Rainbow trout are a medium sized game fish found throughout the world. Rainbow trout are particularly beautiful in their colouration.
Other variations such as the blue trout and the golden trout are equally beautiful. Rainbow trout are targeted by anglers as a good fighting fish, and maybe even a fish to take home for the table.
Rainbow trout (scientific name Onchorhynchus mykiss) are a freshwater game fish of the Salmonidae family. This family is popular with game anglers as it also includes salmon, brown trout and grayling.
Common names given to rainbow trout include “coast angel trout”, “summer salmon” and “salmon trout”. In the UK they are commonly called rainbow trout or rainbows.
There are other variations of rainbow trout which share the same scientific name. The blue trout is a favourite among anglers as they are thought to be the fiercest fighters.
These are rare fish but some fisheries do stock them and they are slowly becoming more common. Blue trout are worth seeking if you are looking for a challenge and something a bit different. Golden trout are again rare, probably rarer than blue trout, but are also becoming more common.
Rainbow trout are an extremely popular eating fish. Unlike many other freshwater fish, rainbow trout are held in high esteem in many western countries where freshwater fish are not popular as eating fish.
There are many fisheries which operate a limited “catch and keep” policy and supermarkets sell the farmed version of the fish. The flesh is prized for being tender with a mild flavour. The flesh is a light pink or light orange colour and is lighter than salmon.
The colour of the fish is as a result of astaxanthin which occurs naturally in rainbow trout. Astaxanthin is a strong antioxidant which makes rainbow trout a very healthy fish to eat.
Popular methods of cooking include baking, frying and grilling. The fish can be eaten once it is gutted, without scaling and without removing the skin. There is also demand for rainbow trout roe in some areas.
Rainbow trout were introduced to other countries in the late 19th century, however it was only in the 1950s when commercial production really took off.
The largest producers are Chile and Norway. Over 600,000 tonnes of fish annually have been recorded in recent years with a value over $2.5 billion.
Rainbow trout are farmed on a large scale to supply the demand to supermarkets and for use to stock fisheries. In the UK, 17,000 tonnes are harvested each year with approximately 75% of this to supply supermarkets.
All of the farmed fish in the UK which are used for food or for stocking fisheries are either female fish or triploid (infertile) fish.
This is probably as a result of the fact that the species is not native to the UK and there are concerns that rainbow trout could damage the ecosystems of brown trout which are native. Rainbow trout require clean, oxygenated and fresh water in order to grow successfully.
Distribution and Habitat
Rainbow trout are an extremely popular fish and are widespread across the world. In fact, they can be found on every continent on earth with the exception of Antarctica! Given how widely spread across the world the fish has become, it has a limited native range which belies the ubiquity of this fish.
Rainbow trout are native to parts of the USA and Canada in North America. They are also native to Russia and Armenia. They have slowly been introduced to more countries over the last 125 years.
Rainbow trout have been introduced across the world as a food fish (including their roe) and also as an angling fish. Amazingly, they can be found as far afield as South American countries including Brazil, Ecuador, Uruguay and Venezuela. In Africa, they can be found in many countries including Madagascar, South Africa, Kenya and Mauritius.
They can be found in Asian countries where they are not native, including India, China, Iran and Japan. They can be found in European countries where they are not native, including Germany, France, Italy, the UK and Spain.
They can also be found in the Oceanic countries of Australia, New Zealand and Papua New Guinea.
Rainbow trout are a competitive species and there is the potential for them to edge out native trout species to areas where they have been introduced.
There are limited attempts to control the spread of rainbow trout in some areas where they threaten other species such as salmon and native trout species.
Rainbow trout can be found in freshwater, saltwater (rainbow trout in saltwater are called “steelheads”) and brackish waters. Some populations of the species will live solely in freshwater, where others will spawn and live as juveniles in freshwater before migrating to live in saltwater.
Rainbow trout generally prefer cooler waters. Some examples of the places which they live include estuaries, streams, rivers, lakes, ponds and coastal seas. Rainbow trout are a hardy species and can tolerate poorer water conditions than other species of trout and salmon.
Rainbow trout are medium sized fish. They have silvery brown coloured backs, silver flanks and white bellies. They are covered in black spots which tend to congregate higher on the fish.
They have a purple stripe which goes from their gills to their tail. They may also have blue bands going down their bodies.
Rainbow trout have large eyes and their eyelids look bulbous, they can see very well above but their vision is blurred at the side.
Rainbow trout have an excellent sense of smell by using small holes in their bodies known as “nares”, they can use this sense of smell to return to the area where they were born as they know what their home stream smells like.
Rainbow trout have pale fins with black spots, which are most pronounced on the dorsal and tail fins. This is probably the rainbow trout’s most distinguishing feature as other members of the Salmonidae have darker fins.
