Journal

Stream Wintering Habitat For Trout

††† As the water temperature drops and ice starts to build along our flowing trout streams, a migration takes places, below the surface. Trout start to move to their wintering habitats, which consist of deep runs and pools, along the streamís length.

††† These wintering habitats maintain adequate depth, below the surface ice, and also a sufficient food supply to support a population of trout over the winter months.

††† In the cold winter of the north country, a troutís metabolism slows down and the fishes food consumption is reduced, so not much food is required thru the winter months.

††† Sometimes trout will migrate a great distance to reach their wintering pools and runs. On our stretch of the Bow River, between the Ghost Dam and Bearspaw Reservoir, the vast majority of trout will move downstream into the Bearspaw Dam.

††† It is only when the ice is gone from the streams and the insect hatches beginthat the trout will start to move into their spring, summer and fall habitats.

†† The active insect hatches will allow trout to spend the open water seasons in much shallower and faster flowing habitats. The distribution of trout over a greater area is good news for the sport fly fisher and the birds of prey.

Above: These brook trout are hold in a wintering pool, they were visible thru an opening in the ice. Brook trout donít mind occupying pools and runs in denser numbers than other trout, such as brown trout. Brown trout are very territorial and donít like to sharing habitats with others, even of their own kind.

††† On small creeks, the amount of deep pool and run habitat can be limited, especially during a period of low flows. This is where beaver dams can be of tremendous importance to the streamís trout population. They create a lot of pond habitat for wintering trout.

††† If there are a series of dams in a given reach of stream, this is even more helpful to maintaining a good, healthy trout population. The trout may be locked in during the winter months, but during the spring break-up of ice, the trout can access the creekís other seasonal open water habitats.

††† Beaver dams are also refuge to small minnows and suckers, which are part of a troutís diet. Along with a good population of aquatic invertebrates that prefer slow water flows or still water habitats. This insures a good food supply in the winter months, when trout stack up in the dams.

††† In the beaver dams, there is usually minimal current, but often enough to maintain a thinner layer of ice than on a lake. The spring water that feeds the creeks keeps the water warmer than in the nearby river. A good covering of snow also helps to insulate the warmer stream water in small creeks.

Beaver Dams Make Great Wintering Habitats

Above: A pair of trout try to spawn in a silt covered streambed.

Snow Helps Shape Overhead Cover For Trout

††† When native willows are planted along the waterís edge, as part of our riparian recovery program, the plants will provide excellent overhead cover, over time. Eventually, the branches will suspend over the edge of the streamís surface and provide shade and cover for resident stream trout.

††† A major influence in this end result is winter snow falls. When a heavy snow falls on the newly planted willow plants, the weight of the snow helps droop the limbs down towards the surface of the stream. A wet, heavy snow is the best type of snowfall to get this job done.

††† If the snow happens when the branches are long and thin, the better the end result. Once the heavy snow melts away, some of the branches remain bent over, more so than prior to the snow fall. This causes the limbs to grow out over the stream channel.

††† As the limbs continue to grow, their weight insures that they stay suspended over the water and also extend towards the centre of the creek. Eventually, some limbs will die off and stay intact along the edge of the stream bank. Some will be forced down into the water, below the surface of the stream.

††† This is all good for resident trout though, they utilize all of the woody debris and live branches as habitat. The dense growth along the stream bank, both above the surface and below, will help to constrict the flow in the channel. Stream flow construction helps increase velocity and this in turn, cleans silt from the bottom of the stream channel.

††† The added live and dead branches, below the surface, create or enhance the aquatic invertebrate habitat, which means more food for the streamís resident trout.

Above: This heavy-wet snowfall has caused the planted willows to droop down over the stream channel. This has also caused a constriction of flow in the stream channel. This will benefit the streamís resident trout population.

Below: These planted willows were influenced by winter snows, causing then to hang out and over the stream channel. This type of growth along the edge of the stream is very beneficial for trout and aquatic invertebrates.

Canary Grass And Willows-Great Overhead Cover

††† Presently, there is an abundance of Canary Grass on Bighill Creek. Of all of the local wetland grasses, Canary grass is the most valuable for providing great overhead cover and shade along our small area streams.

††† This grass, combined with a good crop of native willows along the waterís edge, is doing a wonderful job of keeping streams like Bighill Creek flowing narrow and deep. The deeper sections of the creek are those that are of low gradient, where beaver dams once existed and they will again over time.

††† The depth along the long low gradient reaches is a result of good channel flow constriction. The dense willow growth and canary grass provides good root stability and growth below the surface of the stream tightens the flow cross section and increases velocity.

††† Every fall, when the canary grass relaxes down onto the waterís surface, it creates a floating matt of dead grass. This accentuates the undercut stream banks and provides optimal overhead cover for the streamís resident trout population.

††† I have observed numerous aquatic invertebrates that utilize the dead canary grass as a submerged, suspended habitat. Canary grass is full of insect life when it is alive and growing, so the grass provides a good supply of trout food, year round. Over time, the growth of canary grass will contribute to a narrowing of the stream channel, which is always good for the health of a trout stream.

††† Combined with a good crop of native willows, canary grass provides the best stream bank trout habitat that a small creek like Bighill Creek could have.

Above: Midge larva like to attach themselves to small diameter twigs or canary grass stems, below the water.

 

Left: Canary grass laid down along the stream bank on Bighill creek.

Trout Redds-Trout Egg Nests

††† You may have heard the term trout redd before. It is what fisheries biologists use to describe trout nests constructed in the gravel of a streambed. It is where trout lay, fertelize and bury their eggs during spawning.

††† Once you know what to look for, they can be relatively easy to spot in the shallows of a streambed. The gravel is cleaned by the fanning of the female trout, when excavating the redd and when covering the eggs.

Right photo:

The clean gravel shows where a pair of trout have spawned. The small cluster of larger rocks at the upstream side of the redd showsthe last place that the female trout fanned. It is in the larger stones that the trout lays her eggs, before covering them with smaller gravel.