We analyzed a diverse set of 1,646 north-temperate lakes to evaluate the nutrient-color paradigm ... more We analyzed a diverse set of 1,646 north-temperate lakes to evaluate the nutrient-color paradigm that integrates total phosphorus (TP) and colored dissolved organic carbon to define lake trophic status. Our objectives were to quantify the combined influence of TP and color (Col) on lake trophic status, to determine if TP and Col had similar relationships with hydrogeomorphic (HGM) variables, and to examine how TP and Col affected the balance of heterotrophic and autotrophic processes. For the latter we examined the Col to chlorophyll a ratio (Col : Chl a), an index of allochthonous contributions of carbon to pelagic consumers, and deviations of lake pCO 2 from atmospheric, an index of net heterotrophy. Both Col and TP had strong effects on Chl a (positive) and Secchi transparency (negative), suggesting that ignoring Col would lead to misinterpretation of these widely used trophic status indicators. Lakes with high TP and Col tended to be shallower with large catchment to lake area ratios. Negative correlations with water retention time (WRT) were stronger for Col than for TP. Both TP and Col were related to forest and wetland land cover, although the direction of the relationships were opposite. Only 29% of the lakes had relatively high allochthony according to their Col : Chl a ratios; these were predominately high color, oligotrophic or mesotrophic lakes with short WRT. Over 90% of a subset of 682 lakes were net heterotrophic, with pCO 2 exceeding atmospheric levels. The positive relationship between pCO 2 and Col : Chl a suggests that only in very heterotrophic systems was the transfer of allochthonous carbon to pelagic consumers appreciable. Our results provide strong empirical support for the nutrient-color paradigm and highlight its importance both for management applications and for expanding our understanding of how lakes are influenced by terrestrial subsidies of carbon and nutrients.
We quantified relationships between local wetland cover in the riparian lake buffer and lake tota... more We quantified relationships between local wetland cover in the riparian lake buffer and lake total phosphorus (TP) and water color (color) using multilevel mixed-effects models that also incorporate landscape features such as hydrogeomorphology and land use at broad regional scales to determine the following: (1) Within regions, are local wetland relationships with TP and color affected by interactions with local land use or hydrogeomorphic variables? (2) Across regions, are local wetland relationships with TP and color different? And if so, (3) Are differences in local wetland relationships with TP and color a result of cross-scale interactions? We answered these questions by analyzing TP, color, and multiscaled landscape data for 1790 north temperate lakes. Local wetland-TP and wetland-color relationships were not affected by local-scale interactions. However, these same relationships were different when compared across regions, and these differences were related to cross-scale interactions with regional landscape characteristics. For example, regional human land use affected local wetland-TP relationships such that in regions with high amounts of agriculture, local wetlands were associated with decreased lake TP. However, in regions with low amounts of agriculture, local wetlands were associated with increased lake TP. In contrast, regional hydrogeomorphic characteristics influenced local wetland-color relationships such that in regions with high groundwater contribution, the strength of local wetland relationships were weak. Regional landscape setting influences local wetland relationships with TP and color through crossscale interactions, and lake TP and color are controlled by both local-scale wetland extent and regional-scale landscape variables.
Ecologists increasingly recognize the need to understand how landscapes and food webs interact. R... more Ecologists increasingly recognize the need to understand how landscapes and food webs interact. Reservoir ecosystems are heavily subsidized by nutrients and detritus from surrounding watersheds, and often contain abundant populations of gizzard shad, an omnivorous fish that consumes plankton and detritus. Gizzard shad link terrestrial landscapes and pelagic reservoir food webs by consuming detritus, translocating nutrients from sediment detritus to the water column, and consuming zooplankton. The abundance of gizzard shad increases with watershed agriculturalization, most likely through a variety of mechanisms operating on larval and adult life stages. Gizzard shad have myriad effects on reservoirs, including impacts on nutrients, phytoplankton, zooplankton, and fish, and many of their effects vary with ecosystem productivity (i.e., watershed land use). Interactive feedbacks among watersheds, gizzard shad populations, and reservoir food webs operate to maintain dominance of gizzard shad in highly productive systems. Thus, effective stewardship of reservoir ecosystems must incorporate both watershed and food-web perspectives.
