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Distribution of Brook Trout in Eastern North America

Started by Dank, November 03, 2008, 11:38:28 AM

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Helo all,
Like everyone here I have a love for trout fishing but I am particularly fond of Brook Trout. My interest in the species led me to write a paper on the fish for a Biogeography class Im taking as part of my BA in Geography. The paper attempts to explain the current Eastern North American range of the Brook Trout. I encourage anyone interested in the fish or trout science to take a look at the paper and leave some feedback. Any advice or criticism would be greatly appreciated. Thanks,

Distribution of Brook Trout in Eastern North America

Salvelinus Fontinalis commonly known as the Brook Trout is a species of char belonging to the genus Salvelinus. The word Salvelinus is latin in origin and means coming from a spring. The family of fish referred to as Salmonidae includes salmons, trouts, freshwater whitefishes, graylings, and chars including the Brook Trout. Commonly mistaken for a trout the Brook Trout is actually a char along with other species such as the Dolly Varden, Lake Trout, and Arctic Char. In many regions Brook Trout are known as speckled trout or specks due to the marble patterned vermiculations found along the side of the fish and the distinctive red dots surrounded by halos. Male Brook Trout are know to display brilliant red and yellow colors on their bellies when spawning.  The Brook Trout is highly valued as a sport fish particularly by fly fishermen and is know to only be found in the most pristine cool water with a variety of aquatic and insect life forms. The species is so popular in the United States that it is the state fish for New Hampshire, Michigan, Virginia, New Jersey, New York, North Carolina, West Virginia, and Pennsylvania. Brook Trout are native to spring fed ponds, creeks, streams, and lakes.

Although the Brook Trout can be found in many areas of the world, the populations this paper will be focusing on are found in the Eastern United States. This population historically extended south along the crest of the Appalachian Mountains to North East Georgia and in the Northern reaches extended through the Eastern part of Canada to the Arctic Circle. Western limits included Manitoba and the Great Lakes region. Throughout this range Brook Trout persist through a variety of climate types including polar, snowy, and mild humid from north to south. Key attributes of the range areas are moderate levels of precipitation and water temperatures between 0 and 20 degrees Celsius, the upper and lower survivable temperature limits for Brook Trout. Brook Trout can be separated into two basic ecological forms, a small form living three to four years found in small cold streams and lakes, and a larger form living eight to ten years associated with large lakes, rivers, and estuaries. New England and the Great Lakes region mark the northern limit of the smaller form with the larger form occupying the range north of this boundary. The largest recorded specimen weighed fifteen pounds but most fish, particularly the southern form, are in the one to two pound size range. While most Brook Trout live and spawn in freshwater some anadromous populations migrate to the sea to spawn and most often are the larger northern form. These specimens are usually larger and more predacious in nature in addition to having a silver appearance from exposure to salinity. (HIS 24) Within the Brook Trouts North American range there exist several other species of fish with similar ecosystem tolerances and requirements. These species are often found in the same waters as Brook Trout and are considered competitors. The most common of these competing species are the Small Mouth Bass, Brown Trout, and Rainbow Trout.

This historic Pre-European range once accounted for approximately 70% of the total distribution of Brook Trout throughout the United Sates. In this pre-industrialized North America the only factors influencing this distribution of Brook Trout were the forces of the natural world. Population increase and an array of anthropogenic influences have completely wiped out 20% of this original eastern range. The remaining range area has been severely degraded and fragmented, many populations being relegated to headwater streams where conditions are still suitable.(roadmap) This paper will focus on the natural influences, which bind the Brook Trout to this particular part of the world and also attempt to explain the reduction in the distribution of fish in this area as a result of anthropogenic influences. Often times human activity can have unforeseen effects on the local ecosystems. This paper will investigate some of the prominent anthropogenic influences, which are diminishing fish populations across this range. To begin however it is important to have an understanding of the habitats and conditions Brook Trout are found in.

