Lake Erie Tributaries Research Articles

Assessing potential barriers to migratory Walleye in the Sandusky River, Ohio

AbstractObjectiveThe Sandusky River, Ohio, is one of the major Lake Erie tributaries that supports migratory Walleye Sander vitreus reproduction. Following the construction of the Ballville Dam in 1913, Walleye spawning was limited to an area downstream near Fremont, Ohio. After the removal of the dam in 2018, several natural and human‐made features were identified that may impede Walleye passage by collecting woody debris and altering flow conditions. In this study, we use hydrologic modeling and migratory sampling to understand the spatial and temporal dynamic nature of the blockages caused by the remaining anthropogenic and natural barriers.MethodsWe created a fine‐scale Hydrologic Engineering Center's River Analysis System (HEC‐RAS) model to examine these potential natural and human‐made barriers to Walleye passage during spawning. Using our model, we compared swim speeds (10 min maintained and burst) of small, medium, and large Walleye under three flow scenarios with five levels of blockage to assess whether the area was passable. Further, we conducted electrofishing surveys during annual spawning runs from 2020 to 2021 to assess Walleye presence upstream and downstream after dam removal.ResultOur model predicted that Walleye were able to pass the barriers under most of the scenarios by maintaining burst swim speed. Additionally, we captured Walleye above the former dam site in 2021, suggesting that Walleye can access newly available spawning habitat during certain river conditions.ConclusionRemoving the Ballville Dam restored fish passage, increased access to spawning habitat, and could improve Walleye production in the Sandusky River.

Controls on in-stream nitrogen loss in western Lake Erie tributaries

Management efforts to reduce cyanobacterial harmful algal blooms (cHABs) in the Great Lakes have focused on decreasing tributary inputs of phosphorus (P). Recent research has indicated that reduction of both P and nitrogen (N) can lessen cHABs severity. Microbially mediated N cycling in streambed sediment may reduce N riverine loads, yet little is known about in-stream N processing rates in the Maumee River Basin, a major source of nutrients to Lake Erie. During summer of 2019 and 2021, we sampled streambed sediment to measure potential nitrification and denitrification rates using the acetylene block method at 78 sites throughout the Maumee River network. We used structural equation models to identify indirect and direct drivers of denitrification. Precipitation was greater in 2019, resulting in a 67 % increase in mean discharge, 41 % of farm fields to be fallow, and a 50 % reduction in fertilizer use. During summer field surveys, median stream-water nitrate concentrations were not different between 2019 and 2021. Median denitrification rates were 13.3 mg N/m2/h and 31.2 mg N/m2/h, respectively, indicating high potential to remove N. Nitrate concentrations and nitrification rates were strong direct drivers of denitrification, especially in 2019 when coupled nitrification–denitrification sustained denitrification. Nitrate concentrations varied with land use. Notably, nitrate concentrations increased with the area of fallow land, which may indicate the presence of a legacy N source. These findings indicate that promoting streambed denitrification could reduce N loads to Lake Erie, but legacy N currently stored in the system may mask N reduction efforts.

Drivers of annual suspended sediment and nutrient yields in tributaries to Lake Erie

Abstract In the early 2000s, harmful algal blooms and hypoxia returned to Lake Erie following a period of ecosystem recovery from the late 1980s through the 1990s. This corresponds to a drastic increase in dissolved reactive phosphorus loads and flow-weighted mean concentrations in the major tributaries to the Western Lake Erie Basin. However, there is substantial variability in suspended sediment and nutrient yields across Lake Erie tributaries. It is well known that agricultural and urban land uses lead to increased watershed sediment and nutrient yields, especially in the absence of proper management practices. Yet attributes such as watershed soil types and slope can also affect yields. We examined the influence of watershed land use, hydrology, soil type, and slope on annual nutrient and sediment yields from tributaries to Lake Erie monitored as part of the Heidelberg Tributary Loading Program. A minimum of one sample and, during storm runoff, up to three samples a day are analyzed for all major nutrients and suspended sediments. The 5-year average annual yields across these watersheds exhibited distinct geographic patterns from west to east, with high suspended sediment but lower nutrient yields from the eastern most tributaries (Cuyahoga, Old Woman Creek, Huron) and the lowest sediment along with lower nutrient yields from the western most tributaries (Raisin, Tiffin, Lost). The Maumee, Portage, Sandusky, along with select subwatersheds tended to have intermediate sediment yields with high nutrient yields. Altogether, the % cultivated crops and poorly drained soil in the watershed increased nutrient yields whereas a higher % slope and lower % pasture increased sediment yields. These patterns highlighted unique regional differences that can help guide management decisions for these watersheds that ultimately would improve the health of Lake Erie.