Transactions of the American Fisheries Society, 1999
Recruitment success of larval fishes can determine subsequent effects of older life stages on eco... more Recruitment success of larval fishes can determine subsequent effects of older life stages on ecosystem structure and function. Because size and abundance of juvenile gizzard shad Dorosoma cepedianum determines, in large part, their effects on zooplankton abundance and sport-fish recruitment, we investigated recruitment of larval gizzard shad to the juvenile stage. We hypothesized that larval survival would correlate positively with availability of small (<0.40 mm) zooplankton and reservoir productivity and would dictate abundance of individuals reaching the juvenile stage. In downstream and upstream areas of four Ohio reservoirs ranging from mesotrophic to hypereutrophic, we evaluated larval gizzard shad success by comparing hatch, growth, and survival of weekly cohorts of larvae with availability of small zooplankton, and then we determined whether larval success could predict juvenile gizzard shad size and abundance. Total larval hatch abundance increased with reservoir productivity and was higher upstream than downstream. Weekly cohorts that produced abundant survivors reflected not only high hatch but also high survival in upstream areas during periods of abundant small zooplankton. Overall, larval hatch and survival predicted juvenile abundance but not juvenile size. Juvenile abundance increased with reservoir productivity, particularly in upstream areas, whereas juvenile size reflected the combined influence of juvenile abundance and reservoir productivity. Across mesotrophic to eutrophic conditions, juvenile gizzard shad size decreased with increasing abundance; but across eutrophic to hypereutrophic conditions, juvenile gizzard shad size increased despite continued increasing juvenile abundance. A conceptual framework for management, which incorporates reservoir productivity and anticipated effects of juvenile gizzard shad, should improve our success in attaining fisheries objectives across disparate systems. Fisheries ecologists typically view larval fish as quite distinct from juvenile or adult fish. Considering larval fish, we often investigate how system characteristics (i.e., prey availability, temperature, or water level fluctuations) affect larval survival and ultimately recruitment (Sale 1990; Pepin 1991; Leggett and DeBlois 1994). Beyond the age at which recruitment is set, we often investigate the effects of fish either on other fishes (i.e., competitive or predatory interactions; Knight et al. 1984; Kitchell and Crowder 1986; Olson et al. 1995) or on food web dynamics (i.e., effects of top predators on primary production and water clarity; McQueen et al. 1989; Kitchell and Carpenter 1993). Considering both success of larval fish and effects of older fish on system dynamics, variability among systems often compromises single explanations and challenges managers striving to achieve similar objectives in disparate systems. Further, larval success and fish effects are not independent, for the intensity of impact of older fish depends, in part, on their recruitment success. For example, interannual variability in recruitment of a top predator can produce interannual variability in food web dynamics (Carpenter 1988). Because fish recruitment not only varies interannually but among systems as well, intersystem recruitment variability should produce variable food web dynamics among systems. Within this context, we investigated recruitment of larval (age-0, <25 mm) gizzard shad Dorosoma cepedianum and subsequent food web effects of juvenile (age-0, >25 mm) gizzard shad along a productivity gradient of midwestern reservoirs. All shad lengths given throughout are total length. Juvenile Gizzard Shad Effects During the past 50 years, both gizzard shad and threadfin shad D. petenense have been stocked extensively in midwestern and southeastern reservoirs in attempts to improve sportfish production, but mixed results preclude a general conclusion about how shad influence sportfishes (Noble 1981; DeVries and Stein 1990). Even less is known regarding the specific effects of juvenile gizzard shad on sportfish recruitment. For example, juvenile gizzard shad may positively affect success of age-0 largemouth bass Micropterus salmoides if the shad remain vulnerable to this predator throughout its first summer (Storck 1986; Adams and DeAngelis 1987; Garvey and Stein 1998). Conversely, in shallow, hypereutrophic reservoirs, rapid growth rates of juvenile gizzard shad quickly make them invulnerable to age-0 largemouth bass predators (DeVries and Stein 1992; Stein et al. 1995). In these systems, consumption of zooplankton by juvenile gizzard shad can severely depress midsummer zooplankton (Dettmers and Stein 1992; DeVries and Stein 1992), which can lead to exploitative competition with, and poor recruitment of, zooplanktivorous larvae of later spawned fishes, particularly bluegills Lepomis macrochirus (DeVries et al. 1991; DeVries and Stein 1992; Stein et al. 1995; Garvey et al.1998a). In turn, existence of fewer age-0 bluegills in these hypereutrophic systems translates to slower growth of their age-0 largemouth bass predators (DeVries et al. 1991; Stein et al. 1995; Garvey and Stein 1998). Thus, both direction (i.e., positive or negative) and intensity of effects of juvenile gizzard shad on age-0 sportfish depend on juvenile gizzard shad size (which primarily dictates their vulnerability to predators) and abundance (which primarily dictates their consumptive demand for zooplankton), both of which vary across reservoirs (Noble 1981; Willis 1987; Buynak et al. 1992; Michaletz 1997). To date, we know little regarding the relationships among juvenile gizzard shad size and abundance and reservoir productivity. Yet variation in juvenile gizzard shad size and abundance among systems must be understood to generate broadscale management plans that incorporate variability in juvenile gizzard shad effects. Specifically, by identifying ecological mechanisms underlying juvenile gizzard shad size and abundance, we can determine the feasibility of manipulating gizzard shad populations to improve sportfish recruitment.
