As global marine catches have stagnated and even declined, fishing effort has greatly expanded over the past 70 years. Over the same period, the level of global marine catches has not even doubled, suggesting a steep decline in the catch per unit effort, often considered a measure of fishing productivity.
At the global level, the data show that, overall, global fisheries have foregone US$83 billion of rent in 2012. Fisheries are heavily subsidized and in many countries, resource rents from fisheries are negative—meaning that revenues do not
fully cover the costs of fishing.
Fisheries economists use resource rent (i.e., what remains after fishing costs and subsidies are deducted from revenue) as an indicator of fisheries performance
Read the report here (Chapter 10): http://hdl.handle.net/10986/29001