Considering all of the species in the Salvelinus genus, the Brook Trout are the most generalized and adaptable. The species has been introduced to countries worldwide. Brook Trout have proven so prolific as an introduced species they threaten to replace or out compete many organisms including fish and amphibians in their introduced range.  Ideal habitat conditions include a cold temperate climate, cool spring fed ground water, and moderate precipitation. Optimal riverine habitat is characterized by a silt free rocky substrate in riffle-run (shallow) areas, an even ratio of riffles and pools, which provide areas of slow deep water, well vegetated stream banks, abundant instream cover, and relatively stable water flow, temperature regimes, and stream banks. Optimal lacustrine habitats include clear cold lakes and ponds, which are usually oligotrophic. Water chemistry is also a crucial factor in determining the range of Brook Trout. Water temperature is considered the most important limiting factor for the Brook Trout. Optimum water temperatures are around 14 degrees Celsius, however they can tolerate temperatures as warm as 20 degrees Celsius and as cold as 0 degrees Celsius. Stream temperatures have a huge influence on the southern and northern limits of the Brook Trout's range. In the southern reaches of the range hot summer days bring stream temperatures above 20 degrees Celsius and limit the Brook Trout from inhabiting waters south of Northern Georgia. In the north freezing stream temperatures below 0 degrees Celsius limit the fish. Brook Trout also require high levels of dissolved oxygen as low as 0.9 ppm and as high as 1.8 ppm. Compared to Brown Trout and Rainbow Trout, Brook Trout are tolerant to a wider range of pH. Brook Trout are tolerant to a pH of 4.0-9.5, however optimal pH lies between 6.5-8. (Hsi)
Brook Trout are opportunistic sight feeders, and as a result require clear water with low levels of turbidity to locate food. The species is euryphagous and adaptable to many new food sources. In the proposed eastern North American range they feed on a wide variety of bottom dwelling and drifting aquatic macroinvertebrates and terrestrial insects. Fish are also an important food source particularly for the larger northern form. (Hsi) Streamside vegetation is recognized as a crucial part of any trout stream habitat but plays an especially vital role in the Brook Trouts stream ecosystem. In addition to providing a variety of terrestrial food forms to the fish it also provides additional habitat cover in the form of debris and logs, which fall into the stream. Streamside vegetation also provides important shade, which can relieve Brook Trout from high summer temperatures. Shade levels of 50 to 75% during the midday are considered ideal for small trout streams. In the southern reaches of the Brook Trouts range this natural source of shade in addition to deep pools, undercut banks, and instream vegetation and debris is what keeps the fish alive during the hottest of summer days. (hsi) Presence of streamside vegetation is an indicator of ecosystem productivity, is closely tied to the success of Brook Trout populations, and can allow the fish to survive warm days, which may have been unbearable without this vital source of shade. Another useful aspect of streamside vegetation is its use as a filter to particulate matter, which can lead to stream sedimentation. Sedimentation in streams is known to degrade Brook Trout spawning substrate and reduce macroinvertebrate habitat, which can reduce fish populations. Streams with greater amounts of streamside vegetation are less susceptible to sedimentation from fine particles. This vegetation also helps to control bank erosion and maintain the undercut nature of these banks.

Having an understanding of the conditions and habitat types favored by the Brook Trout will allow for a better understanding of the effect some anthropogenic influences can have. Humans have managed to adversely effect almost every condition listed above as favorable to the Brook Trout. We have altered temperatures throughout the region in multiple ways, changed the pH of many habitat areas, reduced streamside vegetation, increased sediments and other pollutants in many streams, overdeveloped many of the watersheds, altered stream flow, and increased population fragmentation. Understanding the various ways humans influence the Brook Trout will help to explain the current diminishing distribution.

Global climate change as a result of greenhouse gas emissions threatens to influence almost every organism on the planet if action is not taken to stop contributing to this problem. As stated above water temperature is the most important limiting factor in determining the Brook Trout's Range. Various Global Circulation Models predict temperature increases of 2 to 5 degrees Celsius over the next hundred years in this region. Such a change in temperatures could greatly effect the distribution of Brook Trout. In the southern reaches of the Brook Trout's range this temperature increase would force fish to higher latitudes and elevations in search of appropriate water temperatures during the hot summer months. Many populations would be forced to isolate themselves on islands at the top of mountains. Small fragmented populations of fish are at a greater risk for local extinction. This temperature change would increase population fragmentation and eliminate many of the southern populations of Brook Trout. In the northern reaches of the Brook Trout's range an increase in temperatures could prove beneficial to the distribution of this fish. This increase in stream temperatures could allow the Brook Trout to survive the coldest of months in streams where the temperatures may have historically been too cold to support fish populations. (flebbe) Climate change is also predicted to effect precipitation in ways that aren't completely understood. This could affect stream flow, which is another important aspect of Brook Trout habitat.

The release of sulfur dioxide and nitrogen oxides into the atmosphere from anthropogenic sources such as power plants and automobiles has led to an increase in acid precipitation over the past hundred years. This acidic rainwater has lowered the pH of many Brook Trout habitats to levels, which are lethal to the fish and many other organisms. Acid mine drainage has also contributed to the acidification of these streams. Streams located in watersheds that harbor abandoned or active mines, often coal or metal mines, are subject to acidification from acidic pollutant laden runoff. Appalachian coal producing states such as Pennsylvania and the Virginias have seen more severe acidification of their streams. The effects of acidification from these anthropogenic sources can be devastating for Brook Trout and the ecosystems they occupy.
Also detrimental to Brook Trout populations across the entire range, especially the southern areas, has been the introduction of farm related pollutants such as pesticides, herbicides, and fertilizers. These chemicals are applied to plants and grounds and are subsequently accumulated in storm water runoff which runs downhill to the nearby stream or river. Brook Trout habitat in watersheds containing farms are subject to contamination from these pollutants through runoff. These chemicals have severely degraded the water quality of many Brook Trout habitats throughout the range leaving many streams uninhabitable.
Logging and urbanization over the past hundred years across the entire range has led to reduced streamside and watershed vegetation and degraded Brook Trout habitats.(selection logging Michigan) Logging practices such as clear cutting and even the more benign selection logging reduce streamside and watershed vegetation. This vegetation plays a vital role as a source of shade, stabilization for the stream banks, cover in the form of in stream debris, habitat for terrestrial insects and other food sources, and filtration for fine particles, sediments, and runoff. Development in many watersheds has led to increased stream temperatures and degraded water quality. This can be attributed to less vegetation, more paved grounds, and the pollutants associated with developed areas. As storm water runoff travels over these paved developed areas it takes on a warmer temperature and any pollutants in the area. This runoff is then drained into the local river or stream leading to increased water temperatures and degraded water quality. Constant logging and land development across the entire range has led to extinction or degradation of many Brook Trout populations.

