Matt Weberg
Stream Habitat Management
The Role of Stream Habitat Management in the Rehabilitation of Coaster Brook Trout in
the Lake Superior Basin
Problem Statement
Brook trout (Salvelinus fontinalis) and lake trout (Salvelinus namaycush) are the only indigenous
salmonid species in the Lake Superior basin. Once highly abundant, both species have
experienced dramatic declines since the region’s settlement (Hansen 1994). Coaster brook trout
are described as those that spend part of their lives in Lake Superior, and ultimately return to
their natal streams to spawn (Figure 1). Upon migration to the lake, they prefer near shore
habitats, and protected coves and inlets. Unlike lake trout, which were re-established through
stocking and sea lamprey (Petromyzon marinus) management, coaster brook trout have yet to be
rehabilitated after 50 years of management efforts (Schreiner et al 2008).
By the late nineteenth century, word spread regarding the tremendous brook trout fishing that
could be had in Lake Superior, and its tributaries (Hansen 1994). Coaster stocks were rapidly
depleted due to its habitat preferences, and aggressive nature. This period coincided with the
industrialization of the region. Poor land management, clear-cutting and log drives, along with
installation of dams degraded many of the tributaries beyond recognition. Furthermore, the
invasion of the exotic sea lamprey, and the introduction of brown trout (Salmo trutta) along with
several species of Pacific salmon (Oncorhynchus spp.) likely impacted the coaster brook trout.
Within 50 years, coaster brook trout had been extirpated from most streams and near-shore
regions, with only a small number of remnant populations persisting.
Around 1930, management agencies recognized the rapid decline of coaster brook trout, and
began stocking as a means of re-establishing the coaster populations (Schreiner et al 2008). Not
surprisingly, stocking efforts failed and declines continued. In 1960, agencies from Minnesota,
Wisconsin, Michigan, and Ontario began implementing more restrictive bag limits, which was a
step in the right direction but were not considered restrictive enough. Stocking has remained
prevalent in management plans, with no satisfactory returns on the investment seen to date.
More recent efforts by management agencies appear to finally identify the root of the problem,
degraded stream habitats.
On the surface, habitat improvement seems like a straightforward answer to bringing this
majestic fish back. However, inter-agency and geomorphic differences complicate the issue.
Lake Superior is the largest freshwater lake in the world (by surface area), bordered by Ontario,
as well as Minnesota, Wisconsin, and Michigan. Additionally, the U.S. Fish and Wildlife
Service and several Native American tribes are actively involved in fisheries management on
Lake Superior. While collaboration between agencies exists on this issue, specific rehabilitation
methods, and management plans differ. Nested within this issue are the geomorphic and
ecological differences between regions, which vary greatly within the vast Lake Superior basin.
I propose that a common framework is required to maximize agency collaboration, and provide
unified assessments for use in habitat rehabilitation plans. Regardless of regional differences,
stream functions can be generalized to identify limiting factors in the rehabilitation of coaster
brook trout by investigating the hydrology, hydraulic, geomorphology, physiochemical, and
biological fuctions (Fischenich 2006, Figure 2). By identifying current impediments to stream
functions based on brook trout habitat requirements, rehabilitation efforts can be maximized.
Using this framework provides the ability for inter-agency evaluation of projects to gauge their
success, or failures to ensure rehabilitation moves forward.
Identification of habitat requirements for coaster brook trout
Minimum habitat requirements for stream dwelling brook trout are well described in the
literature (cold, well-oxygenated water). Coaster brook trout though, often exhibit an adfluvial
strategy in the Lake Superior basin and specific in-stream habitat requirements are not fully
understood. Using a telemetry study, Mucha and Mackereth (2008) identified both habitat use
and movement patterns of adult coaster brook trout in Nipigon Bay, Ontario. They found coaster
brook trout utilized shallow, nearshore areas of the lake before beginning migrations into streams
in the late summer, when pool habitats were heavily used until spawning began. Spawning
events occurred in early October with strong site fidelity, indicating the importance of suitable
spawning substrate. Van Grinsven et al. (2012) corroborated this conclusion by identifying
specific spawning sites in the Salmon Trout River, MI were selected due to significant
groundwater flux’s present in the river. Moore (2007) provided the most in depth analysis of
stream habitat usage by coaster brook trout using a watershed and reach scale analysis to identify
important variables for the persistence of brook trout in Lake Superior tributaries. Moore found
that at the reach scale large wood (LWD), low conductivity, shallow depths, a high proportion of
riffles, and steep gradient were habitat requirements for brook trout. Moore also examined
young of the year (YOY) growth rates as a measure of fitness and related them to available
habitat. This study indicated that brook trout require large substrate, low conductivity, and few
competitors to persist (i.e. non-native salmonids). More importantly from a stream assessment
standpoint, Moore defined important watershed scale characteristics as those with little
development, high conifer abundance, few road crossings, greater volumes of standing water
(wetlands). These findings provide the background I will use in developing a stream habitat
assessment framework for coaster brook trout rehabilitation.
