Angler Numerical Response Across Landscapes and the Collapse of Freshwater Fisheries

Abstract

Recreational angling opportunities in lakes are distributed across landscapes and attract anglers based on the combination of angling quality, travel distance, and availability of facilities. The relationship between angler density and fishing quality, as measured by catch rate, represents a numerical response that is analogous to a predator numerical response to variability in prey abundance. We quantified this numerical response of anglers to rainbow trout, Oncorhynchus mykiss, populations distributed over a large lake district in south-central British Columbia, Canada. We developed a harvest dynamics model by linking this empirical description of the spatial numerical response of anglers to a logistic population growth rate model. The model was parameterized for rainbow trout and simulated spatial patterns of angler density and catch rates over a landscape. At locations distant from urban centers, angler density is low and catch rate high, suggesting near pristine conditions; at intermediate distances angler density is higher while catch rates are lower and approximate maximum sustainable levels; and at short distances angler density is sufficiently high to harvest to local extirpation. We extrapolated the model to other lake districts varying in human population size using an empirically derived angling participation rate relationship. Extrapolation to lake districts with one-tenth the human population maintained viable fisheries close to the urban area, and districts with 10 times the human populations could not maintain viable fisheries across much of their lake district. Landscape-scale spatial patterns differed quantitatively for species varying in rates of intrinsic population growth and carrying capacity, but the qualitative spatial patterns were consistent among species, demonstrating the pervasive impacts of the angler numerical response. To achieve a management goal of sustaining fisheries across landscapes, a change in management perspective is necessary, from that of individual lakes to one of dynamic harvest processes across landscapes. This new approach makes it clear that a one-size-fits-all management approach must be replaced with a mosaic of approaches cognizant of landscape-scale processes.

Smartphones Reveal Angler Behavior: A Case Study of a Popular Mobile Fishing Application in Alberta, Canada

“…Our finding that anglers visited lakes that were within a reasonable driving distance of large population centers is nothing new; it is consistent with conventional data from Alberta and well established in the literature (e.g., Post et al 2008;Ward et al 2013). However, the fact that we observed angler preferences (and movement networks) by applying fairly basic analyses to data from the uncoordinated use of an app that was not developed for research demonstrates the enormous potential of this technology.…”

Angler effort and catch within a spatially complex system of small lakes

“…It is often assumed that anglers are highly mobile and are responsive to spatial (among waterbodies) and temporal (among years) differences in fish abundances (Johnson and Carpenter, 1994;Carpenter and Brock, 2004;Post, et al, 2008). We expected 20-25% of angler parties to move among the lakes during a single trip, but the percentage of angling parties that moved among lakes was less than expected.…”

“…The factors involved in the decision to move from one lake to another was unclear, although it may be related to catch as a majority of the parties that moved did not catch any fish at their first location. However, catch is often not the primary motivation for angling (Driver and Knopf, 1976;Fedler and Ditton, 1994) and the decision to move to another lake may be related to other noncatch-related factors (Johnson and Carpenter, 1994;Hunt, 2005;Post et al, 2008;Johnston et al, 2010;Hunt et al, 2011). For example, Johnston et al (2011) observed that trout anglers were not attracted to high-catch-rate fisheries and they suggested that angler behaviour is complex and may be strongly influenced by harvest regulations.…”

Decline in angler use despite increased catch rates: Anglers’ response to the implementation of a total catch-and-release regulation

“…Indeed, earlier research has emphasized that angler effort responses are determined by multiple catch and non-catch related factors, including angling regulations (Aas et al, 2000;Oh et al, 2005;Hunt, 2005), and are not simply linked to fishing successes alone (Johnson and Carpenter, 1994;Hunt, 2005;Post et al, 2008;Johnston et al, 2010;Hunt et al, in press). In particular, harvest regulations may alter the attractiveness of a fishery if they are perceived to constrain anglers' opportunities to harvest fish (Radomski and Goeman, 1996;Dorr et al, 2002;, or if they alter anglers' expectations about the fishery Cook et al, 2001;Beard et al, 2003).…”