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Omori K.L.,Virginia Institute of Marine Science | Hoenig J.M.,Virginia Institute of Marine Science | Luehring M.A.,Great Lakes Indian Fish and Wildlife Commission | Baier-Lockhart K.,Center for Marine Resource Studies
Fisheries Research | Year: 2016

Fisheries can be managed based on surplus production models when only catch and effort data are available. However, reported catch and effort may not equal the true values. We studied the effects of jointly underestimated catch and effort on surplus production model parameter estimates (e.g., MSY, Bmsy and Fmsy) as well as estimates of key ratios (e.g., F/Fmsy). We used ASPIC to examine various scenarios of underreporting for three example fisheries, North Atlantic swordfish, northern pike in Minnesota and queen conch in the Turks and Caicos Islands. With constant underestimation of catch and effort throughout time, MSY, Bmsy and Bnext are all underestimated by the same percentage, while Flast and the ratios, F/Fmsy and B/Bmsy, are not affected. As a result, harvest regulations can be set based on fishing mortality and the ratios. That is, when one thinks the harvest is MSY with F = Fmsy, one is achieving MSY and Fmsy even though the catch is actually larger than it is thought to be. However, increasing or decreasing trends in underreporting of catch and effort over time lead to errors in the parameter and ratio estimates whose direction is case-specific and whose magnitude can be high or low. Each fishery model responded differently to the simulated scenarios, which may be a result of different exploitation histories or the quality of the fit of the production model to the data. The wide range of outcomes observed may be due to the fact that underestimation of catch and effort can lead to a gain or reduction in data contrast. Simulations of a variety of possible scenarios similar to the methods in this study should be conducted if catch and effort are believed to be underestimated to determine how the surplus production model responds. © 2016 Elsevier B.V. Source

McCann N.P.,Purdue University | Zollner P.A.,Purdue University | Gilbert J.H.,Great Lakes Indian Fish and Wildlife Commission
Journal of Wildlife Management | Year: 2010

Low adult marten (Martes americana) survival may be one factor limiting their population growth >30 yr after their reintroduction in Wisconsin, USA. We estimated annual adult marten survival at 0.81 in northern Wisconsin, with lower survival during winter (0.87) than summerfall (1.00). Fisher (Martes pennanti) and raptor kills were infrequent, and each reduced marten adult annual survival <10. Annual adult survival was similar to or higher than survival in other areas, suggesting that it was not unusually low and therefore did not limit recovery of marten populations in northern Wisconsin. We captured few juvenile martens, suggesting low reproduction or reduced juvenile survival. © 2010 The Wildlife Society. Source

McCann N.P.,Purdue University | McCann N.P.,Apple Inc | Zollner P.A.,Purdue University | Gilbert J.H.,Great Lakes Indian Fish and Wildlife Commission
Journal of Mammalogy | Year: 2014

Effective conservation efforts often depend on accurate identification of habitat requirements. Studies that identify habitat requirements for animals typically investigate use of structural habitat (vegetation) instead of functional habitat (conditions for biological fitness). The spatial scale of data could bias the match between functional and structural habitat because broadscale structural habitat maps exclude small habitat patches (inclusions) and broadscale location error can bias estimates of habitat use. To investigate how spatial scale affects the match between functional and structural habitat, we backtracked American marten (Martes americana) and fisher (Pekania formerly Martes pennanti) movement paths during winter and compared results from selection and tortuosity analyses conducted with broadscale (4 ha) and fine-scale (0.02 ha) structural habitat data. Functional habitat (rest sites and prey kill sites) occurred disproportionately in hemlock-cedar. Fine-scale structural habitat data detected greater selection and tortuosity within hemlock-cedar by traveling martens, but broadscale structural habitat data did not, which demonstrates that combining fine-scale location data with fine-scale structural habitat data improves the match between functional and structural habitat and understanding of habitat requirements. Selection and tortuosity indexes were poorly correlated, indicating that factors other than structural habitat influenced movement patterns. Within-stand structural habitat heterogeneity is important to martens and fishers, especially when heterogeneity includes mature conifer inclusions within primarily deciduous forests. Broadscale data may identify structural habitat associated with required types, rather than required habitat itself, when functional habitat corresponds with landscape features such as inclusions. © 2014 American Society of Mammalogists. Source

Moody E.K.,University of Wisconsin - Madison | Moody E.K.,Arizona State University | Weidel B.C.,University of Wisconsin - Madison | Weidel B.C.,United States Geological Survey Great Lakes Science Center | And 3 more authors.
Journal of Great Lakes Research | Year: 2011

Differences in the preferred thermal habitat of Lake Superior lake trout morphotypes create alternative growth scenarios for parasitic sea lamprey (Petromyzon marinus) attached to lake trout hosts. Siscowet lake trout (Salvelinus namaycush) inhabit deep, consistently cold water (4-6 °C) and are more abundant than lean lake trout (Salvelinus namaycush) which occupy temperatures between 8 and 12 °C during summer thermal stratification. Using bioenergetics models we contrasted the growth potential of sea lampreys attached to siscowet and lean lake trout to determine how host temperature influences the growth and ultimate size of adult sea lamprey. Sea lampreys simulated under the thermal regime of siscowets are capable of reaching sizes within the range of adult sea lamprey sizes observed in Lake Superior tributaries. High lamprey wounding rates on siscowets suggest siscowets are important lamprey hosts. In addition, siscowets have higher survival rates from lamprey attacks than those observed for lean lake trout which raises the prospect that siscowets serve as a buffer to predation on more commercially desirable hosts such as lean lake trout, and could serve to subsidize lamprey growth. © 2010 Elsevier B.V. Source

Pauli B.P.,Purdue University | McCann N.P.,Purdue University | McCann N.P.,Apple Inc | Zollner P.A.,Purdue University | And 3 more authors.
PLoS ONE | Year: 2013

Complex decisions dramatically affect animal dispersal and space use. Dispersing individuals respond to a combination of fine-scale environmental stimuli and internal attributes. Individual-based modeling offers a valuable approach for the investigation of such interactions because it combines the heterogeneity of animal behaviors with spatial detail. Most individual-based models (IBMs), however, vastly oversimplify animal behavior and such behavioral minimalism diminishes the value of these models. We present program SEARCH (Spatially Explicit Animal Response to Composition of Habitat), a spatially explicit, individual-based, population model of animal dispersal through realistic landscapes. SEARCH uses values in Geographic Information System (GIS) maps to apply rules that animals follow during dispersal, thus allowing virtual animals to respond to fine-scale features of the landscape and maintain a detailed memory of areas sensed during movement. SEARCH also incorporates temporally dynamic landscapes so that the environment to which virtual animals respond can change during the course of a simulation. Animals in SEARCH are behaviorally dynamic and able to respond to stimuli based upon their individual experiences. Therefore, SEARCH is able to model behavioral traits of dispersing animals at fine scales and with many dynamic aspects. Such added complexity allows investigation of unique ecological questions. To illustrate SEARCH's capabilities, we simulated case studies using three mammals. We examined the impact of seasonally variable food resources on the weight distribution of dispersing raccoons (Procyon lotor), the effect of temporally dynamic mortality pressure in combination with various levels of behavioral responsiveness in eastern chipmunks (Tamias striatus), and the impact of behavioral plasticity and home range selection on disperser mortality and weight change in virtual American martens (Martes americana). These simulations highlight the relevance of SEARCH for a variety of applications and illustrate benefits it can provide for conservation planning. Source

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