The Glenariffe Stream was the site of a salmon research station operated by the National Institute of Water & Atmospheric Research (NIWA) until it was sold to private interests in 1999 and closed soon after. This article was written by Nelson Boustead and first published in 1997. We have not changed or updated the text in any way. However, salmon anglers will find much of interest contained within. Special thanks to Nelson Boustead for his generous permission to republish it here. All photographs courtesy of Nelson Boustead.
Though the salmon fishing season has long since closed, for salmon their upriver migration doesn’t finish until June. This is the time when adult salmon complete spawning in high country streams. Counts of these spawning populations are carried out by Fish and Game Council officers throughout the salmon rivers of Canterbury but salmon returning to the Glenarffe Stream on the Rakaia River have had more intense scrutiny over a longer time than any other salmon population in the country. This is because of the substantial permanent fish trap on the Glenariffe Stream and the research activities carried out there by the National Institue of Water and Atmospheric Research (NIWA) and predecessors.
There are two traps at Glenariffe, an older trap referred to as the wild trap, which has a fence or rack on the stream to direct salmon into the trap. A second trap, the hatchery trap, was installed as part of the hatchery expansion in 1988. This is located in hatchery waters before they discharge into Glenariffe Stream. It is unusual in that it has no accompanying fence across the stream to direct fish into the trap. Salmon that enter this trap do so voluntarily by making a left turn out off the Glenariffe Stream and up a small fish ladder.
The waters supplying the two traps are a little different. The wild trap is fed by the Glenariffe Stream whereas the hatchery trap is fed by a smaller adjoining tributary stream. This difference, and perhaps the influence of hatchery activities appears to be sufficient for salmon to distinguish between the two streams and choose the one they were reared in. For example in 1997, 92 percent of tagged fish turned into the hatchery trap from where they were reared rather than continue upstream.
Salmon entering the Glenariffe Stream have been counted for 33 years since the trap was first installed in 1965. The work involved in trapping and counting returning salmon was initially done as part of studies on the wild run. The records provide a good indicator of the ups and downs and health of the salmon over the years. There has been great variability in the numbers of salmon returning from record lows in 1973 of 424 fish to the best season in 1985 when 7288 salmon returned, although of this total, about half was made up of fish of hatchery origin.
In 1997 the provisional total returns were 3589 salmon made up of 1359 untagged salmon entering the wild trap, 1405 untagged salmon entering the hatchery trap, and 825 tagged salmon most of which entered the hatchery trap. This was down on the 1996 returns of 5442 salmon (2228 fish entered the hatchery trap, 2518 fish entered the wild trap and another 696 tagged salmon were recovered).
The hatchery-reared salmon that return to Glenariffe were previously released from the Glenariffe Salmon Research Station for three principle reasons. Initially, tagged salmon were released as part of a comprehensive study on the influence of time and size of release on the nature and magnitude of subsequent returns of adult salmon. More recently a new study, the JUNIPEX study, has involved the release of salmon tagged at the family level. JUNIPEX is the Joint University of Washington Population Experiment and is looking at the influence of genetic and environmental effects on the evolution of New Zealand salmon populations.
The third reason for releases was to provide a supply of ova from hatchery-reared salmon for sale as eggs or fish to clients that included Fish and Game Councils, the Salmon Anglers Association and commercial salmon farms. NIWA will make a release of tagged salmon in 1998 as part of the JUNIPEX program but releases from Glenariffe for the time and size experiment have finished and there will be no more releases of large numbers of salmon for the provision of ova. Future ova supplies will be met by smaller releases from NIWA’s Silverstream Research Station near Kaiapoi. In the past, releases of hatchery fish have put in excess of 40,000 salmon into anglers bags as they have had first crack at the salmon all the way from the river mouth to the hatchery located 100 km upriver. The impact of stopping releases on the angler’s catch and the Glenariffe salmon run remains to be seen.
Anglers may be wondering what happens to salmon after they are caught in the traps at Glenariffe. By the time they enter the traps, they are unsuitable for human consumption and in prime condition for spawning. About 70 percent enter the traps ripe and within a few days of spawning. The females are swollen with eggs but the flesh is thin, white and tatty as the salmon have used much of their body reserves in the rigours of the upstream migration and to develop the ova.
In the wild trap, all non-tagged salmon are measured, recorded and then passed still alive and kicking into a pipe from which they can swim above the trap to spawn naturally in the Glenariffe Stream. All tagged fish, which by virtue of being tagged must have originated from the hatchery are kept to recover the tag as part of the scientific research carried out by NIWA.