Evaluation of current rehabilitation strategies
Minnesota-(MN DNR 2008)
There are 65 tributaries to Lake Superior found in Minnesota, most of which feature cascades,
and barrier falls. While most of these tributaries flow through public or protected lands,
significant habitat degradation has occurred through land-use practices such as mining, logging,
and shoreline development. Limited groundwater supplies (surface water dominated) and
sedimentation caused by said land-use strategies appear to be the main impediments to brook
trout in the Minnesota tributaries. The goal for coaster brook trout stated by the Minnesota
Department of Natural Resources (MN DNR) is to “protect and maintain self-sustaining coaster
stocks in original locations where practical”. The objectives of this goal focus primarily on
habitat protection through watershed management, and more restrictive harvest regulations.
Additionally, this plan cites improvements to road crossings, monitoring of spawning
populations, and potentially identifying methods from creation of artificial upwelling to increase
spawning habitat.
Analysis
The coaster brook trout plan laid out by the MN DNR is highly generalized. They recognize that
impediments exist for brook trout rehabilitation. However, the plan doesn’t mention any
assessment of current stream functions, or identification of limiting factors for coaster brook
trout. Furthermore, they forego any strategy for habitat restoration beyond development of more
spawning habitat despite citing a watershed management initiative. No reference streams were
identified for spawning habitat rehabilitation activities.
Michigan (Wiland et al. 2006, MI DNR 2008)
The upper peninsula of Michigan possesses approximately 33 tributaries that are believed to
have supported coaster brook trout, while Isle Royale and it’s tributaries continues to support a
self-sustaining sub-population. Primary causes of habitat degradation to Michigan tributaries
include logging and mining operations, an impoundments blocking movement. While no formal
rehabilitation plan currently exists for Michigan Tributaries, there are a number of research
projects ongoing which primarily focus on stocking of Lake Superior strain brook trout. Returns
of stocked fish in these tributaries have been for the most part non-existent. The Salmon Trout
River remains a stronghold for coaster brook trout in the Upper Peninsula, however rehabilitation
strategies simply focus on more restrictive harvest limits, and a seasonal closure of the fishery.
In a report supporting the listing of coaster brook trout as endangered species (MI DNR 2008), it
states that future habitat assessments are planned for several tributaries, however no specific
methodology is provided.
Analysis
The Salmon Trout River of Michigan possesses one of the only extant populations of coaster
brook trout found in the United States. While many research projects have been conducted on
this stream, there was no mention of its use as a reference for rehabilitation work in other
Michigan tributaries. It appears that stream assessments are just getting underway in this region,
although no distinct methodology was documented. Of the three states, Michigan is the only one
which appears to be heavily invested in stocking efforts, despite limited returns over several
decades of monitoring.
Wisconsin-(WI DNR 2005)
The geology of the Wisconsin shoreline consists primarily of red clay plain, leading to surface
water dominated streams only able to sustain brook trout populations in the upper reaches above
barrier falls. However, the Bayfield sand plain consists of deep aquifers that provide tributaries
with steady base-flows annually, and high quality brook trout habitat. Clear-cutting, followed
negative impacts by beavers (Castor canadensis) are blamed for the majority of habitat
degradation in Wisconsin tributaries. The goal for coaster brook trout rehabilitation cited by the
Wisconsin Department of Natural Resources (WI DNR) is” the protection and improvement of
brook trout populations for both migratory and stream life history strategies”. Within their plan,
the WI DNR lays out specific strategies for assessing each of the aforementioned stream
functions. While no reference streams are available due to the degree of degradation, their plan
cites the use of historical photography, and records to investigate pre-disturbance conditions to
set rehabilitation goals. Additionally, they plan to develop a list of Best Management Practices
(BMPs) for forestry, agriculture, road construction, and riparian zones.
