Despite the hazardous working environment, crab fishing is a highly lucrative business. Although the price of crabs fluctuates, they can fetch anywhere from US$4 to US$5 per half-kilo, equivalent to US$25 to US$40 per crab.

Crab season lasts less than four weeks. Vessels patrol the Bering Sea, hoping to snag any of the prized species of crab: red king crab, blue king crab and golden king crab. The fishermen don't only face treacherous conditions; catching the crabs depends on skill, hard work - and luck. Skippers rely on a combination of intuition and experience to determine a location to set their 320-kilogram traps, called 'pots'.

In other professions, a sonar system is commonly used to detect objects in water. The device emits a sound and 'listens' for a return signal. By measuring the echoes, the system can determine the presence of objects and calculate the distance from the boat.

But for the most part, a sonar device is unable to detect crabs. They lie slightly buried beneath the ocean floor, crawling along the bottom, feeding on leftover bits of fish, as well as plankton and algae. Sonar somehow is unable to pick up their movements.

Vessels are equipped with heavy machinery, nets and long fishing lines. Compounded by frigid temperatures, treacherous waves, wet, rolling surfaces, and limited hours of daylight, crabbing is truly a deadly job. The fate of an entire crew is only one imprudent move away from death.

Making things more difficult is the fact that an injured or dead crab could poison an entire pot. Crabs also spoil easily - unless the water they are kept in is fresh and warm, they may as well be kept out of water. Moreover, only male crabs of a certain size can be kept; the rest are released back into the sea.

Yet, in spite of all these hurdles and dangers, crab fishing remains popular and, as Deadliest Catch proves as it enters its sixth season, exhilarating to watch.

Season six of Deadliest Catch premiers at 11pm tomorrow on Discovery Channel

Crabby Quiz, courtesy of Discovery Channel

1 How many legs does a crab have?

a. 6

b. 8

c. 10

d. 12

2 In order to grow, a crab must shed its shell and grow a new one.

a. True

b. False

3 When a crab loses a leg to a predator or injury, it can grow a new one.

a. True

b. False

4 How many species of king crab are fished near Alaska?

a. 1

b. 2

c. 3

d. 4

5 . How much did the largest king crab on record weigh?

a. 2.7kg

b. 5.5kg

c. 11kg

d. 22kg

Crabby quiz answers

1. c

A crab has five pairs of legs. The first pair ends in a set of claws and the last pair is used for mating or swimming. The middle pairs are used for walking.

2. a

A crab's exoskeleton does not grow with the crab, so it must moult, or shed its shell, about 15-20 times during its lifetime. When it is ready to moult, the crab absorbs seawater until the shell cracks open, and then backs out, often leaving a few body parts behind. The crab secretes calcium to create a new shell, which hardens over a few weeks.

3. a

When a crab loses a leg, it will gradually re-grow a new one as it moults. It generally takes about three moults for the new leg to grow back to its normal size.

4. c

Three species of king crab are commercially fished: red, blue and golden (or brown). Red king crab is the largest and most sought-after; the scarlet king crab, is too small and rare to have much commercial value.

5. c

The largest king crab on record was an adult male weighing about 11kg and measuring nearly 1.5 metres across (including legs). It was estimated to be 20-30 years old.