Why the salmon run has fallen and what can be done about it

Press, 12 September 1988, Page 16

Why the salmon run has fallen and what can be done about it

R. F. Stead,

a keen angler, proposes action

to help restore Canterbury’s depleted rivers

THE AUTUMN salmon run of 1988 ended in May, and what a depressing run it has turned out to be by comparison with former times. The numbers of fish in the spawning streams have been counted, so readers can form their own opinions of the run from the following figures (last year’s in brackets): Glenariffe, Rakaia, M.A.F. 2550 (6225), N.Z. Salmon Co., L. Coleridge, approx 200 (2000), Winding Creek, Waimakariri, N.C.A.S. 111 (299), Cass Hill Stream, Waimakariri, N.C.A.S. 50 (135), Grasmere Stream, Waimakariri, N.C.A.S. 21 (38).

In addition, those who have observed the spawning run in the Hydra waters (a major Rakaia spawning area) for at least 30 years will agree that this run is very much depleted. This is significant as there is no artificial stocking in this river, so it appears the natural spawning numbers of fish, without supplementary stocking, are not holding their own.

In view of the observations it is disappointing to hear a public figure, Mr Maurice McTigue, National member of Parliament for Timaru, say words to the effect that it has not yet been established the salmon run has decreased. To make such a statement he must be unaware of the facts; or perhaps the commercial needs of the district for which he is the member are uppermost in his mind. What are some- of the factors one might consider pertinent to the decrease of the salmon run? 0 River conditions for the juvenile fish;

• Sea conditions for the adult salmon; 0 Netting at sea;

• A huge increase in fishing pressure on the autumn. upstream migration. Perhaps some comment on the above headings would be constructive. River conditions for the juvenile fish: Nothing can be done about these seasonal and

variable river conditions, so the fluctuations must be accepted as normal.

Sea conditions for the adult salmon: An interesting fact emerges here. In 1987, when most anglers were blaming the netting in that season for poor returns, the salmon that did return were of poor condition and rather small. So while one could reasonably attribute lack of numbers to the efficiency of the netting, it would be hard to credit the nets with influencing either the size or poor condition of those fish that did return.

Therefore, in the sea, conditions existed that were not favourable to salmon growth. Was it shortage of krill, or did the cold food-bearing currents not reach the Canterbury coasts that year? Netting at sea: Let us divide the commercial fishing trawlers into two groups. Those shorter than 15m and those longer than 15m.

The small trawlers working out of the local harbours are probably towing nets 22m to 24m long and 3.6 m to 4.5 m in height. They may travel up to 2>/ 2 knots. They catch an occasional salmon, and present no appreciable danger to the fishery. Contrast this with the large trawlers, more than 15m, towing a net that may be 45m long, up to 15m in height, and at speeds between 2*4 and 4 knots. I would not know the maths involved, but these trawlers could be 100 times more lethal than the small trawlers. They do catch a large number of salmon, and so would have the numbers of fish to warrant the transfer of this, bycatch at sea if they so desired. It is encouraging to see the Minister of Fisheries has curbed the activities of these larger trawlers by placing a ban on their fishing in the Banks Peninsula area from December 15 to

the end of February and has also imposed a distance of. one nautical mile from a river mouth before any legal trawling may occur. It will be the duty of the Ministry of Agriculture and Fisheries to ensure that the enforcement of these netting limits is speedy and efficient; otherwise the achievement that it is hoped these restrictions will effect will be lost.

Unfortunately, one must accept, however, that it will probably not be for two years that the full change of fish numbers will become apparent. Already large numbers of salmon which would have started their upstream migration this summer will have been caught around Banks Peninsula last year.

The increase in fishing pressure: Up to now it would be safe to assume that not one angler in fifty will be thinking they can also participate in the conservation of fish. Yet I do believe this should be done. The commercial trawlers having now been legally forced to make a contribution to the salmon fishery, are the anglers going to let their share fall by the wayside through parochialism and discord.

On April 1 the Rangitata, upstream of the irrigation race intake, the Rakaia and the Waimakariri at the gorge bridges, the Hurunui on the main road bridge to Culverden, and the Waiau at the Leslie Hills bridge should all be closed. This would undoubtedly allow extra hundreds of deteriorating salmon to reach the spawning grounds. It would be difficult to say how beneficial this would be, but since in many cases the available spawning gravels are not fully utilised what change there was would be advantageous.

One must remember that it is by full utilisation of the spawning grounds that the suitable gravels receive their annual raking over in the : autumn. This is most important; for, without this, the gravels used for spawning tend to become silted up and grow weed. They then cease to be of further use as potentially suitable areas for spawning redds. With the advent of commercial salmon farms the programme of spawning stream improvement seems to have been forgotten. This is a very great pity and I think it is still just as important to take every opportunity to improve the spawning conditions in the small streams as it ever was. In the upper Waimakariri basin there are no commercial farms, so the fish still have to rely solely on a number of not very satisfactory spawning streams.

Let us follow the history of one of these streams, the Cass Hill stream, or Bullock Creek as it was once known. Field officer Ross Novis, North Canterbury Acclimatisation Society, has written of this stream: “The section of the Cass Hill stream which impresses me most for salmon spawning is the length of stream which was made out of a dry stream bed in about 1975 by members of the Salmon Anglers Association with the help of a bulldozer. The North Canterbury Acclimatisation Society had dams pushed up to protect this area, and there have been a number of working bees connected with clearing the stream bed and planting trees for flood protection.”

This is a good example of local participation in the development of a spawning stream. About three years after this stream was literally “created” (by joining

together two otherwise useless streams) I counted 400 salmon spawning in it. When one considers that these 400 salmon could have represented 600 entering at the mouth one can see how vastly valuable the improvement of just one little stream can be. Dave Hughey, Steven Sparrow, and others will well remember the pleasure the success of the development of this stream gave all concerned. Sadly now, through neglect, the Cass Hill stream has fallen in to disrepair. Access for fish is very difficult because of large areas of shallow water near its confluence with the Waimakariri. It would be a monument to their success if the Salmon Anglers could adopt this stream and spend a day or so working on it with a grader, or digger — something that would cut a channel through the shallows. It is vital that the adult spawning salmon get as far upstream as possible, so the young fish, after hatching, have a mile or more of stable clear water before reaching the unstable river system of the Waimakariri. I would also suggest, and assist, in the purchase of young fry from M.A.F. so the improvements effected can come to fruition in the soonest possible time. I mention the Salmon Anglers here because they have a greater capability of personal input than the North Canterbury Acclimatisation Society. However, I would certainly hope that the Acclimatisation Society would fully support this endeavour, particularly as its field officer, Ross Novis, is without peer for his knowledge and dedication to the spawning streams of the Waimakariri basin.

I have commented on several aspects of the salmon fishery. It is to be hoped there are still sufficient people interested and enthusiastic enough to help make beneficial changes. There is no doubt at the moment that the good seasons are becoming poorer and the bad seasons worse.