Geology topics

Research about Lake Ontario

Source-linked reports with geographic coverage including Lake Ontario.

At least 37 records · Page 2Linked to original sources

USGS2023

Lake Ontario August gillnet survey and Lake Trout assessment, 2022

Lake Ontario Lake Trout (Salvelinus namaycush) rehabilitation has been annually assessed with fishery independent surveys since 1983, in an effort to evaluate program benchmarks and compare observations with management objectives. These surveys provide information on the abundance, strain composition, and condition of the adult Lake Trout stock, as well as information on levels of natural recruitment, Sea Lamprey (Petromyzon marinus) wounding rates, and abundance indices of other coldwater fish species (Burbot Lota lota, Cisco Coregonus artedi, and Lake Whitefish C. clupeaformis). In 2022, the catch per unit effort (CPUE) of total Lake Trout in gillnets remained high (18.9 fish/lift; highest since 1998) compared to lows observed during 2005–2009 (average = 7.5 fish/lift). The CPUE of immature Lake Trout in the 2022 survey was the highest since 1994. Wild-produced mature Lake Trout remain rare in the adult population (2.4% of adult catch). Strain composition of stocked fish indicated more than half (56%) of all coded-wire tagged Lake Trout captured in 2022 were from the Superior Klondike strain. Sea Lamprey wounding rates were above target levels in 2022 (3.15 A1 wounds per 100 Lake Trout) and were nearly double the 2021 rate. Lake Trout condition (predicted weight at length) was the highest since data collection began in 1983. Overall, the 2022 survey results indicate that adult Lake Trout are abundant and of high condition but composed mostly of hatchery-origin strains, suggesting recruitment of wild-produced offspring to the adult stock continues to be limited.

Lake Ontario↗

USGS2023

Lake Ontario April prey fish survey results and Alewife assessment, 2023

The April bottom trawl survey and Alewife Alosa pseudoharengus population assessment provides science to inform Lake Ontario fisheries management. The 2023 survey included 215 trawls in the main lake and embayments, and sampled depths from 6.5 to 252 m (21-833 ft). The survey captured 1,012,178 fish from 32 species with a total weight of 12,136 kg (26,700 lbs.). Alewife were 92% of the catch by number while Rainbow Smelt, Osmerus mordax , Deepwater Sculpin, Myoxocephalus thompsonii , and Round Goby, Neogobius melanostomus , comprised 3%, 3%, and 1% of the catch, respectively. To improve the accuracy of prey fish biomass and density estimates we reanalyzed trawl sensor data from each of three participating survey vessels and created vessel-specific relationships predicting how bottom trawl bottom contact time, wing width, and area-swept varies with depth. Total Alewife biomass increased in 2023 due to growth and survival of the abundant 2020 year class (now age-3) and an abundant 2022 year class (age-1). The 2023 mean Alewife biomass (81.1 kg·ha -1 ) was the largest since whole lake sampling began in 2016 and was the ninth largest value observed in the modern time series (1997-2023, maximum value in 2000 = 91.8 kg·ha -1 ). The 2023 Alewife density (6795 n·ha -1 ) was the greatest density observed in the modern time series. These high biomass and density values are due to above average Alewife reproductive success in 2020 and 2022. Simulation modeling suggests the 2024 and 2025 Alewife biomass index may be substantially higher than the 2023 observations. In 2023, the Rainbow Smelt biomass index increased relative to the 2022 index, as did the biomass index for Cisco, Coregonus artedi . In contrast, Emerald Shiner Notropis atherinoides and Threespine Stickleback Gasterosteus aculeatus , biomass values continue to be low (< 0.01 kg·ha -1 ). Three Bloater Coregonus hoyi , were captured during the 2023 survey. Hydroacoustic sampling conducted during the bottom trawl survey estimated prey fish densities in pelagic habitats not sampled by the bottom trawl (3 m below the surface to 3 m above the lake bottom) and these densities were hundreds to thousands of times lower than bottom trawl-based densities. These results support the idea that, in April, when the warmest water is on the lake bottom, Alewife and most other pelagic prey fish are near the lake bottom and can be effectively sampled with bottom trawling.

