Acid Test for Firth Fisheries

Acidification of the ocean due mostly to fossil-fuelled CO2 emissions could have devastating effects on the aquaculture and fish-food industries, and recreational fishing in the Firth of Thames.

So far the oceans have taken up more than a third of the CO2 we’ve been pumping into the air, and as a result the water is becoming more acidic.  Many marine experts rank ocean acidification as the most serious threat to New Zealand’s marine habitats.

This excess carbon dioxide can dissolve the shells of mussels and oysters, and harm plankton that is at the base of the food chain.  Higher acidity can cause the larvae of some fish such as snapper to lose their sense of direction, become more reckless and at risk from predators. Squid, kina, paua, and crayfish are also directly at risk from acidification. Harm caused lower in the food chain will ultimately affect other fish species and marine mammals.


The Firth of Thames already shows acidity levels that are not projected for the open ocean until the end of this century.


Meanwhile, some local decision-makers have taken their eye off the ball and are fixated on turf war squabbles about how the Gulf is managed.  This is akin to a group standing on the tracks arguing about who should manage the railways while a freight train is approaching. They know about the train or think its hoax yet fail to do anything to slow it down or stop it.

Scientists have begun some urgent research into unproven mitigation methods such as depositing shells under mussel beds and aerating the water (power supply required).  They concede the costs may be prohibitive. What about other threatened marine species?  Will there be aeration of the water around all kina, crayfish, paua, snapper larvae, and plankton?

The harsh reality is that the only practical solution to ocean acidification is to cut CO2 emissions. Our emissions per person were the fifth-highest of 41 developed countries with international commitments on climate change.  As award-winning columnist Rachel Stewart said in a recent article

it’s time to stop getting caught up in the individual fights and realize that climate change is a mission that must be tackled on a World War II scale. All hands on deck.”

If we don’t mobilize on a World War II scale then there may not be an aquaculture or commercial fish industry or recreational fishery to squabble over.   They could be ruined – forever.

So come on all you fisher folk and other lovers of the Gulf – all hands on deck and start shouting from your boats and rooftops that you want urgent, strong, effective action on climate change from your local and central government representatives – not excuses and turf war quarrelling.