Spatial Patterns of Fish Communities in Lake Michigan Tributaries

Understanding spatial patterns in freshwater fish communities is critical for the successful management of natural resources as well as a vital component for understanding aquatic ecosystems. Spatial patterns of species similarity of freshwater fish assemblages can be affected by dispersal processes and environmental conditions. We hypothesized that as distance increased between study systems, species similarity would decrease. We sampled 15 drowned river mouths (DRMs) connected to Lake Michigan by conducting 10-minute electrofishing transects (n = 5-6 per DRM) parallel to the shoreline in each DRM to characterize littoral fish assemblages. At each transect, we also characterized environmental conditions (e.g., specific conductivity or number of houses/buildings along shoreline). We captured 3,080 individual fish representing 45 species across the 15 DRMs, with catch among DRMs ranging from 115 to 358 individuals per system and species richness ranging from 11 to 26 species per system. The most abundant species in the catch were yellow perch Perca flavescens (13.9%), pumpkinseed Lepomis gibbosus (10.9%), and bluegill Lepomis macrochirus (9.8%). We found a weak positive correlation between species similarity and distance between each pair of DRMs (R2 = 0.03), which did not support our hypothesis that species similarity would decrease with distance, even though we found evidence of spatial autocorrelation of environmental variables. A potential explanation for our findings is related to gear selectivity associated with boat electrofishing. We suggest that sampling fish with additional gear or approaches is necessary to more rigorously test for the spatial pattern of species similarity among DRMs

Reducing effects of dispersal on the bias of 2-sample mark-recapture estimators of stream fish abundance

The 2-sample mark-recapture method with Chapman’s estimator is often used by inland fishery managers to estimate the reach-scale abundance of stream fish. An important assumption of this method is that no dispersal into or out of the study reach occurs between the two samples. Violations of this assumption are probably common in practice, but their effect on bias (systematic error) of abundance estimates is poorly understood, especially in small populations. Estimation methods permitting dispersal exist but, for logistical reasons, often are infeasible for routine assessments in streams. The purpose of this paper is to extend available results regarding effects of dispersal on the bias of Chapman’s estimator as applied to reach-scale studies of stream fish abundance. We examine for the first time the joint effects of dispersal and sampling variation on the bias of this estimator. To reduce the bias effects of dispersal, we propose a modified sampling scheme in which the original study reach is expanded, a central subreach is sampled during the mark session (sample 1), and the entire reach is sampled during the recapture session (sample 2). This modified sampling scheme can substantially reduce bias effects of dispersal without requiring unique marking of individual fish or additional site visits. Analytical and simulation results show that sampling variation tends to create negative bias with respect to study-reach abundance, while dispersal tends to create positive bias; the net effect can be positive, negative, or zero, depending on the true abundance, capture probabilities, and amount and nature of dispersal. In most cases, simply expanding the study reach is an effective way to reduce dispersal-related bias of Chapman’s estimator, but expanding the study reach and employing the modified sampling scheme we propose is a better alternative for accurately estimating abundance with the same level of sampling effort

Sampling a Littoral Fish Assemblage: Comparison of Small-Mesh Fyke Netting and Boat Electrofishing

We compared small-mesh (4-mm) fyke netting and boat electrofishing for sampling a littoral fish assemblage in Muskegon Lake, Michigan. We hypothesized that fyke netting selects for small-bodied fishes and electrofishing selects for large-bodied fishes. Three sites were sampled during May (2004 and 2005), July (2005 only), and September (2004 and 2005). We found that the species composition of captured fish differed considerably between fyke netting and electrofishing based on nonmetric multidimensional scaling (NMDS). Species strongly associated with fyke netting (based on NMDS and relative abundance) included the brook silverside Labidesthes sicculus, banded killifish Fundulus diaphanus, round goby Neogobius melanostomus, mimic shiner Notropis volucellus, and bluntnose minnow Pimephales notatus, whereas species associated with electrofishing included the Chinook salmon Oncorhynchus tshawytscha, catostomids (Moxostoma spp. and Catostomus spp.), freshwater drum Aplodinotus grunniens, walleye Sander vitreus, gizzard shad Dorosoma cepedianum, and common carp Cyprinus carpio. The total length of fish captured by electrofishing was 12.8 cm (95% confidence interval ¼ 5.5– 17.2 cm) greater than that of fish captured by fyke netting. Size selectivity of the gears contributed to differences in species composition of the fish captured, supporting our initial hypothesis. Thus, small-mesh fyke nets and boat electrofishers provided complementary information on a littoral fish assemblage. Our results support use of multiple gear types in monitoring and research surveys of fish assemblages. Copyright by the American Fisheries Society 2007, Originally published in the North American Journal of Fisheries Management 27: 825-831, 2007

