Determining the habitat limitations of Maumee River walleye production to Western Lake Erie fish stocks

Transcription

1 The University of Toledo The University of Toledo Digital Repository Theses and Dissertations 2017 Determining the habitat limitations of Maumee River walleye production to Western Lake Erie fish stocks Brian A. Schmidt University of Toledo Follow this and additional works at: Recommended Citation Schmidt, Brian A., "Determining the habitat limitations of Maumee River walleye production to Western Lake Erie fish stocks" (2017). Theses and Dissertations This Thesis is brought to you for free and open access by The University of Toledo Digital Repository. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of The University of Toledo Digital Repository. For more information, please see the repository's About page.

2 A Thesis entitled Determining the Habitat Limitations of Maumee River Walleye Production to Western Lake Erie Fish Stocks by Brian A. Schmidt Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master of Science Degree in Biology Dr. Christine Mayer, Committee Chair Dr. Edward Roseman, Committee Member Dr. Richard Becker, Committee Member Dr. Richard Kraus, Committee Member Dr. Patricia R. Komuniecki, Dean College of Graduate Studies The University of Toledo May 2016

3 Copyright 2016, Brian Anthony Schmidt This document is copyrighted material. Under copyright law, no parts of this document may be reproduced without the expressed permission of the author.

4 An Abstract of Determining the habitat limitations of Maumee River Walleye Production to Western Lake Erie by Brian A. Schmidt Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master of Science Degree in Biology The University of Toledo May 2016 Tributaries support diverse spawning habitats for three of the four major substocks of Lake Erie walleye (Sander vitreus). Despite a long history of anthropogenic degradation and the extirpation of other potamodromous species, the Maumee River continues to support one of the largest fish migrations in the Laurentian Great Lakes. To determine if spawning habitat availability and quality could limit production of Maumee River walleye, the longitudinal distribution and relative abundance of walleye eggs deposited in a 34 km stretch of river were assessed. Eggs were collected using a diaphragm pump at ten sites in 2014 and eight sites in 2015 from mid-march to early May. In both years, a sharp decline in mean relative abundances from downstream spawning sites than upstream sites at river kilometer 30 suggest that spawning habitat connectivity in the Maumee River is lower than was previously known, and may be limiting production from the system. iii

5 I would like to dedicate my thesis work to my family and friends who have supported my throughout my time at the University of Toledo. I would like to express my gratitude to my parents, Paul and JoAnn Schmidt, for being supportive of my endeavors and instilling in me a strong set of morals and values. I would like thank my sister Allison for her sarcastic, yet genuine insight as she works towards her Master s degree at the University of Clemson. She pushes me to remain the favorite child. Also, special consideration to Jessica Meyer, Jacob Gahart, and Seth Nelson for being voices of reason and support when times were tough.

6 Acknowledgements I wish to thank my committee members, Dr. Edward Roseman, Dr. Richard Kraus, and Dr. Richard Becker, for providing insight and knowledge throughout the course of my project. A special thanks to my advisor Dr. Christine Mayer for the amount of work she put in reading and reviewing my work, and challenging me become a better writer and scientist. My sincere gratitude is given to Dr. Chris Vandergoot for his interest and involvement in my project. Finally, I would like to thank my fellow lab members, Dustin Bowser, Jeremy Pritt, Jessica Sherman, Mark DuFour, Ryan Andrews, Ben Kuhaneck, Rachel Johnson, Kristen Hebebrand, and Wendy Stevens for their help in the field and in the lab. v

7 Table of Contents Abstract... iii Acknowledgements...v Table of Contents... vi List of Tables... viii List of Figures... ix List of Abbreviations...x Chapter1. Determining the Habitat Limitations of Maumee River Walleye Production to Western Lake Erie Fish Stocks Introduction Methods Study Area Egg Collection Spawning Habitat Data Collection Spatial Analyses Comparison of Water Velocity to Walleye Swimming Speed Results Longitudinal Distribution of Walleye Egg Seasonal Trends 14 vi

8 1.3.3 Identification and Quantification of Spawning Habitat Comparison of water velocity to walleye swimming speed Comparisons between spawning Substrate and Egg Deposition Discussion Explaining Connectivity Loss Management Implications References...26 Tables 30 Figures.. 35 vii

9 List of Tables 1.1 Estimated annual walleye egg distribution in the Maumee River Areal coverage estimates based on substrate and depth in the lower 56km of Maumee River Summary of site descriptions for egg collection Areal coverage estimates based on substrate and depth downstream of Jerome Rapids Estimates of total egg deposition and habitat requirements of walleye in the Maumee River...34 viii

10 List of Figures 1-1 Annual larval production of walleye in the western basin of Lake Erie Map of study area, the Maumee River, Northwest, Ohio Satellite image of barrier at Jerome Rapids Mean relative abundance of walleye eggs in 2014 and Seasonal discharge and water temperatures relative to egg deposition in Seasonal discharge and water temperatures relative to egg deposition in Map of walleye spawning habitat suitability in the Maumee River Cross Sectional Velocity at Jerome Rapids compared to Walleye Swim Speeds Longitudinal distribution and relative abundance of walleye eggs compared to habitat suitability map in 2014 and Location of water treatment plant relative to Jerome Rapids Aerial photograph of Jerome Rapids...45 ix

11 List of Abbreviations rk...river Kilometers [Note: River kilometers measured as distance from the mouth of the river. WAE...Walleye (Sander vitreus) WTG..Walleye Task Group, subcommittee of Great Lakes Fish Commission m/s...meters per second x

12 Chapter 1 Determining Habitat Limitations of Maumee River Walleye Production to Western Lake Erie Fish Stocks Habitat loss and degradation is a major contributor to species decline and extinction (Tilman et al. 1994; Fahrig 1997; Pimm and Raven 2000). Rivers provide critical habitat for migratory fish species by connecting ocean and lake habitats to spawning grounds but are often subject to high levels of anthropogenic stress. Rivers that enter coastal areas of large systems, such as oceans or the Great Lakes, are often especially degraded habitats because of high densities of people, industrial development, and agricultural effluents (Hartman 1972; Karr et al. 1985). These impairments may reduce connectivity to spawning areas for both sensitive species and stocks of more abundant commercially or recreationally important fish species. Therefore, identifying and quantifying impairment to river habitat connectivity is important to conservation and management of migratory fish. The Maumee River, Ohio provides critical spawning and nursery habitat for many native potamodromous fish in Lake Erie including walleye (Sander vitreus), Morone spp., and many non-game species. The Maumee River is the largest tributary to western Lake Erie (Karr et al. 1985), which produces more fish biomass than any other area of the Great Lakes (Leach and Nepszy 1976). This site may house the largest migration of 1

