Depensatory effects of intensive aquaculture: Beyond the fishmeal debate

Aquaculture production has increased 10-fold over the past three decades. The proportion of total production given over to high trophic level species is also growing rapidly. The net ecological, social and economic benefits offered by commercial scale aquaculture are sources of fractious debate. Within ecological circles the growing profile of cultured carnivorous species and the reliance of these production systems on fish meal and oil tends to dominate attention. However, analysis of the farmed salmon industry undertaken to understand the root causes of such issues as escapes and epizootic events  revealed significant depensatory effects which have remained largely cryptic since they operate across large gradients of scale and cross disciplinary boundaries. The conclusions of this work suggest that mitigation of ecological issues associated with commercial scale aquaculture will not be possible without first addressing their underlying economic and political drivers.