Disappearing Crayfish

It was not until crayfish became scare around the shores of the Hauraki Gulf that they obtained any real commercial value. Before World War Two crayfish were everywhere and could be easily harvested amongst the rocky reefs close to Auckland.

“Initially there were sacks coming off Waiheke and North Head. Fishermen didn’t need to travel to get crayfish … the problem wasn’t lack of crayfish. They were everywhere … After the war, crayfish were worth very little, something like thruppence a pound.”

Crayfish in pots
Crayfish being harvested in pots around the Red Mercury Islands. Note the generally small size of the animals, many which are under the limit and therefore have to be returned to the sea.

Then things changed. New equipment, such as echo sounders, enabled crayfishermen to  locate new reefs to target. Improved gear such as winches enabled fishermen to lift many more pots a day and larger boats enabled them to travel further afield. Once the export market opened up for live crayfish in Japan very high prices could be obtained, reaching over $80 a kilo. This incentivised continued crayfishing even when catch rates plummeted. Recreational divers also target crayfish increasing pressure on the stocks.

“Now catch rates are so poor, at only around a third of a kilo per pot, that crayfishermen are reliant on high prices to survive.”

Crayfishing out from Whitianga
Hauling a crayfish pot in fishing grounds out from Whitianga with a poor catch.

Scientific models suggest that, prior to human arrival, crayfish were the third most ecologically important benthic invertebrate group in the Hauraki Gulf. However, the impact of fishing activity since then has been so great that they are now considered to be ecologically extinct. Stocks are probably less than a quarter of their original levels.

There has been poor recruitment of crayfish into the Hauraki Gulf over the past 6 or so years, and this has exacerbated stock depletion, as a high level of fishing activity has continued during this period.

This has had flow on effects throughout the food web, as crayfish prey on sea urchins which in turn graze on kelp. When the number of crayfish in a system is reduced, the sea urchin numbers rapidly increase due to a lack of predation and they end up stripping the kelp off the rocks. This results in ‘kina barrens’ which are depauperate of reef life. This is why it is important that crayfish stocks are rebuilt to ensure healthy reef systems throughout the Hauraki Gulf.

Kina barren
A kina barren showing what happens when top predators such as crayfish and snapper are overfished, the kina explode in numbers and strip the rocks of kelp and other seaweeds.

2 thoughts on “Disappearing Crayfish”

  1. Thanks for the information. It is crucial that cray stocks are revived. A balanced environment is really needed. Kina barrens exist because of ‘human greed & disregard for the consequences of their ‘bad behaviour & ignorance’. Kina are fabulous, thankfully the ‘capitalists’ have no appreciation of their true value.

  2. Immediately after WW2 all fishing boats requisitioned for war service and used for New Zealand coastal patrols and mines weeping were returned to be restored for fishing duties. The population of New Zealand at that time was little over one and a quarter million. Fish caught was for the home market . There was an abundance of every species and crayfish was not caught commercially as it is today.
    We turned to crayfishing round our home base on Kawau Island in 1971 before Leigh Fisheries started. We delivered by road to the Onehunga wholesalers our first catch for which we were paid $1 per pound!!!!!
    I am very fond of kina .. but now in retirement crayfish and kina are but a dream

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