Bottom fishing assessment tool: An R package to model the effects of bottom trawling on the marine benthos.

Bottom trawl fisheries are recognized to be a global threat to marine biodiversity and a dominant driver of sea floor ecosystem change. Although the mechanism of trawling impact on benthic life is more and more documented and empirically verified, there is still no standard toolbox that enables the prediction of impact in any area and that is soundly based on existing knowledge. We provide an R package ("Bfiat") endowed with functionalities that enable researchers as well as managers to assess the vulnerability of benthic organisms and associated ecosystem functions to trawling. The Bfiat package includes a deterministic modeling framework that predicts the state of benthic species following trawling disturbance as a fraction of pre-disturbance state. Benthic state is predicted according to the logistic population growth model combined with trawling parameters and organism functional traits. While trawling parameters determine the disturbance, functional traits express vulnerability through instantaneous sensitivity and longer term recoverability in the model response. We illustrate the potential of the package through a large-scale case study with species communities of contrasting functional compositions. Benthic response to trawling disturbance is exemplified from single species to entire community as well as from single station to larger spatial extent.