Flying in a chopper over Andaman sea (1000 feet ASL); all of sudden I saw something unique happening on an otherwise calm surface of the blue sea. A big school of fish was jumping out together with a big splash. My aviator colleague told me that these were mullets! They seem to do this when sea is calm, and often jump twice or occasionally three times in a short space of time. Why do they do this? Today, I thought why not me share this unique moment with you on TN. Sorry for the quality of picture but this is all I could do from a chopper with gusty winds from the rotor-air downwash.
Although many unrelated fish are called mullet, the true mullet are extremely active fish that travel in large schools throughout the tidal zones searching for food. Mullets are distinguished by the presence of two separate dorsal fins, small triangular mouths, and the absence of a lateral line organ. They feed on detritus, and most species have unusually muscular stomachs and a complex pharynx to help in digestion.
Over the years there have been numerous theories concerning the leaping of mullet. There seems to be two categories of leaping: predator avoidance and aerial respiration.
Leaping to avoid predators usually involves more than one fish jumping simultaneously, retaining an upright posture and entering the water cleanly.
The second type of leaping involves a single fish that does a slower, shorter leap, often flipping onto its side or even onto its back. They may also roll at the surface or move with their head above the water.
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.
Several lines of circumstantial evidence suggest that striped mullet, Mugil cephalus, use the upper posterior portion of the pharynx for aerial respiration, the air obtained either by jumping, rolling, or holding the head above the water and moving the air into the upper pharyngeal chamber. The principle evidence is that jumping frequencies are inversely correlated with dissolved oxygen concentration, and that the pharyngobranchial organ is capable of holding gas. This means the number of jumps is correlated with the concentration of oxygen in the water. The less oxygen, the more jumps.
Secondly, Sea Mullet feed during the day often in bottom sediments that have low oxygen concentrations. Jumping occurs much more commonly during the day. Sea Mullet rarely jump at night.
2. Jumping mullet — the internal diving bell hypothesis
Journal Environmental Biology of Fishes
Publisher Springer Netherlands
ISSN 0378-1909 (Print) 1573-5133 (Online)
Issue Volume 13, Number 4 / August, 1985
Now this is the kind of thing one rarely sees! You have so many rare opportunities...in the days of the 60's we used to say "it blows my mind'...which has many meanings but implies in this case...WOW!
Hello Subhash !
At first I wondered what you were trying to capture here, but then I read your very interesting notes and I doscovered an animal behavior which I didn't know - we learn new things every day ! :-) Mut have been great to watxh this. Very well done !