Crayfish

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Crayfish Reproduction (important)

1.     Mating and reproduction are easily accomplished under intensive culture conditions

2.     Mating and egg fertilization are asynchronous (non-gravid vs. gravid)

3.     Egg-laying typically occurs in burrows

4.     Eggs (~300/female) are attached to the swimming legs of the female by glair (viscous material of egg white)

5.     Eggs hatch in about 3 weeks at water temperatures of 20 degrees C.

Decapods

1.     Ten paired legs

2.     Abdomen (tail) Carapace (body) – 5 pair of legs on each the abdomen and carapace.

3.     Legs on abdomen are swimming legs

4.     Legs on carapace are walking legs

Crayfish ponds

-Crawfish are cultured in shallow open ponds. Pond areas vary from 2 to 16 ha (LA, TX)

-Pond depth is generally 30-60 cm bud deeper ponds are required in areas that have hotter summers

-Ponds have to be located near a source of good quality surface or well

-Water hardness = ~100+ or – 40 calcium

-DO (dissolved oxygen) > 3 ppm

-Grow-out = >10 cm in total length (20-50 grams) in 3-6 months

Crayfish are omnivores – they eat everything basically

Double cropping (crayfish / Rice – Polyculture)

Rice – crawfish – rice rotation

Management Actions

March/April – Plant rice ~4 months to harvest

June – At permanent food, rice grows to 20-25 cm high // stock 50-60 kg of adult crawfish/ha in new ponds

August – drain pond over 1 week period and harvest rice

October – re-flood pond

November-March – Harvest crawfish

March/April – Replant rice. No restocking of crawfish necessary.

Single crow crawfish pond (monoculture)

-Two additional months of crawfish harvest

April/May – stock 50-60 kg of adult crawfish/ha in new ponds

May/June – Drain pond over 3-4-week period

June/August – Plant forage crop October – Re-flood pond

November to May – Harvest crawfish

May/June – Drain pond over 3-4-week period. No restocking of crawfish is necessary.

Advantages of Polyculture – Additional crop (rice) / Environmentally friendly

Advantages of monoculture – Ponds flooded during hot summer months / 2 harvests of crawfish

Disease, pest and predator control

1.     Primary loss of crawfish from Louisiana ponds is to bird predators, such as herons and egrets

2.     North American species carriers of a fungal disease, the “crawfish plague”. While not problematic for North American species it is deadly to many other crayfish species in the world

3.     Introduction of Louisiana crayfish into Africa and Europe have devastated native species susceptible to the “crawfish plague”

Two species dominate crayfish harvest in the US

1.     Red swamp crawfish 85%

2.     White river crawfish 15%

Trap Harvest (both fishery and aquaculture)

-       Three-funnel pyramid trap made from ¾ inch mesh PVC-coated wire

-       The ~2.0 cm mesh size commonly used to construct the traps allow escape of crawfish less than ~8cm in length (considered the minimum marketable size)

Crawfish Production

1.     40% USA

2.     40% China

3.     20% Spain

Crayfish traps

1.     Density = 25 – 50 traps/hectar

2.     Baited (1/3 lb fish or manufuactured bait) and harvest

Crawfish distribution

1.     Sacked for distribution in “onion” sacks with ¼ mesh; 35 lbs/sack (must turn onion sack over once in a while to relief pressure off bottom crawfish)

2.     Storage at 4-7 C for 5 days without excessive mortality (Q10 effect, low temperature means lower metabolism)

3.     Turned once a day, stacked no more than 3 sacks high