to cope with future environmental conditions). In this study, researchers are exploring how the timing and occurrence of a number of highly migratory marine animals is changing due to a series of climatic and ecological shifts. First, using existing long-term historical data series, they will determine the direction and magnitude of how migration, abundance, or other phenological factors have changed for marine mammals, sea turtles, and fishes that migrate into the Gulf of Maine on a seasonal basis. Because marine animals are inherently difficult to detect, the team will apply dynamic occupancy models to evaluate seasonal migration patterns and habitat use across multiple habitats in the Gulf of Maine region. The project team will also synthesize regional information on a key, ecologically-important prey fish, sandlance, whose timing and abundance is a strong predictor of the occurrence and behavior of predator species targeted in this study as well as a range of other regional fish and wildlife of conservation and management concern. Results from this component of the project will identify coastal fish and wildlife species that are relatively more or less able to adapt and thus potentially vulnerable to climate change; determine the likely primary drivers of those changes; and identify data gaps and future monitoring needs. Ultimately, this information will be available and useful for regional coastal management and adaptation decisions that will allow managers to effectively plan for the future. In a second component of the project, researchers will focus specifically on changes in migration patterns of the endangered North Atlantic right whale. While shifts in the distribution and time of recurring life events are adaptive responses that may help species cope with climate impacts, they can also lead to changes in how species interact with humans. The North Atlantic right whale is one of the most endangered whale species on the planet. In the North Atlantic Ocean, ship strikes and entanglements with commercial fishing gear represent fatal threats to right whales. Recent reports suggest that North Atlantic right whale migration patterns have changed. Many researchers posit that shifts in migration are responsible for recent increases in the overlap between right whales and human activities, especially fishing. To help understand how changes in right whale movements and behaviors may overlap with ship traffic, and thus put the animals at risk of encountering vessels, we will combine right whale habitat models with ship traffic maps. The end result will be a set of maps identifying risk levels.

Gulf of Maine↗
USGS2020

Species and genetic diversity in Lake Huron in 2018

Fish community objectives (FCOs) for species and genetic diversity (DesJardine et al. 1995) complement the species- or genera-specific objectives by recognizing that diversity within and among species can improve ecosystem resiliency through portfolio effects (DuFour et al. 2015). In Lake Huron, native species (such as Lake Trout and Lake Whitefish), and non-native species (such as Alewife and Pacific salmon) play important roles in the ecosystem. The FCOs recognize the importance of genetic diversity within all fish populations to ensure their long-term sustainability. This section summarizes the current state of species diversity and recent genetic analyses of important biota in the fish community.

Lake Huron↗
USGS2020

Lake trout rehabilitation in Lake Ontario, 2019

Each year we report on the progress toward rehabilitation of the Lake Ontario lake trout ( Salvelinus namaycush ) population, including the results of stocking, annual assessment surveys, creel surveys, and evidence of natural reproduction observed from all standard surveys performed by USGS and NYSDEC. The catch per unit effort of adult lake trout in gill nets increased each year from 2008-2014, recovering from historic lows recorded during 2005-2007. Adult abundances declined each year from 2015 to 2017; and in 2017 were about 35% below the 2014 peak and 17% below the 1999-2004 mean. Adult abundance increased in 2018 by 51% over the 2017 value and increased and addition 16% in 2019. The 2019 rate of wounding by sea lamprey (Petromyzon marinus) on lake trout caught in gill nets (0.53 A1 wounds (fresh wound) per 100 lake trout) was below target (2 wounds per 100 lake trout). Estimates from the NYSDEC fishing boat survey indicated angler catch rate of lake trout was low in 2019 and among the lowest recorded for the time series. Condition values for an adult lake trout, indexed in September from the predicted weight for a 700mm lake trout from annual length-weight regressions and Fulton’s K for age-6 males, were among the highest levels observed for the 1983-2019 time series. Predicted weight for a 400mm lake trout from July 2019 bottom trawl catches was near the long-term average while age-2 K was among the lowest for the time series. Reproductive potential for the adult stock indexed from the CPUE of mature females ≥ 4000g was again above the target in 2019 continuing a trend observed in nine of the last ten years. The 2019 catch of young native lake trout marked the 25th observation in the last 26 years, however the low numbers of native adults observed during that time period continues to indicate substantial restoration impediments still exist.

Lake Ontario↗