Otago Harbour Salmon Future Looks Grim

Otago Harbour smolt release November 2020. Photograph: New Zealand Salmon Anglers Association Otago Branch.
Otago Harbour smolt release November 2020. Photograph: New Zealand Salmon Anglers Association Otago Branch.

Otago Harbour Salmon Future Looking Grim

By Allan Burgess

The Otago Harbour salmon fishing scene looks grim. Salmon returns are now so poor the annual contest has been cancelled indefinitely. The underlying problem is that the relatively shallow water in Otago Harbour is just too warm for salmon over the summer months.

The salmon are just not coming into the harbour due to rising water temperatures according to the Otago Salmon Anglers Association president Colin Williams. Conditions for salmon at sea are most probably not ideal either. 

Salmon are cold-water fish. Their optimum temperature range for fast growth is between 12 and 14 degrees Celsius.

As we’ve seen with King Salmon’s farming operations in the outer Marlborough sounds over the past few summers, once the water temperature gets up to 18 and 19 or more, the salmon start dying in significant numbers.

The problem is made much worse when these higher temperatures are sustained for any time. Prolonged water temperatures above 20 degrees Celsius are lethal for trout and salmon. 

All you need to catch a salmon in Otago Harbour is a rod and reel, along with a healthy dose of persistence. You can even travel to the wharves on a bus or bicycle.
All you need to catch a salmon in Otago Harbour is a rod and reel, along with a healthy dose of persistence. You can even travel to the wharves on a bus or bicycle.

“At 16 degrees, they survive. At 18 degrees, the enzymes that help them digest food start to die off. If water temperatures are at 18 degrees for a few weeks, the salmon’s immune system breaks down. They get sick. They die.” Quote from Salmon farmers seek cooler waters as climate changes, by Marc Daalder at Newsroom.co.nz

New Zealand King Salmon farms reported significant losses from their operations in the outer Marlborough Sounds over the summer of 2021-22. Water in the sea cages was just too warm for salmon to survive.

Warmer water contains less oxygen and higher levels of dissolved toxins. 

According to a report on Radio New Zealand dated 29th of March 2022, “between December and February, trucks from Havelock and Picton made 160 trips to the Bluegums Landfill in Blenheim, dumping 1269 tonnes of dead fish and waste from New Zealand King Salmon farms.” Obviously, that very sad state of affairs is just not sustainable.

View across part of the inner Otago Harbour. Large king salmon could be caught without leaving the city of Dunedin.
View across part of the inner Otago Harbour. Large king salmon could be caught without leaving the city of Dunedin.

When sea temperatures are too high for Quinnat salmon just about anything you try to do to enhance the fishery is going to result in failure.

An increase in water temperatures of just a few degrees can make all the difference to the survival of salmon which are cold-water fish.

Salmon fishing has been an important part of the local Dunedin fishing scene over the last three decades. It all started back in 1985 (37 years ago in 2022)  when I.C.I. Watties, a New Zealand food manufacturing company specializing in canning released thousands of quinnat salmon smolt into a river near Dunedin.

A couple of years later big salmon were being caught regularly from the wharves in Otago Harbour. A new fishery was born! 

Salmon fishing in Otago Harbour. Note the number of rods.
Salmon fishing in Otago Harbour. Note the number of rods.

Otago Harbour on the East Coast of New Zealand’s South Island, and Vancouver, Canada, are the only two cities in the world where large salmon can be caught right in the middle of town! Otago Harbour really was a magnificent salmon fishery. I say “was” because clearly it’s time now appears to be up –  at least in the short term! 

The reason the salmon fishing competition was run was to raise money for the 60,000 smolts that were released into the harbour each year at a cost of about $30,000.

Dunedin Harbour was a put-and-take salmon fishery. It had to be regularly restocked by the Otago Branch of the Salmon Anglers Association and the local Community Salmon Trust in order to remain viable. This work was carried out by tireless volunteers.

A special note of thanks must also be made to the many local and national businesses that contributed valuable prizes for the annual fishing competition.

Three anglers with a salmon each taken trolling on Otago Harbour. You don't need to travel far from the boat ramp to catch a good fish.
Three anglers with a salmon each taken trolling on Otago Harbour. You don’t need to travel far from the boat ramp to catch a good fish.