13 potamodromous fish in North America and provides critical habitat connecting the lake to spawning areas. However, several species that historically spawned in the Maumee have been extirpated (e.g. muskellunge (Esox musquinongy), northern pike (Esox luscious), and lake sturgeon (Acipenser fulvescens); Karr et al. 1985). Many of the extirpated species were lithophilic spawners, and require the same clean, hard substrate for spawning and egg incubation as walleye. Optimal spawning conditions for walleye include well oxygenated water, moderate water velocity ( m/s), depths from 0.5 to 2.0 meters, and gravel, cobble substrates (Lowie et al. 2001). Therefore, identifying and quantifying the availability of current walleye spawning habitat within the system will inform potential habitat restoration actions that might increase river connectivity for walleye and other more sensitive species in the Maumee River. Although relatively abundant, walleye in Lake Erie experience large annual fluctuations in year class strength (Hartman 1973; Mion et al. 1998; Roseman et al. 2000; Vandergoot et al. 2010). The population is supported by dominant year classes, leading to an unbalanced size and age structure (Vandergoot et al. 2010) and high variability. Relatively weak recruitment has led to steadily declining population estimate of age 2+ walleye since 2005 (WTG 2015). Therefore, understanding sources of variability in walleye population recruitment requires knowledge of existing spawning and egg incubation habitat. The Maumee watershed historically was predominantly wetland, but was drained for logging and agriculture in the mid-19 th century (Richards 2009). The river is dammed in several locations, with the first dam being 56 km upstream of the mouth. Dams present a physical barrier to longitudinal migrations and create spatially segregated stocks. There 2

14 are two water treatment facilities in the study area, one just upstream of the mouth of the river and one at river kilometer (distance upstream from the mouth) 30. The lower 17 km of the river have been dredged and channelized for shipping. The culmination of these anthropogenic changes has resulted in a drastically altered system prone to high flashiness and sedimentation. Sedimentation decreases embeddedness of gravel and cobble substrates, reducing spawning habitat suitability and egg survival for walleye and other lithophilic spawning fish (Hartman 1973). Flood pulses are more severe due to the loss of wetlands and channelization, because energy can no longer be dissipated upstream of spawning areas (Zedler and Kercher 2005). High discharge events may limit upstream migration of walleye at one of the many set of rapids in the Maumee River. There are several sets of rapids that occur from river kilometers (rk) 30, 37, 41, and 44. Increased water velocity at any one of these set of rapids may cause a restriction point to upstream migration, and thus limit connectivity to historic upstream spawning locations in the Maumee River. Jerome Rapids, located at (rk) 30, appears to be the upstream end of current walleye spawning extent. In addition, the increased intensity of flood pulses result in increased egg and larval mortality by dislodging eggs from favorable areas and placing additional physical stress on the eggs and larval fish (Mion et al. 1998; Jones et al. 2003). Walleye productivity is related to the quantity and quality of available spawning habitat (Schupp 1978; Kerr et al. 1997). Reduced egg and larval survival can be partially attributed to variability in environmental factors including temperature, wind and wave action, flood pulses (Mion et al. 1998; Roseman et al. 2001). The early life history stages in walleye are one of the critical periods that will determine year class strength and recruitment of the walleye spawning stock in a given year (Mion et al. 1998, 3

15 Roseman et al. 2000, Ludsin et al. 2014). Therefore, environmental conditions and connectivity of spawning habitat to source populations may limit stock productivity. The Lake Erie walleye population consists of primarily four separate stocks; one that spawns over an open lake reef complex, and three potamodromous stocks that migrate into the lake s major rivers: the Maumee, Detroit, and Sandusky (Hartman 1973, Trautman 1981, Manny et al. 2007). Currently, larval production is dominated by the reef stock, with lesser production from the three riverine stocks (Figure 1, data from DuFour et al. 2015). The Lake Erie walleye population is unique in regards to the Laurentian Great Lakes because only four stocks contribute to the lake-wide populations. In contrast, 37 different stocks contribute to the Lake Huron population, and so poor recruitment from a given stock is relatively inconsequential in terms of lake-wide recruitment. Spawning habitat diversity provides a system of checks and balances that help reduce recruitment variability in the system (DuFour et al. 2015). However, production from river stocks requires that high quality habitat is available and accessible to fish migrating from the lake. Increasing production from riverine stocks could stabilize population size and structure by reducing variation in inter-annual recruitment (DuFour et al. 2015). Trends of low to variable recruitment in recent years have led to these depressed population estimates and skewed age structure where the population is dominated by fish in older year classes. (WTG 2010). In both the Sandusky and Detroit Rivers, restoration efforts are in place to improve spawning habitat and improve production from the system. The ongoing removal of the first upstream dam in the Sandusky River could potentially result in a 17 fold increase in larval walleye production by increasing spawning substrate availability 4

16 (Jones et al. 2003). In the Detroit River and St. Claire Rivers, six artificial spawning reefs have added 12.4 acres of quality spawning habitat, and ~1900 m of shoreline have been softened to improve larval nursery habitat and benefit nearshore fish communities (Manny et al. 2010, Roseman et al. 2011, Roseman, personal correspondence). In the Maumee River, which is estimated to have the largest larval production of the three river stocks (DuFour et al. 2015), there have been no fisheries related restoration actions in place to improve habitat quality for early life history stages. In the Maumee River, walleye migrating upstream from Lake Erie are limited to a fraction of their historic range within the system. This reduction in available habitat can impact production through density dependent mortality. Despite anthropogenic degradation within the system, the spawning stock size in the Maumee River remains over 500,000 individuals (Pritt et al. 2013). Estimates of female spawning stock in the Maumee annually range from 78,000 to 237,000 individuals. Each individual female requires approximately 20 m 2 of spawning habitat under ideal conditions (Manny et al. 2010), and ideal carrying capacity of gravel, cobble substrates is approximately 4,325 eggs per m 2 (Jones et al. 2003). Densities exceeding these values in spawning areas may increase egg mortality due to increased disease transmission or suffocation (Jones et al. 2003). If the spawning stock size exceeds the amount of habitat available, eggs will either exceed the carrying capacity of the spawning habitat, or be deposited in suboptimal locations. Egg production is important factor in evaluating the overall health of a walleye stock (Roseman et al. 2006). Therefore, year-class fluctuations could be attenuated by increasing egg survival and subsequently larval production from river stocks (DuFour et al. 2015). 5

17 The goal of this project is to determine whether available spawning habitat could be a limiting factor to the production of larval walleye from the Maumee River. I hypothesize that Jerome Rapids at river kilometer (distance upstream of the mouth) 30 is a migratory barrier to upstream migration of spawning walleye. The objectives of this study were 1) assess longitudinal distribution and seasonal trends of walleye eggs downstream of the first dam in the Maumee River, and 2) to determine if habitat is limiting production in the Maumee River by a) identifying and quantifying preferred substrates, b) determine if longitudinal range of walleye spawning is restricted, c) comparing available space to the number of spawning adult females, and d) how present range relates to historic range. By identifying where possible spawning habitat restrictions may exist, directed habitat restoration efforts could maximize increased larval production. Further, walleye provide a surrogate for other lithophilic spawning species such as lake sturgeon, suckers, and lake whitefish; identifying habitat impairments for migrating walleye can assist the conservation of threatened species or the reintroduction of extirpated species. Methods: Study Area: The Maumee River (Figure 2.) drains the largest watershed of any tributary to the Laurentian Great Lakes, draining approximately 16,000 square kilometers (reference?). Historically, the majority of the Maumee watershed was part of the Great Black Swamp, a massive wetland complex which featured flooded meadows and oak/hickory forest, 6

