Guide to Identification of Red Claw Crayfish (Cherax quadricarinatus)

1. The first feature to look for is the red claw, which gives the species its common name. The soft red patch on the outside of the claw is only seen in males, and becomes increasingly prominent through successive moults. The red claw is relatively small in the specimen illustrated (Fig. 1). This particular specimen shows the typical colouration of this species, which is often traded under the name blue or electric blue lobsters. (other species are also traded under these names)

Figure 1.

Picture of Red Claw Crayfish

2. The second major diagnostic feature is the presence of four long and distinct carinae (ridges) on the dorsal surface of the cephalon (hence quadricarinatus). The inner (longer) parallel carinae extend onto the rostrum, which typically bears three pairs of lateral spines and terminates in a distinct point (Fig. 2).

3. Figure 2 also shows secondary characteristics from the claws, namely the single mesial spine on the carpus (small mid segment of the claw), and dense ventral patch of setae (hairs) on the merus (inner segment of claw).

Figure 2.

Carinae on Dorsal Surface of the Cephalon
4. This species has a single prominent cervical groove between cephalon and thorax, rather then a distinct pair of grooves (cervical and branchiocardiac). Three distinct lateral cervical spines are situated laterally along this groove (Fig. 3).

Figure 3.

Single Cervical Groove on Red Claw Crayfish

5. The tail fan (Uropod) has a number of distinct features (Fig. 4):

Telson (mid-piece) and rami (mid and outer sections) are conspicuously membranous over their posterior halves;

The telson has two caudolateral spines

Inner rami have outer lateral and median spines

Outer rami have a line of very small indistinct spines

Figure 4.

Tail fan of Red Claw Crayfish

6. Thorax (ventral). The sternal keel between the 5th pereiopods (back legs) is developed into a distinct triangular spine, and sternal pores are visible on other lateral processes of the sternum (Fig. 5).

Figure 5.

Thorax of Red Claw Crayfish

7. Abdomen. Pleopods are absent from segment 1 (anterior) of the abdomen in females, and are vestigial in males (Fig. 5 shows male). This is a feature that identifies the family Parastacidae from the other two crayfish families, rather than distinguishing the individual species. The Parastacids are the Australasian crayfish.

8. If the crayfish in your possession does not have the features described above, it is probably being kept illegally, and you should contact the Fish Health Inspectorate for further advice.