Experiments have been made in hybridizing (crossbreeding) brown trout and rainbow trout with American brook trout, to produce two new types of sporting fish.
The resultant hybrids (crossbreeds) are sterile and do not reproduce in the wild.
The American brook trout has been crossbred with the brown trout to produce a fish called the tiger trout.
The rainbow trout has been crossbred with the American brook trout to produce the cheetah trout.
The tiger trout (American brook trout x brown trout) enjoys a very limited distribution in rivers and still-waters, and where present behaves like a brown trout.
The cheetah trout (American brook trout x rainbow trout) is rarely encountered, and where present behaves like a rainbow trout.
Fish Farm Trout
Today, many brown trout and almost all rainbow trout in Britain, begin life under artificial conditions in the hatcheries of fish farms.
A small fish farm produces about 20 tonnes of trout each year.
Most of the trout reared are marketed commercially as “table trout” for cooking and eating: trout of 225g(9 oz) for sale fresh or frozen; trout of 454kg(1 lb) for processing and specially treated pink-fleshed trout of 1.5kg (3lb 5 oz) and above, for sale as high-priced “salmon-trout”.
Fish farm brown trout and rainbow trout, hatched in fresh water, can be “grown-on” in floating cages in the salt water of the sea, for sale to commercial outlets as “table trout”.
Fish farm trout of about 300g (10 1/2oz) in weight, and of good general appearance and colour, might be selected to “grow-on” in fresh water for sale to fisheries for stocking in the flowing waters of rivers and streams, and the still waters of lakes, reservoirs, pits and ponds.
Trout hatched and raised on fish farms to stock angling waters are known as stock fish (commonly called “stockies” by anglers).
Stock fish trout are intensively fed in stew ponds or floating cages until they reach the desired weight: brown trout are usually considered ready for release at weights of around 0.7kg (1 1/2lb) and above; rainbow trout may not be released until they weigh 5kg (11 lb) and over!
Fish farm trout are protected and cared for in optimum conditions; they are nourished on high-protein food pellets from alevin stage, to the moment of release in their host waters as new stock fish.
Newly stocked brown trout and rainbow trout are tame; see people as protectors and their primary source of food; have little sense of danger, and no learned hunting and feeding skills. Their life can be too short.
Stock-fish brown trout and rainbow trout that survive the rigours of stocking, natural predators, and anglers attempts to capture them, may take 2 years to completely adapt to life in the wild, and even then they will never be truly wild trout; though any offspring they produce in the wild will be wild trout.
Life-cycle of wild trout
A wild trout is a trout which is born, lives and reproduces under natural conditions in the wild.
All wild trout are born in fresh water.
Wild rainbow trout
Rainbow trout are rarely able to reproduce naturally in Britain; only a few waters hold self-sustaining breeding stocks of naturalized wild rainbow trout.
The artificially stocked rainbow trout in most of Britain’s waters are unable to shed eggs (spawn), or sperm (milt).
Wild rainbow trout that do breed in Britain usually lay their eggs (spawn) between March and May.
The life-cycle of wild rainbow trout is similar to that of wild brown trout.
Wild brown trout
The male (cock) brown trout is usually mature at 2-3 years of age; the female (hen) brown trout is usually sexually mature at 3-4 years of age.
When brown trout are sexually mature, they are ready to begin feeding (spawning).
Female brown trout like to lay their eggs (spawn) in the clean gravel of clear, oxygen-rich flowing water, where the water temperature is between 40F (4.4C) and 55F (12.8C)/
Trout living in the still-water of lakes and ponds seek out the flowing water of feeder or outflow streams to breed.
In early winter (October/November/December), the female trout blasts a hollow (redd) in the gravel bed with powerful sweeps of her tail. As the eggs (spawn) are being laid, the male trout fertilizes them with sperm (milt). The fertilized eggs (spawn) are then covered with gravel by the female trout.
Birth of a Trout
The female trout lays up to 1,500 orange eggs, each egg measuring 6mm (1/4 inch) across, in the gravel hollow (redd). Large female trout carrying many eggs may excavate and fill several redds over the space of 2 days, until the female trout is “spent” and has no eggs left.
Depending on the water temperature, the eggs (spawn) may take 3-5 weeks to show signs of life as eyed ova, and a further 4-7 weeks to hatch into alevins. The alevin is about 25mm (1 inch) long and remains attached to the nourishing yolk-sac for 2-3 weeks before leaving the gravel hollow (redd) to seek food.
After 3-6 months the alevin has taken the shape of a tiny young fish (fry). The fry grows fast and becomes a parr (immature young trout), which has a distinctive bluish finger-like markings along its sides.
The young trout may remain a parr for between 1 and 4 years, depending on the quantity and richness of food available in the water.
Eggs (spawn), alevin, fry and small parr are eaten voraciously by many water creatures, ranging from the underwater larvae of large flies and beetles to minnows and larger fish, including trout.
Enemies of young trout
When a brown trout has reached maturity it may develop a silver color and swim toward the sea. These silver-sided trout are called smolts and will become sea trout, living and feeding at sea, returning to rivers and streams to spawn.
After their first breeding (spawning) season, brown trout and sea trout spawn annually in October/November/December.
Male and female brown trout and sea trout that have just completed are called kelts. After the effort of spawning the trout are considerably weakened, some fie.
Most trout regain peak physical fitness 4-5 months after spawning; depending on the severity of winter and availability of food.
Brown trout normally live for between 6 and 10 years, but can exceed 20 years in age. The large, older trout, turn cannibal and live almost exclusively on a diet of small fish. Large cannibal trout seldom waste energy snatching at small flies.