Data from: Evolutionary impact of size-selective harvesting on shoaling behavior: Individual-level mechanisms and possible consequences for natural and fishing mortality

Intensive and size-selective harvesting is an evolutionary driver of
life-history as well as individual behavioral traits. Yet, whether and to
what degree harvesting modifies the collective behavior of exploited
species is largely unknown. We present a multi-generation harvest
selection experiment with zebrafish (Danio rerio) as a model
species to understand the effects of size-selective harvesting on shoaling
behavior. The experimental system is based on a large-harvested (typical
of most wild capture fisheries targeting larger size classes) and
small-harvested (typical of specialized fisheries and gape-limited
predators targeting smaller size classes) selection lines. By combining
high resolution tracking of fish behavior with computational agent-based
modeling we show that shoal cohesion changed in the direction expected by
a trade-off between individual vigilance and the use of social cues. In
particular, we document a decrease of individual vigilance in the
small-harvested line, which was linked to an increase in the attention to
social cues, favoring more cohesive shoals. Opposing outcomes were found
for the large-harvested line, which formed less cohesive shoals. Using the
agent-based model we outline possible consequences of changes in shoaling
behavior for both fishing and natural mortality. The changes in shoaling
induced by large size-selective harvesting may decrease fishing mortality,
but increase mortality by natural predators. Our work suggests an insofar
overlooked evolutionary mechanism by which size-selective harvesting can
affect fishing and natural mortality of exploited fish.