18 originally half the size of the Florida Everglades. The Great Black Swamp was drained in the late 19 th century for logging and eventually agriculture (Kaatz 1955). Approximately 90% of the Maumee River watershed is now agriculture (Richards 2009), contributing to anthropogenic perturbations in water quality (Karr et al. 1985, Richards et al. 2008). Wetland destruction and deforestation discontinued deposition of sediment onto floodplains, instead being transported downstream. As a result of changes to the watershed, the Maumee River is prone to high flashiness, large sediment loads and deposition, which can contribute to egg and larval mortality (Karr et al. 1985, Mion et al. 1998). Suitable walleye spawning habitat begins approximately 25 km upstream from the mouth of the river, in highly oxygenated riffles near Perrysburg/Maumee, OH (ODNR 2010). The river from the riffle habitat at Perrysburg upstream to the Independence and Grand Rapids dams is relatively shallow, and substrate is comprised mostly of bedrock, gravel, and sand (Boase 2008). The majority of the river below the rapids downstream from the rapids at Perrysburg is comprised of silt (79%) or silt sand/zebra mussel (Boase 2008). Egg Collection: Walleye egg sampling was conducted over a two-year period at sites identified as having preferred spawning substrates, i.e. gravel and cobble. Sampling occurred weekly in 2014 and 2015, beginning shortly after ice out and continuing until early May when spawning ceased. Criteria for selecting sites in the initial 2014 sampling season were based primarily on their proximity to public access points, and secondarily on data from 7

19 ARCGIS substrate maps provided by the U.S. Fish and Wildlife Service (Boase 2008). Sites were selected in order to sample a relatively favorable walleye spawning substrate types and depths to determine the longitudinal distribution of walleye spawning within the Maumee River. While a random site selection would have facilitated statistical analysis, logistics of accessing sites safely during high flow events made this unfeasible. Travel from site to site by boat was not possible due to several sets of large rapids dispersed throughout the upper portion of the river. In 2015, eight of the ten sampling locations from 2014 were resampled. Travel to one site (Bluegrass Island, rk 28) was impossible due to a road closure following a large flood event on March 12 th, Miltonville site (rk 34), was abandoned due to difficulty transporting equipment to and from the river. At each site GPS coordinates (Garmin Montana 650t; ~1m accuracy), depth, water temperature, substrate type, and water velocity (m/sec) were recorded. At each site, at least three samples were collected per visit in order to determine relative abundance of eggs. These samples transected the river perpendicular to the current, with the first sample occurring within 10 meters of the shoreline. Remaining samples were distributed regularly throughout the river channel. Sampling occurred two to three times per week from April 1 st to May 7 th in 2014 and March 24 th to May 5 th in 2015 to capture the entire spawning season, visiting three to five sites daily. Average daily discharge and gauge height data was recorded from March 15 th to June 15 th from the U.S.G.S Waterville gauge to elucidate correlations between water levels and upstream migrations. Eggs were collected using a diaphragm pump with a flexible 5.0 cm hose, with modified 2 PVC handle attached. The modified handle was equipped with a 4 PVC 8

20 reducer, with 0.5 x 0.5 in hardware cloth fitted to prevent large debris from entering the pump. Eggs and benthic debris were deposited into 0.5 m diameter basket lined with 0.5 mm 2 mesh (Roseman et al. 2002). The diaphragm pump was deployed from a metal boat when water depth exceeded 1 m. In water less than 1m, the pump was place on an electrofishing barge and towed by hand, in order to access areas not available by boat. Water depth measurement and velocities at 60% total depth were taken using a Marsh McBirney Flo-Mate 2000, (Frederick, MD) flow meter and locations of each sample site recorded with Garmin Montana 650t. Samples were kept on ice in the field until processing occurred in the lab. Samples were sorted the same day whenever possible (Roseman et al. 2002). Samples remaining unsorted were frozen to preserve the genetic integrity of the eggs, and sorted at a later date. Egg samples were sorted in a glass pan, and were identified based on egg diameter (mm), egg color, and secondary characteristics such as presence/absence of oil globules (Roseman et al. 2002). In 2014, a sub sample of eggs was sent for genetic confirmation of species identity by Dr. Wendy Lee Stott (USGS Great Lake Science Center, Ann Arbor MI). Spawning Habitat Data Collection: In order to quantify spawning habitat within the Maumee River, substrate samples were collected in transects perpendicular to the shore. In areas likely to consist of unfavorable substrates for spawning (e.g., sand, silt, or clay), physical habitat samples were collected at three sampling points along transects crossing the channel every 1.5 kilometers. In areas likely to be composed of suitable spawning substrate (e.g., gravel or 9

21 cobble), habitat sampling was conducted every 250 m and samples were collected at either three points along the transect (river width <200 m) or four points (river width >200 m). River width was measured using a Zeiss Victory PRF range finder. When the river was bisected by islands within a transect, samples were taken within all channels around the islands. When an island occurred within a transect, but the river width was <200m, four samples were still obtained (two on each side of the island). Where water levels were sufficient for boat access, transects were sampled using an Ekman dredge (size?) to gather substrate samples. All other sections of the river were sampled by wading substrates within a 0.5 m 2 quadrat was visually assessed and categorized into the following groups: organic, silt, clay, sand (1-5 mm), gravel (>5-64 mm), cobble (> mm), boulder (>250mm), or bedrock. All samples were georeferenced using a Garmin 650t Montana hand held GPS. Water depth measurements were collected with a meter stick when wading, or Hummingbird 998c Sonar Unit when sampling was conducted from a boat. In addition, previous samples from the U.S. Fish and Wildlife using similar methods (Boase 2008) were used in the analyses. Spatial Analyses: Physical habitat data collected in 2014 were imported into ArcGIS, and merged with data collected in 2006 (Boase 2008). Differences in water level are accounted for using gage height and discharge data from the U.S.G.S. gauge at Waterville. Depths were standardized at a discharge of m 3 /s, which is the approximate mean springtime flow. Given that the upstream portion of the stretch is sediment starved, annual variations in substrate deposition are limited (i.e. seasonal sand bars). Delineation of substrates 10

22 used many of the same criteria described in Boase (2008), including primary and secondary substrate classes, depth, and geographic coordinates. I created physical habitat layers for substrate class and depth in ArcGIS using inverse distance weighted interpolation. Substrate classes were assigned values ranging from 1.0 to 8.1, based on primary and secondary substrate types. These values were generalized into six main groups (Table 1.). In all, there were 478 points from river km 56 downstream to the mouth, with increased effort around sites of interest (gravel and cobble substrates). The two physical habitat layers were combined using map algebra to create a final habitat layer where individual cells corresponded to how suitable they were for walleye spawning based upon substrate and depth. The habitat suitability layer was used to calculate the area of ideal spawning habitat in the Maumee under normal spring conditions. If the calculated area does not meet or exceed the spatial requirements of spawning stock size, spawning habitat availability may reduce egg survival and subsequently larval production. Jones et al. (2003) reports that carrying capacity of gravel/cobble substrates for walleye eggs is approximately 4,325 eggs/m 2. Spawning stock size in the Maumee River is reported between 78,000 and 237,000 female walleye annually, with the most likely value being approximately 126,000 individuals (Pritt et al. 2013). Using a mean fecundity of ~225,000 eggs/female, total annual egg deposition in the Maumee River is between and billion eggs, with the most likely value being approximately billion. To determine the amount area needed to optimize egg survival, total egg deposition was divided by the carrying capacity of gravel cobble substrates reported by Jones et al

