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A field manipulation that evaluates size through time, habitat-specific diet, isotope values, and distribution of early spawn and natural spawn age-0 largemouth bass

Robert L. Mapes, M.S. Student
Dr. Martha Mather

Largemouth bass (Micropterus salmoides)

Project Supervisor
Dr. Martha Mather
Kansas Department of Wildlife, Parks, and Tourism
Hillsdale and Perry Reservoirs

December 2017
Kansas Department of Wildlife, Parks, and Tourism
Kansas State University
Characterize the diet and stable isotope values of age 0 largemouth bass in Hillsdale and Perry reservoirs.

Determine if early spawn largemouth bass and natural spawned largemouth bass occupy the same habitats.

Assess habitat utilization by age-0 LMB and fish and invertebrate prey species across seasons.

Determine if early spawn age-0 LMB are larger than natural spawned age-0 LMB by the end of their growing season.

Progress and Results
Largemouth bass (Micropterus salmoides) is an important predator and a popular sportfish. However, adult survival is often poor because of size-structured interactions in the first year of life. For example, a link has been observed between poor first year survival and small size during the first summer. Many fish grow faster when they consume fish prey instead of invertebrate prey. If age-0 largemouth bass can switch to fish prey early during their first summer, they can grow faster, overwinter at a larger size, and possibly survive better as adults. However, age-0 largemouth bass are gape-limited predators (i.e., the size of prey eaten is limited by mouth size). Consequently, naturally spawned age-0 largemouth bass often are not large enough to consume young-of-year fish prey.

To test the role of size-structured interactions among age-0 largemouth bass, fish prey, invertebrate prey, fish competitors, and fish predators, we will compare habitat-specific size through time, diet, stable isotope values, and distribution among three groups of age-0 largemouth bass [(1) stocked phase 1 early-spawned bass, (2) stocked phase 2 early-spawned bass, (3) naturally spawned bass] in a treatment reservoir (Hillsdale Lake) compared to an unstocked control with naturally spawned largemouth bass only (Perry Lake). The results of this whole-system manipulation will provide useful guidance for fisheries management and advance basic ecological knowledge about controls on first-year survival of this important predator.

Graduate students will collect data for the common grant objectives. For this, we will sample multiple habitats within each lake twice a month to collect data on age-0 largemouth bass distribution, abundance, size, diet, isotope, and prey. Graduate students will also develop independent, hypothesis-based research projects that will result in graduate degrees. We are exploring a food web approach as a mechanism to unravel the complex biotic interactions that affect a size-structured freshwater fish community. We are considering whether landscape-scale variables (e.g., habitat type, size, and arrangement) can explain variations in size-structure interactions across systems and years. Both graduate students have written initial proposals. Since this project started six months ago, we have identified a standardized sampling plan, formulated standardized, science-based protocols, and have started our sampling in Hillsdale and Perry Lakes.

Mapes. R. M., and M. E. Mather. 2015. Using the land mosaic concept to test how habitat heterogeneity alters the distribution of young-of-year largemouth bass in a Great Plains Reservoir. Midwest Fish and Wildlife Meeting, Indianapolis, IN.

Mapes, R., M.E. Mather, J.M. Smith, S.M. Hitchman and A. Earl. 2015. Is All Heterogeneity Created Equal? How Types of Habitat Heterogeneity Differentially Alter Distribution, Abundance, and Diets of Age-0 Largemouth Bass. Portland, Oregon.