Analysis
The management plan developed by the WI DNR is by far the most complete, and specific
regarding habitat rehabilitation for coaster brook trout. Unlike rehabilitation plans developed by
other agencies involved, the WI DNR provides a specific framework for assessment at the
watershed scale, and they also provide strategies for ameliorating current impediments. More
importantly, the plan focuses on restoring limiting habitat required throughout the life history of
brook trout.
Ontario-(Newman and Dubois 1996)
The Ontario tributaries of Nipigon Bay, Lake Superior hold the most abundant coaster brook
trout populations currently seen in the basin. Much of this region remains undeveloped or lightly
developed. The greatest threat to brook trout persistence in this region is likely fishing mortality,
and stream habitat degradation due to logging and hydroelectric operations. Being so, the
Ontario Ministry of Natural resources have reduced bag limits and season lengths to mitigate
harvest levels, and through cooperation with Ontario Hydro have developed flow regimes that
protect spawning beds and nursery areas. A Nipigon strain captive brood stock is also being
used to produce fish for stocking within the region.
Analysis
Ontario tributaries of Lake Superior likely have the greatest potential for use as reference
streams. However, they recognize stream degradation remains an issue, warranting habitat
assessment and rehabilitation action. Also, since brook trout remain somewhat abundant, and
have been monitored for a long period of time, there is potential for the detection of changes in
the population size through finer scale habitat rehabilitation.
Federal and Tribal agencies (Wiland et al. 2006)
Federal agencies such as the U.S. Fish and Wildlife Service (USFWS), National Park Service
(NPS), U.S. Forest Service (USFS), and the U.S. Geological Survey (USGS) are all involved to
some degree in coaster brook trout rehabilitation. However, none of these organizations have
completed a stream rehabilitation plan, but more so have participated actively in the planning
stages for projects, and development of native strain brook trout brood stock for stocking in U.S.
waters of Lake Superior. There are four tribal governments involved to some degree in coaster
brook trout rehabilitation including the Bad River, Grand Portage, and Red Cliff Bands of Lake
Superior Chippewa, as well as the Keweenaw Bay Indian Community. I could not find a specific
management for any of these tribes, although they have all been cited as cooperators in past
coaster brook trout rehabilitation efforts.
Analysis
Since none of these organizations appear to have a primary role in stream habitat rehabilitation, it
is tough to say what their actual impact could be beyond providing fish for re-stocking efforts.
While I don’t believe stocking is appropriate, it may have some utility if major rehabilitation of
stream habitat is achieved, and the limiting factor is the presence of brook trout.
A unified framework for coaster brook trout habitat assessment and rehabilitation
Information gathering
Only the WI DNR rehabilitation plan mentioned an information gathering phase, yet with the
large amounts of data now available to managers and researchers this is an important step before
any plan is formed. Critical data useful in understanding the historical status of Lake Superior
tributaries include aerial photography and land surveys, hydrologic, and biological surveys. The
mainstream accessibility of GIS and remote sensing data has greatly increased a manager’s
ability to develop snapshot assessments of watershed and stream condition over time. Use of
GIS analysis along with historical biological data (fisheries surveys, creel data,
macroinvertebrate indices) should allow managers to develop a priority list of streams that
currently or historically accommodated coaster brook, and an understanding of potential impacts
to these streams.
Habitat assessment
Findings by Moore (2007) identified specific habitat parameters important to survival of coaster
brook trout at micro- and macro-habitat scales. Van Grinsven et al. (2012), and Mucha and
Mackareth (2008) also identified spawning substrate requirements of coaster brook trout
necessary for rehabilitation. Therefore, we can focus on these critical parameters at a course
scale when assessing stream functions to identify sources of habitat impediments for
rehabilitation strategies, and potential reference streams (Table 1). Once reference streams are
identified (those that meet all habitat requirements, and possess a viable coaster brook trout
population) benchmarks can be set for each assessment parameter, and stream specific
rehabilitation plans can be developed based around findings from the assessment.
Hydrology
Hydrology relates to the processes involved in transport of water from the watershed to the
stream channel (Fischenich 2006). Based on Moore (2007), brook trout were positively
correlated with high levels of standing water at the watershed scale. Critical parameters to assess
hydrology (and ultimately wetland and riparian functionality) are precipitation to runoff
relationships, percent impervious area, and flow duration.