23 Comparison of Water Velocity to Walleye Swimming Speed: To support the hypothesis that Jerome Rapids (rk 30) is a longitudinal barrier under high discharge conditions I compared water velocity to walleye swimming speed. I calculated channel wide velocity of the 800 m long stretch of river corresponding with the approximate length of the prominent limestone outcropping at Jerome Rapids as determined by satellite imagery. Velocity at Jerome Rapids was estimated using the equation: Equation 1: m m = Discharge ( 3 s ) s Depth Bankfull Width Bankfull width was calculated using satellite imagery at three points longitudinally distributed over 800 meters that encompassed the entire shallow bedrock shelf. Bankfull width was delineated by the presence of terrestrial vegetation. Assuming that river width is often less than bank full width, the estimation of average velocity across the channel is likely conservative. Depth was approximated using the difference in gage height, using baseline data collected during egg sampling under lower discharges. Because the gage is less than five kilometers upstream, and the channel in this section of the river is fairly homogenous, using the difference in gage height was appropriate. Bed roughness was not calculated, limiting the accuracy of our estimation. Estimated cross sectional velocities were compared to walleye swimming speeds calculated from Peake et al. (2000) using the equation for prolonged swimming speed minus ground speed: 12

24 Equation 2: Ucrit 10 ( m ) = fork length (m) temp ( C) s The longitudinal component of Jerome Rapids was estimated to be 120 meters long using satellite imagery (Google Earth Pro) as the section of the bedrock shelf the extended across the entire river channel. Prolonged swim speed had to exceed downstream water velocity and minimum ground speed to traverse Jerome Rapids (Figure 3.). Walleye should not be able to access spawning areas upstream of the longitudinal barrier until prolonged swim speed exceeds water velocity. Results: Longitudinal Distribution of Walleye Eggs: In 2014 walleye eggs were present at all ten sites sampled. However, there was a decline in the proportion of samples in which eggs were present and the mean relative abundance of eggs at sites upstream of Jerome Rapids (rk 30). Jerome Rapids was characterized by a shallow, narrow dolomite limestone shelf and high water velocities. Counts of walleye eggs per two minute sample observed at the four downstream sites had a mean of ± SD (N=14), whereas the mean of the six upstream sites was 9.4 ± 26.9 SD (N=36). Eggs were found in 100 percent of samples downstream, compared to 55.6% upstream. Mean relative abundances at each site drastically decreased upstream of Jerome Rapids in 2014 (Figure 4A.) 13

25 The two sites lost because of flooding in 2015, Bluegrass Island (rk 28) and Miltonville (rk 34), were downstream and upstream of Jerome Rapids, respectively. Despite losing two sites, there was an overall increase in sampling effort and duration in We observed a pattern similar to 2014 s, with relative abundances significantly higher at sites downstream of Jerome Rapids, compared to those found upstream (Figure 4B.) Counts of walleye eggs per two minute sample at the 3 downstream sites had a mean of ± (N=46), whereas the five upstream sites averaged 3.5 ± 11.6 (N=57). Walleye eggs were found in 80.4% of samples downstream, compared to 26.3% upstream. In both years, despite large inter-annual variability in relative abundances, egg deposition significantly decreased upstream of Jerome Rapids. Site averages remained fairly similar, especially at the upstream sites. Walleye spawning in the Maumee River appears to be longitudinally restricted to the lower 10 km reach of the study segment, despite large areas of available habitat suitable for spawning in the upper reaches. Seasonal Trends: There were slight seasonal differences between the two sample years. The 2014 spawning season was interrupted by a large discharge event during the peak of the spawning season (Figure 5.), whereas as in 2015 a large discharge event corresponding with snow melt occurred well before the onset of spawning. In general, 2015 spawning occurred earlier in the year, with peak relative abundances of walleye eggs occurring when water temperatures reached approximately 8 C around April 9 th (Figure 6.). In 2014, peak relative abundances occurred following a large discharge event during the first week of April. Egg relative abundances were low on the only sample day before the 14

26 discharge event on April 1 st. We were unable to sample again until April 17 th. Eggs were present at a higher concentration earlier in the season in The highest relative abundances were observed when water temperatures were between 6 C and 12 C degrees Celsius. Because relative abundances of eggs were obtained throughout the entire spawning period (early spawn, peak spawn, and late spawn) a wide range of egg densities were observed, leading to increased variability throughout the study (Katt et al. 2012) Identification and Quantification of Spawning Habitat: Substrate data collection included 478 data points, including 298 from the 2008 U.S.F.W.S survey and 180 in 2014 as part of the current study. Data points were distributed throughout the lower 56 km of the Maumee and were used to assess water depth and substrate classification, with additional effort in locations where preferred spawning substrates (e.g. cobble, gravel) were thought to be found. The upper 36 km of the sample area were dominated by bedrock or gravel, cobble, and boulders. Gravel and cobble substrates occupy approximately a third of the total area of the entire 56km stretch (Figure 7.). In the lower 20 km of the river, there appears to be a transitional area predominantly covered by sand, and finally dominated by silt and clay substrates in areas maintained for the shipping channel (~17km). Depths were standardized based on the mean gage height from the U.S.G.S gauge (U.S.G.S ) at Waterville, Ohio from March 15 th June 15 th in the collection year of Much of the upper segment of the river had depths less than 1 m throughout much of the spring, characterized by bedrock channels (Figure 7.). Throughout the upper river, areas where water depths were 1-3 m were associated with channels 15

27 surrounding islands, and the area immediately upstream of the shipping channel. The majority of the shipping channel exceeded 5 meters in depth, with marginal areas outside the main channel often exceeding three meters. The majority of this section of river is channelized and riparian areas have been replaced by corrugated metal retaining walls. The habitat map that results from combining depth and substrate layers revealed that areas designated as optimal for walleye spawning with areas 1-3 m deep and having gravel or cobble account for ~7.67 million m 2 of the total million m 2, or 6.54% of the 56 river km stretch (Table 2.). We found that an additional million m 2 (29.25%) in the lower 56 km of the river are considered moderately good for walleye spawning, with a one variable being less than ideal for walleye spawning (e.g. bedrock substrate but preferred depth). The remaining portions of the river were not ideal for walleye spawning, limited by depth or substrate (e.g. mud, silt). Comparison of water velocity to walleye swimming speed: The calculated mean cross sectional velocities at Jerome Rapids throughout the duration of the spawning season were plotted against prolonged swim speeds (Ucrit 10 ) for walleye of fork lengths 0.35 m, 0.61 m, and 0.71 m (Figure 8.). The prolonged swim speed equation used water temperature data acquired from the NOAA GL0201 gauge, corroborated from field measurements. Based on swimming speed relative to velocity, walleye should not have been able to traverse the velocity barrier at Jerome Rapids until April 23rd in The first eggs sampled upstream were found on April 22nd. In 2015, walleye should not have been able to traverse Jerome Rapids until April 29 th. Eggs were 16