Whole-lake techniques are increasingly being used to selectively remove exotic plants, including ... more Whole-lake techniques are increasingly being used to selectively remove exotic plants, including Eurasian watermilfoil ( Myriophyllum spicatum L.). Fluridone (1-methyl-3-phenyl5-[3-(trifluoromethyl)phenyl]-4(1 H )-pyridinone), a systemic whole-lake herbicide, is selective for Eurasian watermilfoil within a narrow low concentration range. Because fluridone applications have the potential for large effects on plant assemblages and lake food webs, they should be evaluated at the whole-lake scale. We examined effects of low-dose (5 to 8 ppb) fluridone applications by comparing submersed plant assemblages, water quality and largemouth bass ( Micropterus salmoides ) growth rates and diets between three reference lakes and three treatment lakes one- and two-years post treatment. In the treatment lakes, fluridone reduced Eurasian watermilfoil cover without reducing native plant cover, although the duration of Eurasian watermilfoil reduction varied among treatment lakes. Large pre-treatment ...
... connections, terrestrial features and human effects at multiple spatial scales Patricia A. So... more ... connections, terrestrial features and human effects at multiple spatial scales Patricia A. Soranno, Katherine E. Webster, Kendra S. Cheruvelil and Mary T. Bremigan Introduction ... Biol. 43: 477497. KRATZ, TK, KE WEBSTER, CJ BOWSER, JJ MAGNUSON &amp; BJ BENSON. 1997. ...
North American Journal of Fisheries Management, Jan 8, 2011
We developed a linear discriminant function (LDF) using surface area, mean depth, fetch, and thre... more We developed a linear discriminant function (LDF) using surface area, mean depth, fetch, and three substrate descriptors to discriminate the presence and absence of walleyes Sander vitreus (formerly Stizostedion vitreum) in 120 northern Wisconsin lakes. The resulting LDF correctly classified 90% of walleye lakes and 85% of nonwalleye lakes. For model validation, the model classified 90% of walleye lakes and 93% of nonwalleye lakes in an independent set of 100 randomly selected lakes. In contrast, within walleye lakes, an LDF using the same variables correctly classified only 60% of 30 self-sustaining walleye lakes and 50% of 30 stocked walleye lakes. For model validation, the model classified 30% of self-sustaining walleye lakes and 73% of stocked walleye lakes in an independent set of 40 randomly selected lakes. To further assess the differences between walleye lakes with self-sustaining and stocked populations, the angler catch rates for largemouth bass Micropterus salmoides, smallmouth bass M. dolomieu, northern pike Esox lucius, and muskellunge E. masquinongy obtained from creel surveys during 1990-2001 were analyzed by means of a principal components analysis. The first principal component explained 29% of the variation and represented a linear contrast between the relative abundance of walleyes and muskellunge and the relative abundance of largemouth bass and northern pike. High largemouth bass and northern pike densities characterized lakes with stocked walleye populations, whereas high walleye and muskellunge densities characterized lakes with self-sustaining walleye populations. We conclude that physical features may be used to discriminate lakes where walleyes presently occur from lakes where walleyes do not presently occur, and that fish community differences exist between stocked and self-sustaining walleye populations in northern Wisconsin.
Growth and survival of stocked Sander spp. fingerlings can be influenced by timing of stocking in... more Growth and survival of stocked Sander spp. fingerlings can be influenced by timing of stocking in relation to the peak in density of larval gizzard shad Dorosoma cepedianum. However, coordinating stockings to coincide with peaks in gizzard shad density is difficult due to temporal ...
Fishing regulations are a common tool used by fisheries agencies to manage both the biological an... more Fishing regulations are a common tool used by fisheries agencies to manage both the biological and social aspects of fisheries. Given the prevalence with which fisheries agencies use regulations as management tools, there is a great need to improve our understanding of their effects. This symposium will address our current understanding of the effectiveness, consistency, and uncertainty of implementing angling regulations. Presentations span from the history of regulations to geographically broad case studies to synthetic reviews of what we know about implementation, evaluation and success of regulations. The symposium will review and identify critical areas of uncertainty regarding effects of sportfishing regulations and stimulate discussion centered on the questions like: “What lessons have been learned from notable evaluation efforts?” “How and what should we be measuring to evaluate regulation efficacy?” “How and why is the efficacy of regulations so variable?” “How can we impro...
Given the prevalence with which fisheries agencies use sportfishing regulations as a management t... more Given the prevalence with which fisheries agencies use sportfishing regulations as a management tool, there is great value in improving our assessment and understanding of conditions that influence the success of regulations in achieving their intended goals. Our overall aim is to document and discuss the known and unknown effects of sportfishing regulations from a synthetic perspective that considers the broad diversity of ecosystems and fisheries on which they are placed. To characterize the current state of knowledge, we will present findings from a literature review aiming to: (1) document the extent to which the biological, social, and economic effects of sportfishing regulations have been evaluated, and (2) determine if sportfishing regulations have consistent effects. To date, results of the literature review, which includes simulation modeling studies and field tests of regulations, have revealed some intriguing results. First, field evaluations of regulation effects have ra...
