Some species are found in brooks and streams, where fresh water is running, while others thrive in swamps, ditches, and paddy fields.

In the Eastern United States, "crayfish" is more common in the north, while "crawdad" is heard more in central and southwestern regions, and "crawfish" farther south, although considerable overlaps exist.

[10] They have the potential to eat most foods, even nutrient poor material such as grass, leaves, and paper, but can be highly selective and need variety to balance their diet.

[citation needed] Crayfish all over the world can be seen in an ecological role of benthic dwellers, so this is where most of their food is obtained - at the sediment/water interface in ponds, lakes, swamps, or burrows.

They can be lured into traps with an array of baits from dog biscuits, fish heads, meat, etc., all of which reinforces the fact that they are generalist feeders.

[citation needed] Detritus or mud is a mixture of dead plankton (plant and animal), organic wastes from the water column, and debris derived from the aquatic and terrestrial environments.

They tend to eat to satiation and then take many hours to process the material, leaving minimal chance of having more room to ingest other items.

Crayfish usually have limited home range and so they rest, digest, and eliminate their waste, most commonly in the same location each day.

The most complex study which matched the structure and function of the whole digestive tract with ingested material was performed in the 1990s by Brett O'Brien on marron,[12] the least aggressive of the larger freshwater crayfish with aquaculture potential, similar to redclaw and yabbies.

A further genus of astacid crayfish is found in the Pacific Northwest and the headwaters of some rivers east of the Continental Divide.

Many crayfish are also found in lowland areas where the water is abundant in calcium, and oxygen rises from underground springs.

[26] In Australia, New Zealand, and South Africa,[27] the term "crayfish" or "cray" generally refers to a saltwater spiny lobster, of the genus Jasus that is indigenous to much of southern Oceania,[28] while the freshwater species are usually called yabbies or kōura, from the indigenous Australian and Māori names for the animal, respectively, or by other names specific to each species.

[citation needed] In Singapore, the term crayfish typically refers to Thenus orientalis, a seawater crustacean from the slipper lobster family.

[29][30][31] True crayfish are not native to Singapore, but are commonly found as pets, or as an invasive species (Cherax quadricarinatus) in the many water catchment areas, and are alternatively known as freshwater lobsters.

[32] In the United Kingdom and Ireland, the terms crayfish or crawfish commonly refer to the European spiny lobster, a saltwater species found in much of the East Atlantic and Mediterranean.

[36] The earliest records of other modern families date to the Early Cretaceous, including the parastacid Palaeoechinastacus from Australia which is 115 million years old,[37] the cambaroidid Palaeocambarus from the Yixian Formation of China which is likely around 120 million years old (Barremian-Aptian),[38] and the astacid "Austropotamobius" llopisi from the Las Hoyas site in Spain (Barremian).

In Europe, they are particularly threatened by crayfish plague, which is caused by the North American water mold Aphanomyces astaci.

[40] Species of the genus Astacus are particularly susceptible to infection, allowing the plague-coevolved signal crayfish (native to western North America) to invade parts of Europe.

In whole-ecosystem experiments simulating acid rain at the Experimental Lakes Area in Ontario, Canada, crayfish populations crashed – probably because their exoskeletons are weaker in acidified environments.

At crawfish boils or other meals where the entire body of the crayfish is presented, other portions, such as the claw meat, may be eaten.

[citation needed] Research shows that crayfish do not die immediately when boiled alive, and respond to pain in a similar way to mammals.

Then the stress hormone cortisol is released and this leads to the formation of lactic acid in the muscles, which makes the meat taste sour.

When using live crayfish as bait, anglers prefer to hook them between the eyes, piercing through their hard, pointed beak which causes them no harm; therefore, they remain more active.

[62] Other studies confirmed that transporting crayfish to different environments has led to various ecological problems, including the elimination of native species.

[71] The Protivin brewery in the Czech Republic uses crayfish outfitted with sensors to detect any changes in their bodies or pulse activity in order to monitor the purity of the water used in their product.