Land and Ecosystem Management
Karl M. Polivka
Research Fish Biologist
PNW Research Station
Statement of Research
I am broadly trained in ecology and evolutionary biology; thus my research is not limited to a single study system or taxonomic group. My focus is on the behavioral ecology of fishes as it pertains to habitat selection: (1) Does in-stream modification of fish habitat affect the carrying capacity for species of interest relative to unmodified habitat? (2) How do headwater streams affect the productivity of downstream fishes through delivery of nutrients, sediment, organics, and prey, and how do headwater stream fish population and life history processes vary at the landscape scale? (3) Can productivity and biodiversity hotspots be identified in drainage networks and what is their basin-wide significance? I am also heavily engaged in the study of defoliating insects, their population biology and management of their outbreaks.
Linking Foraging Theory and Habitat Selection.
The use of tools from foraging theory can inform the study of patterns of habitat selection in a variety of study systems. Habitat selection in a group of stream and estuarine fishes (sculpins; Family Cottidae) can be described using the “giving-up density” (GUD) as an indicator of patch use and foraging effort that also reflects the relative productivity and risk involved in selecting habitat types. Although estuaries have long been recognized as habitats with high productivity of fish and other taxa, there has been little experimental work to understand the benefits and costs that promote or limit biodiversity at these freshwater-marine ecotones. The coast range sculpin uses tidal estuaries as nursery areas which are highly productive but also highly risky due to the presence of near-shore marine predators. Populations that remain upstream are subject to lower risks but also lower productivity. The difference in predation risk was reflected in the foraging effort measured by the GUD.
Link to publications:
Alofs, K. M. and K. M. Polivka. 2004. Microhabitat-scale influences of resources and refuge on habitat selection by an estuarine-opportunist fish. Marine Ecology Progress Series 271:297-306.
Polivka, K. M. 2007. Use of techniques from foraging theory to quantify the cost of predation for benthic fishes. Transactions of the American Fisheries Society 136:1778-1790.
Polivka, K. M. 2011. Responses to the foraging/predation-risk trade-off and individual variability in population-level fitness correlates. ISRN Ecology, doi:10.5402/2011/376083, 8 pages.
Effectiveness Monitoring of In-Stream Habitat Restoration.
Figure 1. The Entiat River Basin (left) is located in north central Washington. Intensive restoration efforts include the placement of large wood structures (right panel, foreground) and rock barbs (right panel, across river).
A multi-agency consortium of managers has begun an intensive restoration effort in the Entiat River sub-basin of the Upper Columbia River. Increased human interference with natural fish habitat in the Entiat River basin has resulted in a decrease of suitable rearing habitat for juvenile Chinook salmon and steelhead trout. As a result of population declines, Chinook and steelhead are currently protected under the Endangered Species Act. The Integrated Status and Effectiveness Monitoring Program (ISEMP) is organized by NOAA-Fisheries and funds the monitoring of fish populations in the Entiat and other intensively monitored sub-basins. Other agencies and landowners comprise the Entiat Watershed Planning Unit which manages the installation of in-stream habitat enhancements and the development of other restoration projects aimed at fish population recovery within the sub-basin. My lab is funded by ISEMP to evaluate the effectiveness of in-stream habitat restoration structures consisting of micro-habitat scale engineered log jams and rock barbs extending from the bank of the Entiat River in treated reaches (Fig. 1).
Figure 2. Box and whisker plot of Chinook salmon and steelhead density in early season censuses at microhabitats treated with structures and with no structures.
In the 2009-2011, juvenile Chinook were more likely to be found in areas with the added structures, especially in 2009. Juvenile steelhead were also more likely to be found in areas with added structures in 2009 and 2011, but not in 2010 (Fig. 2). Steelhead are highly variable in their habitat use.In a 2009 mark-recapture experiment, both juvenile Chinook and steelhead were more likely to be recaptured 24 hours after mark and release in habitats with added structures than those that lacked structures (Fig. 3). This response was density-dependent for steelhead, but not for Chinook salmon. This indicates a short-term preference for restored habitat.
Figure. 3. Proportion of fish recaptured 24 hr after mark and release assays in microhabitats with structures present and in untreated microhabitats.
Links to publications:
Polivka, K. M. 2010. Population ecology and effectiveness monitoring of small-scale in-stream habitat restoration structures in the Entiat River. In: Upper Columbia Regional Technical Team 2010 analysis workshop synthesis report. Edited by Ward, M.B., J. Morgan and C. Baldwin. UCRTT and Terraqua, Inc. Wenatchee, WA:UCSRB, pp. 51-54.
Polivka, K. M., L. M. Friedli, J. L. Novak, and K. M. Sirianni in preparation Patterns of distribution of Chinook salmon (Oncorhynchus tschawytscha) and steelhead trout (O. mykiss) in response to in-stream habitat restoration.
Host-pathogen relationship between Douglas-fir tussock moth and its nucleopolyhedrosis virus (NPV).
Management of outbreaks of defoliating insects in national forests across the US is a critical issue where much research is centered and where many questions remain. I am collaborating with Connie Mehmel, an entomologist on the Okanogan-Wenatchee National Forest and Greg Dwyer of the University of Chicago to contribute to long-term studies evaluating the use of NPV as a biocontrol agent to manage the Douglas-fir tussock moth (Orgyia pseudotsugata). We have evaluated a recent spray program on the Methow Ranger District and are conducting specific experimental studies of the relationship between NPV and tussock moth larvae. We have found that both temperature and virus decay affect the virulence and infectivity of NPV, which can have implications for the prediction of the intensity and duration of future insect outbreaks.
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