Sam Judd: Turning snapper into mutants

Day trip snapper fishing on board Ultimate Charters, Westhaven. Skipper Nick helps land a snapper. 30 January 2015 Herald on Sunday photograph by Michael Craig WAG 29Jul15 - SUCCESS: Catching

Ever since the heated debate last year about the quota system for snapper, it has been clear that the people of New Zealand care deeply about this fish.

Out of all the work I have seen that improves water quality, none is so impressive as what has been achieved by Whaingaroa Harbour Care.

They have collaborated with over 40 farms and planted over 1 million trees in their local catchment. Why? To improve water quality so that they can catch more fish. They say that "after 18 years of riparian management, we've seen water quality improve dramatically in the Whaingaroa Harbour. Whitebait catches have increased from 1/2 cup per day to 1/2 bucket per day. Likewise recreational fishing catches have improved. Mudflats previously barren of life are now teeming with crabs, shellfish and wading birds."

Fortunately for those of us who are not lucky enough to live in Raglan, Whaingaroa Harbourcare also provide mentorship to groups outside of their area so that we can all improve our water quality.

One area that appears to be in desperate need of some love is the Kaipara. The environmental pressure on this - New Zealands' biggest harbour and estuary system - is caused by intensive land use, particularly where it combines with areas of poor drainage.

Driving alongside this strikingly beautiful harbour, the situation is very apparent if you know what to look for. Dairy cows can be clearly seen perched on rutted land. Basically, those lines you see on the hillside that make it look like a topographical map are because of the erosion caused by heavy animals and removal of bush cover. The erosion makes sediment pollution very obvious because it discolours the water.

The sediment load in the Kaipara is such that it has even caused snappers' gills to mutate.

Apart from the point that this just seems utterly wrong to me, this is a real cause for concern. In a study of snapper which stretched all the way from Ninety-Mile beach to Mana Island in Wellington, 98 per cent of them were originally juveniles in the Kaipara Harbour.

So it turns out that once again - like the conflict I identified a while back between intensive farming and the aquaculture industry where pollution from the land threatens to cause ocean acidification - we see two interests that are going to have to face up to a challenge.

The difference here is the power of the recreational fishing lobby. Dairy farmers and forestry workers who clear-cut pine trees (washing soil into the harbour) like to catch fish too.

Unfortunately, we just can't have it all. So what can we do? Should we scale up riparian restoration efforts? Stop allowing conversions to dairy? Make clear-cutting of forestry illegal?