Experimental demonstration of catch hyperstability from habitat aggregation, not effort sorting, in a recreational fishery

Abstract

The relationship between angler catch rates and fish abundance can contribute to or hinder sustainable exploitation of fisheries depending on whether catch rates are proportional to fish abundance or are hyperstable. We performed a whole-ecosystem experiment in which fish abundance was manipulated and paired with weekly angler catch rate estimates from controlled experimental fishing. Catch rates were hyperstable (β = 0.47) in response to changes in fish abundance. By excluding effort sorting (i.e., catch rates remaining high because less skilled anglers leave the fishery as abundance declines), our experiment isolated the influence of fish aggregation as a driver of hyperstability. Spatial analysis of catch locations did not identify clustering around specific points, suggesting that loose aggregation to preferred habitat at the scale of the entire littoral zone was enough to maintain stable catch rates. In our study, general, non-spawning, habitat preferences created loose aggregations for anglers to target, which was sufficient to generate hyperstability. Habitat preferences are common to nearly all fishes and widely known to anglers, suggesting that many harvest-oriented recreational fisheries can be expected to exhibit hyperstability.

Technological innovations in the recreational fishing sector: implications for fisheries management and policy

“…Therefore, if the fish are released, the likelihood of the individual fish being recaptured multiple times through targeted fishing increases, although no study exists to support this idea. Moreover, through echo-sounding, cryptic aggregations of fish may be effectively found, increasing the likelihood of hyperstable catch rates (Dassow et al 2020 ) and generally elevated hooking mortality. However, not all anglers utilize advanced boat-based technologies due to a lack of specialization or financial commitment.…”

“…Specifically, certain highly effective catch innovations adopted by a minority of highly avid and skilled innovators can foster overfishing once widely adopted. First, gear innovations may maintain high catch rates even when fish stocks decline, creating hyperstability in catch rates (Post et al 2002 ; Maggs et al 2016 ; Dassow et al 2020 ). Hyperstability reduces the index value of catch per unt.…”

“…Recreational anglers have the capacity to target fish with such high efficacy stocks might collapse (Post et al 2002 , 2008 ; Cooke and Cowx 2004 ). These effects are likely to be exacerbated by technological advances or by range contractions and ability of fishers to find even smaller abundances (Dassow et al 2020 ). There should be concern about the potential for how improved efficiency could affect some fishing systems, particularly those that are already vulnerable due to smaller populations.…”

A comparison of trends in population size and life history features of Atlantic salmon (Salmo salar) and anadromous and non-anadromous Brown trout (Salmo trutta) in a single catchment over 116 years

“…Hyperstability has been shown to occur when fishing catches remain constant during a period of an underlying population decline (Hamilton et al, 2016), thus overestimating the true population size. In contrast hyperdepletion is where a rapidly declining fishing catch rate occurs when the underlying population remains stable (Dassow et al, 2020). Given that catches in the study reported here seem to indicate a declining population, if hyperstability is occurring it must be only reducing the magnitude of the identified change in population size.…”

Frontiers in modelling social–ecological dynamics of recreational fisheries: A review and synthesis

“…Johnston et al., 2010; Johnston et al., 2013; Johnston et al., 2015) implicitly allow for hyperstability through effort switching (van Poorten, Walters, & Ward, 2016; Ward, Askey, & Post, 2013), though this is rarely recognized or discussed. Given the increasing evidence that hyperstability and hyperdepletion can occur in recreational fisheries due to mechanisms including habitat and spawning aggregation and effort sorting (Askey, Richards, Post, & Parkinson, 2006; Dassow et al., 2020; Mrnak, Shaw, Eslinger, Cichosz, & Sass, 2018; van Poorten et al., 2016; Ward et al., 2013), greater attention to these dynamics in our models of recreational fisheries SES seems essential.…”