Hydraulic
Hydraulic stream function is defined as the transport of water in the channel, on the floodplain,
and through the sediments (Fischenich 2006). Hydraulic stream functions are often closely
related to results from hydrologic assessments. Important parameters include bank height ratios
to assess floodplain connectivity, and groundwater to surface water exchange to assess spawning
habitat suitability.
Geomorphology
The greatest number of habitat requirements identified by Moore (2007) fall under the
geomorphology stream function, and therefore may require a significant assessment effort. From
Fischenich (2006), geomorphology is defined as the transport of wood and sediment to create
diverse bed forms and dynamic equilibrium. Based on Moore’s findings critical parameters to
assess include volume of LWD, percent riffle and pool, riparian vegetation density and
composition, sediment composition, and sediment transport capacity. Also, the number of road
crossings should be identified as this variable was an important predictor of brook trout presence.
Physiochemical
Physicochemical conditions required by brook trout are well documented. Limiting parameters
that should be identified include seasonal water temperature and dissolved oxygen levels. Also
Moore (2007) found that conductivity of a stream is important for brook trout survival.
Biology
Changes in the native fish communities of these streams must be addressed to understand the
streams current conditions, and their potential for rehabilitation. Since non-native salmonids
stocked into the Lake Superior basin typically require similar habitats as coaster brook trout, this
parameter can be used as an indicator of a suitable stream. Since competition is likely occurring
between the non-natives and brook trout, abundance of competitors should also be identified.
Also, the WI DNR has identified negative impacts to coaster brook trout by beavers. The density
of beavers along a stream should be assessed to determine if the population is at a level that may
negatively impact brook trout migration, and reproduction.
The next step toward coaster brook trout rehabilitation in Lake Superior
Through my analysis of current management and rehabilitation plans of involved agencies, I
found there are few commonalities when it comes to stream habitat assessment or rehabilitation.
I feel the framework I have presented allows for a unified strategy for determining the current
status of coaster brook trout streams along Lake Superior. This framework also allows agencies
to identify priority areas for stream rehabilitation, making efforts more efficiently focused. For
example, millions of brook trout have been stocked into Lake Superior and its tributaries over the
last 50 years with no observable increases in coaster brook trout populations and no
understanding of why this was the case. Using my framework, agencies can identify
impediments to stream functions in a step by step process of assessment, giving them a true
understanding of rehabilitation required. I also think this framework opens the door to even
greater learning and collaboration between agencies, heightening the chances for coaster brook
trout recovery.
I avoided citing specific techniques for habitat rehabilitation. This is mainly due to the high
variability in geology and accessibility seen throughout the Lake Superior Basin. Similarly,
stream habitat rehabilitation project costs can vary greatly depending on the methodology,
making the choice of techniques likely dependent on funding available. Regardless of the
rehabilitation technique, before and after monitoring must be included in the project design to
allow for greater efficiency and success as more streams are addressed. Additionally, some
variation in specific techniques may be beneficial in distinguishing best management practices,
assuming sufficient monitoring allows for conclusions such as this. Beyond stream rehabilitation
techniques, agencies will likely be faced with difficult fisheries management questions. Nonnative salmonids provide a large source of revenue to both agencies and local economies,
making attempts to extirpate non-natives extremely controversial. However, continued stocking
and management plans in favor of these species may forever prevent coaster brook trout from
making a comeback.
Figure 1.—Example of a coaster brook trout caught in Nipigon Bay, Lake Superior. Coaster
brook trout exhibit an adfluvial life history strategy, and can achieve much larger sizes than that
of stream resident brook trout.
Figure 2.— Example of stream functions assessment framework for coaster brook trout
rehabilitation in Lake Superior, adapted from Fischenich (2006).
Table 1.—List of stream functions used in coaster brook trout stream habitat assessment and
important parameters to assess based on identified habitat requirements.
Stream function
Hydrology
Key parameters for brook trout rehabilitation
Precipitation to runoff relationship
Percent impervious area
Flow duration
Hydraulic
Bank height ratios
Groundwater to surface water exchange
Geomorphology
LWD volume
Percent riffle and pool
Sediment composition
Riparian composition and density
Sediment transport capacity
Number of road crossings
Physiochemical
Conductivity
Dissolved oxygen
Temperature
Biology
Fish community
Abundance of competitors
Beaver impact
Literature Cited
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and brown trout in a laboratory stream, and implications for Great Lakes tributaries.
Transactions of the American Fisheries Society 15:363-381.
Great Lakes Fishery Commission. 2003. A brook trout rehabilitation plan for Lake Superior.
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