Postrelease Survival and Migration Behavior of Adult Walleye Following Intracoelomic Transmitter Implantation Using Two Methods of Electro‐Immobilization

AbstractThe use of electricity as a method of fish restraint (i.e., electro‐immobilization) during field and hatchery operations has increased recently, and a need exists for field‐based assessments of the effects of these techniques on the postrelease physiology, behavior, and survival of wild fish to develop best handling practices. Two common waveforms used in electro‐immobilization are continuous and pulsed DC (cDC and pDC, respectively). With cDC, fish are immobilized through exposure to a continuous weak current and recover almost immediately once the current ceases. With pDC, fish are incapacitated via brief exposure to a strong current and often require several minutes to recover (i.e., regain equilibrium). Here, we present a comparison of cDC and pDC electro‐immobilization techniques and their effects on the postrelease survival and spawning migration behavior of adult Walleye Sander vitreus in a Lake Erie tributary. Fish were intracoelomically implanted with acoustic transmitters and then tracked by a network of acoustic receivers throughout Lake Erie that provided extensive spatiotemporal coverage of posttagging movements. Survival did not differ between the two electro‐immobilization treatments but was somewhat lower than in a control group consisting of fish tagged several years earlier (e.g., 50‐d survival = 69% for the pDC group, 61% for the cDC group, and 90% for control fish). We did not find any plausible or biologically meaningful effects of treatment on downstream movement or migratory behavior over subsequent months postrelease. Our results suggest that the two electro‐immobilization techniques did not differ in their effects on adult Walleye behavior, but more work is needed to elucidate the extent to which electro‐immobilization in general contributes to potential decreases in survival versus other aspects of capture and handling associated with performing surgical procedures.

Influence of Steelhead Trout Stocking Size and Location on Emigration and Adult Returns

AbstractEffective stocking programs are an essential part of maintaining most high‐quality tributary steelhead Oncorhynchus mykiss fisheries in the Great Lakes, requiring sufficient numbers of stocked fish to survive, imprint, and return as adults. New York’s Lake Erie tributaries have long supported popular and economically important recreational steelhead fisheries, attracting anglers from across the country. Recent research has illustrated New York’s dependence on “stray” steelhead from other jurisdictions, making New York fisheries vulnerable to other agencies’ management decisions. We hypothesized that the limited contribution by New York‐stocked steelhead was attributable to poor poststocking survival and imprinting due to the smaller stocking size relative to other Lake Erie jurisdictions. We took an experimental approach to describe how the combination of stocking size and within‐stream stocking location interact to influence emigration and adult returns and identify mechanisms that may be driving these relationships, with the goal of identifying stocking strategies that improve adult returns. Stocked steelhead >150 mm total length emigrated from the stream by the end of May; small‐size steelhead tended to remain in the stream and exhibited upstream migration. The residual population of steelhead lost body condition and likely experienced high mortality. Adult returns from large‐size fish that were stocked 6.4 km upstream were 4.1 times greater than small‐size fish stocked upstream and six times greater than fish stocked near the lake confluence (0.8 km upstream). We conclude that many of the steelhead stocked by New York are too small to imprint and emigrate, instead remaining as stream residents that experience poor survival and ultimately make minimal contributions to the adult fishery. Increases in the stocking size of New York steelhead coupled with stocking well upstream of the lake confluence would result in increased adult returns of New York‐stocked fish to their streams of origin and improved fishery performance and resiliency.

