It so often happens that bad environmental behaviour only gets actioned when it starts affecting human health, but I am waiting to see anything happen in response to a horrible outbreak of illness from tainted shellfish in the Bay of Plenty.

Holidaymakers are flocking to their favourite beaches and many will have to resist the temptation to take shellfish during their break, as about one-quarter of the North Island is closed to shellfish gathering.

Officials are calling it the worst outbreak of shellfish poisoning in the Bay of Plenty's history and it is spreading north and west quickly.

Many Kiwis consider taking shellfish as somewhat of a spiritual right. I know I was looking forward to a couple of beer-battered mussels and will be disappointed not to see them on my summer barbecue - but the question stands: why is this happening and who is causing it?


Paralytic Shellfish Poisoning involves a potentially fatal neurotoxin that comes from algal blooms. The affliction can cause numbness and tingling in your limbs, difficulty swallowing or breathing, dizziness and double vision, and in severe cases, paralysis and respiratory failure.

There is little scientific doubt that the increase in nutrient levels in our waterways are experiencing (called eutrophication) is one of the key factors that produces harmful algal blooms (for a detailed article by a panel of scholars click here).

The algae essentially feeds on the filth that we throw into the water.

This comes back to intensive land use, which as well as urban pollution, again points towards the agriculture industry - especially dairy - with their addiction to nutrient-rich fertiliser combined with poorly managed effluent.

The algae's growth (and the subsequent demise of our shellfish quality) is accelerated by heat, so depleted forest cover around waterways contributes to the problem. The fact that about 75% of our original forest cover is gone (the first 50% was burned by pre-settlement Maori, then forestry and agriculture industries contributed significantly to the rest), means there is less shade and our waterways heat up easier.

Perhaps rather than just nailing a sign to the beaches to warn people of the potentially fatal consequences of gathering a few shellfish, we should look at solutions.

If we took to the waterways with riparian planting - which involves establishing native trees such as flax and kahikatea - we could help to stop people from being hospitalised for enjoying their favourite summer fare. Riparian planting will reduce the nutrients entering the waterways and (over time) increase the shade cover too.

Maybe some of the dairy farmers who have to yet to heed the call of Fonterra (and many others who want people to be able to swim in our rivers again) will eat a tainted mussel or scallop at the beach this summer and receive a painful reminder it is vital they change their ways.

One can only hope.


Our filter-feeders have been affected from Mohakatino (in Taranaki) all the way up the West Coast to Maunganui Bluff (north of Dargaville), including the Manukau and Kaipara Harbours. Also do not take shellfish from Tairua on the Coromandel Peninsula, south to Waihi Beach and along the Bay of Plenty coast to Whakatane Heads.

For updated information on shellfish bans with maps and contact detailed for health officers, click here.