Last updated on May 16th, 2023 at 01:14 pm
The trout life cycle resembles that of brown trout and Chinook salmon. The female digs a redd (nest) and deposits her eggs. The male fertilises them with milt (sperm). Eggs take 20 t0 100 days to hatch, depending upon water temperature level. As soon as the eggs are hatched, the alevins (fry with yolk sacs connected) remain in the gravel for 2 to 3 weeks and feed off their yolk sacs.
When the yolks are almost eaten, the young trout become free-swimming fry.
The trout life cycle is organized into 6 different phases as seen below:
The Trout life cycle Phase 1: Spawning
The trout life cycle starts with the trout laying their eggs in nests in the river gravels, referred to as redds. The female (hen) constructs the nest, typically in between November and January when the water is cold and bring lots of oxygen since that is what the eggs need before they can hatch.
The female trout (hen) tries to find gravel with an excellent flow of water passing through, so the gravels need to be mainly free and loose from silt and should be between 5 and 50mm in diameter.
The hen fish will begin by checking the gravels with her anal fin. If the gravels are great, she will dig a hole, switching on her side and flexing her body.
When a hen fish begins to dig in the gravel, she will bring to the attention of males who will chase after each other and will make effort to remain in place just when she lays her eggs. The procedure of digging and chasing can last for a long time (hours and even days) and at this time it is typically easy to see a trout.
Ultimately the hen fish will launch a few of her eggs into the redd. The male (cock) fish will launch his sperm or milt over the eggs to fertilise them.
The hen then moves on and digs once again to toss-up gravel to cover the fertilised eggs. Often the eggs are fertilised by a little young male trout called a ‘precocious parr’.
The Trout life cycle Phase 2: Eyed-Egg Phase
The next stage in the trout life cycle is the eyed egg stage. On some rivers with clear water, a trout redd can be very apparent and easily seen – it appears like a spot of clean gravel, loaded into a mound typically with a hollow downstream of the mound.
Redds can differ tremendously in size, from 50 cm2 to over 150 cm2. Little trout usually develop smaller sized redds in finer gravel, and huge sea trout can develop redds that is the size of a cooking tabletop with much larger stones. The number of eggs laid likewise depends upon the size of the hen trout, typically a 500g trout will generally deposit around 800 eggs.
The male fertilises the eggs with milt (sperm). Eggs take 20 to 100 days to hatch, depending on water temperature level. When hatched the alevins (fry with yolk sacs connected) remain in the gravel for 2 to 3 weeks and feed off their yolk sacs. When the yolks are almost consumed, the young trout become free-swimming fry.
The Trout life cycle Phase 3: The Alevin Phase (Eggs hatching)
As the eggs developed, you can see trout ova develop within them. This is called the ‘eyed ova’ phase. How rapidly the eggs will hatch depends upon water temperature level, chillier water means slower growth in the egg.
The recently hatched trout are called alevins, and they reside in the gravel, feeding off the rest of the yolk that is connected to their body for 14 to 30 days, once again temperature level affects their rate of development.
Often pronounced as al-e-vun, during this phase of the trout life cycle, the trout emerged from the eggs but has an egg sac still connected to its body.
They don’t move around too much because all their requirements (nutrients, food, etc) is provided by the egg sac. With time, the egg sac gradually shrinks and forms part of the trout’s body. When the trout start swimming to the surface, they enter a brand-new stage call the Swim Upstage, which is when start eating food.
At 7.8C, the eggs will hatch within 60 days but at 4.7C, it will take the eggs 97 days to hatch. Usually, it is presumed that many eggs hatch in February and the age of a trout is determined from this ‘birthday’.
The number of eggs hatch differs tremendously depending upon the quality of the water and gravel, it can be as low as 4%, or surpass 80% where conditions are really excellent.
The Trout life cycle Phase 4: Fry Phase: Trout Fry
As soon as the yolk has actually been shrunk or eaten to form part of the trout body, the alevin becomes fry, emerge from the gravel, relocate towards the light and begin to feed on small insects in the water.
Death rates at this extremely susceptible phase of the trout life cycle are really high. The fry is simply a couple of centimetres long and consumes a great deal of energy, so they need to discover food very quickly, and sometimes, plenty of it.
They likewise become territorial, they will always want to be out of sight of other fries, so they require an environment that has lots of plants and stones to allow them to hide from the neighbours. And they are still really small, so they require shallow water (1 to 40 cm) that isn’t too fast flowing.
The shift from living off the yolk to independent feeding is an important trout life cycle phase and the one at which most of the deaths occur.
Due to the fact that the trout begin taking the form and qualities of what we believe of as brook trout, the fry phase in the trout life cycle is an interesting part of the procedure.
Up until now, the trout has actually primarily been hidden behind the insulation to keep it dark and the water temperature level low. Once they end up being fry they are launched from the smallholding tank and they are freed to check out the remainder of the fish tank.
Due to the fact that they now eat at least two times a day and they are producing more waste, then they need more constant water changes and the water chemistry becomes a little bit more challenging.
At the later part of this phase, they develop vertical lines called par marks. Fry tend to be around 1 inch in length.
The Trout life cycle Phase 5: Fingerling Phase (Trout parr)
A trout of less than one year of age is called a parr. They are easily recognized trout now, however, they have distinct fingerprints or parr marks on their side which they lose as they grow older.
Parr has comparable environment requirements as the fry: a lot of covers to hide from each other and from predators, specifically fish consuming birds.
They can handle much deeper and quicker water as they grow. In order to discover their own territory, they will slowly drop downstream with the flow instead of battling their way up against the flow.
It is rather tough to tell whether a parr is a salmon or trout. One idea is the habitat, salmon parr tends to choose faster riffles than trout as they are more powerful swimmers.
Salmon parr can typically be identified from young brown/sea trout by the more structured shape, deeply forked tail, longer pectoral fin, absence of orange on the adipose fin, smaller-sized mouth, sharper snout, just 1 to 4 spots on the gill cover (frequently one big area), well-defined parr marks.
Trout in this phase are increasing in size, oftentimes in the 1 to 3-inch range. It is at the start of this phase that trout are launched into their natural environment, which is at some point in the middle of May.
The Trout life cycle Phase 6: Adult trout
Adult brown trout that stay in the river maintain their territorial behaviour and will secure their areas or ‘lies’. The majority of trout will have a feeding lie, generally in a location where the river current serves as a conveyor belt for food so they can just deal with upstream and capture invertebrates as they wander past, using up as little energy as possible.
They will also have several resting lies, where they are more secure from predators. Generally, this will be under an undercut bank, tree rock, log or root.
When resting and in warmer weather condition, bigger trout will typically inhabit pools in the river. Deep pools are cooler than the shallow riffles in the summer season, and the depth makes them feel protected from predation.
As they grow older and the trout life cycle moves to the next phase, they can change from consuming invertebrates to consuming little fish (they end up being ‘piscivorous’) and their fishy diet plan can consist of young trout and salmon.
A piscivorous trout is not like a ferox trout, which are discovered in some deep glacial lakes and also consume fish, however, which are genetically rather unique.
As soon as a trout has actually grown beyond the fingerling phase they are considered grownups. A trout life cycle typically does not go beyond 3 years. In this area, they hardly ever grow to be bigger than 12″, and many are significantly smaller sized than that. It is during a trout’s adult phase that the unique square tail, red dots surrounded by blue haloes, and reddish tummy take type.
Trout life span?
Based upon scale readings and the research on the entire trout life cycle, the basic view is that trout will normally live for around 6 to 7 years, however, this figure is extremely variable. There is photographic and anecdotal proof that some trout can live longer than that.