Passive gear‐induced timidity syndrome in wild fish populations and its potential ecological and managerial implications

Abstract

Human exploitation of wild‐living animals has been suggested to create a ‘landscape of fear’. A consequence could be that individuals surviving intensive harvesting, either as a result of behavioural plasticity and/or evolutionary change, exhibit increased average timidity. In the aquatic world, such effects are particularly well documented in passively operated fishing gears common to many commercial and recreational fisheries, such as angling, trapping or gill netting. We thus propose that an exploitation‐induced timidity syndrome should be a widespread pattern in fisheries. Importantly, we argue that the syndrome can be associated with several ecological and managerial consequences for social groups, populations, food webs, fisheries and assessment of stocks. We suggest research priorities to deepen our understanding of how exploited fish populations behaviourally respond to harvesting.

Evolution of boldness and life history in response to selective harvesting

“…Our understanding of fisheries-induced selection and potential for 90 evolutionary changes in traits other than life-history traits, such as behavioral or physiological traits, is far less developed (Uusi-Heikkilä et al 2008;Heino et al 2015; 92 Arlinghaus et al 2017). In particular, there is a gap in the knowledge related to the potential for adaptive effects of fishing on behavioral traits in wild-living fish 94 populations.…”

“…Note, however, that the empirical research based on the relationship 130 of behavioural traits and vulnerability to active gears is much less well developed compared to passive gear types (Diaz-Pauli and Sih in press). Consequently, it is not 132 clear that active gears will always preferentially select shy fishes, but it is safe to assume that fisheries will be generally selective for both size and behavioral traits 134 (Allendorf & Hard 2009;Heino et al 2015;Arlinghaus et al 2017). We therefore explored the whole "sphere of opportunities" in terms of selection acting on the 136 boldness-shyness axis with and without additional selection on size to understand the direction and strength of selection on behaviour and life-history traits in a range of 138 contexts.…”

“…In passively operated fishing gear, vulnerability to capture is likely 560 strongly and often mainly boldness-driven (Klefoth et al 2012;Biro & Sampson 2015), which is why one can expect changes in growth rate and evolution of timidity 562 28 particularly in reaction to exploitation by gill nets, traps or hook-and-line. It will be important to test this clear-cut prediction in the future in empirical settings, because 564 increased timidity will have substantial effects on catchability and hence on stock assessment, fisher well-being and effectiveness of management tools such as protected 566 areas (Januchowski-Hartley et al 2011;Alós et al 2016;Arlinghaus et al 2017).…”

Fast and behavior-selective exploitation of a marine fish targeted by anglers

“…Behavioral traits have been suggested to play a major role, either due to selection directly acting on such traits or due to indirect selection responses emerging from correlation with life-history traits1920. The argument underlying this assumption is that catching a fish with baited hooks, artificial lures, gill nets or traps strongly depends on the behavior-driven encounter probability and the active decision of a fish to attack or ingest the bait/lure or enter the trap or gill net19.…”

Size Selectivity of Active Fishing Gear: Changes in Size, Age and Growth of Cirrhinus Mrigala from the Ganga River, India

“…Fishing may also affect ecological processes at very large scale. Fishing pressure is changes the size structure, age and stock of the fish species [20][21][22][23][24]. They also modify sex ratio, genetics and species composition of the target resources, as well as of their associated and dependent species [22,25,26].…”