Sediment preference of the introduced Japanese mantis shrimp Oratosquilla oratoria in northern New Zealand

ABSTRACT The Japanese mantis shrimp Oratosquilla oratoria (De Haan, 1844) is a large stomatopod crustacean that was first reported from New Zealand in 2009, and is now present in many upper North Island estuaries, including the Kaipara and Manukau harbours. To assess the sediment traits of harbours potentially vulnerable to invasion by Japanese mantis shrimps, we examined its relationship with the sediments in which it forms burrows. We quantified the grain size distribution of sediments from known O. oratoria habitat in the Kaipara, and ran a choice experiment with four sediment types varying in sand and mud content to determine the preferred sediment type for burrow construction. In the Kaipara, O. oratoria occurred in sediments varying widely in mud content, but the mean grain size distribution of those sediments was similar to the ‘sandy mud’ (44% silt and clay) that individual O. oratoria preferred in the choice experiment. The large amount of apparently suitable habitat around New Zealand's coast and estuaries, in combination with the broad temperature tolerance of O. oratoria in its native range, suggest this species could inhabit much of mainland New Zealand, with potentially significant ecological consequences.