Fisheries-induced disruptive selection

Abstract

Commercial harvesting is recognized to induce adaptive responses of life-history traits in fish populations, in particular by shifting the age and size at maturation through directional selection. In addition to such evolution of a target stock, the corresponding fishery itself may adapt, in terms of fishing policy, technological progress, fleet dynamics, and adaptive harvest. The aim of this study is to assess how the interplay between natural and artificial selection, in the simplest setting in which a fishery and a target stock coevolve, can lead to disruptive selection, which in turn may cause trait diversification. To this end, we build an eco-evolutionary model for a size-structured population, in which both the stock's maturation schedule and the fishery's harvest rate are adaptive, while fishing may be subject to a selective policy based on fish size and/or maturity stage. Using numerical bifurcation analysis, we study how the potential for disruptive selection changes with fishing policy, fishing mortality, harvest specialization, life-history tradeoffs associated with early maturation, and other demographic and environmental parameters. We report the following findings. First, fisheriesinduced disruptive selection is readily caused by commonly used fishing policies, and occurs even for policies that are not specific for fish size or maturity, provided that the harvest is sufficiently adaptive and large individuals are targeted intensively. Second, disruptive selection is more likely in stocks in which the selective pressure for early maturation is naturally strong, provided life-history tradeoffs are sufficiently consequential. Third, when a fish stock is overexploited, fisheries targeting only large individuals might slightly increase sustainable yield by causing trait diversification (even though the resultant yield always remains lower than the maximum sustainable yield that could be obtained under low fishing mortality, without causing disruptive selection). We discuss the broader implications of our results and highlight how these can be taken into account for designing evolutionarily informed fisheries-management regimes.

Complexity and stability of ecological networks: a review of the theory

“…Trait adaptation can also be modelled and give rise to complex trophic interaction networks (Brännström et al 2011(Brännström et al , 2012Landi et al 2013Landi et al , 2015Hui et al 2018), and their complexity-stability relationship assessed (Kondoh 2007;Ingram et al 2009). In particular, Kondoh (2007) studied adaptation in predator-specific defence traits, reporting its unimodal effect on the complexity-stability (connectance-persistence and robustness) relationship, while species richness always has a negative impact on stability.…”

Declining size of adults and juvenile harvest threatens sustainability of a tropical gastropod, Lobatus gigas, fishery

“…Anthropogenic impacts on the world's marine ecosystems and associated biodiversity are widespread, including overfishing (Pauly, Christensen, Dalsgaard, Froese, & Torres, ), pollution (Tewfik, Rasmussen, & McCann, ) and climate change (Brander, ), which can cause interacting negative consequences for wild populations (Collier, Probert, & Jeffries, ), livelihoods and food security (Andrew et al, ). In some cases, overfishing has been shown to change contemporary life history, resulting in reduced adult body size, altered demographics and associated fecundity, most often in size‐selective fisheries (Allendorf & Hard, ; Haarr, Sainte‐Marie, Comeau, Tremblay, & Rochette, ; Landi, Hui, & Dieckmann, ; Valles & Oxenford, ). This in turn can undermine future recruitment and economic returns with possible broader ecological and evolutionary consequences (Allendorf, England, Luikart, Ritchie, & Ryman, ; Allendorf & Hard, ; Audzijonyte, Kuparinen, Gorton, & Fulton, ; Kuparinen & Festa‐Bianchet, ; Landi et al, ).…”

“…In some cases, overfishing has been shown to change contemporary life history, resulting in reduced adult body size, altered demographics and associated fecundity, most often in size‐selective fisheries (Allendorf & Hard, ; Haarr, Sainte‐Marie, Comeau, Tremblay, & Rochette, ; Landi, Hui, & Dieckmann, ; Valles & Oxenford, ). This in turn can undermine future recruitment and economic returns with possible broader ecological and evolutionary consequences (Allendorf, England, Luikart, Ritchie, & Ryman, ; Allendorf & Hard, ; Audzijonyte, Kuparinen, Gorton, & Fulton, ; Kuparinen & Festa‐Bianchet, ; Landi et al, ). At the same time a number of researchers have also explored the influence of climate change‐induced rising sea surface temperatures on the size of marine consumers, their distribution and productivity (Baudron, Needle, Rijnsdorp, & Marshall, ; Haarr et al, ; Pauly & Cheung, ; Tu, Chen, & Hsieh, ; Wilson‐Brodie, MacLean, & Fenberg, ).…”

Genetic architecture of age at maturity can generate divergent and disruptive harvest-induced evolution

“…Pike phenotypic trait variance was seen to increase along with intensive fishing, and this was speculated to arise as a combination of selection for, on the one hand, late entry to fisheries but, on the other hand, fast growth of fish vulnerable to fisheries [25]. Similar indications of fisheries selectivity being disruptive have also been provided by theoretical analyses of adaptive fish population dynamics [26]. While these studies suggest that fisheries-induced evolution can indeed be disruptive due to counteracting components of fisheries selection [27,28], our study goes further by demonstrating that fisheries-induced disruptive evolution can arise also as a consequence of the genetic architecture of the trait targeted by fishing.…”