Unveiling Uncertainty and Complexity in Inland Fisheries
Date
2021-08-13
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Abstract
Inland fisheries are valuable from social, ecological, and economic perspectives, but data collected by resource management agencies are typically observational in nature and hence difficult to learn from (i.e., such data rarely originate from well-designed experiments). Thus, a central challenge facing inland fisheries ecology and management is the extraction of reliable information from observational data. The goal of this dissertation was to show that ecological knowledge and understanding in inland fisheries are dependent on the methods used and the assumptions made when learning from applied observational data, and that in general there is more uncertainty and complexity present in these systems than has been previously acknowledged. To demonstrate this claim, tactical modeling tools that probe systems for uncertainties were applied to help inform a set of fisheries management problems in Alberta, Canada. Chapter 2 developed Bayesian capture-recapture models to demonstrate that abundance of Rainbow Trout in the lower Bow River likely declined during 2003-2013, but the available data offered no insights into the causal factor(s) responsible for this decline. Chapter 3 evaluated whether angler concerns about slow-growing Walleye were caused by high densities of conspecifics in lakes. This chapter showed that spatial-temporal growth models outperformed simpler models when simulated data featured spatial-temporal correlation. Applying these models to the Alberta Walleye data then showed that Walleye growth rates did not decline with increasing density of conspecifics, and that growth rate was unrelated to several predictors believed to influence it. Chapter 4 fitted age-structured population dynamics models to data from a landscape-scale monitoring program to assess Walleye population status and reconstruct recruitment dynamics following the collapse of these fisheries during the 1990s. This chapter showed that recovery from collapse was driven by favorable recruitment events during 1998-2002 in 33/55 lakes and that 9/55 lakes featured cyclic recruitment dynamics. Collectively, this work demonstrates the considerable challenges associated with analyzing inland fisheries data, which has broad implications for ecologists and managers seeking to extract reliable information from similar applied datasets.
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Keywords
Inland recreational fisheries, Walleye, Rainbow trout
Citation
Cahill, C.L. (2021). Unveiling Uncertainty and Complexity in Inland Fisheries (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.