The chemical composition of lake water and inflowing river water was investigated in Nam Co (lake), Tibetan Plateau, in September 2005. Lake water samples (n = 76) were collected at different depths along a south-north transect of the eastern part of the lake while water samples were collected from 69 rivers flowing into the lake; a sediment core was collected at 64 m midway along the water survey transect to investigate salt precipitation. Na⁺ and Ca²⁺ were the dominant cations, accounting for 76.2% and 60.6% of the lake and river water cations, respectively while was the dominant anion accounting for 70.8% and 93.4% of lake and river anions, respectively. CaCO₃ precipitation from the water column decreased Ca²⁺ in the lake water, with the relative proportion of other ions increasing significantly. Evaporation-crystallization processes largely control Nam Co lake-water chemistry, while rock weathering is the dominant processes influencing the chemistry of river water; carbonate and silicate weathering are the major sources of ions in these rivers.

We assessed changes in Lake Ontario Zooplankton biomass, production, and community composition before (1987–1991) and after (2001–2005) invasion-induced ecosystem changes. The ecosystem changes were associated with establishment of invasive dreissenid mussels and invasive predatory cladocerans (Bythotrephes and Cercopagis). Whole-lake total epilimnetic plus metalimnetic Zooplankton production declined by approximately half from 42.45 (g dry wt·m^-2·year^-1) during 1987–1991 to 21.91 (g dry wt·m^-2·year^-1) in 2003 and averaged 21.01 (g dry wt·m^-2·year^-1) during 2001–2005. Analysis of two independent data sets indicates that the mean biomass and biomass proportion of cyclopoid copepods declined while the same measures increased for the invasive predatory cladocerans. Changes in means and proportions of all other Zooplankton groups were not consistent between the data sets. Cyclopoid copepod biomass and production declined by factors ranging from 3.6 to 5.7. Invasive predatory cladoceran biomass averaged from 5.0% to 8.0% of the total Zooplankton biomass. The Zooplankton community was otherwise resilient to the invasion-induced disruption as Zooplankton species richness and diversity were unaffected. Zooplankton production was likely reduced by declines in primary productivity but may have declined further due to increased predation by alewives and invasive predatory cladocerans. Shifts in Zooplankton community structure were consistent with increased predation pressure on cyclopoid copepods by alewives and invasive predatory cladocerans. Predicted declines in the proportion of small cladocerans were not evident. This study represents the first direct comparison of changes in Lake Ontario Zooplankton production before and after the invasion-induced disruption and will be important to food web-scale investigations of invasion effects.

The Clinton River watershed near Detroit, Michigan, USA was separated in six different land uses: agricultural, residential, mixed industrial and residential, downstream industrial, Clinton River Spillway, and Lake St. Clair, utilizing As, Cd, Cu, Ni, Pb, and Zn contents of the sediment that has median values of 3, 0.3, 15, 14, 13, and 57 mg kg^-1, respectively. However, trace element concentrations in the lower Clinton River rivaled those in the most contaminated watersheds of the world. Enrichment factors and principal component analysis (PCA) separated trace elements into 2 categories: anthropogenic (Cd, Cu, Ni, Pb, and Zn) and geogenic (Al, As, Ca, Fe, K, Mg, TOC) sources. PCA linked agricultural, residential, and mixed industrial and residential land uses to anthropogenic Cd, Cu, Ni, Pb, and Zn, and lake sediments to geogenic elements, organic matter and clay contents. The downstream industrial zone has a unique source signature. Trace element concentrations varied with land use. The upper Clinton River (>20 km from mouth; residential land use; median concentrations up to 25 mg kg^-1) appeared to meet delisting criteria. Partitioning was also land use and element specific with: (1) exchangeable fraction (up to 94% of total) related to road salt and mobile chloride complex formation; (2) carbonate-bound fraction (up to 100%) resulting from Ca substitution or adsorption; (3) presence of immobile (hydr)oxide-bound fraction (up to 90%) instead of potentially mobile organic matter and sulphide-bound fraction (up to 20%); and (4) residual fraction (up to 65%) originating from geogenic and/or anthropogenic sources.

