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Andrew L. Rypel

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The Safe Operating Space (SOS) of a recreational fishery is the multidimensional region defined by levels of harvest, angler effort, habitat, predation and other factors in which the fishery is sustainable into the future. SOS boundaries exhibit trade-offs such that decreases in harvest can compensate to some degree for losses of habitat, increases in predation and increasing value of fishing time to anglers. Conversely, high levels of harvest can be sustained if habitat is intact, predation is low, and value of fishing effort is moderate. The SOS approach recognizes limits in several dimensions: at overly high levels of harvest, habitat loss, predation, or value of fishing effort, the stock falls to a low equilibrium...
Categories: Publication; Types: Citation; Tags: Fish and Fisheries
Abstract (from NRC Research Press): Walleye (Sander vitreus) populations are declining in Wisconsin and neighboring regions, motivating broader interest in walleye biology amidst ecological change. In fishes, growth integrates variation in ecological drivers and provides a signal of changing ecological conditions. We used a 23-year data set of length-at-age from 353 walleye populations across Wisconsin to test whether walleye growth rates changed over time and what ecological factors best predicted these changes. Using hierarchical models, we tested whether spatiotemporal variation in walleye growth was related to adult walleye density (density-dependent effects), water temperature, and largemouth bass (Micropterus...
Abstract (from http://www.tandfonline.com/doi/full/10.1080/03632415.2016.1160894): To identify past successes and future opportunities for improved fisheries management in Wisconsin, we synthesized size-structure information on 19 gamefish species from 1944 to 2012, incorporating data on more than 2 million measured individuals. Since the 1940s, mean and mean maximum sizes of five “gamefish” species (Lake Sturgeon Acipenser fulvescens, Largemouth Bass Micropterus salmoides, Smallmouth Bass M. dolomieu, Northern Pike Esox lucius, and Sauger Sander canadensis) have stayed fairly stable, and one (Muskellunge E. masquinongy) initially dropped and then rebounded—most likely as a product of increased catch-and-release...
Abstract (from http://www.nrcresearchpress.com/doi/abs/10.1139/cjfas-2014-0394#.Vc36E_lVikp): Understanding variability in fish production, biomass, production/biomass ( P/ B) ratios, and their relationship to exploitation is central to fisheries sustainability. At Escanaba Lake, Wisconsin, USA, data from a compulsory creel census (1965–2009) were combined with survey data on fish populations to test for empirical relationships between annual production and exploitation rates of walleye ( Sander vitreus). Empirical estimates of walleye production were relatively high and temporally variable in Escanaba Lake. Annual production, biomass, and P/ B ratios ranges were 2.4–11.3 kg·ha −1·year −1, 9.1–49.4 kg·ha −1, and...
Abstract (from http://onlinelibrary.wiley.com/doi/10.1002/ecs2.1660/full): Empirically understanding spatial variation in secondary production rates is central to ecology. Yet for most taxa, such patterns are rarely examined, especially at different levels of ecological organization (e.g., species- vs. community-level patterns). We compiled data on biomass, production, and P/B rates of freshwater fish communities and species across latitudes and contrast patterns observed at the community level with those observed for species. At the community level, and at two distinct spatial scales (global vs. continental-North American), negative or neutral relationships were apparent between biomass, production, and P/B with...
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