Geology topics

James E. McKenna

Publications and source records attributed to James E. McKenna.

At least 19 recordsLinked to original sources

USGS2026

A targeted approach for mapping groundwater discharge to surface water and fish thermal refuge in four Lake Ontario tributaries

The duration, magnitude, and frequency of heatwaves are predicted to increase in the coming decades, a combination that can reduce the survival of many fish species. Across the world, there is broad interest in identifying thermal refuge for heat-intolerant fish species and exploring opportunities to enhance or protect these areas. Because deeper groundwater maintains a relatively constant temperature, groundwater-influenced areas along streams can provide cool-water refuge for fish during periods of extreme heat. A targeted approach was developed for identifying existing cold-water zones and areas of substantial groundwater discharge in four high priority Lake Ontario tributaries. Our approach included: (1) predicting where groundwater discharge is most likely with a simple geospatial model and (2) using model predictions to select field sites for intensive high-resolution study, including ground-based mapping of groundwater features (springs, seeps, tributaries) as well as drone-based optical and thermal infrared surveys. Results from field sites were used to both verify model performance and map different types and aerial extents of thermal anomalies. Geospatial modelling successfully predicted regions of widespread groundwater upwelling, later verified and mapped by field and drone surveys. Comparison of model and field survey results further highlighted specific geospatial layers, such as soil/bedrock types and topographic wetness index, as being particularly useful for predicting groundwater influence on streams in the study area. In addition, a comparison of geospatial model results with a model of fish abundances along the studied streams showed significant positive correlations for many heat-intolerant fish species over a wide geographic area. The approach developed in this study can be applied to other watersheds to highlight areas of probable groundwater discharge and could be used by fishery and water resource managers to support cold-water fish habitat management decision-making and resource conservation.

New York↗

USGS2025

How accurately does eDNA reflect the spatial distribution of cold-water fish? Field validation from a temperate lake

Applications of environmental DNA (eDNA) based detection technology to evaluate the distribution of aquatic organisms are increasing; yet field validations of eDNA are important to measure accuracy in study systems. To successfully apply this technology to species conservation, it is critical to understand how both species biology and environmental conditions affect the accuracy of inference from eDNA detection data. We implemented a field assessment of the accuracy and spatial resolution of eDNA-based species distributions for a native cold-water, schooling fish, cisco Coregonus artedi , that has been reintroduced to a deep temperate lake. We leveraged a combination of acoustic telemetry, providing known spatial locations of tagged fish, and lake-wide eDNA sampling to infer their distribution in Keuka Lake, New York, USA. Sub-surface (12 m and 18 m depths) eDNA samples were collected to accommodate the diel vertical migration behaviour of this fish species. The results of this study validated the accuracy of positive eDNA detections with the distribution of tagged fish to coarse spatial scales. Yet, several fine-scale locations revealed a mismatch between eDNA and acoustic telemetry detections; consistent with rapid transport of genetic material via lake currents. Empirical measurements of lake currents using drifters found cisco eDNA detections could deviate from specimens' source locations by as much as 3.3 km at 12 m depth or 1.5 km at 18 m depth over a 24 h transport period. Our study indicates that accurate species distributions estimated from eDNA sampling in lakes may require further understanding of transport mechanisms and persistence of environmental genetic material to relate point detections to source animal locations. Integrating eDNA sampling with additional data collection of species biology and environmental conditions will increase the spatial resolution of fish distribution assessments.

New York↗

USGS2024

U.S. Geological Survey Tunison Laboratory of Aquatic Science research to rehabilitate native prey fish of the Lake Ontario fish community—Coregonine fishes

Restoration of native coregonines to Lake Ontario of the Laurentian Great Lakes will improve the diversity of forage for salmonid predators and ecological function in the lake, but efficacy of experimental releases for native species restoration must be evaluated. The Coregonine Research Program at the U.S. Geological Survey Tunison Laboratory of Aquatic Science encompassed a diverse array of research, with an emphasis on improved culture methods and field assessments of experimentally released juvenile coregonines. This research was carried out to support the Fish Community Objectives of the Lake Ontario Committee, is funded largely by the Great Lakes Restoration Initiative, and was done in collaboration with other laboratories and agencies, particularly, the U.S. Fish and Wildlife Service; New York State Department of Environmental Conservation; Ontario Ministry of Natural Resources and Forestry; and other U.S. Geological Survey laboratories. The Tunison Laboratory of Aquatic Science and partners have developed new and innovative hatchery techniques to raise cisco and bloater to life stages suitable for survival in Lake Ontario; assessed adult bloater survival in Lake Ontario; and evaluated survival, return rate, and reproduction of adult cisco in historic spawning locations in Lake Ontario embayments. Successes, challenges, and research needs are discussed.

