A Young Trout’s Life

The wild trout struggle for suvival starts right from the moment that it is fertilized as an egg. The truth of the matter is that like everything else in the natural world, survival for young trout is low, from egg to larva and then from larva to young fry. As the small trout grow young parr, they will have a better chance at seeing maturity and even reproduction.

A young trout parr is called this, due to the dark spots that they develop in their early stage of life. Their eyes are still very large and their spinal system is still pretty soft. The tail fin is just starting to loose its round edges. When the trout are very tiny, their tails are more rounded in shape.

A brook trout fry will emerge from their gravel spawning beds in the month of January, in spring creeks like Millennium Creek, and as late as mid-May, on the mainstem of creeks like the Bighill Creek. Prior to emergence, the trout larva will develop from an eyed egg into a trout larva with egg sack attached. The small trout will continue to live off of their egg sacks until they are all used up.

The trout larva are still attached to their egg sacks when they are still buried in the gravel spawning beds. It is from the egg sack that they will continue to recieve nutrient. Their fins are still under development.

Larger, mature trout will lay larger eggs, this will result in young trout that are further developed by the time the egg sacks are used up. These trout will also be larger and more able to compete for available food and habitat. So keeping larger trout in a system is of major importance. Fisheries managers sometimes neglect this well known fact about reproduction of wild trout.

I trapped this small trout fry on Bighill Creek in mid-May, during a fisheries study. The small trout measured approximately 22 mm in length. You can see the tail appears very delicate, and this trout was a very poor swimmer. It must have just emerged from the gravel, after living off of the last remains of its egg sack. The small trout is just starting to show its developing parr marks, on its side. These dark, black patches show that the fish is a trout, for sure. The only other young fish that shows such parr marks, in our local streams, is the trout perch. However, trout perch are easily regonizable as something totally different. When mature, trout perch will eat young trout.

There are all kinds of natural predators that feed on young trout, including insects, such as the dragon fly nymph or various beetle larva, among others. Larger trout will also include young trout in their diet, but this is more so if pickings are slim. Then there are the birds, just about any foraging waterfowl will eat young trout, besides their main diet of vegetation. Of course there are some diving waterfowl and ambush feeders, like Blue Herons, which will also feast on young trout.

This free swimming trout fry still has the broad head and small tail fin. Not a very good swimmer yet, but it is protected in its maze of submerged woody debris habitat. There is plenty of food, close to where the trout hide for parts of the day.

Young trout are very curious fish and their curiosity has led to the demise of many a young trout. However, weeks after emergence from spawning beds, the trout start to develop more caution and they also disperse into small micro habitats with plenty of hiding places. Still abundant, predation continues until only a few of the original hatch are left to live into maturity. This is just natures way. If you look at how many willow and tree seeds are dispersed every spring, and only a few will result in germination and then other types of predation and weather conditons will take its toll. This is why both eggs and seeds are so plentiful with fish and plants.

The early winter hatch on Millennium Creek is the most important one on our watershed of the Bighill Creek system. There are no outside influences to prevent a reliable annual spawn and hatch of brook trout on this spring creek. A spring creek with stable flows, good quality water and consistant seasonal water temperatures, is perfect for the brook trout that live in this small stream or those that return to spawn.

This young brook trout explores a world of microscopic life, in the shallow more productive lateral margin habitats, along a crystal clear spring creek.
Young rainbow trout will start to loose their parr marks after a few open water seasons. The trout are still pretty delicate and they require careful handling.

If a trout has plenty of food and places to hide when predators visit their habitats, they will possibly survive into maturity. When the juvenile rainbow trout enter the Bow River, after spending their first year of life in the Jumpinpound Creek, they are faced with the tough challenges of living in a river that is far less productive, but has lots of space for the young trout to disperse into.

Young rainbow trout will grow fast if there are hatches like the brown drake available. It is a big meal for a young trout.

Sit back and enjoy this video of small brook trout fry, on a small spring creek, where they hatched from eggs.