Burrowing crayfish are notoriously difficult to sample owing to their cryptic nature and subterranean habitat. The most commonly employed sampling method is burrow excavation but it is labour-intensive, destroys the burrow and hence is not repeatable. Consequently, non-destructive sampling methods are more desirable, especially for species of conservation significance, but such methods remain poorly investigated.
Capture effectiveness of the original Norrocky Trap (Norrocky 1984) and a design modified specifically to target crayfish of the genus Engaeus Erichson (Decapoda: Parastacidae) were assessed. The modified design had a smaller diameter, used different materials and housed a variation on the trapdoor design found in the Norrocky Trap. Traps were trialled in the Bunyip State Park and the Gippsland region of Victoria, south-eastern Australia where burrowing crayfish of the genus Engaeus are known to occur. Significantly higher capture rates resulted from the modified trap design, with several Engaeus species captured. Further refinements of this or similar trap designs have the potential to improve capture rate.
This work demonstrates that the modified Norrocky Trap is an effective method for Engaeus capture. We envisage the trap design will promote a broader use of non-destructive sampling methods for Engaeus and potentially other burrowing crayfish genera.