Lake Ontario↗

USGS2024

On the survival and habitat use of hatchery-reared cisco (Coregonus artedi) in Lake Erie

Cisco ( Coregonus artedi ) have been extirpated from Lake Erie in North America since the 1960s, but they once supported one of the largest Laurentian Great Lakes fisheries. Numerous potential impediments to rehabilitation have been identified, including summer habitat refugia and predation. We used acoustic telemetry to investigate the thermal habitat use and survival of hatchery-reared adult cisco in Lake Erie. Fish were experimentally released (n = 50 per site) offshore at Dunkirk, New York, in the eastern basin and Huron, Ohio, in the central basin. Cisco in both basins found suitable summer oxythermal habitat in the metalimnion, suggesting that coldwater habitat availability is likely not an impediment for reestablishment. However, track end dates or predation dates were distributed across only four months with the last detection at 155 days. Predation sensors combined with temperature values during digestion indicated different potential predators: lake trout ( Salvelinus namaycush ) for the Dunkirk group and walleye ( Sander vitreus ) for the Huron group. Additionally, digestion temperatures of two tags indicated bird predation was also important, likely underestimated and suggested substantial use of the epilimnion by tagged fish. The results highlight the need for additional studies to address stocking optimization questions in support of future reintroduction experiments and related cisco conservation efforts.

Lake Erie↗

USGS2024

Morphometry, growth, and condition of hatchery-reared Cisco (Coregonus artedi) and Bloater (Coregonus hoyi)

The re-introduction of native species that have been extirpated or in low abundance in the Great Lakes has been a binational initiative between the United States and Canadian governments. Recently, new management programs have been underway that use current hatchery facilities for the restoration of native forage fishes in Lake Ontario. These species include Bloater ( Coregonus hoyi ), which has been extirpated from Lake Ontario for approximately four decades, and Cisco ( C. artedi ), which exists at a fraction of its former abundance. We assessed morphometrics, length-weight relationships, and condition factors during early life development for eight cohorts of Cisco and Bloater reared from 2012-2019. Weekly samples for Cisco and Bloater were measured from hatch until release (29-45 weeks, 133-1,002 samples annually). Head width, gape, mandible length, and mouth height metrics were all larger for Cisco than Bloater at any given size but increased at similar rates for both species. Average condition factors for Cisco and Bloater were 0.54317 and 0.55892, respectively. This information may also improve field identification of these species, helping managers evaluate the relative success of different release strategies for rehabilitation of populations of these native species.

Ecology and Evolutionary Biology↗

USGS2024

Cisco (Coregonus artedi) and bloater (Coregonus hoyi) culture manual

The primary objective of the Coregonine Research Program established at the U.S. Geological Survey, Great Lakes Science Center, Tunison Laboratory of Aquatic Science as mandated by the Great Lakes Restoration Initiative is to restore native coregonines, specifically Coregonus artedi (Lesueur, 1818; ciscoes) and Coregonus hoyi (Milner, 1874; bloaters) into Lake Ontario. This objective focuses on providing an alternative food source for top predators and improving the ecological function of Lake Ontario as it relates to native versus invasive species control. To complete this goal, hatchery techniques were developed to grow ciscoes and bloaters; these techniques are described in this standard operating manual.

Techniques and Methods↗

USGS2024

Atlantic salmon (Salmo salar) culture manual

The primary objective of the Atlantic Salmon Research Program established at the U.S. Geological Survey Tunison Laboratory of Aquatic Science as mandated by the Great Lakes Restoration Initiative is to restore Atlantic salmon (Linnaeus, 1758; Salmo salar ) into Lake Ontario. This objective focuses on evaluating the survival of stocked Atlantic salmon in current Lake Ontario conditions to create a genetic strain that is robust to overcome current physiological and physical barriers. To complete this goal, new and innovative hatchery techniques based on past successful methods and protocols to grow Atlantic salmon to various life stages are described in this standard operating manual.