28 spawned upstream of early in the season (March 24th), but in low numbers. The first appreciable relative abundances occur after April 7 th, which were preceded by relatively low discharges. Comparisons between Habitat Types and Egg Deposition: Overlaying a map of mean relative abundances of walleye eggs in 2014 relative to spawning habitat availability confirmed that there is indeed a longitudinal restriction point in the Maumee River (Figure 9.)., Despite large areas of high quality spawning habitat available upstream, we found few eggs upstream of Jerome Rapids (Table 3.). I began this study with the assumption that walleye spawn all the way to the dam at river kilometer 56, but it is apparent that very few fish make it upstream to the dam. Assuming that Jerome Rapids is a barrier to upstream migration of spawning walleye, the amount of suitable spawning habitat available to walleye in the Maumee is 3.34 million m 2 (Table 4.) In order to support the current stock size of female walleye, 6.55 million m 2 of gravel/cobble (between million) habitat is needed (Table 5.). These results suggest that habitat in the Maumee River may be limiting, and therefore could be limiting production of larval walleye from the system. Discussion: Explaining Connectivity Loss Our results suggest that spawning habitat connectivity in the Maumee River is lower than previously thought. It appears that walleye spawning within the Maumee River is partially restricted to river kilometers Although no attempt was made to 17

29 collect eggs in the area closer to the river mouth, given depth and substrate limitations, it is unlikely that substantial successful spawning occurs there. The barrier at Jerome Rapids reduces the amount of spawning habitat available to walleye in the Maumee River. The impacts of this barrier may include competition for habitat and the use of suboptimal substrates in downstream reaches that can, result in the decreased survival of eggs, and subsequently limiting the production potential of larval fish from the system. I suggest that the apparent longitudinal barrier at Jerome Rapids is likely due to a seasonal velocity barrier under high discharge conditions, but could be influenced by other factors including a water treatment facility immediately upstream or, the loss of a separate riverine resident stock. While determining the relative importance of these factors is currently speculative, knowledge of potential spawning habitat impairments in the Maumee River is relevant to lake-wide management of the walleye population. The water treatment plant located at river kilometer 30 could potentially create thermal or chemical barriers that walleye avoid. Figure 10 shows two plumes of water, the main river flume and separate, smaller plume on the northern bank immediately downstream of a water outflow. Downstream of the outflow, large, dark mats of periphyton can be seen along the northern bank of the river, indicating that the water in the outflow is different in nutrient concentration or water temperature. I did not collect water quality measurements above and below this point and therefore can only speculate on the possible effect of the discharge. However, the effect of slightly warmer water seems unlikely to deter walleye from moving further upstream. Alternatively, Jerome Rapids, which is a dolomite limestone shelf that extends across the entire channel, may have always been a barrier to walleye migrating upstream from Lake Erie. Historically, 18

30 there may have been a separate resident stock of walleye that is now depressed. Historical accounts indicate walleye were common throughout the Maumee River to the Indiana border, although rare in present times (Trautman 1981), and large numbers of spawning fish occurred well upstream of Jerome Rapids (Brown 1815, Lou Campbell 1971, OEPA 2010). It is possible that historical events in the Maumee watershed lead to the loss of the upstream stock. Anecdotal observations reported that there was a marked decline in the fish stocks in the Maumee River beginning as early as Wetland destruction and deforestation may have resulted that may have fouled upstream spawning areas. Between 1871 and 1930, approximately 85% of forested wetlands in the Maumee River watershed had been removed (Toledo Naturalist Yearbook ). Anderson et al. (2006) predicted 15 to 30% reductions in forest cover in central Lake Erie tributaries could reduce larval production 45% to 60% based on data from the Sandusky River, NW Ohio.. In addition, construction of the Grand Rapids Dam 56 rk upstream of the mouth began in the 1840 s and a more permanent structure was installed in Damming and pollution of spawning tributaries have been identified as primary forces impairing walleye production in the Laurentian Great Lakes (GLFC 2006). In central and southwestern Ohio, the construction of dams drastically reduced population of walleye in the Mahoning and Scioto River (Trautman 1981). Dams can disrupt river flows and water temperature regimes, affecting both adult fish and incubating eggs (Colby et al. 1979, Dimond et al. 1996, Acres International 2006, Liskauskas et al. 2007). By 1900, there was public outcry for creel limits on the Maumee River (Campbell 1971). The combination of overfishing, habitat degradation, and a loss of upstream connectivity through the construction of dams may have significantly reduced or extirpated any 19

31 resident walleye populations in upstream sections of the Maumee River. Additional study of this possibility of a remnant upstream stock could be accomplished by future studies that may be able to detect stock differences morphometrically or genetically. It is possible that Jerome Rapids now presents a barrier that did not exist prior to European settlement in the 19 th century due to adverse changes in the hydrology and surrounding landscape. The results of this study support the idea that water velocity at Jerome Rapids may present a barrier to upstream movement. In 2014, walleye eggs were collected upstream of Jerome Rapids the day before walleye eggs were predicted to appear by prolonged swimming speed calculation. In 2015, walleye eggs appeared upstream of Jerome Rapids well before the prolonged swimming speed equation predicted. However, the presence of walleye eggs upstream Jerome Rapids immediately occurred only after the lowest discharge event at that point in the 2015 spawning season. Velocity estimates at Jerome Rapids were coarse estimates of channel wide mean velocity, and did not account for possible utilization of current seams or river margins. It is worth noting that there appears to be correlation between water velocity (discharge) and connectivity to upstream spawning grounds. Reducing the frequency and magnitude of large spring time discharge events would benefit walleye by improving connectivity. There has been a great deal of change to the Maumee watershed that may have increased the effect of a possible velocity barrier at Jerome Rapids. The majority of the Maumee watershed was part of the Great Black Swamp, which was drained in the late 19 th century for logging and eventually agriculture (Kaatz 1955). Wetland destruction and deforestation discontinued sediment deposition onto floodplains, instead being transported downstream. The downstream transport of sediment led to covering of gravel 20