Scientists’ Warning to Humanity: Rapid degradation of the world\u27s large lakes

Large lakes of the world are habitats for diverse species, including endemic taxa, and are valuable resources that provide humanity with many ecosystem services. They are also sentinels of global and local change, and recent studies in limnology and paleolimnology have demonstrated disturbing evidence of their collective degradation in terms of depletion of resources (water and food), rapid warming and loss of ice, destruction of habitats and ecosystems, loss of species, and accelerating pollution. Large lakes are particularly exposed to anthropogenic and climatic stressors. The Second Warning to Humanity provides a framework to assess the dangers now threatening the world\u27s large lake ecosystems and to evaluate pathways of sustainable development that are more respectful of their ongoing provision of services. Here we review current and emerging threats to the large lakes of the world, including iconic examples of lake management failures and successes, from which we identify priorities and approaches for future conservation efforts. The review underscores the extent of lake resource degradation, which is a result of cumulative perturbation through time by long-term human impacts combined with other emerging stressors. Decades of degradation of large lakes have resulted in major challenges for restoration and management and a legacy of ecological and economic costs for future generations. Large lakes will require more intense conservation efforts in a warmer, increasingly populated world to achieve sustainable, high-quality waters. This Warning to Humanity is also an opportunity to highlight the value of a long-term lake observatory network to monitor and report on environmental changes in large lake ecosystems

Environmental Variation, Fish Community Composition, and Brown Trout Survival in the Pigeon River, Ottawa County, Michigan

The Pigeon River, a small coolwater stream in western Michigan, has a history of hydrologic, stream habitat, and water quality degradation that led to the loss of its trout population by the late 1980s. After regulatory and watershed management efforts to reduce point- and nonpoint source pollution in the 1990s, the Michigan Department of Natural Resources reinstituted brown trout (Salmo trutta) stocking in 2003. As part of these efforts, we monitored water quality in the Pigeon River each fall between 1996 and 2008, and conducted stream surveys in 2006 and 2007 to evaluate the fish community and outcome of trout stocking. Water quality tended to improve and stabilize through time, although point- and nonpoint source pollution still contributed to water quality problems. Hydrologic instability, caused by wetland drainage, agricultural land use, and irrigation withdrawals from the lower mainstream, created periods of environmental stress. As a result, the fish community of the Pigeon River was dominated by common tolerant warmwater species, typical of agricultural watersheds in southern Michigan. Nonetheless, brown trout surviving from initial stockings in 2003 and 2004 had attained lengths of between 18 and 24 inches by 2007, suggesting the thermal regime, water quality, stream habitat, and forage base of macroinvertebrates and small fish were suitable to maintain a stocked brown trout population. Continued efforts to improve water quality, protect instream habitat, reduce high stormflows, and maintain adequate summer baseflows are needed to fully restore environmental conditions for the native fish community and stocked brown trout in the Pigeon River

Effects of shoreline and watershed development on eastern Lake Michigan drowned river mouth ecology

Lake Michigan’s drowned river mouths (DRM) are hydrologically unique systems with riverine and large-lake influences that create biologically diverse ecosystems. Serving as focal points for human development due to the ecosystem services they provide, DRMs have experienced a history of industrialization, urbanization, and are now moving towards an era of rehabilitation. Today, DRM shorelines have been hardened, their riparian zones have been severely altered, and their watersheds exist on a latitudinal gradient of less to greater anthropogenic stress (agriculture and development). The main goal of this study was to understand the current ecological state of DRMs related to anthropogenic development across multiple spatial scales. I hypothesized (1) that there is a latitudinal gradient in indicators of water quality in DRM lakes of eastern Lake Michigan, which is the result of natural land cover and anthropogenic land use, and (2) that natural shorelines support more fish species less tolerant to environmental degradation than residential and hardened shorelines in DRM lakes. To assess the impacts of development on DRM fish communities, I sampled the littoral fish community of 6 DRMs at shorelines hardened with riprap or seawall, residential shorelines with lawns and homes, and natural shorelines with intact riparian vegetation. Within DRMs, I did not find that shoreline structure was a significant driver of fish assemblages. However, I found a general gradient in DRMs from north to south with more fish species tolerant to degraded conditions in southern DRMs, corresponding to watersheds with more development and agriculture in southern DRMs than those with more forested land cover in northern DRMs. I also sampled 12 DRMs for water quality and found that chlorophyll-a and total phosphorus (TP) concentrations increase in southern DRMs, which corresponds to increased agriculture and development. My research suggests that the impacts of land use at the watershed scale were a strong driver of fish assemblages and water quality among the DRMs in eastern Lake Michigan, which will be useful to managers and researchers concerned with coastal habitats in Lake Michigan

Water Quality and Land Cover in Lake Michigan Drowned River Mouths

PURPOSE: Lake Michigan’s drowned river mouth (DRM) systems are hydrologically unique due to their riverine and large-lake influences that create biologically diverse ecosystems. DRMs serve as focal points for human development and the confluence of watershed impacts, which can have substantial impacts on DRM ecosystems. We hypothesized that greater anthropogenic development in southern DRM watersheds would be reflected in poorer water quality indicators than less developed northern DRM watersheds. SUBJECTS: We sampled 12 DRMs along a latitudinal gradient in eastern Lake Michigan. METHODS: We used standard methods to measure water quality, and we used publicly available data to characterize land cover. ANALYSES: We then used a combination of univariate (simple linear regression and ANOVA) and multivariate (PCA) statistical tests to examine the significance of spatial patterns. RESULTS: We found that watershed human population density and agriculture were strong drivers of chlorophyll-a and TP – indicators of poorer water quality – and that these measures increase in southern DRMs. Within DRMs, we found that TP concentrations were typically greatest near the river mouth and decreased closer to the outflow into Lake Michigan. CONCLUSIONS: Our results suggest that land use drives chlorophyll-a and TP (i.e., indicators of ecosystem productivity) and will be used to better understand the effects of human development on DRMs