Lake Erie tributary nutrient trend evaluation: Normalizing concentrations and loads to reduce flow variability

Establishing tributary load (i.e., the mass exported over a period of time) targets to reduce anthropogenic nutrient inputs to receiving waters — and thus eutrophication — is a common mitigation strategy in freshwater and coastal ecosystems. However, detecting and quantifying trends can be difficult because annual precipitation strongly influences tributary flow (e.g., average daily stream discharge). This may obscure trends as wet years tend to produce high tributary loads despite management activities to reduce nutrient export, and dry years typically generate low loads, even without management of nutrients. Furthermore, flow and nutrient concentrations are often correlated. Earlier efforts to reduce the effect of flow variability on tributary nutrient assessment were limited by computational and methodological constraints, until the weighted regressions on time, discharge, and season (WRTDS) method was introduced in 2010. Here we use WRTDS to assess nutrient concentration and load changes from 1982 to 2018 in three tributaries to the western basin of Lake Erie, of the Laurentian Great Lakes. Generally, trends revealed by flow-normalization do not contradict those of non-normalized metrics; however flow-normalization made the patterns more perceptible than in non-normalized metrics and reduced the influence of a particularly wet or dry period at the end of records on long-term trend analysis. We demonstrate that using WRTDS for flow-normalization removed the noise arising from annual precipitation variability and makes tributary nutrient trend evaluation more straightforward.

An adaptive management approach for implementing multi-jurisdictional response to grass carp in Lake Erie

The Great Lakes are influenced by established aquatic invasive species (AIS) and the threat of new invaders persists. Grass carp, one of four species commonly referred to as Asian carp, are considered invasive because of their ability to adversely modify aquatic habitat through consumption of aquatic macrophytes. Grass carp have been infrequently detected in the Great Lakes since the mid-1980s. More frequent reports of grass carp captures from commercial fishermen in the early 2010’s elevated the concern of the potential risk of colonization in Lake Erie. This paper provides a case study detailing the development and implementation of a multi-jurisdictional response strategy for grass carp in Lake Erie. To respond to threats of grass carp in Lake Erie, Michigan and Ohio Departments of Natural Resources led targeted responses using a collaborative multi-jurisdictional approach, while simultaneously investing in reducing critical life-history uncertainties to refine strategies in an adaptive and science-based manner. Efforts to address uncertainties about grass carp life history documented spawning in two Lake Erie tributaries. Building on these early responses, the binational Lake Erie Committee developed a five-year adaptive response framework to guide response actions. The collaborative response efforts resulted in the capture and removal of 184 fertile grass carp since 2014, and efforts are ongoing to increase effectiveness of strategies to achieve desired population reduction. Coordinated grass carp response actions under the five-year strategy will continue using adaptive management principles with outcomes providing useful insights for adapting existing response frameworks and more broadly for AIS responses implemented elsewhere.

Seasonal migration and fine‐scale movement of invasive round goby (Neogobius melanostomus) in a Great Lakes tributary

AbstractTo determine whether invasive round goby (Neogobius melanostomus) from Lake Ontario were establishing a year‐round population in a tributary stream or migrating to the lake, we assessed population and individual movement patterns using mark–recapture assessment generated from weekly backpack electrofishing from May until November 2016. Round goby abundance was low in spring, peaked in summer and decreased again in autumn, suggesting seasonal inward stream migration and outward migration back to the lake. Adult round goby movement patterns were positively associated with changes in water temperature, but this was not the case for juveniles. Juveniles displayed a preference for shallow, upstream habitats. Observations of reproductive individuals coupled with a peak in juvenile abundance following the peak in adult abundance indicate that the tributary was used for reproduction and recruitment. The individual movement was primarily upstream in spring, and there was little net movement in summer, likely during reproduction. Downstream movement occurred in autumn over a short time period, suggesting rapid outmigration to the lake. The combined observations of seasonal population structure and individual movement suggest that tributary streams connected to large, infested waterbodies can be used for round goby reproduction and recruitment, rather than year‐round residence. This study provides evidence of round goby seasonal migration and their individual movement patterns within tributary streams, which complements an earlier study in Lake Erie tributaries and may be a common occurrence in other Great Lakes tributaries.

