Henry Hansen

Henry Hansen

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Degree MS in NRES
Address 249 Hardin Hall - Section 22
3310 Holdrege St
Lincoln NE
68583-0962
FAX 402-472-2946
E-mail hansenhenry54@gmail.com
Advisor(s) Mark Pegg

n/a

 

Selected Presentations

Implications of Channel Catfish Movement in An Internationally Managed System
  • Presentation Type: Thesis Defense
  • Date: 1/29/2019
  • Abstract:

    The largescale movements and spatial behavior of channel catfish in the Red River of the North, have direct interactions with geopolitics, anthropogenic structures, and ecosystems. Investigating the spatial dynamics and exploitation of this mobile and internationally managed fish species provides opportunities for resource managers to design evidence-based policy for the diverse interest groups that utilize the fishery. My thesis comprised two parts: 1) characterize system-wide movement and survival patterns using mark-recapture methods and acoustic telemetry and 2) project the interaction of hypothetical exploitation scenarios and alternative movement methodologies to assess the fishery from an ecosystem service flow perspective. Channel catfish were tagged with T-bar tags and acoustic transmitters to track movement patterns and quantify harvest. Approximately 40% of individuals tagged with acoustic transmitters moved into Lake Winnipeg at least once during the study. Conversely, about 30% of T-bar tag recaptures in the U.S.A. had been initially marked in Canada. A large proportion (0.89- 0.97) of the individuals remained within the initial study reach where they were tagged. Fishing mortality was estimated to be less than 0.001, and natural mortality was estimated to be 0.16 across the entire system. Projection models demonstrated that trophy stages of channel catfish were highly sensitive to exploitation and were typically depleted at or below a 0.30 exploitation rate. Depletion of populations and changes in stock structure affected subregions within the Red River system differently which resulted in competing strategies among countries and fishers from the perspective of economic valuation of harvests. We found that recruitment from areas with greatest population size appeared to buffer aspects of harvest within regions and to some extent immediately adjacent regions. Movement, regardless of methodology, was critical in supporting exploitation for regions with low recruitment. The sustainability of exploiting highly mobile fish species from an ecosystem service flow perspective hinges on the ability of fisheries management organizations to incorporate spatial variability and understand the economic consequences of exploitation for competing interests.

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