The introduction of nonnative and hatchery reared species over the past hundred years into native Brook Trout populations has also be detrimental to fish across the entire range. Brook Trout are known to be very adaptable and in many cases have displaced native species in areas where they have been introduced. Ironically Brook Trout are also being displaced by non-native species being introduced into their native eastern range. Common competing species in the eastern North American range include Rainbow Trout (often hatchery reared and stocked in streams for recreational fishing), Brown Trout, and Small Mouth Bass. In its early stages of life, Brook Trout are especially vulnerable to predation from these competing fish. Other issues associated with introduced species include genetic alteration due to interbreeding, introduction of disease, displacement, and degraded Brook Trout populations due to competition for limited resources. Often times when a non native species is introduced the native Brook Trout are out competed and forced to migrate upstream into shallow headwaters where they can carve out there own niches. Overall this leads to further fragmentation and degradation of Brook Trout populations and habitats.

Another harmful anthropogenic practice is the construction of dams and culverts, channelization, and other flood control techniques. Often times these practices fragment fish populations and prevent fish from migrating to more comfortable temperatures throughout the year. Flood control techniques can also modify stream flow, which is an important part of a healthy Brook Trout ecosystem. These perturbations occur throughout the entire range, particularly near more developed areas with greater needs for flood control.

In its eastern North American range the Brook Trout historically has been restricted to certain areas by critical natural influences such as temperature and abundance of streamside vegetation. Prior to the industrial revolution the Brook Trout was able to inhabit most any stream or river as long as water temperatures were in the range of 0 to 20 degrees Celsius and there existed a variety of aquatic and terrestrial organisms. Today the effects of the industrial revolution and rapid population growth have made inhabitable waters much more scarce. Now such factors as pH, sedimentation, temperatures, diminished vegetation, competing species, migration barriers and pollution are reducing the amount of suitable habitat and working against this valued species. Human influence has led to the alteration of every one of these variables. As a result the historic range of Brook Trout in this region has been reduced by 20 percent. Brook Trout still exist in every state occupied by the original range and are not yet considered threatened or endangered. However the remaining distribution of Brook Trout in this region is considered severely degraded from what it previously was. In order to maintain the native distribution of this highly valued species people must work to preserve the remaining viable populations while attempting to restore degraded and lost populations by mitigating the anthropogenic influence in these areas.


It's a pretty good read, I wouldn't change anything. You covered all the high level points.

Turn it in, you should get a good grade.

The object of life is not to be on the side of the majority, but to escape finding oneself in the ranks of the insane.


Good job overall.  But I would definately say that the hemlock wooly adelgid is a much greater threat to brook trout than global warming.


Woolly Bugger

ex - I'm not going to live with you through one more fishing season!

me -There's a season?

Pastor explains icons to my son: you know like the fish symbol on the back of cars.

My son: My dad has two fish on his car and they're both trout!


November 03, 2008, 19:34:41 PM #4 Last Edit: November 04, 2008, 07:17:06 AM by Oldman

Nice paper. Just 5 suggestions.

1 Work on you intoduction paragragh. Be a little more specific. State exactly what it is you want to discuss.

2  Brooks known as "specks" are only know as that in the southern Appilacians and only to old timers. Not that it is important to your paper, but remember this, Who is your audience? (Hillbilly Joe or Professor John)

3  Most brooks in the Southern Apps are far less than 1 lb. Not 1 to 2 lbs. Also, that section should be more wordy (elaborate).

4 You mentioned stream flow.You need to explain what that is. Again, Who is you audience?

5 You could use some examples for clear cutting and logging. One comes to mind. GSMNP. I am sure that there are many more.

Lets us know what kinda grade we make.


DAMN! Nice 1st post...I think. I was readin and I got tired and took a nap, woke and started readin again...got hungry, went and ate, started readin again. I think I'm on chapter 11. Has anyone finished this yet? How'd it end? Did the butler do it? Will there be a sequal? Dont let us mess with you, you have to have a very thick skin here!

"Lead, follow or get the hell out of the way" GEN George S. Patton, 3rd Armor Commander


Thanks for all of the comments everyone. Can anyone think of any issues that I failed to mention? I live in Florida so I am a little removed from all of the latest issues effecting Brook Trout. Thanks again