Discrete Organic Phosphorus Signatures are Evident in Pollutant Sources within a Lake Erie Tributary.

Phosphorus loads are strongly associated with the severity of harmful algal blooms in Lake Erie, a Great Lake situated between the United States and Canada. Inorganic and total phosphorus measurements have historically been used to estimate nonpoint and point source contributions, from contributing watersheds with organic phosphorus often neglected. Here, we used ultrahigh resolution mass spectrometry to characterize the dissolved organic matter and specifically dissolved organic phosphorus composition of several nutrient pollutant source materials and aqueous samples in a Lake Erie tributary. We detected between 23 and 313 organic phosphorus formulas across our samples, with manure samples having greater abundance of phosphorus- and nitrogen containing compounds compared to other samples. Manures also were enriched in lipids and protein-like compounds. The greatest similarities were observed between the Sandusky River and wastewater treatment plant effluent (WWTP), or the Sandusky River and agricultural edge of field samples. These sample pairs shared 84% of organic compounds and 59-73% of P-containing organic compounds, respectively. This similarity suggests that agricultural and/or WWTP sources dominate the supply of organic phosphorus compounds to the river. We identify formulas shared between the river and pollutant sources that could serve as possible markers of source contamination in the tributary.

Increased nutrient concentrations in Lake Erie tributaries influenced by greenhouse agriculture

Greenhouse production of vegetables is a growing global trade. While greenhouses are typically captured under regulations aimed at farmland, they may also function as a point source of effluent. In this study, the cumulative impacts greenhouse effluents have on riverine macronutrient and trace metal concentrations were examined. Water samples were collected Bi-weekly for five years from 14 rivers in agriculturally dominated watersheds in southwestern Ontario. Nine of the watersheds contained greenhouses with their boundaries. Greenhouse influenced rivers had significantly higher concentrations of macronutrients (nitrogen, phosphorus, and potassium) and trace metals (copper, molybdenum, and zinc). Concentrations within greenhouse influenced rivers appeared to decrease over the 5-year study while concentrations within non-greenhouse influenced river remained constant. The different temporal pattern between river types was attributed to increased precipitation during the study period. Increases in precipitation diluted concentrations in greenhouse influenced rivers; however, non-influenced river runoff proportionally increased nutrient mobility and flow, stabilizing the observed concentrations of non-point sources. Understanding the dynamic nature of environmental releases of point and non-point sources of nutrients and trace metals in mixed agricultural systems using riverine water chemistry is complicated by changes in climatic conditions, highlighting the need for long-term monitoring of nutrients, river flows and weather data in assessing these agricultural sectors.

Application of Otolith Chemistry to Investigate the Origin and State‐Straying of Steelhead in Lake Erie Tributaries

