Simulated Equilibrium Walleye Population Density under Static and Dynamic Recreational Angling Effort

Abstract

Understanding the dynamics of angling effort and how fish populations are affected by angler effort is an important and often unappreciated component of fisheries management. Our objective was to determine the extent to which angling‐induced mortality limits walleye Sander vitreus population density in northern Wisconsin lakes. We developed a simulation model to evaluate the effects on long‐term equilibrium walleye population density caused by effort limitations, density‐dependent angling effort, and angling regulations. Equilibrium density was limited by angling effort when effort was held constant but was generally lower when effort was density dependent. Equilibrium density ranged from 3.46 to 21.79 adults/ha when effort was density dependent, similar to the observed median density in lakes sustained by natural reproduction (8.7 adults/ha). Median equilibrium density was 23.3 adults/ha when effort was zero. Equilibrium density was higher when harvest was regulated by a minimum length limit as opposed to no length limit and with no postrelease mortality than with postrelease mortality. Population collapse was more likely and equilibrium density was lower when the population density and effort/ha relationship was strongest. Because the observed relationship between adult walleye population density and effort/ha was weaker, we conclude that open‐access walleye fisheries in northern Wisconsin are generally self‐regulating. However, populations likely persist at lower population densities than would be expected if angling effort were limited to lower levels than those currently observed. Our results are intuitive; however, they suggest that density increases may be on the order of 100% when effort is severely restricted compared with open‐access fisheries with unlimited effort. Other fish species may experience different expected density increases with restricted angler effort depending on a number of factors, but our results suggest that population density changes can be dramatic and that similar modeling exercises may be useful to managers of other fish species if increasing density is of interest. Received December 19, 2011; accepted June 13, 2012

A mechanistic understanding of hyperstability in catch per unit effort and density-dependent catchability in a multistock recreational fishery

“…However, the numerical response of anglers to fish abundance is equally important in understanding whether the interaction between fish abundance and harvest is likely to be sustainable (Schueller et al 2012;Allen et al 2013;Askey et al 2013). Typically there is a positive relationship between fish abundance and angler effort (e.g., Post et al 2008;Schueller et al 2012), yet we observed no significant relationship in this study. It is not clear why there is a lack of correlation in our study, but it could be partially due to differential access or travel costs between lakes .…”

“…It is not clear why there is a lack of correlation in our study, but it could be partially due to differential access or travel costs between lakes . The lack of a relationship between angler effort and fish abundance can be a concern for the sustainability of wild stock fisheries (Walters and Martell 2004;Schueller et al 2012;Allen et al 2013), although the lakes in this study are maintained by stocking. If angler effort does not respond to changes in fish abundance, then the possibility for overfishing exists if angler effort remains high as fish abundance declines.…”

Relationships between angling effort and fish abundance in recreational marine fisheries

“…Others have even suggested that recreational fisheries may self‐regulate (Pereira & Hansen ; Schueller et al . ). Coupled angling effort responses to fish abundance have also commonly been assumed in some modelling simulations studying recreational fisheries (Johnston et al .…”

“…The strength of relationships between recreational angling effort and fish abundance has been the subject of relatively few studies of which some have shown apparent strong relationships between effort and fish abundance Post et al 2008). Others have even suggested that recreational fisheries may self-regulate (Pereira & Hansen 2003;Schueller et al 2012). Coupled angling effort responses to fish abundance have also commonly been assumed in some modelling simulations studying recreational fisheries (Johnston et al 2010;van Poorten et al 2011;Allen et al 2013).…”

Multiple challenges confront a high-effort inland recreational fishery in decline

“…Angler effort restrictions may represent an important management option for maintaining rainbow trout in the LBR. Active management policies that seek to reduce fishing effort are often socially unacceptable (Schueller et al 2012) and hence have rarely been implemented in inland recreational fisheries (Pereira and Hansen 2003). An approach that has been implemented with success, albeit in big-game wildlife management systems, is access limitation via lottery systems (Boxall 1995;Scrogin et al 2000).…”