Common Name Brook Trout
Scientific Name Salvelinus fontinalis
Other Names Speckled Trout, brookie, square-tail, spec
General Appearance: Brook Trout are dark, olive-green on the back. The sides are lighter, with many pale spots and smaller red dots surrounded by bluish halos. The belly is white, and the reddish fins have creamy-white leading ledges. The tail is almost square with little or no fork.back to top
Size: The average Brook Trout in Algonquin Park measures between 30 and 38 centimetres in length. The largest Brook Trout in Algonquin Park rarely grow over 50 centimeters.
Migration: Brook Trout are year round residents of Algonquin Park lakes and rivers and as adults do not migrate from one water body to another. Young Brook Trout are known to take refuge in small creeks and streams that empty into a lake, mainly to avoid large predators that live out in the deeper waters. Adult Brook Trout do utilize different sections of a lake depending upon the season. In winter, Algonquin Park waters are a uniform 4 degrees C, allowing Brook Trout to reside in all sections of a lake. At other times of the year, Brook Trout will move into the middle section of the lake, where temperature and oxygen levels are more suitable.
Learn more about Algonquin Park's lakes and rivers.
Food Sources: Brook Trout are carnivores that feed on a wide range of organisms. These include terrestrial and aquatic insects, worms, leeches, crustaceans, spiders, mollusks, small fishes, salamanders, and even frogs.
Did you know?
- The Algonquin highlands contain over 1500 lakes with at least 230 of these lakes containing native Brook Trout populations. Thus, Algonquin Park contains the greatest concentration of Brook Trout lakes and streams in the world!
- Many anglers come to Algonquin Park each year to try to catch a trophy Brook Trout or Lake Trout. Two of the reasons Algonquin Park is so popular with anglers is because of the outstanding trout fishery, and the easy access from urban areas just south and east of Algonquin Park.
Breeding: Even when a lake has the right food and physical conditions for the survival of Brook Trout, there is no guarantee that they will be able to live in the lake permanently. Brook Trout have very specific requirements for spawning locations. Brook Trout spawning areas are typically gravelly or sandy areas of the lake bottom usually only in several metres of water. But the most important environmental characteristic is an underwater spring or, area with upwelling water coming through the sand or gravel.back to top
Many lakes in Algonquin Park have lots of shallow, sandy, or gravelly areas which look like good Brook Trout spawning sites, but many of these lakes lack a reproducing population of trout since there is no upwelling of water.
The deposition of the female's eggs in these areas helps to ensure the next generation of Brook Trout. Larger, more experienced spawners, will dig a depression with their tail and deposit, and then cover over, their eggs with gravel and sand. This covering of the eggs helps to protect them from predators, chemical shock (e.g. from acid rain), and allows a constant flow of water over the eggs from the upwelling.
Research Habitat: Brook Trout live in cold-water lakes and rivers throughout much of eastern North America, from Newfoundland and Labrador, west to the Ontario-Manitoba border, north to Hudson's Bay and south to the northern United States.
Algonquin Provincial Park has the highest density of Brook Trout lakes anywhere in the world. This is due to Algonquin's unique geography.
The last glacier to cover the Algonquin area melted back 10,000 years ago. The cold melt-waters, which flowed across the Algonquin highlands, were only suitable for colonization by cold-water fish species such as Brook Trout and Lake Trout. As well, the Algonquin area sits on a "dome", which means it is higher in elevation than the surrounding area. This makes Algonquin Park the headwater for five major river systems, which flow out of the Park. This higher elevation, past colder water conditions, and natural barriers, such as waterfalls and rapids, has prevented other fish species, such as bass and pike, from moving upstream to inhabit Algonquin Park waters.
The cold-water lakes and rivers left behind after the last glacier melted in Algonquin Park were ideal for habitation by Brook Trout and Lake Trout. As a result, Algonquin Park has many naturally sustaining Brook Trout lakes. Brook Trout are not found in Algonquin Park's warm water environments, such as shallow ponds, or in waters with high acidity such as spruce bogs.
As waters warm in May and June, Brook Trout retreat to the transition zone in the middle section of the lake. This area is often called "trout water" as it has the necessary conditions for Brook Trout to reside. Brook Trout prefer water temperatures which are below 20 degrees C otherwise they are subject to considerable stress. This prevents them from staying in the upper part of a lake during the summer, although they will come to the surface for short intervals to feed. They also need water which has at least five parts per million (ppm) of dissolved oxygen. In some lakes, there is an ample supply of cool, oxygen-rich water throughout the year. However, by late summer, the lower layers of some lakes have little oxygen left, and the upper layers are too warm for Brook Trout. This creates a "temperature-oxygen squeeze" which restricts the Brook Trout to a small layer in the lake between the bottom and the surface. In the fall, when surface waters cool, and oxygen levels improve, Brook Trout can once again return to feed and spawn in shallow areas.
