Forecasting the distribution of the invasive round goby (Neogobius melanostomus) in Wisconsin tributaries to Lake Michigan

Abstract: The Laurentian Great Lakes host more than 180 non-native species, including several that have resulted in major economic and ecological effects. This list includes the round goby (Neogobius melanostomus), an aggressive, benthic Ponto-Caspian fish that has established large populations in coastal Great Lakes habitats. Here, we document the inland dispersal of round gobies into Wisconsin tributaries of Lake Michigan. Round gobies were detected in 26 of 73 streams (36%) and found >10 km upstream of Lake Michigan in nine watersheds. Round goby presence-absence was modeled using landscape-scale data from these invaded streams. We forecasted the future spread of round goby within Wisconsin's Lake Michigan basin using our best model (80% accuracy), which included watershed area, stream gradient, and watershed slope as predictors. Round gobies were predicted to invade 1369 km of stream habitat up to the first stream barrier, and 8878 km of stream was identified as suitable looking beyond barriers at the broader Lake Michigan watershed (Wisconsin only). Our results depict the Great Lakes as a springboard for invasive species to disperse into inland ecosystems and, because round gobies are not usually reported in small streams in their native range, emphasize the utility of data from invaded regions when forecasting invasive species distributions. Résumé : Les Grands Lacs Laurentiens contiennent >180 espèces non indigènes dont plusieurs ont eu des effets économi-ques et écologiques importants. Cette liste comprend le gobie à taches noires (Neogobius melanostomus), un poisson agressif d'origine ponto-caspienne, qui a formé de grandes populations dans les habitats côtiers des Grands Lacs. Nous apportons des informations sur la dispersion vers l'intérieur des gobies à taches noires dans les tributaires du lac Michigan au Wisconsin. Les gobies à taches noires se retrouvent dans 26 de 73 cours d'eau (36 %) et à >10 km en amont du lac Michigan dans neuf bassins versants. Nous avons modélisé la présence-absence des gobies à taches noires à l'aide de données à l'échelle du paysage provenant des cours d'eau envahis. Nous prédisons la dispersion future du gobie à taches noires dans le bassin versant du lac Michigan au Wisconsin à l'aide de notre meilleur (80 % d'exactitude) modèle qui inclut la surface du bassin versant, le gradient du cours d'eau et la pente du bassin comme variables prédictives. Notre pré-diction est que les gobies à taches noires vont envahir 1369 km d'habitat lotique jusqu'à la première barrière dans les cours d'eau; de plus, 8878 km de cours d'eau au-delà des barrières paraissent des habitats convenables dans le bassin élargi du lac Michigan (dans le seul Wisconsin). Nos résultats décrivent les Grands Lacs comme des tremplins pour les espèces envahissantes vers les écosystèmes de l'intérieur; comme les gobies à taches noires ne se retrouvent pas générale-ment dans les petits cours d'eau dans leur aire de répartition indigène, nos résultats soulignent l'utilité de données provenant des régions envahies pour la prédiction des répartitions des espèces envahissantes. [Traduit par la Rédaction

Spatiotemporal patterns in trophic niche overlap among five salmonines in Lake Michigan, USA

Native lake trout (Salvelinus namaycush) and introduced Chinook salmon (Oncorhynchus tshawytscha), coho salmon (Oncorhynchus kisutch), steelhead (Oncorhynchus mykiss), and brown trout (Salmo trutta) are major predators in Lake Michigan’s complex ecosystem and collectively support a valuable recreational fishery, but declines in their primary prey, alewife (Alosa pseudoharengus), have raised ecological and management concerns about competition and prey allocation. We applied niche overlap analysis to evaluate competition among salmonine predators during rapid forage base change in Lake Michigan. δ13C and δ15N stable isotope ratios indicated that lake trout had a unique trophic niche from inclusion of offshore and benthic prey, with <29% lake-wide niche overlap with Chinook salmon, coho salmon, and steelhead. Brown trout had moderate overlap with other species (45%–91%), while Chinook salmon, coho salmon, and steelhead had high overlap (71%–98%). Regional differences in isotopic signatures highlighted the potential importance of subsystem differences in fish diets in large aquatic systems. The uniqueness of the lake trout niche, and broadness of brown trout and steelhead niches, suggest these species may be resilient to forage base changes. This study further demonstrates how niche overlap analysis can be applied to tease apart competitive interactions and their response to ecosystem change.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

The genetic composition of wild recruits in a recovering lake trout population in Lake Michigan