32 and cobble substrates necessary for many species to spawn. Since 1850, the period when logging and draining of the Great Black Swamp began, 44% of species have declined in abundance or been extirpated (Karr et al. 1985). The historic abundance of currently extirpated species such as northern pike and muskellunge, which often require marshy, emergent vegetation for spawning and nursery habitats suggests that wetland connectivity was historically much higher. In addition to increased sediment loads, these changes have resulted in highly variable and extreme discharge events (Karr et al. 1985, Richards 1990, Richards et al. 2008). Relative abundances of walleye eggs were much lower in 2014 than in 2015, which could be the result of the abnormally large discharge event during the middle of the spawning period. The Maumee River watershed is prone to high flashiness and large sediment loads and deposition, which can contribute to egg and larval mortality (Karr et al. 1985, Mion et al. 1998).Weighted useable area (i.e. spawning area available under different water conditions) decreased next to zero during high discharge events in the adjacent Sandusky River watershed due high velocity (Gillenwater et al. 2006). Larval survival decreases with discharge because of gill damage associated with high levels of suspended sediment as well as physical processes of driven against rocks (Mion et al. 1998, Anderson et al. 2006). It is likely that a high discharge event may have contributed to poor larval walleye production from the Maumee River in The loss of wetland connectivity may have had an adverse effect on walleye populations in the Maumee River. It is entirely possible that walleye formerly spawned in locations similar to spawning areas in the Lake Winnebago, WI system. Lake Winnebago and the Western Basin of Lake Erie are similar systems in that they are shallow, eutrophic systems with stocks of walleye spawning on mid-lake reefs (Priegel 1970), but 21

33 also substantial upstream migrations in tributaries by separate, diverse stocks. A major difference between the two systems are land use practices. A larger proportion of seasonal wetlands in the Wolf and Fox River watersheds remained intact through conservation practice, whereas the Maumee River Watershed has been almost entirely been drained for agricultural practices. (citation for this or data sources? The Wolf and Fox rivers also have longer sections of free flowing river than the Maumee. Interestingly, the bank adjacent to Jerome Rapids contains what appears to be an old oxbow channel, and historically may have been a seasonal wetland prior to the arrival of humans (Figure 11.) In the flooded marsh vegetation in the Wolf and Fox Rivers, marshes had both an inflow and outflow point, and may therefore have had current moving though (Priegel 1970). Movement of water through the marsh is necessary for larvae to be transported back into the river to be recruited into the population. Priegel (1970) states that only 25-35% of the marsh habitat was available for spawning based on depth and flow. Further downstream of Jerome Rapids, a second apparent oxbow lake has an outflow back into the river, indicating that that there may have been flow through the historic seasonal wetland, and historically this area could have served as a spawning habitat. If discharges have always prevented upstream migration of spawning walleyes under high discharge events, this adjacent wetland may have provided an alternative spawning location or passage around the rapids. Within the Fox and Wolf River, fish will spawn on both sand and gravel substrates, as well as the seasonal marshes, so it is possible that fish in the Maumee River would have used marginal wetlands during high discharge years, and used upstream gravel and cobble substrates upstream of Jerome Rapids during low discharge years. 22

34 Habitat heterogeneity may have improved year to year production from the Maumee River, but since the loss of marginal wetlands, production is dependent on habitat availability in the main channel which could fluctuate with discharge. Currently within the Fox and Wolf Rivers, fish have to travel between km and km upstream, respectively, to reach suitable spawning marshes (Priegel 1970). Historically, the Great Black Swamp encompassed much of the length of the Maumee River, and could have included thousands of acres of wetlands suitable for spawning (Figure 14). Although, this study does not definitively identify the cause of the velocity barrier at Jerome Rapids, it is important to recognize that walleye are not using upstream habitats because they cannot access them at high spring flows. Management Implications: Assuming that velocity is the barrier at Jerome Rapids, management actions to improve connectivity in the Maumee River would be more effective at the watershed land-use level than a site specific level. In order to improve connectivity and increase the amount of habitat available to walleye, reduction in the magnitude and frequency of discharge events would be necessary to reduce the impact the barrier has on the upstream migration of walleye. A moderated hydrograph would yield prolonged windows of upstream access as opposed to short windows between rain events. Wetlands and forested areas would have ameliorated the magnitude of spring discharge events, but controlling discharge through restoration of wetlands and forested areas seem unlikely. Historical accounts from early settlement refer to the Maumee River as a sluggish, black water river. However, the Maumee River is now a flashy and turbid system, with considerable 23

35 sediment and nutrient transport (Verduin 1969; Richards 1990.; Stow et al. 2015). Average monthly precipitation and discharge have been steadily increasing since 1990 in the Maumee River (Stow et al. 2015). In this same time period, the most pronounced seasonal change has been the steady increase of average precipitation and discharge in March (Stow et al. 2015), coinciding with walleye spawning migration. In addition, there has been a statistical significant increase in Richards-Baker Flashiness Index, in the Maumee River since the mid 1970 s as the result of widespread land use changes (Baker et al. 2004). Walleye are beginning to stage, migrate, and spawn in mid to late March. With maximum annual discharges occurring in March, Jerome Rapids is likely a barrier to early spawning fish. This barrier limits the amount of spawning habitat available that have favorable depths and substrates for egg survival and hatching. In low discharge years, access to areas upstream of Jerome rapids would be available. However, increases in spring precipitation as the result of climate change will further contribute to the problem. Altering the hydrology and flow regime of streams and rivers may have adverse ecological impacts. For example, In recent years the western basin of Lake Erie has been prone to large cyanobacterial blooms due to increased nutrient inputs mostly from the Maumee River. In addition, increased sediment transport during high discharge events increases larval mortality rates (Mion et al. 1998). Reductions in the magnitude and frequency of large discharge events would have positive ecological impacts, and may be obtainable through watershed restoration. Best management practices (BMP) aim to reduce erosion and associated nutrients during storm runoff. Variety of land and water management practices are available including wetland construction, cropland management to increase infiltration and 24

36 decrease surface runoff, controlled drainage, use of permeable paving materials and construction of storm runoff holding basins (Baker et al. 2004). Decreasing storm runoff would decrease nutrient load, and would be beneficial for both reducing the size and severity of harmful algal blooms in Lake Erie and improving habitat connectivity within the Maumee River for walleye migration. Improving habitat connectivity in the Maumee River could result increased annual larval production to Lake Erie, improving inter-annual recruitment. Several stocks within the system are depressed due to a combination of overfishing and habitat loss and degradation, but it is possible to return these systems to near historic conditions through management. Walleye populations in the St. Louis River, a tributary of Lake Superior, are believed near historic levels due to conservative fishing regulations following improvements in water quality (GLFC 2006). Similar improvements in the Maumee River could increase stock production, and bolster the Lake Erie population. 25

