Midwest Fish & Wildlife Conference 2016

AUTHORS: Margaret Hutton*, Purdue University; Paris Collingsworth, Purdue University and Illinois-Indiana Sea Grant; Samuel Guffey, Purdue University; Ed Rutherford, NOAA-Great Lakes Research Laboratory; Mitchell Zischke, Purdue University; Tomas Höök, Purdue University

ABSTRACT: Over the past two decades, Lake Michigan’s ecosystem has undergone numerous changes related to nutrient abatement, climatic effects, and influences of various invasive species. For example, chlorophyll a concentrations have decreased offshore but increased in some nearshore regions, and some secondary and tertiary consumers (e.g., planktivorous fishes) have come to rely more on nearshore production than offshore. However, these spatial shifts do not appear to be ubiquitous throughout the lake. With the increase in relative nearshore productivity and emerging spatial patterns, we hypothesize that the condition and growth (as indexed via RNA:DNA ratios, relative fecundity, and length-at-age) of the invasive predatory zooplankton Bythotrephes longimanus will also reflect these patterns. If Bythotrephes are able to devote more energy to growth (more RNA in the organism) due to increased food availability in nearshore areas, we would expect to see a decreasing RNA:DNA ratio from nearshore to offshore locations. To examine spatiotemporal trends in RNA: DNA, Bythotrephes were sampled from nine transects throughout Lake Michigan in both the northern and southern basins along a nearshore (~15m) to offshore (~105m) gradient. With different production pathways dominating different regions causing heterogeneous shifts in production, we expect the condition of Bythotrephes to mirror these patterns. For example, the increase in production in the last two decades in the northwestern region may allow Bythotrephes to devote more energy to growing and thus have a higher RNA:DNA ratio compared to regions with less nutrient input. Ultimately, we will relate resulting spatial patterns of Bythotrephes condition to both abiotic and biotic variables collected concomitantly.

AUTHORS: April R. Londo Minnesota State University, Mankato Shannon J. Fisher Minnesota State University, Mankato

ABSTRACT: Of all non-native species to become invasive, zebra mussel Dreissena polymorpha, from the Ponto-Caspian region of southern Russia, are considered to be one of the most damaging. Zebra mussels are successful invaders because the species attaches to substrates with byssal threads, can adapt to a wide range of environmental conditions, and have a free-swimming veliger that is easily transported. Although invasive mollusks pose considerable economic and ecological threats to inland waters, our understanding of them in Minnesota lakes remains limited. Therefore, an improved understanding of the factors that influence zebra mussel density, habitat preference, and distribution is an important component of developing management plans for the invasive mussel. The objective of this study was to assess potential associations zebra mussels may have with organic substrates as habitat in a Minnesota chain-of-lakes system. The study lakes were in west-central Minnesota and were all colonized prior to 2009. In the summer of 2014, mussel, vegetation, and substrate surveys were completed via SCUBA. Zebra mussels were enumerated and measured to determine density and size structure. Vegetation was keyed to species and dried to determined density (biomass/unit area). There was a significant difference in zebra mussel attachment to algaes (i.e., filamentous and Chara spp.) than macrophytes (P=0.001). Additionally, juvenile zebra mussels were found more on organic substrates than adults (P

AUTHORS: Kelly Hannan*, University of Illinois Urbana-Champaign; Jennifer Jeffrey, University of Illinois Urbana-Champaign; Adam Wright, University of Illinois Urbana-Champaign; Caleb Hasler, University of Illinois Urbana-Champaign; Cory Suski, University of Illinois Urbana-Champaign

ABSTRACT: The movement and spread of invasive fish species is a topic of recent concern. In the Midwestern US, Asian carp are an invader of particular concern due to the recent expansion of their populations. Gas barriers aimed at deterring fish movement, such as CO2, are gaining in popularity as areas of elevated CO2 have been shown to be effective at deterring fish movement. However, little research has investigated potential consequences of these barriers on non-target species, such as mussels. Freshwater mussels are one of the most imperiled animals worldwide, and have some of their highest diversity in North America, and zones of high CO2 have potential to impact these organisms. The goal of the current study was to quantify the impacts of short-term, chronic, and fluctuating exposures to elevated CO2, and subsequent recovery, on freshwater mussels. Hemolymph ions such as, Ca2+, Cl-, Mg2+, and Na+ were measured along with hemolymph glucose, body condition indices, and metabolic rate. Results from these studies indicate that freshwater mussels experienced physiological disturbances related to acid base disturbance following CO2 exposure, but body condition is unaffected even after chronic exposure, and there is evidence of recovery following removal of the CO2 challenge. Results are further discussed in the context of how CO2 barriers may impact non-target organisms.