Fishing for Rainbow Trout: Salmo gairdneri
The rainbow trout (Salmo gairdneri) is a handsome fish with a dark bluish-green back. Its sides are tinted with pinkish marks and it is profusely sprinkled with small spots. The rainbow has been the subject of controversy ever since it was introduced into Britain more than seventy years ago. Even today, opinions are still divided on whether it is a desirable species to stock. There is a good deal of prejudice against rainbows on the grounds that they are inferior to native brown trout, and these arguments are strengthened when we notice that some Americans prefer brown trout to their own native rainbows.
How to define ‘rainbow trout’? It is not particularly easy, since the blanket word ‘rainbow’ covers several related species, some of which are migratory and some non-migratory. When we reach the stage of sub-species and varieties the subject becomes confused and the best the average angler can do is to accept the definitions given out by some biological authority.
For convenience it may be assumed that there are three North American trouts which may be termed ‘rainbow’. These are: the steelhead (migratory rainbow); Salmo gairdneri (non-migratory rainbow); and the Shasta rainbow. For practical angling purposes the steelhead and the rainbow trout proper may be likened to our own sea-trout and brown trout.
So far as is known, steelheads have never run British rivers. This is so even when rivers contain Salmo gairdneri, some of which might be suspected of having the migratory urge, just as some of our own brown trout stocks have it. An interesting, although inconclusive, case, did however occur on the River Western Cleddau, where several anglers reported the capture of ‘curious-looking salmon’. This river, at that time, had a commercial rainbow trout farm in its upper reaches from which fish sometimes escaped. Unfortunately the strange migrants were not sent for identification.
The value of the rainbow trout is said to lie in its speed of growth, its eagerness to rise to a fly, and the fight it puts up on being hooked. Objectors to the rainbow point out, however, that in many waters it fails to do well and the stocks have tendency to disappear. Both faults could probably be traced a strong migratory urge, for no migratory fish thrives if coop in a lake.
The rainbow has other useful attributes. It enjoys warm water than does the brown trout and will feed well even and a hot summer sun. It is also said to withstand mild pollution better.
Rainbows normally breed later than do brown trout. Some indeed, are spring-spawners and are out of condition when t brown trout season opens, even if they are not actually gravid, For this reason it can be said that fishing for rainbows is at its best in late summer and early autumn.
Egg-binding seems to be a fault with rainbows and causes good deal of mysterious mortality. Rainbows are rather particular about their spawning redds (or shallows) and should these not be quite suitable the female refuses to shed her eggs and dies. This trait may explain why some rainbows disappear without trace even from lakes.
However there are probably other factors at work and th problem of the vanishing rainbow is still of concern to manage of fisheries. In some waters the rainbow thrives and it is per haps significant to note that these are usually alkaline. However just to complicate the issue, at least one acid lake has bee successfully colonized, so it may boil down to the fitness of th spawning redds, after all.
The belief that the introduction of a ‘pure’ strain of non migratory rainbow would solve our stocking problems led to. The importation of the Shasta rainbow, which was supposed be a distinct non-migratory type. The Shasta, however, prove to be as variable as other sorts and in some waters it disappeared, in the usual infuriating way. More research is needed before it can be said that this is due to spawning-bed troubles, migratory urge (fish can escape from lakes up feeder-streams, where many may perish), or food-supply. It may be a combination of all three factors.
Among the few British rivers ‘adopted’ by the rainbow are the Derbyshire Wye, the Chess, and the Derwent. Blagdon and Chew Valley are the chief lakes. Variable success has been scored on some other reservoirs and lakes.
There seems to be no cut-and-dried formula available for anglers who wonder whether their water is suitable for rainbow trout. The only effective method seems to be to have a trial stocking and check on the result. Waters with a pH factor indicating acidity are less likely to become successful rainbow fisheries than those with neutral or alkaline water. It would be interesting to know whether rainbows could flourish in acid lakes containing whitefish shoals. Experimental work is being carried on in Ireland, where between 3,000 and 4,000 rainbows have just been stocked in Lake Keeldra, Co. Leitrim, by the Inland Fisheries Trust.
However, there is absolutely no doubt that they do well and give great sport in stocked ‘put-and-take’ fisheries large and small. They very rarely breed in British still waters though they produce roe and milt in late summer to early winter as if they mean to.
Rainbow trout are usually caught on the same patterns and types as those used for brown TROUT. The rainbow, however, seems to be a more vigorous feeder than the brown. It tends to rise impulsively and this has earned it a reputation — and the mild scorn of some anglers — for being easier to catch.
This impulsive rising means that tinsel-dressed flies, drawn rather fast, often attract rainbows into rising in conditions
where there is little natural fly on the water, and particularly in sunny weather. Moreover, some rainbows seem to rise more than once at the fly before taking it and being hooked.
It is useful to have a really bright fly in the box for rainbow trout in sunny weather. Here is a really sparkling pattern that often does well:
Body: Gold tinsel from the bend of the hook to the shoulder, dressed flat
Wing: Fibres from the eye of a peacock eye-feather
Hackle: Soft hen dyed pale blue, dressed very sparse
Hook: 8s, 10s, and 12s
This fly should be drawn smoothly and steadily through the upper few inches of water. Fish probably take it for a fry or a beetle.
In still water rainbows go for bright offerings such as Dunkeld, Whisky flies, Muddler Minnows, Black Ghosts early in the season fished fairly — sometimes very — deep. In summer they give fine sport on smallnear or on the surface including Pheasant Tail, buzzers green and yellow. They rise well to and on warm evenings to sedges.
Fly tackle as suggested for brown TROUT is quite suitable. For fishing the bigger lakes, such as Chew, a 2.85 m (9-1/2 ft) split-cane or fibre-glass rod, a No. 3 self-floating line, and tapered leaders down to as fine as 2 kg (4 lb)are very satisfactory. The precaution of always pointing the rod away from the fly saves breakages by taking fish as explained earlier.