What does it look like?
The Japanese mantis shrimp is light grey and can grow up to 185mm long (18.5cm). It has two spiny claws to capture food. Japanese mantis shrimp can easily be confused with a native species that is of similar size and colour. However, Japanese mantis shrimp has red-maroon ridges running down the mid-length of its body and the outer surface of the tail fan is blue and yellow (it is grey and yellow in the native species).
Japanese mantis shrimp live in burrows in soft sediments, sand and mud in sheltered bays and estuaries. It is native to the north-western Pacific where it is most common in temperate waters of China and Japan.
Why is it a problem?
The Japanese mantis shrimp preys on shrimps, crabs and thin-shelled molluscs and can alter habitats through its burrowing activities. When abundant, they can play a role in structuring benthic communities and may compete for food and space with other crustaceans.
In its native range, Japanese mantis shrimps live for 3 to 3.5 years. Males attained sexual maturity at 4-5 cm body length and females at 7 cm. Females can brood a maximum of 50,000 eggs and remain in their burrows when caring for the embryos. After hatching, larvae pass through several free-swimming stages, with an estimated larval life of around 2 months.
You must notify the Northland Regional Council if you suspect the presence of this organism
You can avoid spreading marine pests by:
• Regularly cleaning your boat’s hull – ideally keep fouling growth to no more than a light slime layer.
• Applying good thorough coatings of antifouling paint and keep it in good condition
• Ensuring your hull is clean and free of fouling before you go travel to a new region
• Cleaning and drying any marine equipment (e.g. ropes, lines, pots) before using in a new location.
• Inspecting areas on your boat that retain water in case they’re harbouring marine life.
• Checking anchors, trailers and other equipment for tangled weeds.