There are no rivers flowing into the harbour. A very small amount of natural spawning in the Water of Leith and Lindsay Creek takes place but is nowhere near enough to sustain the salmon fishery in the harbour, according to Otago Fish & Game Council chief executive Ian Hadland. 

With the Dunedin, Community Salmon Trust hatchery at Sawyers Bay now closed there will be no further smolt releases into the harbour. It is challenging to see salmon being caught by anglers fishing in the harbour in future years.

The annual salmon fishing contest was held in Otago Harbour either in late February or early March for many years. 

The 2022 event was cancelled due to Covid. 

In 2021 not a single salmon over the minimum weight was caught during the contest. 

This was the winning salmon from the Otago Harbour Salmon Fishing Competition from 20 years ago. it is not only bigger and heavier, but it is also deeper in the body suggesting that it has fed well while at sea and is in good physical condition. The overall health of a salmon fishery isn’t just measured by the number of returning fish. When the only salmon coming back are relatively thin and lightweight for their length, it is a pointer that the fishery is under stress for some reason or reasons.

In 2020 Steve Racz caught his winning 5.34kg (11.7 lb) salmon from a boat. Only three salmon were caught over the two days of the comp. The second heaviest fish weighed 3.70kg (8 lb), and in third place, the salmon weighed just 2.24kg (4.9 lb). However, there was good salmon caught from the wharves during January and February leading up to the competition.

In 2019 the competition produced a total of 6 salmon. 1st and 2nd place were won by Lofi with a 5.780kg (12.7 lb) and a 4.740kg (10.4 lb) fish, 3rd – Lance Moore with 4.685kg (10.3 lb), 4th – Nick Love with 4.590kg (10.1 lb), 5th – Dave Taylor 1.690kg (3.7 lb) and 6th – Cara Luxmoore 1.260kg (2.7 lb).

These numbers contrast dramatically with earlier years when not only were the salmon heavier, there were a lot more of them. I remember travelling to Dunedin for the competition when as many as 40 good-sized salmon were weighed in over the two days.

Many of the locals were catching 20-plus salmon from the wharves each season.

Boys on a fishing trip to the Otago Harbour wharves.
Boys on a fishing trip to the Otago Harbour wharves.

The decline in the number of salmon returning to Otago Harbour is almost certainly due to an increase in sea temperatures over recent years. Higher water temperatures affect not only the salmon themselves but also the species they prey on while at sea.

Waitaki Salmon Fishing Contest Results Interesting

Older salmon anglers may recall that the 1999/2000 salmon season was a poor one with fish numbers well down. The salmon that did return were underweight for their length in comparison to the previous bumper years. From 1993 to 1997 returns were very good with salmon landed that reached 35 pounds.

It appears that salmon returns are cyclical to some extent. Foraging conditions for the salmon while they are at sea are a major factor. There seems to be a correlation between good years for red krill and good years for salmon.

Good years for red cod (which also feed on krill) also appear to be the same years for salmon. Krill grow faster in cold water. Global warming leads to warmer sea temperatures which would not be good for krill.

After poor salmon returns in 2000 and 2001, the Waitaki salmon fishing contest was cancelled. You can read about the Waitaki River Salmon Fishing Contest and the weights of the winning fish in this article.

Fishing Around Dunedin

On a lighter note, schools of large kingfish have been seen swimming around the wharves in the inner Otago Harbour.  Perhaps anglers may be able to fish live baits under balloons, poppers and jigs to target these powerful ocean predators now that salmon are few and far between.

I note also that many Dunedin anglers are now making regular fishing trips to the Twizel Canals. Obviously, it is a long car journey compared with the local Otago Harbour wharves, but the chances of catching good salmon are much greater!

Hunting and Fishing, Dunedin, 141 Crawford Street, Central Dunedin, Dunedin 9016

More about Otago Harbour salmon fishing.

One of the last really good salmon to come from Otago Harbour was this beauty caught by Jeff Sharp on 21 January 2016. It weighed in at 10.82kg (23.85 pounds).
One of the last really good salmon to come from Otago Harbour was this beauty caught by Jeff Sharp on 21 January 2016. It weighed in at 10.82kg (23.85 pounds).

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