Read shark researcher Mark Marks' responses on the following shark topics:
Disappearing sharks
Shark evolution
Shark deterrent?
Nonstop swimmers?
Shark posturing
Swimming with the sharks?
Shark diving
Shark education
Shark enemies
Shark reproduction
Great white disposition
Favorite shark
Shark eyes
Shark companions
Bite pressure
Bladderless sharks
Warmblooded killers
Hammerheads
Thresher sharks
Great whites in captivity
Shark protection
Q: On Shark Swim Skills
Hi Mark,
I have heard sharks will drown if they stop swimming for even a few seconds. Is that true for great whites as well? Is this condition peculiar to elasmobranchs, or does it go for the osteichthyes too?
Sony
Your question touches upon one of the oldest myths about sharks. In fact, a great many species of shark, especially their cousins the skates and rays, spend long periods of time stationary and motionless on the bottom, not swimming at all. Many elasmobranchs pump water over their gills during respiration by the contraction of gill muscles sucking water into their mouth. Some species have small openings behind each eye called "spiracles," which work like a non-respiratory water pump drawing water into the oral cavity and over the gills. Those species, which have to swim forward to force water into and through their mouth to breathe, are called "ram ventilators." Ram-ventilating sharks will suffocate if trapped in nets or restricted from swimming when caught on a long line. The white shark is a ram ventilator and must remain swimming to ensure adequate water flow over the gills. Since bony fish possess a gas-filled swim bladder, they can remain stationary, or even move backward, by contracting their bony gill-plate cover (called the "operculum"), which they use to pump water over their gills.