Techniques and Methods↗

USGS2024

Historical and morphological evidence for a remnant population of Lake Erie cisco Coregonus artedi (albus) in Crystal Lake, Pennsylvania

The cisco ( Coregonus artedi ) population in Crystal Lake, Pennsylvania, is of great scientific interest as it either originated from Lake Erie or Lake Ontario. Cisco in Lake Erie once supported the largest freshwater fishery in the world, but populations were extirpated by 1960. We conducted a morphological analysis of Crystal Lake cisco to determine whether it was consistent with a distinctive Lake Erie form ( albus ), which was also historically documented, albeit rarely, in western Lake Ontario. Using principal component analysis, we compared eight morphometric ratios and one meristic from our Crystal Lake cisco collection with historical and contemporary collections of cisco from Lakes Erie and Ontario. Maximum likelihood ellipse overlaps between Crystal Lake cisco and presumed albus (the dominant Lake Erie form prior to extirpation) collections averaged 54%. For all groups, the greatest morphological overlap (73.9%) occurred between Crystal Lake and 1957 Lake Erie cisco, which only differed from Crystal Lake cisco in dorsal fin length. Alternatively, overlap between Crystal Lake cisco and all other Lake Ontario collections averaged 3.2%. Our results demonstrate that Crystal Lake cisco are likely an albus form; furthermore, historical documentation and our morphological results suggest a Lake Erie origin. Substantial overlap between Crystal Lake cisco and Lake Ontario albus collected in 1917 is likely explained by continuous entrainment of Lake Erie larvae into Lake Ontario. We suspect this created an albus metapopulation spanning Lakes Erie and Ontario, yet albus are no longer observed in either lake today.

Pennsylvania↗

USGS2023

Conservation decision support for Silver Chub habitat in Lake Erie

Objective Conservation and restoration of aquatic species is difficult, especially for rare species, because their habitats are typically disturbed, obscuring the natural ability of the habitat to support each species. The Lake Erie population of Silver Chub Macrhybopsis storeriana struggles to sustain itself in a habitat disturbed by a wide spectrum of anthropogenic factors. Application of multiple model predictions can provide indications of conservation or restoration opportunities for this species. Methods A combination of models that predict the best potential for Lake Erie habitat to support Silver Chub and the effects of anthropogenic disturbances on that population were used to identify habitat conditions throughout the western aquatic lake unit. Result As many as 76 combinations of best habitat potential and disturbance conditions were present, but the best opportunities occurred in <12% of the study area. Some of the best protection opportunities were farthest offshore, and extensive areas of least disturbed habitat for restoration were near the southern and western shores. The location-specific model predictions provide fine-scale decision support for Silver Chub habitat protection or restoration. Conclusion The approach applied here may help identify compatibilities among species to achieve the desirable fish community for Lake Erie and reconcile conflicting management actions.

Michigan, Ohio, Ontario↗

USGS2023

Larval cisco and lake whitefish exhibit high distributional overlap within nursery areas

Coregonine fishes, including lake whitefish ( Coregonus clupeaformis ) and cisco ( C. artedi ), are socioecologically important in the Laurentian Great Lakes and of conservation concern, but the processes driving recruitment variability are unclear. In Lake Ontario, cisco and lake whitefish exhibit similar spawning behaviours and early life histories, but population trajectories are diverging. One hypothesis is that sympatric cisco and lake whitefish larvae occupy distinct habitats and experience dissimilar local environmental conditions, despite co-occurrence within nursery areas. We described the spatiotemporal distributions of larval cisco and lake whitefish among multiple Lake Ontario embayment nursery areas, characterised physical habitat features associated with their distributions, determined the degree of spatial habitat partitioning between species and evaluated how habitat niche divergence occurred along an ontogenetic progression. Both species were widely distributed across larval nursery areas, though lake whitefish were less abundant and more narrowly distributed than cisco. Within the yolk sac stage, lake whitefish occupied more nearshore, shallower and colder waters than cisco, indicating potential habitat niche partitioning between congeners. However, distributional differences were subtle and likely driven by differential hatch timing and staggered ontogenetic habitat shifts. Combined, our results illustrate similar habitat use between cisco and lake whitefish through the larval stage and demonstrate that ontogeny and species-specific phenology influence habitat use for these species. This study provides additional evidence that the early life histories of cisco and lake whitefish are highly similar and does not support the hypothesis that larval habitat use differences are a major driver of differential recruitment success for these species.