For most Brook Trout Lakes in Algonquin Park the trout water averages about 43% of a lakes total volume and extends from three to twelve metres below the surface.
Learn more about Algonquin Park's lakes and rivers.
Did you know?
back to top
- The introduction of Smallmouth Bass (Micropterus dolomieui) into many of Algonquin Park lakes that bordered the old Ottawa, Arnprior, Parry Sound Railway, eliminated the native Brook Trout where they once thrived. Early Park managers thought they were doing a good thing by introducing this non-native species of game fish into Algonquin Park, but what they did not realize is that Smallmouth Bass will out-compete Brook Trout for the same food sources.
- Humans have illegally introduced Northern Pike (Esox lucius), and Rock Bass (Ambloplites rupestris) into lakes just east of the Highway 60 Corridor of Algonquin Park causing detrimental effects upon native trout populations. To learn more about the impacts of this, and other illegal fish introductions, pick up a copy of The Fishes of Algonquin Provincial Park.
How many Brook Trout live in an AFAU study lake like Dickson Lake?
The question of "how many" is often a difficult question to answer. For species like Moose, one could theoretically observe and count all the species in a given area. But for fish, no visitor or biologist can see all the organisms in a lake at the same time " unless one was to drain the lake (which is not an option in a protected area like Algonquin Park). For Brian Monroe, determining "how many" poses a challenging dilemma, especially on a large water body like Dickson Lake*. "One question in particular that has occupied a great deal of our time is: How many Brook Trout are there in a particular lake, and are their numbers going up or down? Since we can not see or count all the fish directly, we have to use an indirect method to estimate the population size. One approach is to use a mark-recapture method, in which we tag (mark) as many fish as we can, release them, and then look for tagged fish later." says Brian. On Dickson Lake, Brook Trout are captured, measured and tagged during the fall spawning period, then recaptured the next year. The ratio of tagged to untagged fish in the recapture phase can be used to give an estimate of the total number of fish in the lake. The results from estimates suggest that there may not be as many adult Brook Trout in Algonquin Park lakes as many people thought. A typical lake may have only a few hundred adult fish.
One of the formulas used for calculating numbers of adult Brook Trout is the Petersen formula. In its simplest form, it is:
N = M x C / R, where
N = number of adult Brook Trout in the lake at time of tagging (i.e. year one)
(this is the number we are trying to estimate)
M = number of fish tagged and released in year one.
C = number of fish examined in year two
R = number of fish tagged in year one that were recaptured in year two
"In practice, we set a minimum size for tagging in the fall (30 cm) then adjust our count of fish in the recapture phase to account for fish growth. This means that if a 30 cm Brook Trout grew on average 7 cm between time of tagging and recapture, then only fish 37 cm or greater would be included in C in the Petersen formula."
Over the years, estimates of adult Brook Trout on Dickson Lake have been relatively stable, ranging from approximately 700 to 1300 fish.
The formulas for calculating population size are relatively simple, but they only work if certain critical assumptions are met. Unfortunately, the assumptions are not always met, and biologists end up with biases in their estimates.
"We try to identify and account for as many sources of bias as possible, but there is always a degree of uncertainty in our estimates. So it is always better to have several methods of estimating the numbers of fish, and if they agree, we can have some confidence in the results." explains Brian.
One method they are currently developing is a Brook Trout Index Netting (BTIN) protocol. Index netting is another indirect way of estimating the abundance of fish in a lake. Small-mesh gillnets are set for a short time interval, and the captured fish are counted and released. Conventionally, it has been assumed that if the nets are set randomly around the lake, the catch rate in the nets will be proportional to the density of fish in the lake. For the BTIN method, Brian wanted to test this assumption. "To do this, we stocked eleven lakes with a known number of Brook Trout, and then netted each lake a few days later. We compared the catch rate of Brook Trout in our netting program to the densities of Brook Trout in each lake. Densities were calculated by dividing the number of fish stocked in the lake by the volume of water the lake holds. We found that in this study at least, there was a good relationship between BTIN catch rates and Brook Trout densities." explains Brian.