Background/Question/Methods We examined how a zooplankton assemblage of a eutrophic reservoir (Ac... more Background/Question/Methods We examined how a zooplankton assemblage of a eutrophic reservoir (Acton Lake) is responding to improvements in agricultural practices in the watershed. These improvements caused substantial declines in phosphorus and non-volatile suspended sediment (NVSS) inputs to this reservoir over the last 13 years. Mean annual phytoplankton biomass (chlorophyll) increased during this period, apparently due to decreased light limitation. Using a 12-year data set (1994-2006), we tested three hypotheses. 1. Zooplankton biomass will increase with time due to increases in chlorophyll and decreased NVSS concentrations. 2. Zooplankton community composition will shift from rotifer dominated to crustacean dominated. 3. Temporal changes in biomass and community composition will differ between spring and summer, because NVSS inputs are higher in spring while phytoplankton biomass is higher in summer. Results/Conclusions Zooplankton dynamics were very different in 1996 compared...
Catchment land uses, particularly agriculture and urban uses, have long been recognized as major ... more Catchment land uses, particularly agriculture and urban uses, have long been recognized as major drivers of nutrient concentrations in surface waters. However, few simple models have been developed that relate the amount of catchment land use to downstream freshwater nutrients. Nor are existing models applicable to large numbers of freshwaters across broad spatial extents such as regions or continents. This research aims to increase model performance by exploring three factors that affect the relationship between land use and downstream nutrients in freshwater: the spatial extent for measuring land use, hydrologic connectivity, and the regional differences in both the amount of nutrients and effects of land use on them. We quantified the effects of these three factors that relate land use to lake total phosphorus (TP) and total nitrogen (TN) in 346 north temperate lakes in 7 regions in Michigan, USA. We used a linear mixed modeling framework to examine the importance of spatial extent, lake hydrologic class, and region on models with individual lake nutrients as the response variable, and individual land use types as the predictor variables. Our modeling approach was chosen to avoid problems of multi-collinearity among predictor variables and a lack of independence of lakes within regions, both of which are common problems in broad-scale analyses of freshwaters. We found that all three factors influence land use-lake nutrient relationships. The strongest evidence was for the effect of lake hydrologic connectivity, followed by region, and finally, the spatial extent of land use measurements. Incorporating these three factors into relatively simple models of land use effects on lake nutrients should help to improve predictions and understanding of land use-lake nutrient interactions at broad scales.
Walleye represent the focus of a shared harvest fishery in the interconnected system of Mullett, ... more Walleye represent the focus of a shared harvest fishery in the interconnected system of Mullett, Burt, Pickerel and Crooked Lakes (Michigan’s Inland Waterway). However, a walleye population estimate in 2009 in Mullett Lake was 82% lower than an estimate conducted in 1998, which spurred interest in factors affecting overall walleye recruitment in this system. We conducted a survey of young-of-year walleye recruitment dynamics within the Inland Waterway and connecting rivers in the spring and summer of 2011-2012 in order to determine if low natural reproduction is contributing to the low walleye population. We hypothesized that low recruitment is a likely consequence of low larval walleye production and inadequate food resources to support larval walleye in this system. We sampled Ichthyoplankton and zooplankton concurrently in lake and river habitats to determine the spatial distribution and abundance of larval walleyes and their primary food source. Initial results indicate that riv...
In 2006 Michigan black bass fishing regulations were changed to include a spring catch-and-immedi... more In 2006 Michigan black bass fishing regulations were changed to include a spring catch-and-immediate release(CIR) season prior to a traditional possession season. During this time spawning male bass are vulnerable to the negative effects of angling. While the negative effects of angling on individual bass nests have been well documented, effects on population recruitment remain uncertain. Our research is part of an evaluation of potential population level effects of spring fishing on black bass. We used nest monitoring (2 lakes, 2009-2010, 32-132 nests per lake-year), experimental angling (1 lake 2010), young of year surveys and genetic techniques to assess the effects of spring fishing on bass recruitment. Young of year bass were assigned to their nest of origin based on pedigree reconstruction using multi-locus genotypes to determine the proportional contribution of each nest to recruitment. Results revealed that nests experimentally angled (CIR) produced five times fewer young of...
North American Journal of Fisheries Management, 2014
The accuracy of the Content should not be relied upon and should be independently verified with p... more The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden.
Transactions of the American Fisheries Society, 2012
This article may be used for research, teaching, and private study purposes. Any substantial or s... more This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.
Applying Landscape Ecology in Biological Conservation, 2002
24 Aquatic Conservation Planning: Using Landscape Maps to Predict Ecological Reference Conditions... more 24 Aquatic Conservation Planning: Using Landscape Maps to Predict Ecological Reference Conditions for Specific Waters PAUL W. SEELBACH, MICHAEL J. WILEY, PATRICIA A. SORANNO, AND MARY T. BREMIGAN 24. l Introduction Regional planning for ...
