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Saving New Zealand’s dying wild salmon fishery – 101

By Rex N. Gibson

Early this year (mid-season) I landed a sea-run salmon at Kairaki (Waimakariri mouth). My first reaction was “about time”. A lot of hours had gone into its pursuit. It became the beautiful smoked salmon on our dining table over several meals. However a “regular” who spends the salmon season at the Kairaki motor camp and fishes most days, later advised me that no other salmon were landed there for the subsequent two weeks. Have I caught my last wild salmon?

We are talking here about the second most heavily fished location in New Zealand, and one of the traditional congregating places for Canterbury’s salmon anglers! For decades an average of over 60 anglers fish there each day; January to April. For these people it is a vital part of their heritage and both their mental and social well-being.

Canterbury’s salmon fishery is one of only two Quinnat (Chinook or King) salmon fisheries established outside its Northern Pacific homeland. It thrived in Canterbury’s larger braided rivers from the Waitaki north after the introduction of these northern Californian fish in 1905 until the end of the 20th Century. It was a cornerstone of the region’s outdoor recreation, but since the 1990s something has changed to almost destroy that.

Top of the North Canterbury Fish and Game Council list of priorities is to resurrect the region’s wild salmon fishery. It was the platform on which many had been elected last October. The following tables from F & G show the dramatic decline in those fish returning to spawn. The numbers for the Central South Island are just as depressing.


North Canterbury Preliminary Spawning Escapement Numbers 2019

Waimakariri 2001 2019 Rakaia 2001 2019

Poulter 63 51 Hydra Waters 476 122

Winding Creek 27 27 Double Hill 103 32

Cass Hills St 117 48 Glenariffe 100 55

Cora Lyn 28 10 Manuka Pt 43 103

One Tree Swamp 17 19 Mellish St 133 120

Total Count 252 149 Total Count 855 432

Peak Count x 1.5 + 50% harvest = Total Return of 336 (Waimakariri) and 908 (Rakaia) in 2019.

NB Equivalent figures in 2001 were 567 (Waimakariri) and 1,924 (Rakaia).

Figures provided by North Canterbury Fish and Game.


The spawning counts, over these two major rivers, are thus down 66%, and the Peak Count totals down 50%. This fishery now fits the recognised description of an endangered species. Less well known salmon rivers like the Hurunui, Waiau and Clarence have similar declines. The numbers for the Central South Island region (Rangitata, Orari, Opihi and Waitaki) are even more depressing.

Fish & Game face these questions: Why has this happened, what is/are the cause(s), and how can you stop the decline? F & G’s national salmon committee is advising on this. Past F & G Councils in Canterbury had faced the same problems. When they considered “solutions” they found that many licence holders were more prepared to shoot the messengers than face the possible (difficult) consequences. The “denial and hope” forces dominated.

The new Council (new because 10 of the 12 had not stood in the previous election) have unanimously decided to use science and data, rather than “political” pressure and gut feelings, to dominate their decision-making. Cawthron reports, salmon symposia notes, NZ Salmon Anglers Association data, staff surveys, and documentation dating back as far as the days when the Marine Department oversaw the fishery, provided a wealth of information.

The dramatic demise in the salmon population had occurred when several ecological limiting factors hit it at the same time:

· Massive increases in the amount of water being taken into irrigation races following the intensification of dairying on the Canterbury plains post 1990; much was sprayed, and then evaporated, in the middle of the day without reaching plant roots.

· This also reduced river flows and the number of braids serving as rearing habitat on their journey to the sea.


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Virtually every water off-take had non-compliant and ineffective fish screens.

· Rapid depletion of underground aquifers adjacent to salmon rivers (also used for irrigation). Many of these aquifers are hydraulically connected and draw their replacement from the same rivers by seepage. The Canterbury Plains are primarily porous outwash gravels from past glaciations.

· Significant changes in land use (intensive farming practices) around several key traditional high country spawning streams.

· Changes in chemical composition of the waterways through escalating amounts of nitrate and phosphate run off from the largely unchecked intensive farming practices.

· Regular spraying of the river beds with glyphosate, and a cocktail of other herbicides by the regional council.

· Major changes have been occurring in the marine species composition and physical conditions off the Canterbury coast where the salmon spend much of their lives.

· Large releases of commercial salmon farm smolt/fry have affected both the genetics and competitive advantage of the wild salmon.

· Increased harvesting of salmon holding up in the pools below the spawning streams.

· The lower numbers of salmon running up the rivers to spawn in the late summer and early autumn season caused by an increasingly higher percentage being harvested.

What did these factors affect most directly?

1. Salmon fry were not making it down to the sea. Instead they were ending up on irrigated paddocks. The most recent estimate is that 30 - 40% die in this way. Seventy percent of New Zealand’s total irrigation now occurs around the main Canterbury salmon rivers.

2. The reduced summer water flows owing to over-abstraction, resulted in higher river water temperatures. Shallow water over hot stones heats rapidly and salmon are distressed by temperatures over 18 degrees, and will often die by 22+ degrees. Last season the Waimakariri ran at 22 degrees for most of the peak two months of the normal salmon season.

3. The ex-salmon-farm stock were competing for both food and, eventually, spawning gravels with the wild stock at crucial times. These wild stocks are less well equipped to produce successful off-spring. They had been specifically in-bred to just grow fat quickly rather than for the variability that is essential for survival during environmental fluctuations (natural selection 101).

What are the solutions?

There is no single answer for Fish and Game to turn to for a remedy of all these issues, i.e. the over-abstraction of water, non-compliant/ineffective fish screens, changing conditions at sea, threats posed by farming practices on private land, nitrate and phosphate run-off, and the regional councils’ chemical warfare practices.

All F & G can do is look at season length, closing fishing areas, commercial releases, and daily (or season?) catch limits; which they are doing. A new regulatory model based on linking the allowable catch with the spawning return rate is also being worked on for 2020-21. They will also need to regulate in common across both F & G regions to even the impact of changes; new territory for them. F & G is thus only able to treat the symptoms of this chronically ill recreational pursuit.

So who can deal with the other factors and perhaps save the fishery? That answer is simple; it is the regional council. Environment Canterbury (ECan) is responsible for all other limiting factors, except the conditions at sea. ECan covers both of Canterbury’s Fish and Game regions. For the last nine years their government appointed commissioners have shown little inclination to take these issues seriously. Sadly environmentally unsustainable intensive farming has been the priority.
















It is up to every Central South Island and North Canterbury person of voting age, with a love of clean water and outdoor recreational pursuits, to vote in an environmentally responsible council next October. It is obvious that everyone needs to fully research the candidates’ backgrounds, and vote accordingly, or the malady currently affecting New Zealand’s major sea-run salmon fishery will surely become terminal and salmon fishermen will not rest in peace.

Footnote: Rex N. Gibson is the Freshwater Spokesman for the NZ Federation of Freshwater Anglers. He is an ecologist and scientist and with a deep personal interest in rivers and outdoor recreation.