We evaluated whether or not the invasive round goby (Neogobius melanostomus) represents an important prey source for seven native fish predators in Lake St. Pierre (St. Lawrence River, Canada). The frequency of occurrence of round goby in the stomach contents of brown bullhead (Ameiurus nebulosus) and channel catfish (Ictalurus punctatus) was very low (<5%), while for the five other predators, it varied between 22% (yellow perch; Perca flavescens) and 65% (sauger; Sander canadensis). Several competing models linking the probability of occurrence of round goby in stomach contents to variables related to space, physical habitat, biotic interactions and predator size were tested for the five species feeding on round goby. Results indicated that space variables influenced round goby occurrence in stomachs for all species. In addition, physical habitat variables had an influence for sauger and walleye (Sander vitreus); biotic variables had an influence for yellow perch, walleye and sauger; and size had an influence for northern pike (Esox lucius), smallmouth bass (Micropterus dolomieu) and walleye. These results are discussed in light of known biological features of the round goby and native predators studied here and have important implications in terms of understanding round goby invasion success in the Great Lakes-St. Lawrence system.

We compared round goby (Neogobius melanostomus) population structure and biomass, estimated the quantity of prey consumed by round goby and assessed predation on round goby in two areas of the Bay of Quinte (upper and lower bay) that were invaded by this species two years apart. A bioenergetics approach was used to estimate round goby consumption and to illustrate the influence of changes in the round goby biomass, from May to October in both areas of the bay. Mean round goby biomass was 5 tonnes/km² for the upper bay and 11.2 tonnes/km² for the lower bay. Round goby populations were dominated by age-0 to age-2 individuals; older individuals were rare although they constituted a greater portion of total biomass in the earlier invaded lower bay than the upper bay. Estimated round goby consumption was 78.4 tonnes/km² for the upper bay and 127.1 tonnes/km² for the lower bay; dreissenids were the most important prey followed by chironomids, Zooplankton and amphipods. Diet analysis showed that round gobies were consumed by all predator species analyzed, and constituted a high percentage of stomach content biomass in yellow perch (Perca flavescens), largemouth bass (Micropterus salmoides) and northern pike (Esox lucius). Age structure differences between the upper and lower bay are consistent with those expected between expanding and stable populations.

Ecological classifications of stream ecosystems have been used to develop monitoring programs, identify reference and impacted systems, and focus conservation efforts. One of the most influential, but highly variable, components of stream ecosystems is water temperature but few geographically broad-scale and long-term programs exist to assess and monitor temperatures. This study evaluated if existing ecological classifications could be used to categorize the similarities and differences in stream temperatures across the Ontario portion of the Great Lakes Basin. Concordance between the spatial variability in temperatures and an existing ecological classification would support the use of that classification to define areas with similar temperatures, guide the development of a monitoring program, and inform management programs. The five classifications evaluated were the ecoregions and ecodistricts defined in the National Ecological Framework for Canada, the ecoregions and ecodistricts defined in the Ecological Land Classification of Ontario, and the aquatic ecosystem units defined in the Aquatic Ecosystem Classification (AEC) for the Ontario portion of the Great Lakes Basin. Hierarchical linear modelling and corrected Akaike Information Criterion indicated that the ecodistrict classifications characterized more of the spatial variability in temperatures than the ecoregion and AEC classification but temperatures were more variable among sites within classes than between classes. Therefore, none of the existing ecological classifications could be used to characterize thermal variability. Future research should examine if the inability of the existing classifications to capture the thermal variability translates into inaccurate classification of other ecosystem components such as water quality, and macroinvertebrate and fish assemblages.

Thiaminase induced thiamine deficiency occurs in fish, humans, livestock and wild animals. A non-radioactive thiaminase assay was described in 2007, but a direct comparison with the radioactive ¹⁴C-thiamine method which has been in use for more than 30 years has not been reported. The objective was to measure thiaminase activity in forage fish (alewife Alosa pseudoharengus, rainbow smelt Osmerus mordax, and slimy sculpin Cottus cognatus) consumed by predators that manifest thiamine deficiency using both methods. Modifications were made to the colorimetric assay to improve repeatability. Modification included a change in assay pH, enhanced sample clean-up, constant assay temperature (37 °C), increase in the concentration of 4-nitrothiophenol (4NTP) and use of a spectrophotometer fitted with a 0.2 cm cell. A strong relationship between the two assays was found for 51 alewife (R² = 0.85), 36 smelt (R² = 0.87) and 20 sculpin (R² = 0.82). Thiaminase activity in the colorimetric assay was about 1000 times higher than activity measured by the radioactive method. Application of the assay to fish species from which no thiaminase activity has previously been reported resulted in no 4NTP thiaminase activity being found in bloater Coregonus hoyi, lake trout Salvelinus namaycusch, steelhead trout Oncorhynchus mykiss or Chinook salmon Oncorhynchus tshawytscha. In species previously reported to contain thiaminase, 4NTP thiaminase activity was measured in bacteria Paenibacillus thiaminolyticus, gizzard shad Dorosoma cepedianum, bracken fern Pteridium aquilinum, quagga mussel Dreissena bugensis and zebra mussels D. polymorpha.

