Fig. 3
![Fig. 3](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs40064-015-1391-y/MediaObjects/40064_2015_1391_Fig3_HTML.jpg)
Tuna tube apparatus. a Six tubes attached to an aluminium frame and placed inside a 300 L tank. Note the oxygen regulator on the bottom of the picture and the water inlet pipes at the top. b A plastic funnel positioned at the bottom of the tube, directs the water over the snout and mouth of the fish. c One of two 1500 gallon per hour bilge pumps connected to the tubes’ water system to recirculate the water from the tank to the tubes