Lake Ontario↗

USGS2022

Spatial and temporal variability in lake trout diets in Lake Ontario as revealed by stomach contents and stable isotopes

Lake trout ( Salvelinus namaycush ) are an ecologically and economically important piscivore with reported differences in diet and feeding behaviour throughout its range. Eleven stomach content and stable isotope-based metrics were used to describe diets of 349 lake trout between two years (2013 and 2018) and among geographic zones (west, central, east, Kingston basin) in Lake Ontario. Using individual (e.g., volumetric, %V) and aggregate (e.g., index of relative importance, %IRI) diet metrics, we found an overwhelming dominance of alewife ( Alosa pseudoharengus ) in lake trout diets among some zones in 2013 (%V = 23.3 – 92.7; %IRI = 12.2 – 99.5) and all zones in 2018 (%V = 83.9 – 96.7; %IRI = 96.5 – 100). Round goby ( Neogobius melanostomus ) and rainbow smelt ( Osmerus mordax ) were secondary lake trout prey items with relative diet percentages only marginally reflected by spatial and temporal variation in prey abundance (round goby: %V = 1.0 – 33.3, %IRI = 0.1 – 13.2; rainbow smelt: %V = 2.5 – 54.0, %IRI = 0.1 – 54.0). Carbon (δ 13 C) and nitrogen (δ 15 N) isotopic niche areas and orientations were similar across all year-zone combinations reinforcing temporal and spatial consistency in lake trout diet. The findings of this study advance the time series in describing Lake Ontario lake trout diets and can be used to complement stock assessments and management decisions associated with carrying capacity for the diverse salmonid community.

Lake Ontario↗

USGS2022

Contemporary spatial extent and environmental drivers of larval coregonine distributions across Lake Ontario

Coregonine fishes are important to Laurentian Great Lakes food webs and fisheries and are central to basin-wide conservation initiatives. In Lake Ontario, binational management objectives include conserving and restoring spawning stocks of cisco ( Coregonus artedi ) and lake whitefish ( C. clupeaformis ), but the spatial extent of contemporary coregonine spawning habitat and the environmental factors regulating early life success are not well characterized. In Spring 2018, we conducted a binational ichthyoplankton assessment to describe the spatial extent of coregonine spawning habitat across Lake Ontario. We then quantified the relative importance of a suite of biophysical variables hypothesized to influence coregonine early life success using generalized additive mixed models and multimodel inference. Between April 10 and May 14, we conducted 1,092 ichthyoplankton tows and captured 2,350+ coregonine larvae across 17 sampling areas, predominantly within embayments. Although 95% of catches were in the eastern basin, coregonine larvae were also found in historical south shore spawning areas. Most coregonine larvae were cisco; <6% were lake whitefish. Observed catches of both species across sampling areas were strongly and similarly associated with ice cover duration, but the importance of site-specific characteristics varied, such as distance to shore and site depth for cisco and lake whitefish, respectively. These results suggest that regional-scale climatic drivers and local environmental habitat characteristics interact to regulate early life stage success. Furthermore, strong regional and cross-species variation in larval distributions emphasize the importance of lake-wide assessments for monitoring both the current eastern basin populations and potential expansions into western Lake Ontario habitats.

Lake Ontario↗

USGS2022

Depth drives growth dynamics of dreissenid mussels in Lake Ontario

Understanding dreissenid mussel population dynamics and their impacts on lake ecosystems requires quantifying individual growth across a range of habitats. Most dreissenid mussel growth rates have been estimated in nutrient rich or nearshore environments, but mussels have continued to expand into deep, cold, low-nutrient habitats of the Great Lakes. We measured annual quagga mussel ( Dreissena rostriformis bugensis) growth at 15 m, 45 m, and 90 m in Lake Ontario using caged mussels near Oswego, New York, USA from June 2018 to May 2019. Quagga mussel growth (starting size 12 mm) was greatest at 15 m (mean shell length increase = 10.2 mm), and was lower at 45 m (5.9 mm) and 90 m (0.7 mm). Caged mussels were obtained from near the 90-m site and those reared at 15 and 45 m developed thicker shells than those that were caged at 90 m. We observed relatively high colonization by quagga and, to a lesser degree, zebra mussels ( Dreissena polymorpha ) at 15 m, very few colonizers at 45 m, and none at 90 m. Higher growth potential, but low natural mussel densities observed at 15 m and 45 m suggest factors other than growth limit dreissenid abundance at these depths. The relatively slow dreissenid growth rates observed in offshore habitats are consistent with the gradual abundance increases documented in these zones across the Great Lakes and suggest new mussels that become established in these habitats may contribute to ecosystem effects for decades.

