Question:
I believe the regulations say you must carry an abalone gauge and a fishing license when diving for abalone. Does that mean both need to be on my person when diving or is having those items in my float tube sufficient?

Answer:
It depends on the circumstances. The short answer is that they may be left in the dive tube only if the dive tube remains in your immediate possession. The long explanation follows:

According to Department of Fish and Game (DFG) Lt. Dennis McKiver, all individuals including divers must have an Abalone Report Card in their immediate possession while fishing for or taking red abalone (California Code of Regulations Title 14, Section 29.16(a)). In addition, every person while taking abalone shall carry a fixed-caliper measuring gauge (CCR Title 14, Section 29.15(f)). As long as the dive tube is in the immediate possession of diver, then the diver may leave their Abalone Report Card and abalone gauge in their dive tube. It is required that "undersize abalone must be replaced immediately to the same surface of the rock from which detached," therefore it is always best if you carry your measuring gauge with you.

Let's say you surface with an abalone and then have to swim a distance to retrieve your dive tube and abalone gauge, only to measure and discover the abalone is undersize. Now that you have had to swim away from the location where the abalone was taken, you may not be inclined or able to return and find "the same surface of the rock from which detached." If you are being watched by the warden and fail to replace the abalone "immediately to the same surface of the rock from which detached," then you might be cited for violating CCR Title 14, section 29.15(d),failure to immediately reattach abalone to the same surface of the rock from which detached, and also section 29.15(f), failure to carry a measuring device while taking abalone as required. The measuring device should remain in your immediate possession, so your best bet is to anchor your float tube close by so it doesn't drift away while you are diving and your gauge and license are always close at hand.