37 References Anderson, R.M., B.F. Hobbs, and J.F. Koonce Modeling effects of forest cover reduction on larval walleye survival in Lake Erie tributary spawning basins. Ecosystems (9) Auer, N.A., editor Identification of larval fishes of the Great Lakes basin with emphasis on the Lake Michigan drainage. Great Lakes Fishery Commission Special Publication Baker, D.B., R.P. Richards, T.T. Loftus, and J.W. Kramer A new flashiness index: characteristics streams. Journal of the American Water Resources. 40(2) Berkman, H.E., C.F. Rabeni Effect of siltation on stream fish communities. Environmental Biology of Fishes 18(4) Boase, J Annual Report: evaluation of lake sturgeon spawning in the Maumee River, Ohio. U.S. Fish and Wildlife Service. Busch, W.D.N., R.L. Scholl, W.L. Hartman Environmental factors affecting the strength of walleye (Strizostedion vitreum vitreum) year-classes in western Lake Erie, J. Of the Fisheries Research Board of Canada 32(10) Cooper, C.L., W.C. Bartholomew, C.E. Herdendorf, J.M. Reutter and F.L. Snyder Limnetic larval fish of the Maumee and Sandusky River Estuaries. J. Great Lakes Res. 7: DuFour, M.R., J.J. Pritt, C.M. Mayer, C.A. Stow, S.S. Qian Bayesian hierarchical modeling of larval walleye (Sander vitreus) abundance and mortality: accounting for temporal and spatial variability on a large river. Journal of Great Lakes Research. Fahrig, L Relative Effects of Habitat Loss and Fragmentation on Population Extinction. The Journal of Wildlife Management 61: Flowers, J.H., J.E. Hightower A novel approach to surveying sturgeon using sidescan sonar and occupancy modeling. Marine and Coastal Fisheries: Dynamics, Management, and Ecosystem Science 5(1) Gillenwater, D., T. Granata, U. Zika GIS-based modeling of spawning habitat suitability for walleye in the Sandusky River, Ohio, and implications for dam removal and river restoration. Ecological Engineering. 28(3)

38 Great Lakes and Mississippi River Interbasin Study (GLMRIS.) Commercial fisheries baseline economic assessment-u.s. waters of the Great Lakes, Upper Mississippi River, and Ohio River basins. U.S. Army Corps of Engineers. 92 pp. Hartman, W.L Effects of exploitation, environmental changes, and new species on the fish habitats and resources of Lake Erie. Great Lakes Fish. Comm. Tech. Rep. 22: 43 pp. Herdendorf, C. E Assessment of the larval fish populations in the Maumee River estuary and Maumee Bay of Lake Erie. CLEAR Technical Report 75. Johnston, N.T., P.A. Stanley Fish habitat assessment procedures. Watershed Restoration Technical Circular No. 8. British Columbia Ministry of Environment, Lands and Parks and Ministry of Forests. Jones, M.L., J.K. Netto, J.D. Stockwell, J.B. Mion Does the value of newly accessible spawning habitat for walleye (Stizostedion vitreum) depend on its location relative to nursery habitats? Canadian Journal of Fisheries and Aquatic Sciences 60(12) Kaatz, M.R The black swamp: A study of historical geography. Annals of Association of American Geographers 45(1) 1-35 Karr, J.R, L.A. Toth, D.R. Dudley Fish communities of Midwestern Rivers: a history of degradation. Bioscience 35(2) Kerr, S.J., B.W. Corbett, N.J. Hutchinson, D. Kinsman, J.H. Leach, D. Puddister, L. Stanfield, N. Ward Walleye habitat: a synthesis of current knowledge with guideline for conservation. Percid Community Synthesis: Walleye Habitat Working Group. 98 pp. Lake Erie Walleye Task Group (WTG) Report for Presented to Standing Technical Committee, Lake Erie Committee, Great Lakes Fishery Commission, Niagara Falls, New York-March 27-28, pp. Leach, J.H. and S.J. Nepszy The Fish Community in Lake Erie. Journal of Fisheries Research Board Canada 33: Lowie, C.E., J.M. Haynes, and R.P. Walter Comparison of walleye habitat suitability index (HSI) information with habitat features of a walleye spawning stream. Journal of Freshwater Ecology 16(4) MacDougall, T.M., Wilson, C.C., Richardson, L.M., Lavender, M., and P.A. Ryan Walleye in the Grand River, Ontario: an Overview of Rehabilitation Efforts, Their Effectiveness, and Implications for Eastern Lake Erie Fisheries. Journal of Great Lakes Research 33(1): Madenjian, C.P., J.T. Tyson, R.L. Knight, M.W.Kershner, M.J. Hansen First-year growth, recruitment, and maturity of walleyes in western Lake Erie. Transactions of the American Fisheries Society 125(6)

39 Manny, B.A., G.W. Kennedy, J.D. Allen, J.R.P. French III First Evidence of Egg Deposition by Walleye (Sander vitreus) in the Detroit River. Manny, B.A., G.W. Kennedy, J.C. Boase, J.D. Allen, E.F. Roseman Spawning by Walleye (Sander vitreus) and White Sucker (Catostomus commersoni) in the Detroit River: Implications for Spawning Habitat Enhancement. Journal of Great Lakes Research 36(3): Mion, J.B., R.A. Stein and, E.A. Marschall River discharge drives survival of larval walleye. Ecological Applications 8: Mueller, Z Feasibility study of removing the Grand Rapids-Providence dams, Maumee River (NW Ohio) based on HEC-RAS models. Electronic Thesis. Ohio Department of Natural Resources Lake Erie Strategic Plan. Web Source. older/fishingfairportstratplan/tabid/6167/default.aspx Ohio Division of Wildlife (ODW) Ohio s Lake Erie Fisheries, Annual Status Report. Federal Aid in Fish Restoration Project F-69-P. Ohio Department of Natural Resources, Division of Wildlife, Lake Erie Fisheries Units, Fairport and Sandusky.118 pp. Ohio EPA (OEPA) Appendices to the Biological and Water Quality Study of the Maumee and Auglaize Rivers. Ohio EPA Technical Report EAS/ Patterson, R.L., K.D. Smith Impact of power plant entrainment of ichthyoplankton of juvenile recruitment of four fishes in Western Lake Erie in Journal of Great Lakes Research 8(3): Pimm, S.L. and P. Raven Biodiversity: Extinction by numbers. Nature 403: Pritt, J.J., M.R. DuFour, C.M. Mayer, P.M. Kocovsky, J.T. Tyson, E.J. Weimer, C.S. Vandergoot Including independent estimates and uncertainty to quantify total abundance of fish migrating in a large river system: walleye (Sander vitreus) in the Maumee River, Ohio. Canadian Journal of Fisheries and Aquatic Sciences 70(5): Pritt, J.J., M.R. DuFour, C.M. Mayer, E.F. Roseman, and R.L. DeBruyne Sampling little fish in big rivers: larval fish detection probabilities in two Lake Erie tributaries and implications of sampling effort and abundance indices. Transactions of the American Fisheries Society 143(4) Pritt, J.J. E.F. Roseman, M.R. DuFour, C.M. Mayer, R.L. DeBruyne, B.A. Schmidt. In Prep. Climate change and fish spawning in the Laurentian Great Lakes: potential for climate-driven decoupling of spawning and nursery habitats Richards, R. P., Baker, D. B., Kramer, J. W., Ewing, D. E., Merryfield, B. J. and Miller, N. L. (2001), Storm Discharge, loads, and average concentrations in Northwest 28