We analyzed a diverse set of 1,646 north-temperate lakes to evaluate the nutrient-color paradigm ... more We analyzed a diverse set of 1,646 north-temperate lakes to evaluate the nutrient-color paradigm that integrates total phosphorus (TP) and colored dissolved organic carbon to define lake trophic status. Our objectives were to quantify the combined influence of TP and color (Col) on lake trophic status, to determine if TP and Col had similar relationships with hydrogeomorphic (HGM) variables, and to examine how TP and Col affected the balance of heterotrophic and autotrophic processes. For the latter we examined the Col to chlorophyll a ratio (Col : Chl a), an index of allochthonous contributions of carbon to pelagic consumers, and deviations of lake pCO 2 from atmospheric, an index of net heterotrophy. Both Col and TP had strong effects on Chl a (positive) and Secchi transparency (negative), suggesting that ignoring Col would lead to misinterpretation of these widely used trophic status indicators. Lakes with high TP and Col tended to be shallower with large catchment to lake area ratios. Negative correlations with water retention time (WRT) were stronger for Col than for TP. Both TP and Col were related to forest and wetland land cover, although the direction of the relationships were opposite. Only 29% of the lakes had relatively high allochthony according to their Col : Chl a ratios; these were predominately high color, oligotrophic or mesotrophic lakes with short WRT. Over 90% of a subset of 682 lakes were net heterotrophic, with pCO 2 exceeding atmospheric levels. The positive relationship between pCO 2 and Col : Chl a suggests that only in very heterotrophic systems was the transfer of allochthonous carbon to pelagic consumers appreciable. Our results provide strong empirical support for the nutrient-color paradigm and highlight its importance both for management applications and for expanding our understanding of how lakes are influenced by terrestrial subsidies of carbon and nutrients.
We quantified relationships between local wetland cover in the riparian lake buffer and lake tota... more We quantified relationships between local wetland cover in the riparian lake buffer and lake total phosphorus (TP) and water color (color) using multilevel mixed-effects models that also incorporate landscape features such as hydrogeomorphology and land use at broad regional scales to determine the following: (1) Within regions, are local wetland relationships with TP and color affected by interactions with local land use or hydrogeomorphic variables? (2) Across regions, are local wetland relationships with TP and color different? And if so, (3) Are differences in local wetland relationships with TP and color a result of cross-scale interactions? We answered these questions by analyzing TP, color, and multiscaled landscape data for 1790 north temperate lakes. Local wetland-TP and wetland-color relationships were not affected by local-scale interactions. However, these same relationships were different when compared across regions, and these differences were related to cross-scale interactions with regional landscape characteristics. For example, regional human land use affected local wetland-TP relationships such that in regions with high amounts of agriculture, local wetlands were associated with decreased lake TP. However, in regions with low amounts of agriculture, local wetlands were associated with increased lake TP. In contrast, regional hydrogeomorphic characteristics influenced local wetland-color relationships such that in regions with high groundwater contribution, the strength of local wetland relationships were weak. Regional landscape setting influences local wetland relationships with TP and color through crossscale interactions, and lake TP and color are controlled by both local-scale wetland extent and regional-scale landscape variables.
Ecologists increasingly recognize the need to understand how landscapes and food webs interact. R... more Ecologists increasingly recognize the need to understand how landscapes and food webs interact. Reservoir ecosystems are heavily subsidized by nutrients and detritus from surrounding watersheds, and often contain abundant populations of gizzard shad, an omnivorous fish that consumes plankton and detritus. Gizzard shad link terrestrial landscapes and pelagic reservoir food webs by consuming detritus, translocating nutrients from sediment detritus to the water column, and consuming zooplankton. The abundance of gizzard shad increases with watershed agriculturalization, most likely through a variety of mechanisms operating on larval and adult life stages. Gizzard shad have myriad effects on reservoirs, including impacts on nutrients, phytoplankton, zooplankton, and fish, and many of their effects vary with ecosystem productivity (i.e., watershed land use). Interactive feedbacks among watersheds, gizzard shad populations, and reservoir food webs operate to maintain dominance of gizzard shad in highly productive systems. Thus, effective stewardship of reservoir ecosystems must incorporate both watershed and food-web perspectives.
