Modeling Exploitation in Recreational Fisheries and Implications for Effort Management on British Columbia Rainbow Trout Lakes

Abstract

We developed and evaluated a new model for predicting exploitation from recreational fishing effort. The model assumes that fish exchange between available and unavailable states and that fishery catches are taken only from the available pool. This limited vulnerability model exhibits a nonlinear, negative relationship between fishing effort and catch rate that manifests itself in the effort−exploitation relationship as an apparent decline in catchability with increasing effort. Decreasing catchability leads to an exploitation rate asymptote that may be less than unity as well as to a wide range of fishing effort over which exploitation is insensitive to changes in effort. Model predictions were consistent with the observed relationship between fishing effort and exploitation obtained from creel surveys and mark–recapture studies on rainbow trout Oncorhynchus mykiss lakes in British Columbia. We combined the exploitation modeling approach with an age‐structured model for a naturally reproducing rainbow trout population to evaluate both optimum fishing effort policies and critical fishing effort levels that lead to population collapse. Optimum fishing effort (±SD) was 18.8 ± 3.7 angler‐days/ha (AD/ha) for a stock that exhibits high recruitment compensation and 9.4 ± 2.4 AD/ha for a stock with low recruitment compensation. Critical effort did not exist for the high‐compensation scenario; the estimate of critical effort for the low‐compensation scenario was 23.2 ± 5.1 AD/ha. The estimator traditionally used to predict exploitation gave a poor fit to observed data, and resulting effort levels were twice those obtained from the limited vulnerability model.

Impacts of domestication on angling vulnerability of common carp, Cyprinus carpio: the role of learning, foraging behaviour and food preferences

“…Predator-prey relationships like those between anglers and their target fish are regulated by the fish's antipredator behaviours (Cox & Walters 2002;Van Poorten & Post 2005;Askey et al 2006). Antipredator behaviour in fish has a genetic basis (Seghers 1974;O'Steen et al 2002;Ghalambor et al 2004), but experience and learning over time can strongly influence the development of antipredator responses (Kieffer & Colgan 1992;Kelley & Magurran 2003;Griffin 2004).…”

Influence of spear guns, dive gear and observers on estimating fish flight initiation distance on coral reefs

“…However, while evidence that fishing alters fish behaviour, and potentially fishing success, has been reported from freshwater recreational fisheries (Cox & Walters 2002, Askey et al 2006) and commercial trawls (Pyanov & Zhuykov 1993), knowledge of the influence of behavioural changes on catchability of coral reef fishes is lacking, despite indications that fishing can influence fish detectability (Kulbicki 1998). Using the metric flight initiation distance (FID), which estimates how close an animal can be approached before it flees (also referred to as flight or approach distance) (Ydenberg & Dill 1986), it has been established that fishes on near-shore, shallow reefs open to fishing consistently flee from an observer at a greater distance than fishes in notake marine reserves (NTRs) (Cole 1994, Gotanda et al 2009.…”

Full Issue PDF Volume 39, Issue 6

“…Differences in the distributions of Largemouth Bass anglers and Largemouth Bass lend support to Martin's (1958) and Cox and Walters' (2002) hypothesis that a population is composed of fish vulnerable to angling and invulnerable to angling. However, tag return data indicated these apparently invulnerable offshore behavior individuals were just as likely to be captured as onshore behavior fish, signifying no difference in vulnerability to angling.…”

“…However, these studies largely ignore within-lake spatial interactions between anglers and fish. Consequently, small-scale spatial interactions between anglers and fish have been hypothesized to lead to areas where fish are "safe" from, or invulnerable to, angling due to interactions between angler and fish behavior (Martin 1958;Cox and Walters 2002). Many factors can lead to fish being less vulnerable or invulnerable to angling, including angler heterogeneity in skill, knowledge, and motivation (van Poorten and Post 2005;Hunt et al 2011;Seekell et al 2011) and variations in fish behavior affecting habitat selection and movement rates Botsford et al 2003;Grüss et al 2011).…”

“…The objectives of this study were to (1) test evidence for the Martin (1958) and Cox and Walters (2002) hypothesis that a portion of a fish population is spatially invulnerable to angling due to spatial patterns of angler or fish behavior and (2) determine whether anglers were distributed according to the IFD. In order to achieve these objectives, the spatial distributions of both anglers and fish were evaluated, exchange rates of fish between areas targeted and areas not targeted by anglers were quantified, and data from angler tag returns were used to empirically test whether a portion of the population remained invulnerable to angling.…”