Most of the salmon that enter the hatchery trap are of hatchery origin and these fish are stripped to provide ova and milt for future releases and commercial activity. The returns of hatchery-reared fish frequently provide more salmon than required and in past years excess salmon from the hatchery trap have been released into the Glenariffe stream to spawn naturally. In 1996 over 1600 surplus hatchery fish were transferred from the hatchery trap to the Glenariffe stream. This practice will be discontinued as numbers of fish returning to the hatchery cease. While some believe that these transfers add to the stocks in the river and provide more fish returning in future years for the angler to catch, others believe they may have a detrimental effect.
Photo Gallery of the Old Glenariffe Salmon Research Station
There is a fair mix of fish of hatchery origin, and wild fish, that return to the Glenariffe stream and anglers frequently debate the merits of hatchery fish versus wild fish. Some will argue strongly that wild fish are somehow superior but we have yet to see any proof of that.
Fundamental to this discussion is that anglers are able to clearly recognise the difference between a hatchery and wild fish. In most cases, this is not as simple as it seems. If a fish is tagged it is perfectly obvious that it is a hatchery fish from the absence of the adipose fin. This fin is removed when the fish is tagged so that anglers can recognise that the fish has a 1 mm long tag in the nose. However, not all salmon released from hatcheries are tagged. In any release from Glenariffe as few as ten percent may be tagged, the remainder have their adipose fin intact and will appear to anglers indistinguishable from a wild fish.
At Glenariffe salmon are raised for release at relatively low densities with an abundant supply of clean stream water. This tender loving care means that at release most fish still have the v-shaped tail that is characteristic of normal fish. After they have spent between one and three years at sea and return to freshwater, most salmon of Glenariffe hatchery origin cannot be distinguished from wild fish by their body or fin shapes. However, we need to distinguish the untagged hatchery fish from the wild fish for our research programs. This is done by examination of salmon scales. Salmon scales have a pattern of growth rings rather like rings visible in a cross-section of a tree trunk. These can only be seen with the aid of a microscope and the pattern of rings can reveal if it is of hatchery or wild origin. The pattern can also indicate the age of the fish and how long the fish spent in freshwater before migrating to sea.
A few fish in the salmon run are obviously of hatchery origin and have eroded fins and a paddle-shaped tail. These fish are likely to have come from escapes from a sea cage. With the exception of fish from this unusual event, it is impossible to reliably determine by eye, if adult salmon returning to freshwater are of wild or hatchery-origin.
The size of salmon is also not a good indicator of hatchery or wild origins. Salmon return to freshwater predominantly at age three with a smaller proportion at age two and four. The two-year-old salmon are quite a lot smaller than three and four-year-old fish. These small two-year-old fish may come from either hatchery or wild origins. Two-year-old wild fish are slightly larger as they have a faster growth rate in the sea than their counterparts in a hatchery, but by the time fish reach three or four years old, the hatchery origin fish have caught up to be of similar size.
Records of average fish weights from the Rakaia and Waitaki fishing competitions have shown the average size of salmon vary from an average weight of 4 kg in poor years (Rakaia, 1991) to an average of 8.4 kg in good years (Waitaki 1994). These enormous differences between good and poor years vastly outweigh any differences between sizes of hatchery and wild fish. The differences in annual average weights are believed to be due to different conditions influencing growth rates at sea.
Late in 1997 will see the start of another salmon fishing season. The success of that season will be measured by anglers according to the number and size of salmon they catch. For the NIWA staff associated with the traps at Glenariffe we will measure it by the numbers of tagged and untagged fish returning to the traps. At this time those numbers are anybody’s guess.
Since this article was written the North Canterbury Fish and Game Council have a salmon hatchery at Montrose, lower downstream on the Upper Rakaia River. The video below is of the Montrose hatchery.
This post was last modified on 22/12/2017 7:36 pm
Perch - Perca fluviatilis - introduced freshwater fish Perch are a European freshwater fish species first introduced into New Zealand…
Rudd - Scardinius erythophthalmus One of the species of coarse fish that we target here in Canterbury is the much-maligned…
Cooking Your Catch In the Wok with Keith Chin I'd heard a bit about the Liquidator and had even seen…
Sockeye Salmon - Oncorhynchus nerka - only landlocked stocks are found in New Zealand by Allan Burgess Most New Zealand…
Poor Salmon Returns – Where have all the salmon gone? By Allan Burgess The decline of the South Island salmon…
Kaikoura Coast Fishing, Part 2 - Tips, spots, species Kaikoura Coast Fishing part 2 Kaikoura Coast Fishing part 2, follows…
All Rights Reserved © fishingmag.co.nz 1999 - 2021Read More