Projects Completed This Year

 Climate Change and Resilience of Sport Fisheries in Lakes

Investigators: Steve Carpenter, Center for Limnology, University of Wisconsin-Madison
Funding: US Geological Survey
Expected Completion: August 31, 2016

It is increasingly evident that climate change is having long term directional impacts on fisheries. Climate change is a major concern for sport fisheries, as drivers like temperature and precipitation impact lake conditions, which in turn influence fish communities and production. Researchers and managers from state and federal agencies and two universities undertook a collaborative project to investigate the resilience of sport-fisheries to climate change in Wisconsin’s inland lakes. This investigation focused on the economically and culturally important walleye (Sander vitreus) fishery, which has been declining since the mid 1990’s. The group developed a framework for how to learn about and manage the resilience of heterogeneous resources like the statewide walleye fishery. Lake comparisons suggested that walleye declines may be being driven by a survival bottleneck in the first year of life (recruitment) and declining adult productivity. Monitoring data showed that successful walleye recruitment is more likely in large, cold, conductive lakes with lower shoreline development. Further, walleye recruitment was higher in cooler lakes where black bass abundance is lower than in warmer lakes where black bass dominates. Evidence also showed that young walleye were larger in lakes where bass were abundant. A comparative study among lakes found that predation by bass on larval walleye is very rare, but that adult walleye and bass overlap in their diets. In addition, there has been a trend of decreasing production and production per unit biomass, which is making populations more vulnerable to overharvest. Food web models that incorporate uncertainty in predator-prey relationships suggest that stocking young walleye and bass removal have ambiguous consequences for walleye, but walleye consistently increase when harvest is reduced. Management actions have been implemented to test the application of stocking, restricted walleye harvest, and liberalized bass harvest to restore the walleye fishery. A large scale centrarchid reduction experiment is being initiated to test for causal linkages between predators, competitors with young walleye, and walleye recruitment success.

 Vulnerability of Hawaiian Forest Birds to Climate Change – Using Models to Link Landscape, Climate, Disease, and Potential Adaptation

Investigators Michael D. Samuel, USGS, University of Wisconsin-Madison
Funding:         US Geological Survey – Hawaii Climate Change Center
Expected Completion: June 30, 2016

Avian malaria, transmitted by Culex mosquitoes, is a primary factor contributing to recent population declines, extinctions, and range limitations for many endemic Hawaiian forest birds. Because avian malaria is strongly influenced by climate (rainfall and temperature) future climate changes are expected lead to shifts in transmission of avian malaria to higher elevations and increases in existing transmission that could lead to significant population declines and potential extinction of highly susceptible species remaining in high-elevation forests. Based on potential future malaria risk to native bird populations, we evaluated the viability of alternative conservation strategies to preserve endemic Hawaiian bird populations throughout the 21st century. Because predicted climate changes are likely to have larger impacts in high-elevation forests where current low rates of transmission create refugia for birds that are highly susceptible to malaria, mitigating malaria transmission should be a primary conservation goal.  Specifically, strategies that maintain highly susceptible species like Iiwi in high-elevation forests will likely be beneficial for other threatened and endangered Hawai’i species. Because predicted transmission rates of malaria will be higher than currently observed, several conservation strategies including predator control and use of competing mosquito species were generally insufficient to maintain forest bird populations at current levels. However, mosquito control strategies offer potential long-term benefits to Hawaiian forest birds at high elevation. Combined strategies will likely be needed to preserve endemic birds at mid elevations.

CWD Deposition and Environmental Reservoirs

Investigators: Michael D. Samuel, USGS, University of Wisconsin-Madison and Joel Pedersen, Department of Soil Science, University of Wisconsin-Madison
Funding: US Geological Survey, Contaminants Program
Expected Completion: February 30, 2015

We tested the urine and feces of 3 species (elk, mule, and white-tailed deer) of orally inoculated captive cervids at 6, 12, 18, and 24 months post inoculation to evaluate temporal, species, and genotype specific factors affecting shedding.  We found that all three cervid species were shedding PrPCWD by 6 months, 3 months earlier than previously reported.  Fecal samples were consistently CWD positive for all three cervid species (88%) and were more likely to be positive than urine (28%).   Genetically more susceptible cervids (94%) were more likely to be shedding PrPCWD than less susceptible genotypes (64%).  All cervids with positive urine also had positive feces (n = 5) but the reverse was not true.  Our results indicate that CWD shedding in feces may provide an important avenue for depositing prions in the environment.