AbstractIn Lake Erie, the fishery for steelhead Oncorhynchus mykiss is overwhelmingly dominated by stocking from state agencies in Michigan, New York, Pennsylvania, and Ohio. Managers that stock steelhead may become concerned if a sizeable portion of the fish they stock do not return to the waters in which they were released and instead stray to other states (“state‐straying”). During fall 2009, spring 2010, and spring and fall 2015, we evaluated the origin and state‐straying of adult steelhead in five annually stocked tributaries of Lake Erie. We also investigated spatial differences in the origin and state‐straying of adult steelhead at different stream locations in two tributaries during 2015. Otolith chemistry signatures were first used to discriminate among yearling steelhead from each of the state hatcheries that stock Lake Erie and wild juveniles from Cattaraugus Creek, New York, and the Grand River, Ontario, resulting in a mean jackknifed classification accuracy of 88% (range = 72–100%). Otolith chemistry analysis was then performed on unknown‐origin adult steelhead collected in Lake Erie tributaries during the fall and spring spawning runs, and natal sources were identified by using source‐specific otolith chemical signatures. State‐strays averaged 46% (range = 13–88%) of the adult fish collected, and high percentages of strays were identified in Chautauqua Creek, New York (72%), and Cattaraugus Creek (88%). Steelhead collections in these New York tributaries during a second year revealed that the percentage of strays present was consistently high, and large proportions of strays were identified in both upstream and downstream locations. These results suggest that state‐straying is widespread in Lake Erie tributaries and that strays make up a large proportion of New York's Lake Erie tributary fishery. Strategies to reduce straying may include practicing upstream releases and reducing the number of hatchery fish that are released in some states.

Application of Otolith Chemistry to Investigate the Origin and State-straying of Steelhead in Lake Erie Tributaries

Application of Otolith Chemistry to Investigate the Origin and State-straying of Steelhead in Lake Erie Tributaries

Novel aspects of stocked juvenile steelhead emigration patterns as revealed using dual-frequency identification sonar

Abstract We used a Dual-Frequency Identification Sonar (DIDSON) near the mouth of a small Lake Erie tributary to monitor juvenile steelhead emigration. Data were recorded continuously over two stocking seasons (April–May 2014; April–June 2015) and total emigration counts were determined every hour. Fish lengths at time of emigration were estimated using the DIDSON fish measuring tool and quantified through time. Percent survival to emigration was high with > 71% of individuals reaching the river mouth in both years. Photoperiod was the best predictor of peak emigration timing, and steelhead were most likely to emigrate at night. Larger individuals were more likely to emigrate shortly after stocking; however, the size range of fish that emigrated throughout the study period was wide. Residual population estimates performed after the DIDSON sampling period revealed that in both years 2 months after stocking. Most of these fish (63%) were

Spawning site fidelity and apparent annual survival of walleye (Sander vitreus) differ between a Lake Huron and Lake Erie tributary

AbstractFidelity to spawning habitats can maximise reproductive success of fish by synchronising movements to sites of previous recruitment. To determine the role of reproductive fidelity in structuring walleye Sander vitreus populations in the Laurentian Great Lakes, we used acoustic telemetry combined with Cormack–Jolly–Seber capture–recapture models to estimate spawning site fidelity and apparent annual survival for the Tittabawassee River in Lake Huron and Maumee River in Lake Erie. Walleye in spawning condition were tagged from the Tittabawassee River in Lake Huron and Maumee River in Lake Erie in 2011–2012. Site fidelity and apparent annual survival were estimated from return of individuals to the stream where tagged. Site fidelity estimates were higher in the Tittabawassee River (95%) than the Maumee River (70%) and were not related to sex or fish length at tagging. Apparent annual survival of walleye tagged in the Tittabawassee did not differ among spawning seasons but was higher for female than male walleye and decreased linearly as fish length increased. Apparent annual survival of walleye tagged in the Maumee River did not differ among spawning seasons but was higher for female walleye than male walleye and increased linearly as fish length increased. Greater fidelity of walleye tagged in the Tittabawassee River than walleye tagged in the Maumee River may be related to the close proximity to the Maumee River of other spawning aggregations and multiple spawning sites in Lake Erie. As spawning site fidelity increases, management actions to conserve population structure require an increasing focus on individual stocks.