The Great Lakes Water Quality Agreement specifies “fish tumors or other deformities” as one of the 14 beneficial use impairments that can be used to declare a geographic area within the Great Lakes an Area of Concern (AOC). The International Joint Commission has suggested that the fish tumor impairment can be delisted when fish tumor incidence in the AOC does not exceed rates at unimpacted control sites. This paper presents a statistical technique utilizing Bayesian hierarchical logistic models to estimate tumor incidence on brown bullheads (Ameiurus nebulosus) in an AOC and in candidate least impacted control sites (LICS). Liver and skin tumor incidence are estimated using age, length, weight, and gender as possible covariates using a hierarchical framework to account for a sampling design in which sites are sampled over multiple years and/or at multiple sublocations within the site. By utilizing a Bayesian approach, estimates of uncertainty for tumor incidence in sites with no observed tumors can be obtained. The posterior distributions of tumor incidence can then be used to identify LICS for the watershed and subsequently compare the tumor incidence in the AOC to the LICS using a Bayesian form of the two one-side tests for equivalence procedure. Presque Isle Bay (Erie, PA) in the Lake Erie watershed is used as a case study to demonstrate the technique.

Features of light absorption are critical to optical aspects of water quality and in regulating the signal available for remote sensing. Spectral characteristics and spatial patterns of light-absorbing components, and their relationships with optically active constituents, are documented for the Sturgeon River, Keweenaw Bay, and Lake Superior based on analyses of samples collected on two cruises (2006 and 2007, 20 sites). The absorption coefficient, a (m^-1), is partitioned according to the additive components (a_x) of colored dissolved organic matter (a_CDOM). non-algal particles (a_NAP), phytoplankton (a_φ;), and water itself (a_w; known). The role of minerogenic particles and their iron content in regulating a_NAP is evaluated based on paired measurements by an individual particle analysis technique (Peng et al., 2009), through empirical analyses and Mie theory calculations of absorption by these particles (a_m). Spectral characteristics of a_NAP and a_φ; were consistent with those reported for other case 2 (i.e., phytoplankton not dominant) systems. However, the slope values that describe a_CDOM spectra for the bay and the lake were unusually low, suggesting an atypical composition for the lake's CDOM. The dominant absorbing component in the blue wavelengths was CDOM, representing ≥ 75% of a at a wavelength of 440 nm at all sites in the 2006 survey. A general gradient in both a_CDOM and a_NAP extended from the Sturgeon River, through the bay, into eastern Lake Superior in that survey. Relationships between a_x and optically active constituents were within the broad ranges reported for other case 2 systems. Minerogenic particles, related to their iron content, are demonstrated to be an important component of a_NAP.

Lake Michigan's Sheboygan Reef is contained in a refuge for lake trout (Salvelinus namaycush) restoration, and is one of several deep midlake reefs that historically were productive spawning and fishery grounds. The summits of these reefs are rocky and deeper than the photic zone. We propose that the basis of trophic support for lake trout and their prey is allochthonous and based, at least in part, on the principle of “topographic blockage” of descending vertical migrators (Mysis diluviana), as has been proposed for oceanic seamounts. We estimated slimy sculpin (Cottus cognatus) and Mysis densities via ROV (unmanned submersible) electroshocking and collected slimy sculpins for diet analyses via ROV and beam trawl. Slimy sculpin densities were greater or similar to that for its shallow-water (photic zone) congener, the mottled sculpin (C. bairdi), and not distinguishable from a random distribution. Mysis densities were highly contagious. The diet of the slimy sculpin was variable: Mysis typically predominated, followed by Diporeia and midge larvae. We argue that Mysis and Diporeia originate from off Sheboygan Reef because the summit of Sheboygan Reef is much shallower than the preferred daytime depth of Mysis and there is no suitable soft substrate for Diporeia, which is a burrowing amphipod. The probable mechanism for delivery of these two prey to Sheboygan Reef is topographic blockage.

