Carl R. Ruetz

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

Abstract 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 Sande...

Gear Bias in Fyke Netting: Evaluating Soak Time, Fish Density, and Predators

Abstract Knowledge of gear bias is critical for conducting valid population and community assessments. We studied the biases in fyke netting by investigating the individual effects of soak time (fyke nets were fished for 6, 24, or 48 h), fish density (fyke nets were stocked with 0, 30, or 60 fish/net), and predators (fyke nets were stocked with one or zero bowfin Amia calva) on the escape probability and number of individuals captured (i.e., catch) for three fish species. Overall, escape probabilities were consistently lower for round gobies Neogobius melanostomus than for bluntnose minnows Pimephales notatus and banded killifish Fundulus diaphanus. Both escape probability and catch increased with soak time. Escape probabilities were lower at high fish densities and in the presence of a predator, whereas catch appeared to be unaffected by both factors. We documented predation on fish stocked in fyke nets by free-ranging bowfins and yellow bullheads Ameiurus natalis, which is a potential source of bias tha...

Current Status and Trends in Muskegon Lake, Michigan

ABSTRACT A long-term monitoring program was initiated in 2003 to determine the ecological status of Muskegon Lake, a Great Lakes Area of Concern. This paper presents data generated from the first 3 years of the monitoring program, discusses how the data are being used to establish and justify lake restoration targets, and assesses how water quality conditions have changed over time. Between 1972 and 2005, lake-wide averages of total phosphorus and soluble reactive phosphorus from the water surface have declined from 68 to 27 μg/L and from 20 to 5 μg/L, respectively. In addition, average chlorophyll α concentrations have declined from 25 to 6 μg/L over this period, while Secchi disk depths have increased from 1.5 to 2.2 m. Wastewater diversion, and perhaps dreissenid filtering activity, is most likely responsible for these changes. However, nitrate concentrations have increased from 70 to 270 μg/L over the same time period. During 2003–2005, phytoplankton abundance and fish catch were lower in the spring compared to the summer and fall. Microcystis was the most abundant phytoplankton genus; the fish community generally was dominated by round goby (Neogobius melanostomus) in spring and summer, and sunfishes (Centrarchidae) in the fall. Dreissenid abundance was highly variable over time, but densities were low relative to Saginaw Bay. Approximately 65% of the Muskegon Lake shoreline has been hardened (i.e., physically altered). Overall, the water quality of Muskegon Lake has improved over the past 30 years, but environmental challenges still exist, including contaminated sediments, loss of natural habitat, and invasive species.

Evaluating Passive Integrated Transponder Tags for Marking Mottled Sculpins: Effects on Growth and Mortality

Abstract We examined the efficacy of marking mottled sculpins Cottus bairdii with passive integrated transponder (PIT) tags in a 28-d laboratory study. A 2 × 3 factorial experiment was used to compare growth and mortality of tagged fish with those of a control group (i.e., not injected with tags) among three size-classes (55–59, 60–69, and ≥70 mm total length [TL]). Fish were measured on the day of tagging and each week thereafter. Among 26 tagged fish (56–83 mm TL), both survival and tag retention were 96% or greater. Survival was 100% among 25 control fish (56–85 mm TL). Instantaneous growth rates (calculated on a cumulative basis for each sampling period based on mass) for tagged fish were significantly lower than those for control fish during the first 14 d, suggesting that mottled sculpins recovered from PIT tagging after 14–21 d. Additionally, fish size did not significantly affect the instantaneous growth rate of PIT-tagged fish relative to that of the control group. More importantly, we found (on ...

Distribution of Round Gobies in Coastal Areas of Lake Michigan: Are Wetlands Resistant to Invasion?

ABSTRACT Great Lakes coastal wetlands may be more resistant to invasion by certain nonindigenous species and thus serve as refuge habitats for native species. As a first step in testing this hypothesis, we investigated the distribution of round goby (Apollonia melanostomus, formerly Neogobius melanostomus) in the lower reaches of several Lake Michigan tributary systems that contain both wet-land and lake habitats near their confluences with Lake Michigan. Using fyke nets, we sampled round gobies in lake and adjacent wetland habitats in four systems in 2004 and six systems in 2005. In each macrohabitat (lake or wetland), we sampled three microhabitats (mono-dominant stands of Nuphar, beds of submersed aquatic vegetation, and bare sediment). We found that round goby catch was generally lower in wetland macrohabitats than adjacent lake macrohabitats and that round gobies appeared to prefer beds of submersed aquatic vegetation in lakes among the three microhabitats. The majority of round gobies in all habitats were relatively small (< 7 cm standard length). We also found a significant negative correlation between round goby catch and distance of sampling points from the Lake Michigan shoreline in 2005, suggesting that 1) Lake Michigan nearshore waters (including the connecting navigation channels and pier areas) may be serving as round goby spawning and nursery habitats with subsequent dispersal into the tributary lake/wetland complexes, and 2) round gobies may still be invading these systems from Lake Michigan. Our results provide evidence that coastal wetland habitats are more resistant to invasion by round gobies than adjacent lake habitats.