Hydrologic and biogeochemical controls on phosphorus export from Western Lake Erie tributaries

Understanding the processes controlling phosphorus (P) export from agricultural watersheds is essential for predicting and mitigating adverse environmental impacts. In this study, discharge, dissolved reactive P load, total P load, and suspended sediment time-series data (1975–2014) from two Lake Erie tributaries, the Maumee and Sandusky rivers, were evaluated to determine whether hydrologic or biogeochemical processes were responsible for observed patterns in P export. Findings indicate that hydrologic processes in these watersheds controlled P loading patterns, as P export was transport-limited (i.e., P loading was strongly correlated to watershed discharge) and P concentrations exhibited effective chemostatic behavior (i.e., low variability in concentration relative to discharge). The nature and behavior of observed P transport likely stems from a large, ubiquitous source of P present within each watershed as results were similar to those found for geogenic constituents (i.e., silica). Results suggest that changes in both precipitation patterns (e.g., precipitation variability) and watershed hydrologic response (e.g., water residence time) are likely explanations for observed increases in water and P loading in the Maumee and Sandusky watersheds. Future P loading in these watersheds should be expected to continue to be proportional to water flux as long as the magnitude and availability of the P source remains at its current level. Current P management strategies may therefore need to be reevaluated to better balance agricultural P requirements and watershed P loadings.

Do intracoelomic telemetry transmitters alter the post‐release behaviour of migratory fish?

AbstractElectronic tags have become a common tool in fish research, enhancing our understanding of how fish interact with their environment and move among different habitats, for estimating mortality and recording internal physiological states. An often‐untested assumption of electronic tagging studies is that tagged fish are representative of untagged conspecifics and thus show ‘normal’ behaviour (e.g. movement rates, swimming activity, feeding). Here, we use a unique data set for potamadromous walleye (Sander vitreus) in Lake Huron and Lake Erie tributaries to assess whether the lack of appropriate controls in electronic tagging could seriously affect behavioural data. We used fish tagged in previous years and compared their migratory behaviour during the spawning season to fish tagged in a current year at the same location. The objective of the study was to determine whether intracoelomic acoustic tag implantation altered downstream movement of walleye after spawning. Fish tagged in a given season travelled slower downstream from two river spawning sites than fish tagged in previous years. Fish tagged one or two years earlier showed no differences between each other in downstream travel time, in contrast to fish tagged in a given year. Our results support notions that standard collection and intracoelomic tagging procedures can alter short‐term behaviour (i.e. days, weeks, months), and as such, researchers should use caution when interpreting data collected over such time periods. Further, whenever possible, researchers should also explicitly evaluate post‐tagging effects on behaviour as part of their experimental objectives.

Sampling Little Fish in Big Rivers: Larval Fish Detection Probabilities in Two Lake Erie Tributaries and Implications for Sampling Effort and Abundance Indices

AbstractLarval fish are frequently sampled in coastal tributaries to determine factors affecting recruitment, evaluate spawning success, and estimate production from spawning habitats. Imperfect detection of larvae is common, because larval fish are small and unevenly distributed in space and time, and coastal tributaries are often large and heterogeneous. We estimated detection probabilities of larval fish from several taxa in the Maumee and Detroit rivers, the two largest tributaries of Lake Erie. We then demonstrated how accounting for imperfect detection influenced (1) the probability of observing taxa as present relative to sampling effort and (2) abundance indices for larval fish of two Detroit River species. We found that detection probabilities ranged from 0.09 to 0.91 but were always less than 1.0, indicating that imperfect detection is common among taxa and between systems. In general, taxa with high fecundities, small larval length at hatching, and no nesting behaviors had the highest detection probabilities. Also, detection probabilities were higher in the Maumee River than in the Detroit River. Accounting for imperfect detection produced up to fourfold increases in abundance indices for Lake Whitefish Coregonus clupeaformis and Gizzard Shad Dorosoma cepedianum. The effect of accounting for imperfect detection in abundance indices was greatest during periods of low abundance for both species. Detection information can be used to determine the appropriate level of sampling effort for larval fishes and may improve management and conservation decisions based on larval fish data.Received August 12, 2013; accepted March 7, 2014