We used protein misfolding cyclic amplification (PMCA) to demonstrate that prions are commonly detected in both soil and water from mineral licks used by white-tailed deer in a CWD infected area of Wisconsin. These environmental reservoirs likely facilitate indirect CWD transmission to susceptible deer and potential exposure of other wildlife and domestic animals that are attracted to these licks for minerals. Prion uptake by plants grown in contaminated soil indicates plants growing in proximity to contaminated mineral licks may also take up prions that can be consumed by foraging animals. Our results also indicate that other areas where cervids concentrate (i.e., feeding and baiting sites), where prions are deposited and later consumed, may also provide environmental reservoirs for CWD infection to cervid and non-cervid species.

Valuing Wildlife in the US

Investigators:    Michael D. Samuel, USGS, University of Wisconsin-Madison and David Drake, Department of Forest and Wildlife Ecology, University of Wisconsin-Madison
Funding: US Geological Survey
Expected Completion: October 31, 2015

Existing literature and unpublished data for individual and government expenditures were utilized to determine the total, annual economic benefits of free roaming, terrestrial wildlife in the United States. We found the total economic benefit of wildlife is approximately $340 billion annually. Direct economic inputs by government-funded conservation programs are significant and result in almost $100 billion in economic benefits. In addition, the amount of economic benefits derived through individual expenditures is nearly two and a half times this amount and illustrates the importance of wildlife resources at both the governmental and personal levels of US citizens.  A significant portion of expenditures and economic benefits of non-consumptive wildlife-related activities result from feeding of all types of wildlife; the largest percentage of these expenditures is for feeding birds. Hunting of big game species resulted in more expenditures and economic benefits ($48 billion) than all other hunting combined. Migratory bird and small game hunting contributed approximately $15 billion of annual economic impact while other animal hunting and trapping contributed about $7.5 billion. The amount of economic activity generated for non-consumptive wildlife-related recreation is likely to increase by 50% by mid-century. In contrast, hunting participation is predicted to level-off or decline due to the growing urbanization of the US population.

Palmer, Antarctica Long Term Ecological Research: Looking Back in Time Through Marine Ecosystem Space

Investigators:  Hugh Ducklow, Marine Biological Lab, Woods Hole, MA, William Fraser, Polar Oceans Research Group, Sheridan, MT, and Christine Ribic, USGS, University of Wisconsin-Madison
Funding:  National Science Foundation (Polar Programs)
Expected Completion: September 30, 2016

A primary research objective of the Palmer Long Term Ecological Research (LTER) program has been to identify and understand the factors that regulate the demography of Adélie penguins (Pygoscelis adeliae).  In this context, our work has justifiably been focused on variability in the marine environment on which this species depends for virtually all aspects of its life history.  However, there are patterns evident in the population dynamics of Adélie penguins that are better explained not by variability in the marine system, but rather by variability in breeding habitat quality that are driven by interactions between the geomorphology of the terrestrial environment and its effect on patterns of snow deposition. Our seabird research in the Palmer LTER region has historically focused on five island rookeries that at the inception of investigations in 1974 held 15,202 breeding pairs of Adélie penguins.  During the 2011/2012 field season, these same rookeries held 2,411 breeding pairs, an 83% decrease in abundance relative to original estimates.  However, changes in these populations have not been symmetrical, but instead encompass trends that are island-specific. Most noteworthy among these, is that of the five original populations, only four remain, as the Litchfield Island population went extinct in 2007.  This is a unique event, as the island’s paleoecological record indicates this population has been in existence for at least 500 years.  We have previously shown that snowfall in our primary study areas on the five islands accumulates disproportionally on landscapes with a southwest exposure due to wind scour from the northeast, the predominant wind direction characterizing regional low pressure systems.  We have also demonstrated that on these southwest-facing landscapes, there is a disproportionately higher number of recently abandoned and extinct colonies, a pattern that led us to hypothesize that island geomorphology plays a strong role in determining breeding habitat quality (classified as optimal versus suboptimal). Following this line of thought, we expanded previously developed hillshade models to incorporate entire island landscapes in order to assess the relationship between island-specific breeding habitat suitability and their corresponding penguin population trends (change in breeding pairs/year).  Our hillshade models were informed by geomorphology and predominant wind direction to predict island-specific snow deposition patterns. We found that habitat suitability varied by island, with the proportion of suboptimal habitat being greatest for Litchfield Island and least for Torgersen and Humble Islands.  Importantly, the slope of the population trend was related to the amount of suboptimal habitat; specifically, populations decrease faster as the areal extent of suboptimal habitat increases.  Although it has recently been proposed that variability in the biomass of Antarctic krill (Euphausia superba) is the dominant driver of demographic change in Adélie penguins, our findings suggest that models of population change based on food web processes alone may be insufficient to account for the observed variability.