Transactions of the American Fisheries Society, 1999
Recruitment success of larval fishes can determine subsequent effects of older life stages on eco... more Recruitment success of larval fishes can determine subsequent effects of older life stages on ecosystem structure and function. Because size and abundance of juvenile gizzard shad Dorosoma cepedianum determines, in large part, their effects on zooplankton abundance and sport-fish recruitment, we investigated recruitment of larval gizzard shad to the juvenile stage. We hypothesized that larval survival would correlate positively with availability of small (<0.40 mm) zooplankton and reservoir productivity and would dictate abundance of individuals reaching the juvenile stage. In downstream and upstream areas of four Ohio reservoirs ranging from mesotrophic to hypereutrophic, we evaluated larval gizzard shad success by comparing hatch, growth, and survival of weekly cohorts of larvae with availability of small zooplankton, and then we determined whether larval success could predict juvenile gizzard shad size and abundance. Total larval hatch abundance increased with reservoir productivity and was higher upstream than downstream. Weekly cohorts that produced abundant survivors reflected not only high hatch but also high survival in upstream areas during periods of abundant small zooplankton. Overall, larval hatch and survival predicted juvenile abundance but not juvenile size. Juvenile abundance increased with reservoir productivity, particularly in upstream areas, whereas juvenile size reflected the combined influence of juvenile abundance and reservoir productivity. Across mesotrophic to eutrophic conditions, juvenile gizzard shad size decreased with increasing abundance; but across eutrophic to hypereutrophic conditions, juvenile gizzard shad size increased despite continued increasing juvenile abundance. A conceptual framework for management, which incorporates reservoir productivity and anticipated effects of juvenile gizzard shad, should improve our success in attaining fisheries objectives across disparate systems. Fisheries ecologists typically view larval fish as quite distinct from juvenile or adult fish. Considering larval fish, we often investigate how system characteristics (i.e., prey availability, temperature, or water level fluctuations) affect larval survival and ultimately recruitment (Sale 1990; Pepin 1991; Leggett and DeBlois 1994). Beyond the age at which recruitment is set, we often investigate the effects of fish either on other fishes (i.e., competitive or predatory interactions; Knight et al. 1984; Kitchell and Crowder 1986; Olson et al. 1995) or on food web dynamics (i.e., effects of top predators on primary production and water clarity; McQueen et al. 1989; Kitchell and Carpenter 1993). Considering both success of larval fish and effects of older fish on system dynamics, variability among systems often compromises single explanations and challenges managers striving to achieve similar objectives in disparate systems. Further, larval success and fish effects are not independent, for the intensity of impact of older fish depends, in part, on their recruitment success. For example, interannual variability in recruitment of a top predator can produce interannual variability in food web dynamics (Carpenter 1988). Because fish recruitment not only varies interannually but among systems as well, intersystem recruitment variability should produce variable food web dynamics among systems. Within this context, we investigated recruitment of larval (age-0, <25 mm) gizzard shad Dorosoma cepedianum and subsequent food web effects of juvenile (age-0, >25 mm) gizzard shad along a productivity gradient of midwestern reservoirs. All shad lengths given throughout are total length. Juvenile Gizzard Shad Effects During the past 50 years, both gizzard shad and threadfin shad D. petenense have been stocked extensively in midwestern and southeastern reservoirs in attempts to improve sportfish production, but mixed results preclude a general conclusion about how shad influence sportfishes (Noble 1981; DeVries and Stein 1990). Even less is known regarding the specific effects of juvenile gizzard shad on sportfish recruitment. For example, juvenile gizzard shad may positively affect success of age-0 largemouth bass Micropterus salmoides if the shad remain vulnerable to this predator throughout its first summer (Storck 1986; Adams and DeAngelis 1987; Garvey and Stein 1998). Conversely, in shallow, hypereutrophic reservoirs, rapid growth rates of juvenile gizzard shad quickly make them invulnerable to age-0 largemouth bass predators (DeVries and Stein 1992; Stein et al. 1995). In these systems, consumption of zooplankton by juvenile gizzard shad can severely depress midsummer zooplankton (Dettmers and Stein 1992; DeVries and Stein 1992), which can lead to exploitative competition with, and poor recruitment of, zooplanktivorous larvae of later spawned fishes, particularly bluegills Lepomis macrochirus (DeVries et al. 1991; DeVries and Stein 1992; Stein et al. 1995; Garvey et al.1998a). In turn, existence of fewer age-0 bluegills in these hypereutrophic systems translates to slower growth of their age-0 largemouth bass predators (DeVries et al. 1991; Stein et al. 1995; Garvey and Stein 1998). Thus, both direction (i.e., positive or negative) and intensity of effects of juvenile gizzard shad on age-0 sportfish depend on juvenile gizzard shad size (which primarily dictates their vulnerability to predators) and abundance (which primarily dictates their consumptive demand for zooplankton), both of which vary across reservoirs (Noble 1981; Willis 1987; Buynak et al. 1992; Michaletz 1997). To date, we know little regarding the relationships among juvenile gizzard shad size and abundance and reservoir productivity. Yet variation in juvenile gizzard shad size and abundance among systems must be understood to generate broadscale management plans that incorporate variability in juvenile gizzard shad effects. Specifically, by identifying ecological mechanisms underlying juvenile gizzard shad size and abundance, we can determine the feasibility of manipulating gizzard shad populations to improve sportfish recruitment.