Measurements were made along the northwestern shore of Lake Erie, Canada to determine whether grain magnetic properties can be used to identify and distinguish sources of beach sediment. Although surface magnetic susceptibilities were highly variable, ranging from 56 to 9867 × 10^-5 SI (Bartington MS2D), there was generally a gradual increase from the low beach (near the waterline) towards the high beach; there were also narrow, shore-parallel bands with high susceptibility at various points on the beach surface. Magnetic mineralogy on the beaches was dominated by low-Ti magnetite (570°<Tc<580 °C), and the effective grain-size varied from pseudosingle domain in the low beach to multidomain on the high beach. Sandy bluff sediments in the eastern part of the study area had magnetic properties (e.g. S-ratios, hysteresis loops, thermomagnetic curves) that were similar to those on the beaches, whereas the magnetic properties of the extensive till bluffs and river basin sediments were quite different. The data suggested that, whereas the beaches in the western part of the study area are supplied with sediment from bluffs several tens of kilometres to the east, the source of the high magnetic concentrations on the eroding beaches of eastern Point Pelee remains to be determined.

Light-scattering attributes of minerogenic particles from the water column of the western basin of Lake Erie (13 sites, plus one from the central basin and one from Sandusky Bay), collected after a wind event, were characterized by scanning electron microscopy interfaced with automated image and X-ray analyses (SAX). SAX results specified scattering attributes for individual particles, including size and chemical composition, and were used in forward Mie theory calculations of minerogenic scattering and backscattering coefficients (b_m and b_b,m). Clay mineral particles, in the size range of 1–20 µm, were the dominant form of minerogenic scattering, representing > 75% of b_m and b_b,m. Levels of b_m and b_b,m were high in the western basin, apparently in part due to wind-driven sediment resuspension, and wide spatial variability was observed. The credibility of the SAX-Mie estimates of b_m and b_b,m was supported by the extent of optical closure obtained with paired bulk measurements of particulate scattering and backscattering coefficients (b_p and b_bp), and independent estimates of organic particle contributions based on empirical bio-optical models. Minerogenic particles dominated b_p and particularly b_bp, and regulated spatial differences in the related common metrics of optical water quality, including turbidity and clarity. The bbp:b_p ratio was found to be a good predictor of the spatial differences in the relative contributions of minerogenic particles versus phytoplankton to scattering.

The depth selection behaviors of juvenile mysids, Mysis diluviana, exposed to different temperature and light gradients in the laboratory were compared to those observed in previous studies on adult mysids to determine whether mysid light and temperature preferences have an ontogenetic component. Juvenile mysids most strongly preferred 11 °C, which is 5 °C higher than those most preferred by adults, but both size classes completely avoided temperatures of 16 °C and greater. Juveniles and adults preferred light levels between 10^-5 and 10^-6 lx, or ∼10^-7 and 10^-8 “mylux” — a unit of brightness specific for mysid vision; however, juveniles did not display avoidance behaviors until 10^-0.6 mylux (∼44 lx), compared to adults which avoid light levels of 10^-3 mylux, or ∼0.1 lx, and above. Because the differences in preferences between juveniles and adults were more pronounced in relation to temperature than to light, we expect stronger vertical separation of mysid size classes during periods of the year when the water column is thermally stratified versus isothermal. We present limited field data and review past literature to support this hypothesis, as juvenile mysids are typically found higher in the water column than adults, especially during periods of the year when the water column is thermally stratified. This study is one of the first to demonstrate that ontogenetic differences in light and temperature preferences lead to habitat partitioning in a mysid species and highlights the often underreported importance of juvenile mysids to food web structure and function in open waters above the thermocline.