New York↗

USGS2022

Bioaccumulation of perfluoroalkyl substances in a Lake Ontario food web

Per- and polyfluoroalkyl substances (PFAS) are a group of synthetic chemicals detected throughout the environment. To better understand the distribution of PFAS in an aquatic system (the Laurentian Great Lakes), stable isotope enrichment (δ13C and δ15N), fatty acid (FA) profiles, and PFAS were measured in various species from the Lake Ontario (LO) aquatic food web. Sampled organisms included top predator fish, prey fish, and benthic and pelagic macroinvertebrates. The trophic level of each species in the LO food web was determined using δ15N, and FA concentrations (range: <1–139 mg/g wet weight (ww)). The individual PFAS concentrations in the LO food web were ~1.5 to 5 times lower than previously reported. The highest PFAS concentrations were observed in deepwater sculpin (Myoxocephalus thompsonii, 150 ± 35.7 ng/g ww) suggesting a potential source of PFAS from the offshore benthic zone or sediment. The concentration of PFOS and long chain (C9-C14) perfluoroalkyl carboxylic acids (PFCAs) were significantly higher than short chain PFAS indicating the significant impact of hydrophobicity on the bioaccumulation of PFAS in organisms from the food web. However, high molecular weight PFCAs (>C8) did not exhibit increasing biomagnification factors (BMFs) and trophic magnification factors (TMFs) with log Kow, suggesting hydrophobicity does not govern the movement of PFAS from low to high trophic levels in the LO food web.

Lake Ontario↗

USGS2022

Importance of nonindigenous harpacticoids (Crustacea: Copepoda) decrease with depth in Lake Ontario

Harpacticoid copepods can be a substantial component of the meiobenthic community in lakes and serve an ecological role as detritivores. Here we present the first species-level lake-wide quantitative assessment of the harpacticoid assemblage of Lake Ontario with emphasis on the status of nonindigenous species. Additionally, we provide COI-5P sequences of harpacticoid taxa through Barcode of Life Data System (BOLD). Harpacticoids were collected at depths from 0.1 to 184 m and from a range of substrates from August to September 2018 as part of the Cooperative Science and Monitoring Initiative (CSMI) offshore benthic survey. Twenty-six meiobenthic samples were analyzed using microscopy for community composition analysis of harpacticoids. We found thirteen indigenous and three nonindigenous species of harpacticoid, with the introduced species dominating at shallow depths. The community transitioned from nonindigenous to indigenous species dominance as depth increased. Nonindigenous species accounted for 79% of the community (by abundance) at depths <20 m, 55% from 20 to 40 m, and only 24% at depths >40 m. The nonindigenous species encountered included the first detections of Schizopera borutzkyi (Monchenko, 1967) and Heteropsyllus nunni (Coull, 1975) from Lake Ontario. S. borutzkyi was the most abundant harpacticoid species in the lake, approaching a maximum density of 50,000/m 2 and a lake-wide average density of 7,900/m 2 . Numerically important indigenous species included Bryocamptus nivalis (Willey, 1925), Canthocamptus robertcokeri (Wilson, 1958), Canthocamptus staphylinoides (Pearse, 1905), and Moraria cristata (Chappuis, 1929). The prevalence of nonindigenous harpacticoids in the meiobenthos of Lake Ontario suggests further investigations of Great Lakes meiofauna communities are warranted.