40 Ohio Rivers, JAWRA Journal of the American Water Resources Association, 37: Richards, R.P Indicator: Phosphorous loads and concentrations from the Maumee River. Web source. Roseman, E.F., W.W. Taylor, D.B. Hayes, R.L. Knight, and R.C. Haas Removal of walleye eggs from reefs in western Lake Erie by a catastrophic storm. Transactions of the American Fisheries Society. 130(2) Roseman, E.F., W.W. Taylor, D.B. Hayes, J. Fofrich Sr., and R.L. Knight Evidence of walleye spawning in Maumee Bay, Lake Erie. Ohio Journal of Science. 102(3) Roseman, E.F., Taylor, W.W., Hayes, D.B., Jones, A.L., and J.T. Francis Predation on walleye eggs by fish on reefs in Western Lake Erie. J. Great Lakes Research 32: Roseman, E.F., B. Manny, J. Boase, M. Child, G. Kennedy, J. Craig, K. Soper, and R. Drouin Lake sturgeon response to a spawning reef constructed in the Detroit River. Journal of Applied Ichthyology. 27: Snyder, F.L Ichthyoplankton studies in the Maumee and Sandusky River estuaries of Lake Erie. CLEAR Technical Report No. 92. Stow, C.A., Y. Cha, L.T. Johnson, R. Confesor, and R.P. Richards Long-term and seasonal trend decomposition of Maumee River Nutrient Inputs to Western Lake Erie. Environmental Science and Technology. 49: Tilman, D., R. M. May, C. L. Lehman, and M. A. Nowak Habitat destruction and the extinction debt. Nature 371: Trautman, M.B The Fishes of Ohio revised Ed. The Ohio State University Press. pp Walleye Task Group Lake Erie Committee Walleye Task Group Executive Summary Report. Zedler, J.B., and S. Kercher Wetland resources: status, trends, ecosystem services, and restorability. Annual Review of Environment and Resources 30:

41 Range Label Mud Silt Sand Gravel Cobble Bedrock Table 1. Substrate classification based upon primary and secondary substrate characteristics given a discrete value Higher values correspond with harder substrates (i.e. Bedrock overlain with silt would have a lower value than a predominantly bedrock substrate). Values were generalized into six main substrate types to create substrate layer in ArcGIS

42 Habitat Suitability Total Area (m -2 ) Poor 6,093,170 Moderately Poor 18,231,780 Moderate 51,010,970 Moderately Good 34,315,700 Optimal 7,668,450 Sum 117,320,070 Table 2. Summary of areal extent of substrate and depth suitability for walleye spawning habitat in the lower 56 river kilometers of the Maumee River. Areas with optimal depth (1-3 m) and substrate (gravel/cobble) cover only 6.5% of the river. 31

43 Site River km Habitat Suitability 2014 Mean 2014 St. Dev Mean 2015 St. Dev Orleans 23 Optimal Fort Meigs 25 Optimal Bluegrass Is. 28 Moderately Good Null Null Jerome Rapids 30 Moderate Waterville 32 Moderate Miltonville 34 Moderate Null Null Farnsworth 40 Optimal Weir Rapids 41 Optimal Otsego 44 Moderately Good Van Tassel 48 Moderately Good Table 3. Comparisons between sites and habitat quality in 2014 show low relative abundance of eggs at sites upstream of Jerome Rapids, despite spawning habitat deemed Moderately Good or Optimal. 32

44 Habitat Suitability Total Area (m -2 ) Poor 5,459,620 Moderately Poor 8,947,590 Moderate 9,005,180 Moderately Good 10,323,280 Optimal 3,335,800 Sum 37,071,470 Table 4. Summary of areal extent of substrate and depth suitability for walleye spawning downstream of Jerome Rapids (rk 30). This section of the river is readily available to walleye during their upstream spawning migration. Only 2.8% of the river has optimal spawning conditions for walleye. 33

45 Number of Females Total Egg Deposition Area Needed (m 2 ) Low 78, Billion 4.06 Million Median 126, Billion 6.55 Million Upper 237, Billion Million Table 5. Estimates of total egg deposition based on estimates of female abundance (Pritt et al. 2012), using a mean fecundity of 225,000 eggs per female. Carrying capacity of gravel/cobble substrates reported as ~4,325 eggs/m 2 (Jones et al. 2003). 34

46 Figure 1 (DuFour et al. 2015). Annual larval production of walleye from the four major stocks in Western Lake Erie. The mid-lake reef complex dominates larval production, with minimal inputs from riverine stocks. Increasing riverine production could buffer recruitment in years of low production from the reef stock (i.e ). 35

47 36 Figure 2. Maumee River (left) from mouth in Maumee Bay upstream to the first dam at Grand Rapids, Oh. Maumee River enters Lake Erie in the southwest corner of the Western Basin.

48 Figure 3. Total distance to traverse velocity barrier at Jerome Rapids indicated by the red line. In order to pass the 120 meter section, walleye would have to cover 0.2 m/s over ten minutes of prolonged swim speed (Ucrit10, Peake et al. 2000) 37

49 Mean Relative Abundance Mean Relative Abundance A River Kilometer B River Kilometer Figure 4. Mean relative abundance of walleye eggs at each site in 2014 (A) and 2015 (B). In both years, egg relative abundance is relatively high at sites from river kilometer 23-30, and decline substantially upstream of River kilometer 30. Sites upstream of river kilometer 40 averaged 2.5 eggs or less per sample. Notice the difference in scale between the two years. 38

50 A B Figure 5. (A) Discharge and water temperature ( C) throughout the sampling season in (B)Highest observed egg relative abundances occurred around April 17 th, after discharge decreased. Spawning began at approximately 6 C, and continued until 15 C. A large event in early April disrupted sampling, causing a large gap in the data. 39

51 A B Figure 6. (A) Discharge and water temperature ( C) throughout the sampling season in (B) Highest observed egg relative abundances occurred around April 9 th, as water temperatures increased above 8 C. Egg abundances dropped after April 20 th, as water temperatures approached 15 C. 40

52 Figure 7. Areas where spawning habitat are considered optimal, indicated by areas in dark green, for walleye spawning throughout the lower 56 km of the Maumee River based on depth and substrate. Areas considered optimal at have depths of 1-3 meters under average spring flow (4,000 CFS) and have gravel/cobble substrate. 41

53 First Downstream Egg A First Upstream Egg Upstream Mean: 0.25 Downstream Mean: Upstream Mean: 0 Downstream Mean: B Upstream Mean: Downstream Mean: Figure 8A. Calculated mean cross sectional velocity at Jerome Rapids compared against prolonged swim speeds (Ucrit10) for walleye of fork lengths 0.35 m, 0.61 m, and 0.71m adjusted for water temperature in 2014 and (B)

54 A B Figure 9. Mean relative abundances of walleye eggs in (A) 2014 and (B) 2015 show that despite large areas of high quality spawning habitat upstream of river kilometer 30, walleye spawning is concentrated in River Kilometer

55 Figure 10. Location of water treatment plant relative to Jerome Rapids. Physical differences in the channel can be seen immediately downstream of the outflow. The north bank has extensive periphyton growth, likely the result of a nutrient or thermal gradient. This gradient could be a potential barrier for walleye migration. 44

56 Figure aerial photograph of Sidecut Metropark. The large limestone outcropping at the downstream end of Jerome Rapids can be seen in the lower left of the photograph. Adjacent to the northern bank, there are several farm fields, surrounding a remnant oxbow channel. This marginal wetland may historically provide spawning or staging areas for walleye before traversing the rapids. 45