Fecal loading to beach sands and subsequent transport to surface water may result in the degradation of surface water quality. To better understand the relationship between Escherichia coli in sands, beach hydrology, and recreational water quality, we collected surface water, groundwater, and sand samples from three Lake Michigan beaches with varying substrates (fine sand to pebbles, July 2005—June 2006). Sediment cores collected within transects perpendicular to and at fixed distances from the shoreline (0 m, 10 m, 20 m) and surface water samples collected at a depth of 1 m were analyzed for E. coli. Grain size analysis was performed on duplicate core samples to assess the relationship between E. coli density and mean grain size and uniformity. Groundwater samples, collected from shallow drive-point piezometers within the test area, were also analyzed for E. coli. E. coli density in beach sands differed significantly with distance from shore with the highest density occurring at the berm crest (0 m). Mean grain size and uniformity accounted for variation in E. coli density with fine sand of uniform distribution having the highest content. E. coli density in surface water was correlated to E. coli density in beach sand samples at the berm crest. E. coli in groundwater was <10 to 579 MPN/100 ml (2005); none was detected in 2006. Management interventions, including altered beach grooming practices and slope assessments, may be effective in reducing E. coli content at beaches comprised of fine sands of uniform grain size, hence reducing water quality advisories.

Nitrate concentrations in Lake Superior increased fivefold between 1900 and 1980, and have remained nearly constant since that time. Such rapid changes in concentration in a lake with a long hydraulic residence time (∼190 years) are surprising. We developed a model to better understand the causes of the historical changes and to predict future changes in nitrate concentrations. Historical loadings were reconstructed based on average national NO_x emissions estimates, recent (past ∼30 years) atmospheric N deposition data, recent tributary concentration data, and basin-wide runoff estimates. Increases in atmospheric N deposition alone were insufficient to have resulted in the observed trends. However, model runs combining increased atmospheric deposition with increased tributary N loading and/or decreased burial denitrification mid-century reproduced the observed accumulation of N. Because internal N fluxes are an order of magnitude greater than external fluxes, relatively small changes in the lake's internal N cycle may produce relatively large changes in total N concentrations. Land-use changes in the watershed, particularly increases in logging activity, may have altered riverine N inputs. Regardless of the historical mechanisms leading to the rise in nitrate concentrations, it appears as though the system is currently at or is approaching peak N content.

Near-shore surface sediment of the St. Clair River (Ontario) extending along 9 km of waterfront downstream of local industries were contaminated with mercury (Hg), hexachlorobenzene, hexachlorobutadiene and octachlorostyrene based on data collected in 2006 and 2008. However, unlike Hg, concentrations of organic compounds were low at most stations suggesting improvements in sediment quality since 2001 (post sediment remediation projects). Concentrations of Hg were greater than Provincial Sediment Quality Guidelines and ranged as high as 41 µg/g in the surficial 0–5 cm sediment. Measured (2001–2004 data) and estimated (2006 data) concentrations of methyl Hg in invertebrates were greater than concentrations in invertebrates collected from upstream reference stations. Predicted methyl Hg concentrations in walleye using food chain multipliers, benthic invertebrate Hg tissue concentrations and current sediment concentrations exceeded human health consumption guidelines and were consistent with measured sport fish data supporting assumptions about Hg biomagnification. Historical data showed that for fish collected from the lower St. Clair River and Lake St. Clair, Hg concentrations have declined since 1978, but have remained stable since the mid 1980s, consistent with the sediment Hg data. The consistency in the sediment and fish datasets and the absence of a known significant local point source of Hg suggests that the sediment may be an important source of Hg to the St. Clair River food-chain.

In situ measurements of inherent (IOPs) and apparent optical properties (AOPs), along with laboratory measurements of optically active constituents, were made at sites (n = 14) in western Lake Erie following a wind event to advance the characterization of the underwater and emergent light fields of these waters and to support related IOP-based model development and testing. Modern instrumentation was used to make spectral (wavelength,λ) measurements of the IOPs of absorption [a(λ)], particulate scattering ]b_p(λ)], and particulate backscattering [b_bp(λ)] coefficients, and the AOPs of remote sensing reflectance ]R_rs(λ)], and the diffuse attenuation coefficient for downwelling irradiance [K_d(λ)], Optical closure analyses were conducted to demonstrate the credibility of the measurements, by comparing AOP observations to predictions based on radiative transfer expressions that utilized IOP measurements as inputs. Substantial spectral variations in a and its contributing components, and more modest wavelength dependencies for b_p and b_bp, were documented that are consistent with observations reported for marine case 2 systems. The backscattering ratio, b_bp:b_p, was strongly positively related to the contribution of minerogenic particles to the overall concentration of suspended particulate material. Major spatial differences in both IOPs and AOPs were observed that were driven by the attendant differences in the concentrations and composition of the optically active constituents, but particularly minerogenic particles, mediated in part by sediment resuspension. Good optical closure between the independently measured IOPs and AOPs was achieved. Direct measurement of b_bp(λ) was found to be critical to pursue closure for R_rs(λ) and thereby support related remote sensing initiatives.