Whole-lake techniques are increasingly being used to selectively remove exotic plants, including ... more Whole-lake techniques are increasingly being used to selectively remove exotic plants, including Eurasian watermilfoil ( Myriophyllum spicatum L.). Fluridone (1-methyl-3-phenyl5-[3-(trifluoromethyl)phenyl]-4(1 H )-pyridinone), a systemic whole-lake herbicide, is selective for Eurasian watermilfoil within a narrow low concentration range. Because fluridone applications have the potential for large effects on plant assemblages and lake food webs, they should be evaluated at the whole-lake scale. We examined effects of low-dose (5 to 8 ppb) fluridone applications by comparing submersed plant assemblages, water quality and largemouth bass ( Micropterus salmoides ) growth rates and diets between three reference lakes and three treatment lakes one- and two-years post treatment. In the treatment lakes, fluridone reduced Eurasian watermilfoil cover without reducing native plant cover, although the duration of Eurasian watermilfoil reduction varied among treatment lakes. Large pre-treatment ...
... connections, terrestrial features and human effects at multiple spatial scales Patricia A. So... more ... connections, terrestrial features and human effects at multiple spatial scales Patricia A. Soranno, Katherine E. Webster, Kendra S. Cheruvelil and Mary T. Bremigan Introduction ... Biol. 43: 477497. KRATZ, TK, KE WEBSTER, CJ BOWSER, JJ MAGNUSON &amp; BJ BENSON. 1997. ...
North American Journal of Fisheries Management, Jan 8, 2011
We developed a linear discriminant function (LDF) using surface area, mean depth, fetch, and thre... more We developed a linear discriminant function (LDF) using surface area, mean depth, fetch, and three substrate descriptors to discriminate the presence and absence of walleyes Sander vitreus (formerly Stizostedion vitreum) in 120 northern Wisconsin lakes. The resulting LDF correctly classified 90% of walleye lakes and 85% of nonwalleye lakes. For model validation, the model classified 90% of walleye lakes and 93% of nonwalleye lakes in an independent set of 100 randomly selected lakes. In contrast, within walleye lakes, an LDF using the same variables correctly classified only 60% of 30 self-sustaining walleye lakes and 50% of 30 stocked walleye lakes. For model validation, the model classified 30% of self-sustaining walleye lakes and 73% of stocked walleye lakes in an independent set of 40 randomly selected lakes. To further assess the differences between walleye lakes with self-sustaining and stocked populations, the angler catch rates for largemouth bass Micropterus salmoides, smallmouth bass M. dolomieu, northern pike Esox lucius, and muskellunge E. masquinongy obtained from creel surveys during 1990-2001 were analyzed by means of a principal components analysis. The first principal component explained 29% of the variation and represented a linear contrast between the relative abundance of walleyes and muskellunge and the relative abundance of largemouth bass and northern pike. High largemouth bass and northern pike densities characterized lakes with stocked walleye populations, whereas high walleye and muskellunge densities characterized lakes with self-sustaining walleye populations. We conclude that physical features may be used to discriminate lakes where walleyes presently occur from lakes where walleyes do not presently occur, and that fish community differences exist between stocked and self-sustaining walleye populations in northern Wisconsin.
Growth and survival of stocked Sander spp. fingerlings can be influenced by timing of stocking in... more Growth and survival of stocked Sander spp. fingerlings can be influenced by timing of stocking in relation to the peak in density of larval gizzard shad Dorosoma cepedianum. However, coordinating stockings to coincide with peaks in gizzard shad density is difficult due to temporal ...
Fishing regulations are a common tool used by fisheries agencies to manage both the biological an... more Fishing regulations are a common tool used by fisheries agencies to manage both the biological and social aspects of fisheries. Given the prevalence with which fisheries agencies use regulations as management tools, there is a great need to improve our understanding of their effects. This symposium will address our current understanding of the effectiveness, consistency, and uncertainty of implementing angling regulations. Presentations span from the history of regulations to geographically broad case studies to synthetic reviews of what we know about implementation, evaluation and success of regulations. The symposium will review and identify critical areas of uncertainty regarding effects of sportfishing regulations and stimulate discussion centered on the questions like: “What lessons have been learned from notable evaluation efforts?” “How and what should we be measuring to evaluate regulation efficacy?” “How and why is the efficacy of regulations so variable?” “How can we impro...
Given the prevalence with which fisheries agencies use sportfishing regulations as a management t... more Given the prevalence with which fisheries agencies use sportfishing regulations as a management tool, there is great value in improving our assessment and understanding of conditions that influence the success of regulations in achieving their intended goals. Our overall aim is to document and discuss the known and unknown effects of sportfishing regulations from a synthetic perspective that considers the broad diversity of ecosystems and fisheries on which they are placed. To characterize the current state of knowledge, we will present findings from a literature review aiming to: (1) document the extent to which the biological, social, and economic effects of sportfishing regulations have been evaluated, and (2) determine if sportfishing regulations have consistent effects. To date, results of the literature review, which includes simulation modeling studies and field tests of regulations, have revealed some intriguing results. First, field evaluations of regulation effects have ra...
