Story: Crabs, crayfish and other crustaceans
Page 5 – Lobsters, prawns and krill
Scampi (Metanephrops challengeri) are deep-water burrowing lobsters. They have been commercially harvested since the 1980s from the Bay of Plenty, off the Chatham Rise, and around the subantarctic Auckland Islands. They are slender pink animals, up to 30 centimetres long and weighing 100 grams. Scampi are cooked and eaten in the same manner as prawns.
This little crustacean was the subject of a 2003 parliamentary select committee inquiry. There had been allegations of corruption against senior officers of the Ministry of Fisheries regarding scampi quotas. Although the inquiry found there was no foundation to the allegations, it did find that the ministry had given preferential treatment to the fishing company holding most of the scampi quota.
Squat lobsters are eaten in Europe but not in New Zealand, even though they occur in large numbers in New Zealand waters. Munida gregaria (often incorrectly called whale krill) is the most common New Zealand squat lobster. During its bright red phase in summer it can be found swarming close inshore in enormous numbers, from Cook Strait southwards.
Prawns and shrimps
Prawns and shrimps, while superficially similar in body form, are classified quite separately. Like crabs, crayfish and lobsters, they are decapods – 10-legged crustaceans. Shrimps resemble miniature lobsters or scampi, with distinct claws or pincers, and range in size from 2 to 25 centimetres. Prawns differ from shrimps in their breeding habits and in their leg and gill structure – they do not retain eggs, but shed them directly into the water; prawns lack the conspicuous 'claws' that are present in most shrimps.
One of the most familiar shrimps is the semi-transparent Palaemon affinis, a common inhabitant of rock pools.
Some crustaceans are like ecosystem engineers. Each year the burrowing ghost shrimp (Callianassa filholi) churns over 96 kilograms of sediment per square metre of coastal soil. This lets oxygen and organic material get deep into the sediment, which provides the right conditions for very small sediment-dwelling organisms. However, it is detrimental to some shellfish and amphipod species.
A number of krill species are known from New Zealand waters. Typically smaller than shrimps, they reach prodigious numbers in the seas around and south of New Zealand in summer months when their plankton food is plentiful. In turn, they are an important food for squid, fish, seabirds and some whale species.