Population genetic structure of the round goby in Lake Michigan: implications for dispersal of invasive species

Understanding subsequent dispersal of non-native species following introduction is important for predicting the extent and speed of range expansion and is critical for effective management and risk assessment. Post-introduction dispersal may occur naturally or via human transport, but assessing the relative contribution of each is difficult for many organisms. Here, we use data from seven microsatellite markers to study patterns of dispersal and gene flow among 12 pierhead populations of the round goby (Neogobius melanostomus) in Lake Michigan. We find significant population structure among sampling sites within this single Great Lake: (1) numerous populations exhibited significant pairwise FST and (2) a Bayesian assignment analysis revealed three distinct genetic clusters, corresponding to different pierhead locations, and genetic admixture between these clusters in the remaining populations. Genetic differentiation (FST) is generally related to geographic distance (i.e., isolation by distance), but is periodically interrupted at the scale of Lake Michigan due to gene flow among geographically distant sites. Moreover, average genetic differentiation among populations exhibit a significant, negative correlation with the amount of shipping cargo at ports. Our results, therefore, provide evidence that genetic structure of the round goby in Lake Michigan results from limited natural dispersal with frequent long-distance dispersal through anthropogenic activities such as commercial shipping. Our study suggests that while round gobies can undoubtedly disperse and found new populations through natural dispersal mechanisms, their spread within and among the Great Lakes is likely aided by transport via ships. We, therefore, recommend that ballast-water treatment and management may limit the spread of non-native species within the Great Lakes after the initial introduction in addition to preventing the introduction of non-native species to the Great Lakes.

Habitat Use and Diet of the Round Goby (Neogobius melanostomus) in Coastal Areas of Lake Michigan and Lake Huron

ABSTRACT The non-indigenous round goby (Neogobius melanostomus) has caused considerable impact in the Laurentian Great Lakes. We sampled round gobies in shoreline habitats and tributary systems of Lake Michigan and Lake Huron to determine patterns of habitat use and diet, including the extent dreissenid mussels were consumed. Along the shoreline, round goby catch did not significantly differ based on the presence of emergent vegetation, but deeper habitats were preferred relative to shallow areas closer to shore. In tributary systems, submersed aquatic vegetation in coastal lakes was preferred. The majority of round gobies were small, generally between 3 and 7 cm, and had diets comprised mainly of zooplankton and dipterans with few dreissenids. Our results indicate that the round goby has invaded coastal areas inconsistently across habitat types and that the species can proliferate in the absence of dreissenid mussels.

Energy Density of Introduced Round Goby Compared with Four Native Fishes in a Lake Michigan Tributary

Abstract The round goby Neogobius melanostomus is an invasive species that has changed Great Lakes food webs and become an important prey for many predators. We tested whether the round goby from a Lake Michigan tributary was energetically equivalent to four native fishes: Mottled sculpin Cottus bairdii, johnny darter Etheostoma nigrum, bluntnose minnow Pimephales notatus, and rock bass Ambloplites rupestris. We found positive linear relationships between energy density and the percent dry weight of a fish for each species. We also found evidence of temporal and spatial variation in round goby energy density. Energy density was lower in spring and summer than in fall. The spatial variation in energy density may be linked to the inclusion of the low-quality prey, dreissenid mussels, in the diets of larger round goby. For a given size, the johnny darter and bluntnose minnow had the highest energy density while mottled sculpin had the lowest. Our results show that the energy density of the round goby is inte...

Biotic responses to low-concentration urban road runoff

Abstract A major effect of urbanization on streams is the input of stormwater (SW) runoff from impervious surfaces. This water may contain excess nutrients, heavy metals, and other organic contaminants. These inputs are potential stressors or stimulants for algae, invertebrates, and fish within the aquatic community. We conducted a controlled experiment in mesocosms (∼1300-L tanks) to evaluate the effect of SW quality on different trophic levels. SW runoff was collected before it entered Little Black Creek, which is a tributary draining an urbanized subcatchment in western Michigan. The captured runoff was used to create the following treatments: 0% SW (control, n  =  4), 50% SW (n  =  4), or 100% SW (n  =  4). Nested within each mesocosm were exclosure treatments containing different combinations of algae, snails (Physa sp.), and fish (pumpkinseed: Lepomis gibbosus). SW did not have an overall effect on algal biomass or metabolic activity in the mesocosms. Algal community composition in the 0% SW treatment was significantly different from the 100% treatment at the end of the experiment. Mortality and growth rates of the fish and snails were not significantly affected by SW treatment. The absence of a strong effect of SW on algal biomass and metabolism or fish and snail growth in the mesocosms might have been the result of relatively low concentrations of contaminants in the SW. Changes in algal community composition in the mesocosms suggest that community composition is a more sensitive measure of water quality than either algal biomass or mortality and growth rates of fish and snails. SW quality is extremely variable, even among different storm events at the same location, so extrapolating results from one storm or one system to another should be done with caution. Our findings show that SW quality does not necessarily have negative impacts on stream biota.

Recruitment Dynamics of Age-0 Yellow Perch in a Drowned River Mouth Lake: Assessing Synchrony with Nearshore Lake Michigan

Abstract We assessed recruitment dynamics of juvenile Yellow Perch Perca flavescens in coastal habitats of eastern Lake Michigan. To investigate recruitment patterns and associations with environmental factors in a coastal drowned river mouth (DRM) lake, we sampled juvenile Yellow Perch seasonally in Muskegon Lake, Michigan, during 2003–2011. We also sampled three nearshore sites in Lake Michigan each fall to evaluate synchrony between the DRM lake and nearshore habitat. In Muskegon Lake, age-0 Yellow Perch CPUE during fall was high in 2005 and 2007; moderate in 2008, 2010, and 2011; and low in other years. Fall CPUE (age 0) was positively associated with CPUE in the next spring (age 1; slope = 0.98; R 2 = 0.95), which we attribute to high overwinter survival. Fall CPUE of age-0 Yellow Perch showed a positive relationship with June air temperature (R 2 = 0.76), suggesting that warm conditions at early larval stages positively influence recruitment of juveniles. Juvenile recruitment in Muskegon Lake was no...