Lot of articles on line about the increased harvest of tuna over the past 4-5 decades. Read the attached article which contains a lot of information regarding world tuna harvest. Specifically addressing your question, reference first paragraph in section 1.1.6 addressing IUU (illegal, unreported and unregulated) practices. The data in the article only goes through 2000, but focus on the trend lines. If you assume based on technological improvements of commercial fisheries and market prices of tuna the trend lines have continued to increase over the last 18 years, imagine what the harvest numbers are today.

http://www.fao.org/docrep/007/y5428e/y5428e03.htm

Fisheries management have a hard enough time monitoring and quantifying harvest statistics for inshore species, pelagics with the expanse of ocean they travel and number of countries involved is virtually impossible to quantify and or regulate. World wide demand is increasing, prices have sky rocketed and the resource can't keep pace.

Read the article in the below link, published this year, regarding bluefin tuna.

https://www.thenation.com/article/no...-japans-sushi/

Note the following excerpt, "In 2012 only 6 percent of all bluefin were old enough (three to five years) to reproduce; by 2016 the ratio had fallen to only 2.6 percent. Japan, responsible for 75 percent of all bluefin catches in the Pacific between 1980 and 2014, is now under pressure to introduce serious measures to stem the decline." What does that statement bring to mind? Exact same problem NMFS and ASMFC created with the fluke fishery by legislating over harvest of breeders and allowing commercial operators to harvest during the spawn which is why reproduction over the last twenty years has tanked. Easy fixes but unfortunately money and politics prevents remedial decisions from being made.