Check out a few answers I came across. Some are laughable, others could be true!
Why do mullet jump out of the water?
"Mullet jump so they can see where they're going."
If a kid asks me why mullet jump, that is exactly what I am going to tell him. It's just so obvious.
Wouldn't other fish do the same thing, too? In all seriousness, I am pretty sure this is not the reason why. When you're done chuckling, move on to the next theory.
"Mullet jump because they are running from predators."
Yes! And no.
The long jumps where you see mullet sail through the air (like a football being tossed by Drew Brees) are not in response to predatory action. They're just too calm and deliberate in their jumping. Besides, when you see a mullet long jump, you don't ever see predators in the vicinity chasing them.
I do, however, see mullet skitter in a clear frantic pattern to get away from a hungry fish. Finger mullet especially do this. Trust the Blog, when you see it you will have no doubt in your mind!
The dead giveaway is when you immediately catch fish in the area with mullet in their stomach.
"No one knows. Fires burn, the sky is blue and mullet jump."
Touché, Old-Timer Knowledge! You win again, you always do.
Hey, mullet jump because they do. Let's not delve into semantics.
"Mullet jump to get rid of parasites."
While I doubt Myth Busters will be cracking this one anytime soon, I don't believe this to be the case. Consider that other fish are not doing the same thing.
"Mullet jump to breathe air."
After some research, I find it likely to be true. Let this reference explain:
The research of Hoese (1985) suggests that Sea Mullet use this second category of movements to fill the pharyngobranchial organ (an area at the back of the throat) with air.
The trapped air is believed to allow the fish to remain active in water of low oxygen concentration for about five minutes.
I found this information at an Aussie Aquarium Website and find it to be intriguing. Think about the situational awareness this kind of information would give you!
Do your searches on various fishing forums and you will read about mullet jumping a lot in areas of fish kills. You can also find stories about fish swimming more near the surface in areas where there is O2 depletion. What they're doing is called aquatic surface respiration. Interesting, huh?
This makes sense because mullet spend the majority of their life at the top of the water column, where water is warmest. Warmer water holds less dissolved oxygen than colder water, which usually resides at the bottom of the water column.
So now you know the real reason why mullet jump!