Lake Ontario↗

USGS2022

Results of the collaborative Lake Ontario bloater restoration stocking and assessment, 2012–2020

Bloater, Coregonus hoyi , are deepwater planktivores native to the Laurentian Great Lakes and Lake Nipigon. Interpretations of commercial fishery time series suggest they were common in Lake Ontario through the early 1900s but by the 1950s were no longer captured by commercial fishers. Annual bottom trawl surveys that began in 1978 and sampled extensively across putative bloater habitat only yielded one individual (1983), suggesting that the species had been locally extirpated. In 2012, a multiagency restoration program stocked bloater into Lake Ontario from gametes collected in Lake Michigan. From 2012 to 2020, 1,028,191 bloater were stocked into Lake Ontario. Bottom trawl surveys first detected stocked fish in 2015, and through 2020 ten bloater have been caught (total length mean = 129 mm, s.d. = 44 mm, range: 96–240 mm). Hatchery applied marks and genetic analyses confirmed the species identification and identified stocking location for some individuals. Trawl capture locations and acoustic telemetry suggested that stocked fish dispersed throughout the main lake within months or sooner, and the depth distribution of recaptured bloater was similar to historic distributions in Lake Ontario and other Great Lakes. Predicted bloater trawl catches, based on modeled population abundance and trawl survey efficiency, were similar to observed catches, suggesting that post-stocking survival is less than 20% and contemporary bottom trawl surveys can quantify bloater abundance at low densities and track restoration.

Lake Ontario↗

USGS2022

Evaluation of post-stocking dispersal and mortality of juvenile lake trout Salvelinus namaycush in Lake Ontario using acoustic telemetry

Wild reproduction by stocked lake trout Salvelinus namaycush in Lake Ontario has yet to produce a self-sustaining population, requiring a reliance on stocking. Once released, age-1 juvenile lake trout are not typically surveyed until age-2, creating a gap in knowledge of fine-scale post-release behaviors. A method to track fine-scale movements and estimate mortality of juvenile lake trout could complement standard survey methods and benefit management decisions regarding stocking locations. We used acoustic telemetry to estimate post-stocking mortality and observe fine-scale spatial and temporal movements of 38 hatchery-reared, age-1 lake trout from an offshore stocking site in the eastern basin of Lake Ontario from 2017 to 2018. Cumulative post-stocking mortality was estimated at 5.3%, 10.5%, and 26.3% after one week, one month and one year, respectively. The majority of lake trout (68.4%) emigrated from the stocking location within two months and entered deep water (∼50 m) once warm-water incursions at the stocking site exceeded lake trout thermal preferences (15 °C). Lake trout made large movements (i.e., median 1.9 km, maximum 12.4 km straight-line distance) within the first hour post-release and had an average swimming speed of 1.64 km‧hr −1 over the first day. There was no statistically significant relationship between total distance traveled and time of day, although distance traveled tended to be greater during crepuscular and dark periods compared to daylight. Our results provide a conservative estimate of post-release mortality and reveal behaviors of hatchery-reared juvenile lake trout that may be helpful when selecting stocking locations beneficial to restoration program goals.

Lake Ontario↗

USGS2022

Balancing prey availability and predator consumption: A multispecies stock assessment for Lake Ontario

Trophic interactions are drivers of ecosystem change and stability, yet are often excluded from fishery assessment models, despite their potential capacity to improve estimates of species dynamics and future fishery sustainability. In Lake Ontario, recreational salmonine fisheries, including Chinook salmon ( Oncorhynchus tshawytscha ) and lake trout ( Salvelinus namaycush ), depend on a single prey species, alewife ( Alosa pseudoharengus ). To accommodate strong trophic interactions among species, we developed a multispecies statistical catch-at-age assessment (MSCAA) model that links the dynamics of the salmonine fisheries and alewife via prey consumption and predator growth. We found that prey availability had declined since 2015 due to decreased alewife recruitment and increased Chinook salmon biomass, leading to higher alewife mortality rates and lower predator growth rates. Forward projections of predator–prey dynamics suggest that Chinook salmon stocking reductions may improve the probability for alewife population growth, but could be counteracted by increased natural Chinook salmon recruitment. Combined with predator- and prey-monitoring efforts, multispecies assessments show promise as models of intermediate complexity to support a transition to ecosystem-based approaches to fisheries management.

