Consistent selection towards low activity phenotypes when catchability depends on encounters among human predators and fish

PLoS One. 2012;7(10):e48030. doi: 10.1371/journal.pone.0048030. Epub 2012 Oct 24.

Abstract

Together with life-history and underlying physiology, the behavioural variability among fish is one of the three main trait axes that determines the vulnerability to fishing. However, there are only a few studies that have systematically investigated the strength and direction of selection acting on behavioural traits. Using in situ fish behaviour revealed by telemetry techniques as input, we developed an individual-based model (IBM) that simulated the Lagrangian trajectory of prey (fish) moving within a confined home range (HR). Fishers exhibiting various prototypical fishing styles targeted these fish in the model. We initially hypothesised that more active and more explorative individuals would be systematically removed under all fished conditions, in turn creating negative selection differentials on low activity phenotypes and maybe on small HR. Our results partly supported these general predictions. Standardised selection differentials were, on average, more negative on HR than on activity. However, in many simulation runs, positive selection pressures on HR were also identified, which resulted from the stochastic properties of the fishes' movement and its interaction with the human predator. In contrast, there was a consistent negative selection on activity under all types of fishing styles. Therefore, in situations where catchability depends on spatial encounters between human predators and fish, we would predict a consistent selection towards low activity phenotypes and have less faith in the direction of the selection on HR size. Our study is the first theoretical investigation on the direction of fishery-induced selection of behaviour using passive fishing gears. The few empirical studies where catchability of fish was measured in relation to passive fishing techniques, such as gill-nets, traps or recreational fishing, support our predictions that fish in highly exploited situations are, on average, characterised by low swimming activity, stemming, in part, from negative selection on swimming activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Algorithms*
  • Animals
  • Computer Simulation
  • Ecosystem*
  • Fisheries
  • Fishes / classification
  • Fishes / physiology*
  • Humans
  • Models, Biological*
  • Movement / physiology
  • Recreation / physiology
  • Species Specificity
  • Swimming / physiology

Grants and funding

This work was supported by the research project CONFLICT (grant # CGL2008-00958) and REC2 (grant # CTM2011-23835), both of them funded by the Spanish Ministry of Economy and Competitiveness (MINECO, http://www.mineco.gob.es/). Additional funding was received from the research project ARTEVIGO (grant # 09MMA022402PR) financed by the Galician Government, Spain. RA also received additional funding from the German Federal Ministry for Education and Research (BMBF) through the Program for Social-Ecological Research for the project Besatzfisch (grant # 01UU0907, www.besatz-fisch.de). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.