Background/Question/Methods We examined how a zooplankton assemblage of a eutrophic reservoir (Ac... more Background/Question/Methods We examined how a zooplankton assemblage of a eutrophic reservoir (Acton Lake) is responding to improvements in agricultural practices in the watershed. These improvements caused substantial declines in phosphorus and non-volatile suspended sediment (NVSS) inputs to this reservoir over the last 13 years. Mean annual phytoplankton biomass (chlorophyll) increased during this period, apparently due to decreased light limitation. Using a 12-year data set (1994-2006), we tested three hypotheses. 1. Zooplankton biomass will increase with time due to increases in chlorophyll and decreased NVSS concentrations. 2. Zooplankton community composition will shift from rotifer dominated to crustacean dominated. 3. Temporal changes in biomass and community composition will differ between spring and summer, because NVSS inputs are higher in spring while phytoplankton biomass is higher in summer. Results/Conclusions Zooplankton dynamics were very different in 1996 compared...
Catchment land uses, particularly agriculture and urban uses, have long been recognized as major ... more Catchment land uses, particularly agriculture and urban uses, have long been recognized as major drivers of nutrient concentrations in surface waters. However, few simple models have been developed that relate the amount of catchment land use to downstream freshwater nutrients. Nor are existing models applicable to large numbers of freshwaters across broad spatial extents such as regions or continents. This research aims to increase model performance by exploring three factors that affect the relationship between land use and downstream nutrients in freshwater: the spatial extent for measuring land use, hydrologic connectivity, and the regional differences in both the amount of nutrients and effects of land use on them. We quantified the effects of these three factors that relate land use to lake total phosphorus (TP) and total nitrogen (TN) in 346 north temperate lakes in 7 regions in Michigan, USA. We used a linear mixed modeling framework to examine the importance of spatial extent, lake hydrologic class, and region on models with individual lake nutrients as the response variable, and individual land use types as the predictor variables. Our modeling approach was chosen to avoid problems of multi-collinearity among predictor variables and a lack of independence of lakes within regions, both of which are common problems in broad-scale analyses of freshwaters. We found that all three factors influence land use-lake nutrient relationships. The strongest evidence was for the effect of lake hydrologic connectivity, followed by region, and finally, the spatial extent of land use measurements. Incorporating these three factors into relatively simple models of land use effects on lake nutrients should help to improve predictions and understanding of land use-lake nutrient interactions at broad scales.
Walleye represent the focus of a shared harvest fishery in the interconnected system of Mullett, ... more Walleye represent the focus of a shared harvest fishery in the interconnected system of Mullett, Burt, Pickerel and Crooked Lakes (Michigan’s Inland Waterway). However, a walleye population estimate in 2009 in Mullett Lake was 82% lower than an estimate conducted in 1998, which spurred interest in factors affecting overall walleye recruitment in this system. We conducted a survey of young-of-year walleye recruitment dynamics within the Inland Waterway and connecting rivers in the spring and summer of 2011-2012 in order to determine if low natural reproduction is contributing to the low walleye population. We hypothesized that low recruitment is a likely consequence of low larval walleye production and inadequate food resources to support larval walleye in this system. We sampled Ichthyoplankton and zooplankton concurrently in lake and river habitats to determine the spatial distribution and abundance of larval walleyes and their primary food source. Initial results indicate that riv...
In 2006 Michigan black bass fishing regulations were changed to include a spring catch-and-immedi... more In 2006 Michigan black bass fishing regulations were changed to include a spring catch-and-immediate release(CIR) season prior to a traditional possession season. During this time spawning male bass are vulnerable to the negative effects of angling. While the negative effects of angling on individual bass nests have been well documented, effects on population recruitment remain uncertain. Our research is part of an evaluation of potential population level effects of spring fishing on black bass. We used nest monitoring (2 lakes, 2009-2010, 32-132 nests per lake-year), experimental angling (1 lake 2010), young of year surveys and genetic techniques to assess the effects of spring fishing on bass recruitment. Young of year bass were assigned to their nest of origin based on pedigree reconstruction using multi-locus genotypes to determine the proportional contribution of each nest to recruitment. Results revealed that nests experimentally angled (CIR) produced five times fewer young of...
North American Journal of Fisheries Management, 2014
The accuracy of the Content should not be relied upon and should be independently verified with p... more The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden.
Transactions of the American Fisheries Society, 2012
This article may be used for research, teaching, and private study purposes. Any substantial or s... more This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.
Applying Landscape Ecology in Biological Conservation, 2002
24 Aquatic Conservation Planning: Using Landscape Maps to Predict Ecological Reference Conditions... more 24 Aquatic Conservation Planning: Using Landscape Maps to Predict Ecological Reference Conditions for Specific Waters PAUL W. SEELBACH, MICHAEL J. WILEY, PATRICIA A. SORANNO, AND MARY T. BREMIGAN 24. l Introduction Regional planning for ...
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