Lake Ontario↗

USGS2022

Lake Ontario April prey fish survey results and Alewife assessment, 2022

The annual Lake Ontario April bottom trawl survey and Alewife, Alosa pseudoharengus , population assessment provide science to inform management decisions related to predator-prey balance and fish community dynamics. The 2022 survey was conducted from March 31 to April 26, included 235 trawls in the main lake and embayments, and sampled depths from 5 to 219 m (16 – 723 ft). The survey captured 311,770 fish from 30 species with a total weight of 7,740 kg (17,028 lbs.). Alewife were 85% of the catch by number while Rainbow Smelt, Osmerus mordax , Round Goby, Neogobius melanostomus , and Deepwater Sculpin, Myoxocephalus thompsonii , comprised 6%, 4%, and 4% of the catch, respectively. The 2022 biomass index for Rainbow Smelt decreased 80% relative to the high values observed in 2021 as did the value for Cisco, Coregonus artedi , (46% decline). Emerald Shiner, Notropis atherinoides , biomass index increased in 2021 and Threespine Stickleback, Gasterosteus aculeatus , biomass remained low. No Bloater, Coregonus hoyi , were captured during the 2022 survey. In 2022, Alewife biomass in U.S. waters (58.1 kilograms per hectare, kg·ha-1) was substantially higher than Canadian waters (26.3 kg·ha-1). The 2022 Alewife biomass index (41.6 kg·ha-1) decreased 10% from 2021 while the 2022 density index decreased 62% from 2021. Prediction modeling indicated the growth of the abundant 2020 Alewife year class, sampled as age-1 fish in 2021, would cause the adult Alewife biomass to increase in 2022. Although the adult Alewife biomass did increase relative to 2021 (61%), the increase was lower than predicted. The difference between the predictions and observations was because survival of age-1 fish from 2021 to 2022 was lower than had previously been observed. In the three previous years of observations the proportion of age-1 Alewife surviving to age 2 ranged from 0.33 to 0.53; however, that proportion was only 0.21 from 2021 to 2022. Survival estimates of Alewife age-5 through age-8 were higher than previously observed, possibly because salmonid predation focused on the abundant younger Alewife. The catch of age-1 Alewife in 2022, which is a measure of reproductive success in 2021, was below average and similar to the abundances of the 2018 and 2019 year classes. Simulation modeling results indicated the adult Alewife biomass is likely to increase slightly in 2023, whereas predictions for 2024 are less certain. Hydroacoustic sampling was used to estimate prey fish densities in open-water, pelagic habitats not sampled by the bottom trawl. Bottom trawl-based densities from the lake bottom were at least 25 times greater than densities of prey fish in the water column above the trawl. These results support the idea that, in April, when the warmest, most dense water is on the lake bottom, Alewife and most other pelagic prey fish primarily inhabit deep, near bottom habitats and can be effectively sampled with bottom trawling.

Lake Ontario↗

USGS2022

Lake trout (Salvelinus namaycush) rehabilitation in Lake Ontario, 2021

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 standard surveys performed by U.S. Geological Survey (USGS) and New York State Department of Environmental Conservation (NYSDEC). The catch per unit effort (CPUE) 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 remained nearly stable between 2018 and 2021. The 2020 rate of wounding by sea lamprey ( Petromyzon marinus ) on lake trout caught in gill nets was 1.68 A1 wounds (fresh wound) per 100 lake trout and was near target (2 wounds per 100 lake trout). Condition values for adult lake trout, indexed in September from the predicted weight for a 700 mm lake trout from annual length-weight regressions and Fulton’s K for age-6 males, were among the highest levels observed for the 1983-2021 time series. Reproductive potential for the adult stock indexed from the CPUE of mature females ≥ 4000 g was again above the target in 2021 continuing a trend observed in ten of the last eleven years. The 2021 catch of young wild lake trout marked the 27th observation in the last 28 years, however only two sites off the mouth of the Niagara River were surveyed.

Lake Ontario↗

USGS2021

Dynamics of the seasonal migration of Round Goby (Neogobius melanostomus, Pallas 1814) and implications for the Lake Ontario food web