Normally, biologists do not know the numbers of Brook Trout in a lake, so these results give them some confidence that they can apply their BTIN method to known Brook Trout lakes and use the catch rates in their index to estimate Brook Trout densities.
How do researchers accurately estimate the population of fish species in a lake?
Watch a video of capturing, and marking Brook Trout
*Dickson Lake is located just east of Lake Opeongo in a Wilderness Zone in the interior of Algonquin Park. Dickson Lake covers 1000 hectares, has a maximum depth of 18.6 metres, and was named after James Dickson (1834-1926), a Provincial Land Surveyor, who helped to establish Algonquin Provincial Park.
A depth contour map of Dickson Lake.
How many Brook Trout use the main spawning site?
The methods used to estimate numbers of Brook Trout on the spawning site are a variation of those used for determining the population size in the entire lake. Fisheries staff conduct a series of seine hauls on the spawning grounds during the Brook Trout spawning period. After each haul, all fish are tagged, measured and released. Tag numbers of any recaptured fish are recorded. The ratios of tagged to untagged fish are used to estimate total number of Brook Trout on the spawning grounds for that spawning period. When more than two hauls are made, several formulas in addition to the Petersen formula are available for estimating numbers (these are called multiple census methods). Two of the most popular of these are the Schumacher and Schnabel methods. In Dickson Lake, estimates of adult Brook Trout using the main spawning shoal range from 200 to 300.
® Watch video of Brook Trout on the spawning beds.
How many fish can be harvested from Dickson Lake and still maintain a healthy and sustainable fishery?
Catch and harvest data are collected during creel surveys. Fisheries staff interview a sample of anglers, ask what they have caught and released, take length and weights on a sample of their catch, and collect material such as scales and otoliths to determine fish age. The information that is collected is then extrapolated to get estimates for the entire fishing season, or some part of it, e.g. the spring. Some of the statistics that are commonly generated from creel surveys include fishing effort, expressed as rod-hours per hectare of lake surface, catch rates or Catch per Unit of Effort (CUE) as fish caught per hour of fishing, and yield, as total weight of fish harvested per hectare. Typical examples of these statistics from Dickson Lake are 2 to 3 rod-hours per hectare per year for fishing effort, CUEs of 0.2 to 0.3, and annual yields of 0.2 to 0.4 kilograms per hectare. A sustainable harvest is generally expressed in terms of the annual yield that a lake can maintain over a long time period. If the maximum sustainable yield is exceeded, the fish population will decline.
"Estimating maximum sustainable harvest levels is one of the most difficult jobs for a fisheries biologist. Several methods are available, but because they tend to average a lot of variability, they work best when applied to large groups of lakes, and not so good on individual lakes. One method is based on an empirical correlation between fish harvest levels and the morphoedaphic index (MEI). This is calculated as total dissolved solids divided by mean depth, and is a measure of lake productivity. This method gives a value of around 0.67 kilograms per hectare for Dickson Lake."
Another method that fisheries researchers have used to estimate sustainable harvest is based on a computer model called MANSIM (Management Simulation), which was developed by the Ontario Ministry of Natural Resources staff. A "typical" Brook Trout population is set up, and the effects of various management strategies on harvest levels and population size are simulated. When applied to Algonquin Park the model predicted a maximum sustainable yield for this typical population of 0.87 kg./hectare per year.
"All of the methods are approximate, so we generally try to use the more conservative estimate," says Monroe. When harvest levels exceed sustainable levels and a fish population collapses, it can take many years, if ever, to recover. Both of the methods mentioned above suggest that recent harvest levels on Dickson Lake are within sustainable levels.
Did you know?
- Algonquin Park has special fishing regulations to help ensure a sustainable fishery. Two of these regulations include a ban on the use of live bait-fish to help reduce the establishment of exotic fish species, and a ban on ice fishing to reduce the overall fishing pressure in Algonquin Park.
What other questions have arisen from your research?
One question that arose several years ago is whether we can use some form of pattern recognition software to identify individual Brook Trout or Lake Trout. We are currently investigating this possibility with a company in Alaska.
Another question we have started to address is whether data collected for the Ontario Parks reservation system, (especially interior lakes camping permits) can be used to monitor changes in fishing pressure in Algonquin Park's interior. Preliminary analyses suggests this is a promising approach.
Educators: Learn more about Algonquin’s habitats, download readings and worksheets from the Educator Resources section of the Web Site, or you may also learn more through the following publications:
back to top