New York↗

USGS2023

Evaluation of threatened, endangered, and rare fish species and communities of the St. Lawrence River and its tributaries in the United States

Biodiversity is responsible for important ecological processes like productivity and ecosystem stability, and rare species are a major component of biodiversity. Rarity increases a species' vulnerability to disturbances and also makes them difficult to study. Globally, species of freshwater systems are some of the most threatened, and evaluation of rare freshwater species and their habitats is needed to help preserve natural flexibility and ecological function. We conducted an analysis of full fish communities of the upper St. Lawrence River and its major US tributaries, with the goals of determining species locations and abundances, associated environmental conditions, the distribution of distinct fish assemblages across the landscape (with emphasis on communities supporting rare species), and potential threats. From 2009 to 2015, the US Geological Survey (USGS) and Saint Regis Mohawk Tribe (SRMT) worked together using standardized methods to collect community samples within 4 different aquatic realms (shallow and deep lentic, and small and large lotic systems) and determine species-specific fish abundances, frequencies of occurrence, and associated habitat signatures and spatial distributions. Distinct fish assemblages and associated habitat conditions were objectively identified by multivariate and hypothesis-testing methods. We used a geographic information system (GIS) to spatially associate habitat, biotic, and landscape attributes within each stream reach throughout the study area, facilitating quantification of distribution patterns. Comparisons with historical data provided estimates of loss or gain of threatened and endangered species (T&E) colonies. We developed a disturbance index to highlight potential threats to aquatic species. More than 140,000 fishes of 87 species were collected from a total of 1140 sample sites, covering 278 stream reaches, including the endangered Notropis anogenus (Pugnose Shiner), and threatened Hiodon tergisus (Mooneye), Etheostoma pellucidum (Eastern Sand Darter), and Acipenser fulvescens (Lake Sturgeon). We identified 50 distinct fish assemblages differing in species composition, abundance, and/or diversity, but only 13 of those assemblages included a T&E species. The rareness, extent, and patchiness of fish assemblages created a mosaic of fish communities across the landscape, from headwaters to the mainstem of the St. Lawrence River. Comparisons with historic surveys (1978–2008) showed a stable number of T&E species colonies or an increase for some species. The geographic distribution of multimetric disturbance index values showed where combinations of disturbances to fish habitats might affect rare fish species and aquatic communities in the region. The species–habitat associations and fish assemblage distributions can be used for evaluation of species, communities, or habitats that may need protection or restoration.

St. Lawrence River study area↗

USGS2022

Decision support for aquatic restoration based on species-specific responses to disturbance

Disturbances to aquatic habitats are not uniformly distributed within the Great Lakes and acute effects can be strongest in nearshore areas where both landscape and within lake effects can have strong influence. Furthermore, different fish species respond to disturbances in different ways. A means to identify and evaluate locations and extent of disturbances that affect fish is needed throughout the Great Lakes. We used partial Canonical Correspondence Analysis to separate “natural” effects on nearshore assemblages from disturbance effects. Species-specific quadratic models of fish abundance as functions of in-lake disturbance or watershed-derived disturbance were developed separately for each of 35 species and lakewide predictions mapped for Lake Erie. Most responses were unimodal and more species decreased in abundance with increasing watershed disturbance than increased. However, eight species increased in abundance with current in-lake disturbance conditions. Optimum Yellow Perch ( Perca flavescens ) abundance occurred at in-lake disturbance values less than the gradient mean, but decreased continuously from minimum watershed disturbance to higher values. Bands of optimum in-lake conditions occurred throughout the eastern and western portions of the Lake Erie nearshore zone; some areas were less disturbed than desirable. However, watershed-derived disturbance conditions were generally poor for Yellow Perch throughout the lake. In contrast, optimum Smallmouth Bass ( Micropterus dolomieu ) abundance occurred at in-lake disturbance values greater than the gradient mean and continuously increased with increasing watershed disturbance. Smallmouth Bass responses to disturbance indicated that most of the nearshore zone was less disturbed than is desirable and were most abundant in areas that the Yellow Perch response indicated were highly disturbed. Mapping counts of species response models that agreed on the disturbance level in each spatial unit of the nearshore zone showed a fine-scale mosaic of areas in which habitat restoration may benefit many or few species. This tool may assist managers in prioritizing conservation and restoration efforts and evaluating environmental conditions that may be improved.

