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.

This dataset contains data from a shoaling trials performed with groups of 8 adults zebrafish described in the paper: "Sbragaglia et al. (2021) Evolutionary impact of size-selective harvesting on shoaling behavior: Individual-level mechanisms and possible consequences for natural and fishing mortality".

The investigates the effects of size selective mortality on shoaling behavior. The experimental lines of zebrafish have been exposed to directional size-selection for 5 generations and then selection has been halted for further 8 generations. The results presented here are related to F13.

We first tracked shoaling behavior at 150 and 190 days post fertilizatoin with Ethovision in order to measure group-level variable and estimates repeatability of shoaling bhavior between two different ontogenetic period.

Then, we tracked shoaling behavior at 190 using IDtracker in order to measure individual behavior within the shoal and estimates the impact of size-selective harvesting on shoal cohesion, individual speed, and burst rate and inform an agent-based model that has been used to understand the effect of vigilance on shoaling behavior. The model has also been used to perform simulations to assess the impact of size selective harvesting on fishing and natural mortality.

The readme file contains an explanation of each of the variables in the dataset, its measurement units. n/a =  values not available. Information on how the measurements were done can be found in the associated manuscript referenced above.