First evidence of grass carp recruitment in the Great Lakes Basin

We use aging techniques, ploidy analysis, and otolith microchemistry to assess whether four grass carp Ctenopharyngodon idella captured from the Sandusky River, Ohio were the result of natural reproduction within the Lake Erie Basin. All four fish were of age 1+. Multiple lines of evidence indicate that these fish were not aquaculture-reared and that they were most likely the result of successful reproduction in the Sandusky River. First, at least two of the fish were diploid; diploid grass carp cannot legally be released in the Great Lakes Basin. Second, strontium:calcium (Sr:Ca) ratios were elevated in all four grass carp from the Sandusky River, with elevated Sr:Ca ratios throughout the otolith transect, compared to grass carp from Missouri and Arkansas ponds. This reflects the high Sr:Ca ratio of the Sandusky River, and indicates that these fish lived in a high-strontium environment throughout their entire lives. Third, Sandusky River fish were higher in Sr:Ca ratio variability than fish from ponds, reflecting the high but spatially and temporally variable strontium concentrations of southwestern Lake Erie tributaries, and not the stable environment of pond aquaculture. Fourth, Sr:Ca ratios in the grass carp from the Sandusky River were lower in their 2011 growth increment (a high water year) than the 2012 growth increment (a low water year), reflecting the observed inverse relationship between discharge and strontium concentration in these rivers. We conclude that these four grass carp captured from the Sandusky River are most likely the result of natural reproduction within the Lake Erie Basin.

Thermal and hydrologic suitability of Lake Erie and its major tributaries for spawning of Asian carps

Bighead carp Hypophthalmichthys nobilis, silver carp H. molitrix, and grass carp Ctenopharyngodon idella (hereafter Asian carps) have expanded throughout the Mississippi River basin and threaten to invade Lakes Michigan and Erie. Adult bighead carp and grass carp have been captured in Lake Erie, but self-sustaining populations probably do not exist. We examined thermal conditions within Lake Erie to determine if Asian carps would mature, and to estimate time of year when fish would reach spawning condition. We also examined whether thermal and hydrologic conditions in the largest tributaries to western and central Lake Erie were suitable for spawning of Asian carps. We used length of undammed river, predicted summer temperatures, and predicted water velocity during flood events to determine whether sufficient lengths of river are available for spawning of Asian carps. Most rivers we examined have at least 100km of passable river and summer temperatures suitable (>21C) for rapid incubation of eggs of Asian carps. Predicted water velocity and temperature were sufficient to ensure that incubating eggs, which drift in the water column, would hatch before reaching Lake Erie for most flood events in most rivers if spawned far enough upstream. The Maumee, Sandusky, and Grand Rivers were predicted to be the most likely to support spawning of Asian carps. The Black, Huron, Portage, and Vermilion Rivers were predicted to be less suitable. The weight of the evidence suggests that the largest western and central Lake Erie tributaries are thermally and hydrologically suitable to support spawning of Asian carps.

Channel substrate prediction from GIS for habitat estimation in Lake Erie tributaries

The conservation of ecologically and economically important species, as well as the management of invasive species, benefits from the ability to make broad-scale predictions of habitat. In this paper, we revised an existing substrate size model based upon stream power to include variables that are readily-quantifiable in a Geographic Information System (GIS) (i.e. stream slope and drainage area). We found no significant difference between slopes measured in the field using surveying techniques and slopes measured in a GIS using a 10 m digital elevation model and high resolution stream dataset. GIS-derived drainage areas and those measured with hand-delineations were also statistically similar. The revised model can be applied using both GIS and field-derived variables to predict median particle sizes from stream power in northeastern Ohio streams draining to Lake Erie. Integration of such models into a GIS could result in regional estimates of the amount and location of preferred fish habitat, which has important applications in fisheries management. In particular, we provide examples of how the predictive substrate model could improve assessment methodologies for invasive sea lamprey, thereby improving eradication measures, and how we may better understand geographic linkages between walleye spawning and nursery habitats.