Great Lakes↗

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↗

USGS2021

Composition and distribution of fish environmental DNA in an Adirondack watershed

Background Environmental DNA (eDNA) surveys are appealing options for monitoring aquatic biodiversity. While factors affecting eDNA persistence, capture and amplification have been heavily studied, watershed-scale surveys of fish communities and our confidence in such need further exploration. Methods We characterized fish eDNA compositions using rapid, low-volume filtering with replicate and control samples scaled for a single Illumina MiSeq flow cell, using the mitochondrial 12S ribosomal RNA locus for taxonomic profiling. Our goals were to determine: (1) spatiotemporal variation in eDNA abundance, (2) the filtrate needed to achieve strong sequencing libraries, (3) the taxonomic resolution of 12S ribosomal sequences in the study environment, (4) the portion of the expected fish community detectable by 12S sequencing, (5) biases in species recovery, (6) correlations between eDNA compositions and catch per unit effort (CPUE) and (7) the extent that eDNA profiles reflect major watershed features. Our bioinformatic approach included (1) estimation of sequencing error from unambiguous mappings and simulation of taxonomic assignment error under various mapping criteria; (2) binning of species based on inferred assignment error rather than by taxonomic rank; and (3) visualization of mismatch distributions to facilitate discovery of distinct haplotypes attributed to the same reference. Our approach was implemented within the St. Regis River, NY, USA, which supports tribal and recreational fisheries and has been a target of restoration activities. We used a large record of St. Regis-specific observations to validate our assignments. Results We found that 300 mL drawn through 25-mm cellulose nitrate filters yielded greater than 5 ng/µL DNA at most sites in summer, which was an approximate threshold for generating strong sequencing libraries in our hands. Using inferred sequence error rates, we binned 12S references for 110 species on a state checklist into 85 single-species bins and seven multispecies bins. Of 48 bins observed by capture survey in the St. Regis, we detected eDNA consistent with 40, with an additional four detections flagged as potential contaminants. Sixteen unobserved species detected by eDNA ranged from plausible to implausible based on distributional data, whereas six observed species had no 12S reference sequence. Summed log-ratio compositions of eDNA-detected taxa correlated with log(CPUE) (Pearson’s R = 0.655, P < 0.001). Shifts in eDNA composition of several taxa and a genotypic shift in channel catfish ( Ictalurus punctatus ) coincided with the Hogansburg Dam, NY, USA. In summary, a simple filtering apparatus operated by field crews without prior expertise gave useful summaries of eDNA composition with minimal evidence of field contamination. 12S sequencing achieved useful taxonomic resolution despite the short marker length, and data exploration with standard bioinformatic tools clarified taxonomic uncertainty and sources of error.

New York↗

USGS2021

Acoustic tag retention and tagging mortality of juvenile cisco Coregonus artedi

Release of hatchery-reared juvenile cisco ( Coregonus artedi ) is an important tool for recovering Great Lakes populations, but post-release survival is unknown. Telemetry using small acoustic tags provides opportunities to assess the efficacy of hatchery-reared fish releases. However, better understanding of the tolerance of juvenile cisco to acoustic tags is needed. Juvenile cisco mortality and tag retention as a function of tag size:body size (Relative Tag Weight, RTW) was observed for 30 d post tag implantation in the laboratory. Tag loss and mortality increased with RTW. A single mortality occurred for RTW ≤ 3% and tag retention and survival was <50% for RTW > 7.0%. Logistic regression predicted >95% survival and tag retention to 30 d for RTW < 2.5%, with full survival of study fish for RTW of ≤2%. Sedation and surgery times did not affect survival of tagged fish, but results of anesthesia-only and sham surgeries highlight the need to minimize handling effects for effective acoustic telemetry studies. Our findings clarify thresholds of RTW and indicate that juvenile cisco can receive acoustic tag implants. Observing these limitations can improve the effectiveness of acoustic telemetry to assess success of cultured juvenile fish releases for conservation or restoration of native forage fish populations. Evaluation of the effects of acoustic tags over longer time periods and under environmental conditions, like those at release sites, are needed to further validate this technology.