Strain performance evaluations are vital for developing successful fishery management and restoration strategies. Here, we utilized genotypes from 36 microsatellites to investigate hatchery strain contribution to collections of naturally produced lake trout (Salvelinus namaycush) sampled across Lake Michigan. Strain composition varied by area, with recoveries of Seneca Lake strain exceeding expectations based on stocking records in northern Lake Michigan but performing similarly to other strains in southern Lake Michigan. Interstrain hybrids were present at moderate frequencies similar to expectations based on simulations, suggesting that strains are interbreeding randomly. We hypothesize that the superior performance of the Seneca Lake strain in northern Lake Michigan is partially due to adaptive advantages that facilitate increased survival in areas with high mortality from sea lamprey (Petromyzon marinus) predation, such as northern Lake Michigan. However, when this selective pressure is lessened, the Seneca Lake strain performs similarly to other strains. Our study demonstrates that strain performance can vary across small spatial scales and illustrates the importance of conducting thorough strain evaluations to inform management and conservation.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Estimating catch curve mortality based on relative return rates of coded wire tagged lake trout in US waters of Lake Huron

We estimated total mortality using catch curves based on relative return rates (RRs) of coded wire tagged lake trout in US waters of Lake Huron. RR was calculated as age specific CPUE per million of fish stocked. Annual mortality for the late 1990s through early 2000s was estimated as 38% from the 1991-1995 year-classes with an effective age range of 5-10 years, and then was estimated as 24% for the post-2000 period from the 1996-2009 year-classes. The two estimates from simple catch curve regressions based on average RR at age values were the same as from a mixed model with individual RR values from all stocking events. These two estimates were also comparable to the findings from statistical catch-at-age assessments with fundamentally different assumptions. Our approach is not constrained by the assumption that the expected recruitment is a constant over time and thus has the advantage to use multiple observations on each age from multiple cohorts. Our approach has broad applicability to aquatic ecosystems in which multiple mark-and-release events of fish stocking have been implemented.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Temporal Variation in the Niche Partitioning of Lake Michigan Salmonines as it Relates to Alewife Abundance and Size Structure.

Stable isotope analyses offer a useful means for quantifying ecological niche dimensions, though few studies have examined isotopic response of an ecological community with respect to resource gradients such as fluctuations in prey availability. Stable carbon and nitrogen isotopes were measured for Lake Michigan salmonines and their prey collected from 2014 to 2016. Bayesian ellipse and mixing model analyses were used to quantify isotopic niche characteristics and diets, respectively, among species and years. During the three-year study period, abundance and size structure of preferred alewife prey changed substantially and offered an opportunity to explore predator isotopic niche response and diet shifts along a prey resource gradient. Results suggested increased reliance on alewives, especially small alewives, over the study period and were consistent with greater availability of this prey. However, differential use of alewife size classes and alternative prey sources by salmonine predators was apparent, which suggested possible resource partitioning. Characterization of ecological niche overlap using stable isotopes likely requires consideration of shared resource availability as well as specific prey and habitat preferences.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Commonly Rare and Rarely Common: Comparing Population Abundance of Invasive and Native Aquatic Species

<div><p>Invasive species are leading drivers of environmental change. Their impacts are often linked to their population size, but surprisingly little is known about how frequently they achieve high abundances. A nearly universal pattern in ecology is that species are rare in most locations and abundant in a few, generating right-skewed abundance distributions. Here, we use abundance data from over 24,000 populations of 17 invasive and 104 native aquatic species to test whether invasive species differ from native counterparts in statistical patterns of abundance across multiple sites. Invasive species on average reached significantly higher densities than native species and exhibited significantly higher variance. However, invasive and native species did not differ in terms of coefficient of variation, skewness, or kurtosis. Abundance distributions of all species were highly right skewed (skewness>0), meaning both invasive and native species occurred at low densities in most locations where they were present. The average abundance of invasive and native species was 6% and 2%, respectively, of the maximum abundance observed within a taxonomic group. The biological significance of the differences between invasive and native species depends on species-specific relationships between abundance and impact. Recognition of cross-site heterogeneity in population densities brings a new dimension to invasive species management, and may help to refine optimal prevention, containment, control, and eradication strategies.</p></div

Abundance distributions of all invasive and all native species combined.

<p>Probability density of standardized abundance (proportion maximum abundance observed within a taxonomic group) for invasive (light purple) and native (dark purple) species, with all species combined. Abundance values are grouped into 0.05 bins.</p

Effect size of origin (invasive vs. native status) on distributional parameters.

<p>Effects are presented as the restricted maximum likelihood (REML) estimate of the difference on the natural log scale between invasive and native species (or the natural log of the ratio of invasive:native species values). Bars are 95% highest probability density interval from Markov-chain Monte Carlo (MCMC) resampling; bars that do not overlap zero (dashed line) represent significant differences between invasive and native species.</p