As part of a study to develop recommendations for non-indigenous species (NIS) monitoring in Great Lakes areas at risk of invasion, we conducted intensive sampling in the Duluth-Superior Harbor and lower St. Louis River in 2005 and 2006. Of the ∼240 benthic invertebrate taxa identified, 19 were non-indigenous, including 8 first detection records for this system: New Zealand mud snail Potamopyrgus antipodarum; African/Asianorigin cladoceran Daphnia lumholtzi; Eurasian-origin amphipod Echinogammarus ischnus; Eurasian-origin bivalves Dreissena bugensis, Pisidium henslowanum and Pisidium supinum; and possibly range expanding oligochaetes Paranais frici and Pristina acuminata. Dreissenids were by far the most abundant NIS. Several other NIS were also common, but others were detected in only a few of the >200 samples taken. Non-indigenous amphipods and Dreissena were most frequently detected in sweep net and colonization plate samples of littoral vegetation, while NIS oligochaetes, gastropods, and non-dreissenid bivalves were most frequently detected in ponar and bottom sled samples of sediments. Our findings confirm that this major shipping port remains a NIS “hotspot” and emphasize that regular surveys covering a range of habitats with multiple sampling gears and thorough taxonomic effort are needed to detect and monitor non-indigenous species.

Classification is a valuable conservation tool for examining natural resource status and problems and is being developed for coastal aquatic habitats. We present an objective, multi-scale hydrospatial framework for nearshore areas of the Great Lakes. The hydrospatial framework consists of spatial units at eight hierarchical scales from the North American Continent to the individual 270-m spatial cell. Characterization of spatial units based on fish abundance and diversity provides a fish-guided classification of aquatic areas at each spatial scale and demonstrates how classifications may be generated from that framework. Those classification units then provide information about habitat, as well as biotic conditions, which can be compared, contrasted, and hierarchically related spatially. Examples within several representative coastal or open water zones of the Western Lake Erie pilot area highlight potential application of this classification system to management problems. This classification system can assist natural resource managers with planning and establishing priorities for aquatic habitat protection, developing rehabilitation strategies, or identifying special management actions.

Coastal wetland vegetation along the Great Lakes differs strongly with latitude, but most studies of Great Lakes wetland condition have attempted to exclude the effect of latitude to discern anthropogenic effects on condition. We developed an alternative approach that takes advantage of the strong relationship between latitude and coastal wetland floristic condition. Latitude was significantly correlated with 13 of 37 environmental variables tested, including growing degree days, agriculture, atmospheric deposition, nonpoint-source pollution, and soil texture, which suggests that latitude is a good proxy for several environmental drivers of vegetation. Using data from 64 wetlands along the U.S. coast of Lakes Huron, Michigan, Erie, and Ontario, we developed linear regressions between latitude and two measures of floristic condition, the Floristic Quality Index (FQI, adj. r2= 0.437, p<0.001) and the first axis scores from a non-metric multidimensional scaling of wetland plant cover (MDS1, adj. r2 = 0.501, p<0.001). Departures from the central tendency of these regression models represented wetlands of better or worse condition than expected for their latitude. This approach provides a means to identify wetlands worthy of preservation, to establish vegetation targets for wetland restoration, and to forecast changes in floristic quality associated with future climate change.