Seasonal migrations of fish populations can have large effects on lake nutrient budgets and food web dynamics, but the addition of a migrating non‐native species may alter these dynamics. The Round Goby ( Neogobius melanostomus ) arrived in Lake Ontario (USA/Canada) about 20 years ago with a documented history of annual offshore–inshore migrations in its native range. Here we combined nearshore, fixed‐plot video with offshore trawl data to document the annual migration of this population over multiple years. This behaviour was correlated with seasonal, nearshore temperature changes. The population size structure and mean fish length of returning fish were smaller than those of out‐migrating fish. The out‐migrating population contained an estimated 37.7 metric tonnes of phosphorous; and we estimated roughly 20 metric tonnes were translocated to and remained in offshore waters over the winter months, representing an important nutrient subsidy to a variety of offshore piscivorous fish. Lake Sturgeon ( Acipenser fulvescens ) have incorporated Round Goby extensively into their diet and consume a size range of fish matching the size range of missing Round Goby that fail to return to the nearshore. We conclude Round Goby are an important prey within the food web of Lake Ontario and translocate roughly 6.5% of the monthly total phosphorous load entering from surface waters. Further investigations of the nutrient content, population size structure and fate of migrating Round Goby in Lake Ontario are warranted to clarify the extent of this prey and nutrient subsidy in ongoing assessments of lake condition.

Lake Ontario↗

USGS2021

Comparisons among three diet analyses demonstrate multiple patterns in the estimated adult diet of a freshwater piscivore, Salvelinus namaycush

Understanding trophic interactions is critical for successful resource management. However, studying diet patterns (e.g., spatial and seasonal changes) can require extensive effort. Using individual analyses to interpret patterns may be further complicated by assumptions and limitations of the analytical approach. We investigated and compared predicted adult lake trout (Salvelinus namaycush) diet composition and patterns using stomach content analysis (SCA), fatty acid analysis (FAS), and stable isotope analysis (SIA) individually and simultaneously. The three analyses were conducted for fall-captured fish in Lake Ontario and provided different diet composition estimates; SCA suggested alewife (Alosa pseudoharengus) was dominant by frequency and mass, while FAA and SIA suggested rainbow smelt (Osmerus mordax) contributed the most based on similarity among fatty acid signatures and two-stable isotope (carbon and nitrogen) mixing models, respectively. We hypothesize the disagreement among diet estimates is a result of a seasonal shift in diet variably expressed due to differing extent of time reflected by the diet metric: hours to days for SCA, weeks to months for FAA and several months for SIA. Despite variability in diet composition estimates among methods, similar patterns in lake trout diet were observed among the three diet analyses; the contribution of alewife in lake trout diet was greater for larger individuals and for males compared to females, particularly in the east and northeast regions of the lake where alewife density was relatively low. Thus, the complementary results from the three analyses suggest that length, location, sex, and season all influence lake trout diet. Individually, analyses often failed to identify these patterns in lake trout diet with significance, and some of the patterns have not been observed in previous studies of lake trout diet in Lake Ontario. The thorough description of lake trout diet obtained from a single sampling season demonstrates how simultaneous use of multiple diet analyses may allow investigation of spatial and seasonal diet composition and with reduced sampling effort.

Lake Ontario↗

USGS2021

Evidence of host switching: Sea lampreys disproportionately attack Chinook salmon when lake trout abundance is low in Lake Ontario

Lake trout ( Salvelinus namaycush ) is the presumed preferred host of the invasive sea lamprey ( Petromyzon marinus ) in the Great Lakes, but little is understood about this preference outside of laboratory experiments. By preference we mean sea lamprey attacks on hosts are disproportionate to host relative abundance. The purpose of this study was to quantify host preference of sea lampreys in the field for the first time. We focused our analysis on Lake Ontario, where the two dominant host species for sea lampreys are lake trout and Chinook salmon ( Oncorhynchus tshawytscha ). Sea lampreys exhibited a strong preference for lake trout when host abundance was ≥ "> ≥ 32% lake trout, but sea lamprey preference switched to Chinook salmon when host abundance was ≤ "> ≤ 13% lake trout. Model results were equivocal with respect to determining whether the primary predictor of sea lamprey preference was relative or absolute abundance of lake trout. Other evidence, particularly the different spatial distributions of the two hosts, suggests that sea lamprey preference for lake trout is based on a higher encounter probability, driven by absolute abundance of lake trout. This study confirms a widely held concern that observed sea lamprey-induced marking rates on lake trout, used to assess the status of sea lamprey control in the Great Lakes, can be influenced by the abundance of alternative hosts. As an alternative host for sea lamprey parasitism, Chinook salmon may contribute to the persistence of lake trout in Lake Ontario.

