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Tuesday, January 29 • 10:40am - 11:00am
(FISHERIES: GREAT LAKES 2) Density-Dependent and Independent Effects on Walleye Harvest in Lake Erie

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AUTHORS: David Dippold, The Ohio State University; Grant Adams, University of Washington; Stuart Ludsin, The Ohio State University

ABSTRACT: Both density-dependent and density-independent factors can affect the harvest of exploited fish populations. For instance, inter-annual variation in temperature could modify the timing and spatial extent of fish migrations, and in turn, fishery catches. However, this relationship could be mediated by density-dependent factors, if for example, high fish abundance leads to widespread habitat use that reduces the effects of temperature on migration and subsequent harvest. Toward understanding the relative influence of these factors on fishery harvest, we quantified the relationship among temperature, population size, and the temporal and spatial distribution of walleye (Sander vitreus) recreational harvest in Lake Erie during 1990-2015. Knowing that adult walleye migrate eastward from the western basin during spring and summer towards cooler temperatures, we hypothesized that: 1) years with higher spring and summer temperatures would be accompanied by reduced catches in the western basin relative to the deeper, cooler central and east basins; 2) walleye catches in the central and eastern basins would occur earlier during the spring/summer in warmer (relative to cooler) years; and 3) these relationships would be more apparent in years of low population size because in years of high abundance, walleye (especially young adults) would continue to reside in the west basin throughout the summer. To test our hypotheses, we constructed and compared variable coefficient generalized additive models, which used spatially-explicit (10x10 min grids) recreational catch and effort information, as well as temperature, bathymetric, and lake-wide abundance data. Beyond discussing the role of temperature and total abundance in driving spatiotemporal patterns in walleye harvest, we discuss the implications for fisheries management under a changing climate.

Tuesday January 29, 2019 10:40am - 11:00am

Attendees (16)