Environmental DNA (eDNA) is revolutionizing biodiversity monitoring, occupancy estimates, and real-time detections of invasive species. In the Great Lakes, the round goby (Neogobius melanostomus), an invasive benthic fish from the Black Sea, has spread to encompass all five lakes and many tributaries, outcompeting or consuming native species; however, estimates of round goby abundance are confounded by behavior and habitat preference, which impact reliable methods for estimating their population. By integrating eDNA into round goby monitoring, improved estimates of biomass may be obtainable. We conducted mesocosm experiments to estimate rates of goby DNA shedding and decay. Further, we compared eDNA with several methods of traditional field sampling to compare its use as an alternative/complementary monitoring method. Environmental DNA decay was comparable to other fish species, and first-order decay was lower at 12°C (k = 0.043) than at 19°C (k = 0.058). Round goby eDNA was routinely detected in known invaded sites of Lake Michigan and its tributaries (range log10 4.8–6.2 CN/L), but not upstream of an artificial fish barrier. Traditional techniques (mark-recapture, seining, trapping) in Lakes Michigan and Huron resulted in fewer, more variable detections than eDNA, but trapping and eDNA were correlated (Pearson R = 0.87). Additional field testing will help correlate round goby abundance with eDNA, providing insight on its role as a prey fish and its impact on food webs.

Although competition drives self-thinning, its course can be affected by abiotic stress, facilitation and competitive symmetry.

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We propose a formal causal evaluation inference process that uses a local-scale in situ approach and provides statistically defensible correlative conclusions for the biological impairment in 303(d)-listed water bodies. Fish assemblage, water chemistry, and aquatic habitat data from 66 locations in the Limberlost watershed, Indiana, were collected in August 2003 to evaluate the condition of the watershed. Anthropogenic stressors were identified from a numerical classification analysis of fish assemblage data using a biological integrity response gradient. Physical and chemical stressors were evaluated relative to the biological integrity response gradient using the Kruskal Wallis analysis of variance by ranks test. Three water chemistry variables (sodium, chloride, and barium) were associated with biological integrity. The percent run habitat, channel morphology score, and Qualitative Habitat Evaluation Index score varied with the degree of dredging. We observed a negative response between the number of species and the biological integrity gradient and a positive response with the percent tolerant individuals. This local-scale in situ approach to physical and chemical data analysis, combined with concurrent biological data collection, provided correlative relations to the impaired condition with localized environmental stressors.

The Patoka River watershed contains a divergent landscape of oil and gas exploration, intensive agriculture, and surface mining mixed with National Forest, Wildlife Refuges, and a large recreational reservoir. We evaluated species diversity among different land uses, including, commercial, forested, residential, and agriculture, and determined relationships among disturbance scale, habitat requirements, contaminants, and patterns in species distributions. Primary burrowing species, Cambarus polychromatus, Cambarus cf diogenes (Lacunicambarus A), and Fallicambarus fodiens, were tolerant of higher concentrations of contaminants than aquatic tertiary burrowing species. Cambarus polychromatus was among the last species of crayfish at the most disturbed sites, while it was absent from pasture and agricultural landscapes that allowed cattle access along banks. Four species of Orconectes were found in the reference and agricultural landscapes within the watershed, including O. immunis, O. indianensis, O. inermis inermis, and O. propinquus. Orconectes indianensis distribution was determined by the presence of rock habitat and absence of contaminants. No Orconectes species were found in acid mine leachate-affected streams with high levels of molybdenum. Cambarus laevis was found in the highest-quality reference areas, which were associated with karst habitats and no contaminants. Burrowing crayfish species were associated with the oil derricks in the lower and middle watershed, which contained increased concentrations of strontium, phosphorus, and various organic parameters associated with oil brine PAHs.