Lake Ontario↗

USGS2021

Stationary hydroacoustics demonstrates vessel avoidance biases during mobile hydroacoustic surveys of alewife in Lake Ontario

Mobile hydroacoustic surveys are routinely used to estimate pelagic fish abundance . In the Great Lakes, alewife are commonly surveyed with mobile hydroacoustics, however, their behavior often has them associated with epilimnetic habitats which increases the potential for vessel avoidance to bias hydroacoustic observations. Abundance estimates from mobile hydroacoustic surveys are typically made using depth and size thresholds to classify targets to species. In hydroacoustic surveys, fish can appear to be smaller when oriented off horizontal axis, as is common with fish displaying vessel avoidance behaviour. This presents a problem where alewives that are diving may appear too small to be correctly classified. We compared alewife swimming behaviours and target strength distributions between stationary up-looking and mobile down-looking hydroacoustics to quantify how vessel avoidance may bias hydroacoustic observations. Alewives from the mobile survey were found to be diving away from the surface, moving faster and in more linear paths than the undisturbed fish from the stationary survey. In the mobile survey, alewives were observed at smaller target strength values than would be expected if boat avoidance was not occurring. Our results suggest that alewife behavioral changes associated with vessel avoidance affect the number and size of targets classified as alewife from mobile hydroacoustic surveys in Lake Ontario.

Lake Ontario↗

USGS2021

The path toward consistent achievement of sea lamprey abundance and lake trout marking targets in Lake Ontario, 2000–2019

Lake Ontario boasts a diverse fish community comprised of native and introduced species that support vibrant recreational, commercial and Indigenous fisheries. The effective delivery of a program to assess and control the sea lamprey ( Petromyzon marinus ) is crucial to achievement of Lake Ontario Fish Community Objectives of rehabilitating native fish stocks while protecting and maintaining the abundance of introduced salmonines. During 2000–2019, the Great Lakes Fishery Commission (GLFC) and its control agents, Fisheries and Oceans Canada (DFO) and the U. S. Fish and Wildlife Service (USFWS), delivered a consistent program of sea lamprey assessment and control. Beginning in 2004, rising sea lamprey abundance and marking rates on lake trout ( Salvelinus namaycush ) in Lake Ontario coincided with a decline of large lake trout in gillnet surveys. Efforts were undertaken to identify and control important sources of juvenile sea lampreys, including larvae that survived treatment, inhabited deepwater areas, or colonised previously uninhabited stream reaches and tributaries. A renewed reliance on proven conventional controls, including lampricide treatments and barriers, has resulted in consistent suppression of sea lamprey abundance and lake trout marking to prescribed targets in Lake Ontario during 2014–2019. This achievement is unprecedented in the 49-year history of Sea Lamprey Control Program delivery in Lake Ontario, and is attributable to the collaborative efforts of the GLFC, the control agents, and federal, provincial, state, and Indigenous partners.

Lake Ontario↗

USGS2021

A review of sea lamprey dispersal and population structure in the Great Lakes and the implications for control

Understanding the population structure of invasive sea lamprey ( Petromyzon marinus ) in the Great Lakes basin is essential for an effective control program. We review knowledge of lake connectivity, dispersal during the parasitic stage, and results from phenotypic, demographic, and genetic studies to evaluate how sea lamprey populations are structured. There is no evidence for contemporary movement between Lake Ontario and the Atlantic population, although it appears possible. Dispersal between Lake Ontario and the Finger Lakes is more likely, as is contemporary movement between Lakes Ontario and Erie via the Welland Canal, although neither has been directly observed. Downstream movement from Lake Erie to Lake Ontario via the Niagara River has been reported. Bidirectional movement between Lakes Erie and Huron has been observed, and movement of sea lamprey among the upper Great Lakes (especially between Lakes Huron and Michigan) is relatively common, although complete mixing likely does not occur. The maximum straight-line dispersal distance reported for a tagged sea lamprey was 628 km between the St. Marys River and western Lake Erie. Genetic population studies using a variety of molecular markers generally found weak but significant broad-scale population structure (e.g., between freshwater and anadromous populations, and among Lake Ontario, Lake Erie, and the upper Great Lakes), but finer-scale structure was rarely detected. Nevertheless, some within-basin structure is suggested by regional differences in phenotypic and demographic traits (e.g., sex ratio, body size). Further study will be important because management is most efficiently targeted when the geography of demographically independent populations is well-characterized.

Lake Ontario↗