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rock lobster (crayfish)

Stuck between a rock and hard place? Getting to grips with handling and measuring lobster PDF | 455 kb

Getting to grips with handling and measuring lobsters

New Zealand rock lobsters found around our coastline and offshore islands, are referred to as "crayfish", a name more correctly applied to freshwater species. They are often fished by commercial, recreational and by Maori customary fishers.

The sustainable management of our rock lobster fisheries is supported by an extensive research programme and an enforcement and compliance regime.

Description

New Zealand has two common species of rock lobster: the red or spiny rock lobster Jasus edwardsii and the green or packhorse rock lobster Jasus verreauxi.

The packhorse, the world’s largest rock lobster, can be as large as 60 cm and 15 kg. Red rock lobster are generally smaller, but have been measured at 54 cm overall length and weighing over 8 kg.

Life cycle

Mating occurs within a few weeks of the female moult.

Females bear up to 550,000 eggs depending on locality and their size. Eggs are carried under the tail, for up to 6 months before hatching. The eggs hatch into spider-like larvae that drift freely as part of the plankton in open waters for at least 9-12 months, where they fall prey to a variety of plankton feeders. The survivors may move considerable distances with ocean currents, returning to inshore areas to settle on the bottom as transparent puerulii, which resemble miniature adults. At this stage they may suffer heavy predation from bottom feeding fish, until they find adequate shelter.

Recreational fishing can have a significant impact on stocks in some areas.

Distribution, habitat and movement

Both Red rock lobsters and Packhorse rock lobsters are widespread throughout New Zealand, particularly in coastal areas where there is plenty of cover.

Rock lobsters usually move by night to search for food and shelter, returning to the safety of crevices during the day.

They eat a wide variety of bottom life, with a preference for shellfish, crabs, seaweeds, small fish and sea urchins.

There is also a seasonal movement into shallow water for moulting and mating, and another when females move to the edges of reefs to spawn their eggs.

Rock lobster migrate in large numbers. Movements of up to 460 km by red rock lobsters, and up to 1070 km by packhorse lobster have been recorded.

Growth and age

To increase size, a rock lobster must shed or moult its shell and grow a new larger one which is initially soft, leaving it very vulnerable to predators. It absorbs water rapidly and expands to its new size. The shell hardens within a few days, taking longer to thicken to full strength. Moulting frequency and times depend on age and sex.

Legal size is attained in 5-10 years, depending on the sex of the lobster, area, and growth rates. Rock lobster may live for over 30 years.

Recreational fishery

Recreational fishing for the daily limit (6 legal rock lobster per fisher) is largely based on diving, but baited pots are also used.

The need for different minimum legal sizes

Tail width measurement is used to determine the legal size for red or spiny rock lobster. Females of similar body sizes have wider tails than males, so different minimum legal sizes are needed for each. This contributes to the effectiveness of the escape gaps that must be used in all rock lobster pots. Escape gaps reduce the damage to, and possible mortalities of, juvenile rock lobster.

Pot limits

Know the rock lobster pot limits:

  • Individuals may use, set, or possess up to three rock lobster pots in any one day.
  • Two or more individuals fishing from a vessel may use, set, or possess up to six rock lobster pots in any one day.
  • Paterson Inlet – Within Paterson Inlet, Stewart Island (those waters lying inside a line between Ackers Point and Bullers Point on The Neck), there is a limit of two rock lobster pots per person.
  • Mimiwhangata – No person may use more than one pot per person per vessel.

Regulation escape gaps to allow undersized lobsters to escape

Round or beehive pots must have at least 3 escape gaps or apertures (other than the mouth). Each aperture must have an inside dimension of not less than 54 mm x 200 mm.

Square or rectangular pots must have at least two escape gaps or apertures (other than the mouth) in opposite faces of the pot. Each aperture shall not be less than 80% of the height or length of the face of the pot in which the apertures are contained.

Each aperture shall have an inside dimension of not less than 54 mm x 200 mm.

Any rock lobster pot constructed entirely of unaltered spot welded mesh with inside dimensions of 54 mm x 140 mm does not have to have escape gaps or apertures, but pots must be used without covers or liners or have covers or liners that leave unencumbered at least 80% of the surface area of each of 2 opposite sides.

No escape gap or aperture shall be incorporated in either the top or the bottom of any pot.

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Updated : 3 February 2014
 










Getting to grips with handling and measuring lobsters.