Habitat plays an essential role in shaping aquatic communities yet limited information on the type and distribution of bottom features is available in the form of detailed maps. This is especially apparent in large systems where obtaining such information can be both expensive and challenging. Current maps of Lake Michigan substrate are very general and lack suitable detail of substrate composition and geographic extent of rocky areas. This limits our ability to link biological processes, such as fish spawning, to nearshore habitat and makes it difficult to target structurally complex habitats for sampling. We compiled substrate information gathered over 72 years for Illinois waters and incorporated it into a CIS framework to generate more complete documentation of sediment type and particle size distribution in southwestern Lake Michigan. Sediment data for 1682 sites were standardized to phi units; natural neighbor interpolation was used during GIS analysis to predict sediment type in areas lacking data. Predicted sediment values based on this interpolation had a significant positive relationship with observed sediment values (R² = 0.92). Further, we linked existing fishery (yellow perch Perca flavescens) data with newly generated substrate information to identify potential associations between spawning site selection and habitat. Tagging data indicated that substrate quality affected the likelihood of yellow perch returning to their release sites in subsequent spawning seasons; higher fidelity was associated with larger, coarser substrate. The generated map will be a useful tool to enhance our understanding of habitat's importance in the Great Lakes, particularly when linked with fishery data.

Sea lamprey invaded the Great Lakes in the early 20th century and caused an abrupt decline in the population densities of several native fish species. The integrated management of this invasive species is composed of chemical (lampricide) applications, low-head barrier dams, adult trapping and sterile male release. Recently, there has been an increased emphasis on the development of control methods alternative to lampricide applications. We propose as an alternative-control method the use of chemosensory cues as repellents for sea lamprey population management. Based on the available evidence at this time, we suggest that injury-released chemical alarm cues show promise as repellents for sea lamprey and further research should be directed at determining whether sea lamprey show an avoidance response to these types of chemosensory cues. From a management perspective, these chemosensory cues could be used to restrict sea lamprey access to spawning grounds. Repellents could also be used together with attractants like sex pheromones to manipulate sea lamprey behavior, similar to the “push-pull” strategies utilized with insect pests.

In fall 2009, six migrating silver American eels (Anguilla rostrata) originating from a stocking program were caught in the brackish waters of the St. Lawrence Estuary. These maturing eels were all females with gonads developed at a similar stage as other migrating eels in the estuary. Fluorescent Oxytetracycline marks observed on the otoliths allowed us to assert without any doubt that they came from glass eels caught in Nova Scotia and stocked 4 years earlier in the Richelieu River, 500 km upstream from the recapture location. Their length varied between 570 and 668 mm, which is within the size range of naturally recruited female silver eels in Nova Scotia, while silver eel are most generally longer than 80 cm in the St. Lawrence estuary. Their growth rate was also exceptionally fast. This direct observation is the first evidence that American eels stocked as glass eels can migrate seaward at least as far as the estuary in synchrony with naturally recruited female silver eels en route to their spawning grounds in the Sargasso Sea.

Natal philopatry in lake sturgeon (Acipenser fulvescens) has been hypothesized to be an important factor that has lead to genetically distinct Great Lakes populations. Due to declining abundance, population extirpation, and restricted distribution, hatchery supplementation is being used to augment natural recruitment and to reestablish populations. If hatchery-reared lake sturgeon are more likely to stray than naturally produced individuals, as documented in other well-studied species, outbreeding could potentially jeopardize beneficial site-specific phenotypic and genotypic adaptations. From 1983 to 1994, lake sturgeon propagated using eggs taken from Lake Winnebago adults (Lake Michigan basin) were released in the St. Louis River estuary in western Lake Superior. Our objective was to determine whether these introduced individuals have strayed into annual spawning runs in the Sturgeon River, Michigan. Additionally, we estimated a natural migration rate between the Sturgeon River and Bad River, Wisconsin populations. Presumed primiparous lake sturgeon sampled during Sturgeon River spawning runs from 2003 to 2008 were genotyped at 12 microsatellite loci. Genotypic baselines established for the Sturgeon River (n = 101), Bad River (n = 40), and Lake Winnebago river system (n = 73) revealed a relatively high level of genetic divergence among populations (mean F_ST = 0.103; mean R_ST = 0.124). Likelihood-based assignment tests indicated no straying of stocked Lake Winnebago strain lake sturgeon from the St. Louis River into the Sturgeon River spawning population. One presumed primiparous Sturgeon River individual likely originated from the Bad River population. Four firstgeneration migrants were detected in the Sturgeon River baseline, indicating an estimated 3.5% natural migration rate for the system.