Journal of Great Lakes Research↗

USGS2020

Habitat characterization and species distribution model of the only large-lake population of the endangered Silver Chub (Macrhybopsis storeriana, Kirtland 1844)

The endangered Silver Chub ( Macrhybopsis storeriana, Kirtland 1844) is native to North America and primarily riverine, with the only known large‐lake population in Lake Erie. Once a major component of the Lake Erie fish community, it declined and became nearly extirpated in the mid‐1900s. Recent collections in western Lake Erie suggest that Silver Chub may be able to recover, but their habitat and distribution are poorly known. A recent work showed an extensive area of western Lake Erie with the potential to support large numbers of Silver Chub, but was based on a geographically limited dataset. We developed a neural network‐based species distribution model for the Silver Chub in western Lake Erie, improved by new synoptic data and using habitat variables resistant to anthropogenic activities. The Potential model predictions were compared with a model that included anthropogenic‐sensitive variables. The Potential model used 10 habitat variables and performed well, explaining > 99% of data variation and had generally low error rates. Predictions indicated that a large area of the waters approximately 2–9 m deep contained Appropriate habitat and the highest abundances should be supported by habitat in a wide arc through the western end of the basin. The model indicated that Appropriate Silver Chub habitat was associated with relatively deep water, near coastal wetlands, where effective fetch is less than average. Disturbance model predictions were similar, but predicted poorer Silver Chub habitat in more areas than that predicted by the Potential model. Our Potential model reveals Appropriate habitat conditions for Silver Chub and its spatial distribution, indicating that extensive areas of western Lake Erie could support Silver Chub. Comparisons with Disturbance model predictions demonstrate that Potential model predictions may be used in conjunction with analyses of degrading conditions in the system to better conserve and manage for this endangered species.

Michigan, Ohio↗

USGS2020

Does fecundity of cisco vary in the Upper Great Lakes?

Fecundity of fish is influenced by several factors, including body length, condition, population density, and environmental conditions. It follows that fecundity of fish populations can exhibit spatiotemporal variability; thus, periodic quantification of length–fecundity relationships is important for management. We hypothesized that average fecundity of Cisco Coregonus artedi in the upper Laurentian Great Lakes would be lower in Lake Superior than in Lakes Huron and Michigan. The trophic status of these lakes recently converged, but Lakes Huron and Michigan currently support lower Cisco densities; thus, we expected that they would reach larger sizes and have greater fecundity owing to lower intraspecific competition. Ovaries were collected from prespawn Cisco during 2008–2010 to test this hypothesis. We also compared length–fecundity relationships for 2008–2010 to those of precollapse (1930s–1950s) populations to explore how relationships have changed. Average fecundity of Cisco during 2008–2010 was lower in Lake Superior compared to Lakes Huron and Michigan; length–fecundity relationships in the latter two lakes did not vary significantly, so they were combined. Body condition was highest in Lakes Huron and Michigan. We used otoliths to determine age and found that body condition was domed shaped with respect to age in Lakes Huron and Superior. There were no females older than age 5 in our samples from Lake Michigan because that population was just beginning to recover from very low levels. Females of intermediate age had the highest fecundities in both Lake Huron (ages 7–13) and Lake Superior (ages 8–18). We hypothesize that differences in body morphometry may also influence fecundity, with deeper‐bodied C. artedi albus , the predominant form in Lakes Michigan and Huron, having greater fecundity than shallower‐bodied C. artedi artedi in Lake Superior. Moreover, varying Cisco diets and seasonal movement patterns across lakes may have also contributed to differences. Females in Lakes Superior and Michigan are currently more fecund than their precollapse counterparts.

Great Lakes↗

USGS2020

Spatial segregation of cisco (Coregonus artedi) and lake whitefish (C. clupeaformis) larvae in Chaumont Bay, Lake Ontario

Abstract Two of the remaining coregonine species in Lake Ontario, cisco (Coregonus artedi) and lake whitefish (C. clupeaformis), spawn in Chaumont Bay, NY. Larvae co-occur in the spring but are difficult to distinguish morphologically. We applied genetic species identification using microsatellite DNA loci of 268 larvae from known locations in nearshore and offshore habitats in Chaumont Bay to determine the extent of mixing of these species in each habitat. Cisco dominated (95% of larvae) the larvae in offshore habitats and lake whitefish dominated (84%) in nearshore habitats, where seven of eight putative hybrids occurred. Habitat segregation between these two species at the larval stage has implications for productivity estimates. Discrimination between cisco and lake whitefish larvae helps to characterize habitat and basic life history needs and to focus research collections. Genetic species identification should be applied to larger samples of larvae to evaluate changes in larval distributions and associations with environmental conditions.

Chaumont Bay↗