Red Rock Lobster

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Red Rock Lobster Photo: M Francis

 

Red or spiny rock lobster, Jasus edwardsii, is widely distributed around the New Zealand coast and across in Southern Australia, found in waters between 5m and about 50 – 60 m depth, or more. Long known as crayfish, NZ rock lobster differ from lobster species overseas through lacking the very strong pincers on their fisrt pair of walking legs. Lobsters have been heavily fished around the Wellington south coast, being keenly sought after for eating. The species attracts active commercial and recreational/customary fishing. There is an abundance of juvenile lobster at Wellington which suggests that recovery is possible when fishing pressure is reduced. Without utilization pressure individuals can live to 30 years plus.

Habitats

Lobsters live on or about rocky reefs with plenty of cracks and crevices where they can hide.  Being nocturnal they live in cracks and holes in large groups during the day and venture out to feed at night. They are bottom feeding scavengers that live on shellfish, urchins, crabs, small fish or anything else they can find. They are particularly vulnerable to predation during their annual moult, when hard exterior skeletons are shed and replaced, with the soft lobsters becoming prey to octopus, sharks and some fish unless they stick close to their secure crevices. Juveniles may moult several times each year as they grow rapidly.

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Strength in numbers? Lobster packed crevice. Photo: M Francis

Keystone Species

Where lobster have been largely removed, grazing kina (sea urchins often increase dramatically. With few predators controlling their numbers, the kina eat their way through kelp ‘forests’ so effectively that they destroy the kelp beds. When marine reserves are created, the density of lobster and other predators such as snapper increases, kina numbers fall and kelp forests are re-established. This has been well proven at the marine reserve at Leigh.

Life Stages

The rock lobster is a very unusual species in that after fertilised eggs are released in many thousands from females and hatch out in the spring, larvae pass through many larval stages and spend up to 24 months drifting around in the oceans. During this time they pass through 11 different larval stages and can potentially travel 10’s to 100’s, or even thousands of kilometres,  before finding their way back to rocky habitats such as the reefs on the south coast. While drifting with the currents larvae are preyed on by plankton feeders and some fish. Victoria University marine experts have carried out genetic research which has identified some relatively isolated sub-populations in the south of New Zealand, as well as discovering that up to 10% of larvae in northern populations may originate from Tasmania and South Australian sources. This has important implications for fisheries management for the species.

Juvenile rock lobster show some signs of minor migrations, though not as much as a larger distant relative, the green packhorse lobster, (Sagmariasus verreauxi), found mostly in the north of the North Island, where the species moves up the east coast to spawning gatherings in the far north. Still, some rock lobster juveniles tagged in Otago have apparently been recaught in Fiordland. Mass migrations of this species are exceptional

Rock lobster are usually about 5 to 7 years of age on the south coast when they start to breed. Females carry red berrylike eggs for 3 to 6 months, before shedding between 80 000 to 500 000 eggs (the bigger the female the more the eggs) in autumn.

Crayfish Dani

Adult Rock Lobster Photo: Danica Stent
 

Harvest

Rock lobster harvest has often been a boom and bust business, most exemplified in recent years by the incredibly wasteful Chatham Islands  lobster industry, where only the tails were taken for export – until the fishery crashed. Like most rock lobster populations, that at the south coast has been heavily exploited in the past. Current levels of commercial harvest are around 70 to 80 tonnes a year, with recreational take estimated to be approximately of the same order. Regulations specify minimum legal sizes for male lobsters and for females, though the latter may not be taken when carrying eggs. For divers, measurement must be done in the water as lobster maybe blinded by sunlight. Undersized lobster are required to be replaced exactly where they were found. Commercial catch is mostly with pots. Forest and Bird say lobster potting is a relatively harmless fishing method, but it can have impacts on marine mammals, seabirds and sensitive seabed habitats. At Kaikoura, there have been instances when whales have entangled in pot ropes.

Plunder

The Wellington area has a bad reputation as one of the heaviest areas in the country plundered by poachers for both rock lobster and paua. Because the Wellington coasts are relatively easily accessed it is usually possible to find some part of the west, south and east coasts that are sheltered from winds and swells. Active Fisheries compliance staff and NZ Police monitor and prosecute offenders.

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Up close with a reef scavenger. Photo: M Francis
 
Sources: Stuff.co.nz: Forest and Bird.