The blue trout has a blue silver colour all over their bodies, with beautiful blue fins and they still have the trademark black spots. Golden trout have golden flanks with horizontal red lines going down their bodies. Golden trout have yellow or red fins with white edges.
Rainbow trout grow to on average 50 to 70cm in length. The lateral line scale count is 135 – 150.
Rainbow trout grow to approximately 30lb (approximately 13.5kg) in weight. The British record stands at 33lb 4oz.
Rainbow trout are not particularly long lived. The average lifespan is between 4 to 6 years. In some perfect location some fish may live up to 20 years, however this would be the exception rather than the rule.
How they Feed
Rainbow trout are predators. They are highly opportunistic and will eat just about anything which they can fit their mouths around. They are almost always carnivorous, however in some isolated locations they have been known to feed on plankton.
The diet of rainbow trout will depend on their age and size. The smaller fish will feed on insects and invertebrates found in the water and also those which have fallen onto the surface.
The larger fish will eat small fish, insects, insect larvae, fish eggs, worms, shrimp and crustaceans. They are also scavengers and will eat rotting fish found in the water. The rainbow trout in saltwater will consume other fish and squid.
Rainbow trout will eat the eggs of other Samlonidae species such as salmon and brown trout which is one reason why these fish can thought to be invasive.
Rainbow trout spawn at different times to brown trout so it is unlikely that they would ever interbreed. Rainbow trout reach sexual maturity at the age of two years.
The timing of when rainbow trout spawn will depend on the environment. In warm areas such as California they are known to spawn as early as January, however in very cold areas they spawn as late as June.
Most populations of rainbow trout will migrate to find areas to spawn, usually this is over gravelled areas of streams. When rainbow trout are ready to spawn their colour brightens and they will seek out a mate.
The females create small nests in the gravel beds known as a “redd”. The female will deposit her eggs, which number several thousand, and the males will fertilise them.
The eggs are a beautiful light red, dark pink or orange colour. The males will very aggressively defend the redds from predators and other males. Once the eggs have been fertilised, neither parent will guard the eggs.
Once the eggs hatch, which days approximately 21 days depending on the environment, the juveniles will stay attached until they fully consume the yolk sac. The juveniles will remain in the stream where they were born for their first couple of years.
Unlike Atlantic and Pacific salmon which only make one journey to spawn before passing away, rainbow trout will spawn repeatedly and the seagoing fish will move out to sea again before returning to spawn.
How to Catch Rainbow Trout
The trout fishing season runs from 1 April to 30 September. It is likely that you will be fishing for this species in a fishery as the ones found in rivers will probably have escaped from the said fisheries.
You should look at your surroundings and identify areas with plenty of food, for example around overhanging trees with insects on the surface. You could use polaroid glasses to look for the fish which will allow you to see just underneath the surface film.
The types of bait will depend on the type of fishing technique you intend to try. Most people will fly fish for rainbow trout so nymphs, dry flies, caddis and boobies are good choices.
Most of you will fly fish for rainbow trout and therefore this is designed to inform those who wish to try this.
Casting a fly is very different to coarse fishing and it may be beneficial to invest in some lessons on this or watch video tutorials as casting correctly can be a difficult technique to master.
The fly fisherman will choose their flies based on the types of insect which will hatch at the different times of the year, for example at the start of the season fishing with nymphs is perfect.
It is good to get to know the different type of insect which trout will eat through the season and match your flies to this.
In terms of tackle, an 8 – 9 foot carbon fibre rod should be perfect, weighing around 2oz. Couple this with a reel with fly line and backing and a tapered leader of 9 feet with a breaking strain of 3lb. Try to get a few different flies to try as it is always worth changing them during a session.
Fly fishing is a mobile technique so prepare to walk around to find the fish. Fly fishing is an amazing technique and, once you have gotten used to it, it is incredibly rewarding to catch fish this way!
If you are fishing on a catch and release policy, be aware that trout are fairly delicate so don’t overplay them once hooked. You will generally know when a fish is ready as it will allow you to raised its head above the water.
Once it is ready land it with a decent landing net – as you are likely to be mobile a lightweight folding landing net might be a good one to go for.
Allow the fish some time to recover before removing the hook, you could try to unhook in the net if possible.
Once you take the fish out of the water keep it wet and wet your hands so that you do not remove the protective slime. Allow the fish some time to recover once it is back in the water.
If you are taking the fish home for the table, kill the fish humanely and as quickly as possible once out of the water.
Use a blunt instrument to hit the fish above the eyes where the brain is at least twice to make sure it has been stunned. Then cut the throat between the gills and allow it to bleed out.
If you would like more information on how to fish for rainbow trout, or would like some further information on angling techniques, check out our fishing tips page for more information!