Raewyn Peart: Crayfish quota management in the Gulf a failure

Commercial harvesters now have to haul four pots to harvest one legally sized crayfish. Photo / Raewyn Peart
Commercial harvesters now have to haul four pots to harvest one legally sized crayfish. Photo / Raewyn Peart

There are increasing signs that our fisheries management system is broken. The sad fate of the Hauraki Gulf and Bay of Plenty crayfish stock (CRA2) is a case in point. It was supposedly under the watchful eye and care of the Ministry for Primary Industries. But a recently released consultation document has highlighted its dire state.

CRA2 has been in rapid decline since the late 1990s and is at an all-time low. Commercial harvesters now have to haul four pots to harvest one legally-sized crayfish. Few bother to venture west of the Coromandel Peninsula because there are so few crayfish to be found there.

Data from Leigh suggests the population may have crashed to less than 5 per cent of its original size. The industry has only survived in the region to this point because of the extraordinarily high prices being obtained for live crayfish in the Chinese market.

This slow-motion collapse of the stock is a financial calamity for the crayfish industry.

But crayfish is also a highly sought-after local delicacy and non-commercial fishers now struggle to harvest a meal. There are also wider impacts due to the vital role that crayfish play in keeping our reefs healthy.

When large quantities of crayfish are removed the marine ecosystem becomes unbalanced. Crayfish feed on kina, helping to keep their populations in check. But with the crayfish gone, kina populations explode, and they strip the reef bare of kelp. In some parts of the Gulf, more than half of the kelp forests have now disappeared.

Kelp forests are one of the most productive ecosystems on Earth. They are particularly important for crayfish recruitment. Crayfish larvae spend around 18 months in the ocean, before swimming back to the coast and settling on rocky headlands and the like.

We don't know what attracts them back to specific locations, but scientists suspect that cues from kelp forests could be the trigger. This means the loss of kelp could be contributing to poor recruitment into the CRA2 fishery, in an ongoing negative spiral.

The quota management system was supposed to avoid this kind of stock and ecological collapse.

By setting a total allowable catch to cap harvest levels, it was designed to ensure that harvesting was kept within sustainable levels and stocks and the aquatic environment were kept healthy.

When the crayfish stock of the Gulf and Bay of Plenty came into the quota management system in 1990 it was much healthier than it is now. So what happened?

The quota management system is a sophisticated machine. It requires high-octane fuel, in the form of quality scientific information, to run well. In the CRA2 fishery, investment in science has been sparse, so we know little about the state of the fishery apart from data reported by commercial fishers.

No systematic surveys of the stock have been undertaken and no information about the settlement rates for juveniles, which is regularly collected in other cray fisheries, is gathered by MPI in the Gulf and bay of Plenty.

Secondly, fisheries management has been very narrowly focused, largely concentrating on "counting fish" and adjusting harvest caps, rather than on looking at the broader context including marine ecology.

In our complex, fast-changing world, with accelerating climate change effects, an expanding population and burgeoning demand and growing cumulative pressures on our coastal waters, we are likely to see more stock collapses unless fisheries managers move beyond simply counting fish.

Since 2014, MPI has adopted a "management procedure" for the CRA2 stock. This is an automatic control system that adjusts the harvest level according to a fixed decision rule. The rule indicated that all was well and no harvest reduction was required. Unfortunately the crayfish stock was actually being fished down to precipitous levels.

This situation is now so dire that the ministry is proposing cuts of between 40 per cent and 54 per cent. This is too little too late. The fishery needs to be closed before more damage is done.

Crayfish not caught this year will still be there next year. An independent survey needs to be carried out so that we know what the actual status of the stock is and the extent of kina barrens. We can then use the results to develop more robust and sustainable rules for crayfish harvesting.

The problems in the CRA 2 fishery are symptomatic of broader problems within our fisheries management system. We need to bring it back to good health before we experience further calamities.

An excellent way to start would be for the Minister of Fisheries to establish an independent public inquiry into the entire fisheries management system. Public confidence in the present system has been lost and there is ample evidence to justify that position.

• Raewyn Peart is policy director for the Environmental Defence Society and author of 'The Story of the Hauraki Gulf'. Submissions on management options for the CRA 2 stock can be lodged with MPI by tomorrow.

- NZ Herald

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