0:00:07.049,0:00:10.164
Sometimes when a fish [br]is reeled up to the surface

0:00:10.164,0:00:12.160
it will appear inflated,

0:00:12.160,0:00:14.222
with its eyes bulging out of their sockets

0:00:14.222,0:00:16.622
and its stomach [br]projecting out of its mouth,

0:00:16.622,0:00:19.289
as if its been blown up like a balloon.

0:00:19.289,0:00:22.893
This type of bodily damage,[br]caused by rapid changes in pressure,

0:00:22.893,0:00:25.433
is called barotrauma.

0:00:25.433,0:00:30.350
Under the sea, pressure increases[br]by 14.7 pounds per square inch

0:00:30.350,0:00:33.848
for every 33 foot increase in depth.

0:00:33.848,0:00:35.750
So, take the yelloweye rockfish,

0:00:35.750,0:00:38.926
which can live as deep as 1800 feet,

0:00:38.926,0:00:43.423
where there's over 800 pounds of pressure[br]on every square inch.

0:00:43.423,0:00:47.854
That's equivalent to the weight of a[br]polar bear balancing on a quarter.

0:00:47.854,0:00:50.106
Now, Boyle's gas law states

0:00:50.106,0:00:54.416
that the volume of a gas[br]is inversely related to pressure.

0:00:54.416,0:00:58.366
So, any air-filled spaces,[br]like a rockfish's swim bladder,

0:00:58.366,0:01:00.165
or human lungs,

0:01:00.165,0:01:02.469
will compress as they descend deeper

0:01:02.469,0:01:05.077
and expand as they ascend.

0:01:05.077,0:01:09.377
After a fish bites a fisherman's hook[br]and is quickly reeled up to the surface,

0:01:09.377,0:01:12.980
the air in its swim bladder [br]begins to expand.

0:01:12.980,0:01:17.412
Its rapid expansion actually forces[br]the fish's stomach out of its mouth,

0:01:17.412,0:01:22.481
while the increased internal pressure[br]pushes its eyes out of their sockets,

0:01:22.481,0:01:25.403
a condition called exophthalmia.

0:01:25.403,0:01:29.652
Sometimes rockfish eyes will even have[br]a crystallized appearance

0:01:29.652,0:01:31.895
from corneal emphysemas,

0:01:31.895,0:01:35.567
little gas bubbles [br]that build up inside the cornea.

0:01:35.567,0:01:40.505
Thankfully, a scuba diver doesn't have[br]a closed swim bladder to worry about.

0:01:40.505,0:01:45.172
A diver can regulate pressure in her lungs[br]by breathing out as she ascends,

0:01:45.172,0:01:49.472
but must be wary of other laws of physics[br]that are at play under the sea.

0:01:49.472,0:01:53.429
Henry's law states that the amount [br]of a gas that dissolves in a liquid

0:01:53.429,0:01:56.635
is proportional to its partial pressure.

0:01:56.635,0:02:00.720
The air a diver breathes is 78% nitrogen.

0:02:00.720,0:02:02.521
At a higher pressure under the sea,

0:02:02.521,0:02:04.957
the nitrogen from the air in a scuba tank

0:02:04.957,0:02:10.907
diffuses into a diver's tissues in greater[br]concentrations than it would on land.

0:02:10.907,0:02:13.245
If the diver ascends too quickly,

0:02:13.245,0:02:16.434
this built up nitrogen [br]can come out of solution

0:02:16.434,0:02:20.326
and form microbubbles in her tissues,[br]blood and joints,

0:02:20.326,0:02:24.491
causing decompression sickness,[br]aka the bends.

0:02:24.491,0:02:28.921
This is similar to the fizz [br]of carbon dioxide coming out of your soda.

0:02:28.921,0:02:32.172
Gas comes out of solution [br]when the pressure's released.

0:02:32.172,0:02:34.872
But for a diver, the bubbles[br]cause severe pain

0:02:34.872,0:02:37.184
and sometimes even death.

0:02:37.184,0:02:40.519
Divers avoid falling victim to the bends[br]by rising slowly

0:02:40.519,0:02:45.311
and taking breaks along the way,[br]called decompression stops,

0:02:45.311,0:02:48.296
so the gas has time to diffuse [br]back out of their tissues

0:02:48.296,0:02:51.026
and to be released through their breath.

0:02:51.026,0:02:53.022
Just as a diver needs decompression,

0:02:53.022,0:02:56.427
for a fish to recover, [br]it needs recompression,

0:02:56.427,0:02:59.509
which can be accomplished [br]by putting it back in the sea.

0:02:59.509,0:03:02.982
But that doesn't mean that fish[br]should just be tossed overboard.

0:03:02.982,0:03:04.809
An inflated body will float

0:03:04.809,0:03:09.196
and get scooped up by a hungry sea lion[br]or pecked at by seagulls.

0:03:09.196,0:03:10.495
There's a common myth

0:03:10.495,0:03:14.384
that piercing its stomach [br]with a needle will let air escape,

0:03:14.384,0:03:17.023
allowing the fish to swim [br]back down on its own.

0:03:17.023,0:03:19.910
But that is one balloon[br]that shouldn't be popped.

0:03:19.910,0:03:22.449
To return a fish properly to its habitat,

0:03:22.449,0:03:25.213
fisherman can use [br]a descending device instead

0:03:25.213,0:03:29.902
to lower it on a fishing line[br]and release it at the right depth.

0:03:29.902,0:03:32.922
As it heads home and recompression[br]reduces gas volume,

0:03:32.922,0:03:35.652
its eyes can return [br]to their sockets and heal,

0:03:35.652,0:03:38.965
and its stomach can move back into place.

0:03:38.965,0:03:41.153
This fish will live to see another day,

0:03:41.153,0:03:46.926
once more free to swim, eat, reproduce[br]and replenish the population.