Download Turner Sasina Research Paper Draft Env340A BROOK TROUT

Turner Sasina
Research Paper Draft
Env340A
BROOK TROUT CHALLENGES IN THE FACE OF CLIMATE CHANGE
Introduction
Brook trout (Salvelinus fontinalis) a species that - along with other types of cold water
species support a 1.4 - 14 billion dollar industry in the United States (O’Neal 2002). Due to this
profitable industry, brook trout and other trout species are of large concern with projected
temperature changes attributed to climate change. Global warming along with other types of
anthropogenic forces are causing a grim picture to be painted for brook trout. This future
scenario includes habitat loss of 20 to 40% along with pressures of invasive species, the
dramatic effects of temperature however new management practices along with present
practices could help mitigate the effects on brook trout.
Physiological Effects of Temperature
To most this may not be surprising to hear that there is great habitat loss for a species
or many species in the face of global climate change. But even then the habitat that is left may
only be tolerable for the species in question and under these stressed conditions it will reduce
the health of the species. The effects on the species virtually affect the every aspect of the
fish’s ability to maintain homeostasis resulting in higher metabolism due to their exothermic
nature as mentioned. It has been shown to reduce the growth rate of fish, excretion, SDA and
egestion as shown in (Figure1) (Ficke et al 2007).
(Figure 1.) Effect of temperature on
a yellow perch respiration (R),
growth (B), excretion (U), egestion
(F) and Specific Dynamic Action
(SDA) such as food digestion and
processing (from Ficke et al 2007).
The effect of temperature on all of these aspects can be noted in the figure that there is a sharp
decline after an optimum temperature and ultimately death of the fish. One aspect that is
inversely effected by the rising temperatures is the respiration rate and this again is based off o
the fact that fish are exothermic so as it warms their metabolism increases so the need to
respire increasingly. This increased respiration also causes strain on the fish due to the less
oxygen available in the water. The oxygen levels in warmer water is always less than that of
cooler water and with the increased respiration and less oxygen this will undoubtedly cause
stress on the fish in the suboptimal environments (Ficke et al 2007). The result of the higher
metabolism of the fish effected by higher temperatures would also require more food energy to
maintain themselves and were food is readily available this would ultimately led to starvation
for the fish typically in temperate regions. Though it has been shown that the increase
temperatures for some fish species with food in abundance it can lead to increase growth but
even in such cases there is always a threshold. With that said with the increasing temperatures
it is possible that some fish stocks in certain areas could have increased productivity, areas that
are restricted by a very short growing season may have it extended slightly (Ficke et al 2007).
However again the keyword is slightly and if increasing temperatures continue it will eventually
be a detriment. This aspect of seasonality from climate change on brook trout and other cold
water fish include the will effect reproduction. It is possible that the changes in seasons either
the extending of one season or the harshness of one may prove to be an issue. That regular
flooding can cause harm to cold water fish fry and eggs. It could also be that the mild winters
can cause fish eggs of brook trout and other cold water species to hatch prematurely causing
high mortality (Isaak et al 2012). It could also be that flow regimes could change that may affect
certain trout species more than others specifically brook trout would be negatively affected by
increasing winter flows (Wenger et al 2011). This mortality may allow new species to move in
more easily this species usually referred to as invasive. A specific example of these can be
observed in that in some streams char often spawn in the fall while rainbow trout spawn in the
spring and often superimposition the char’s nest increasing mortality (Rahel et al 2008). Other
examples that may pose a problem for brook trout is the brown trout is that they have a an
overlap during their spawning causing unwanted hybrids, Tiger Trout that like most hybrids are
sterile (Cucherousset et al 2008).
Habitat Preference and Loss
In general brook trout prefer colder water temperatures that are found in mountain
streams that are rocky, well-shaded, well oxygenated, and clean and clear (National Park
Service 2014). Book trout tend to prefer water temperatures of around 20 Celsius in the
warmest of months (National Park Service 2014)
Brook trout are sensitive to temperature effects because they are exothermic in
contrast to endothermic (e.g., mammals).Therefore these types of fish have a narrow tolerance
in temperature (Ficke et al. 2007). There seem to have been a few large studies done on this
effect of air temperature and the effects of water temperature as a result of the increasing air
temperature, one such study took a look at over 1700 U.S Geological stream survey stations to
use them to gather temperature data, with the data they looked at the tolerance of the brook
trout and 57 species and compared there temperature tolerances of each species and looked
at what stations stream would be unsuitable, concluding 54.8% habitat reduction for brook
trout (Eaton et al 1996). Another large scale study done on climatic change in regard to cold
water species also showed a great amount of habitat loss and even specified approximate
amounts of habitat loss in the next 100 years, beginning about 2040 at about 15% to 20% and
ending with a projection of about 40% in the year 2090 for brook trout (O’Neil 2002). Other
studies that seemed to follow the same sort of monitoring seemed to all indicate a general rise
in temperature such as one that looked at streams that were managed or unmanaged at the
time all showing an increase in temperature (Isaak et al 2012). A smaller scale study with more
of a in the field approach as in taking the measurements themselves with their own
instruments also seemed to convey the same information, rising temperatures (Trumbo et al
2010). So it can been seen that through these various different studies that went about
assessing the same issue they all arrived at the same conclusion that habitat loss seems certain.
Though the figures may have some fluctuation some as high as 50% habitat loss and the other
somewhat lower it seems to illustrate that even through different methods or models it seems
to still point to a loss of habitat. This can be illustrated in (Figure 2) in that it represents the
habitat loss of in thousands of kilometers under the analysis of several climate models (Wenger
et al. 2011). It can be seen that all of these models represent a decline in habitat in the years to
come in particular ranging from roughly 100,000km to 20,000km for brook trout habitat again
pending on the climate model.
(Figure 2). Habitat loss
(length of habitat in 1000s
of km) using various climate
models indicated in
different colors on an
extended time scale ranging
from 2040 represented on
the left to 2080 represented
on the right in the
histograms. Used with
permission (Wenger 2011)
Effects of Invasive Species
The effect of global warming on the habitat and the loss for brook trout and cold water
species like it opens up an opportunity that allows new species to come in. These invasives that
often move in to the areas do so because they tend to be more adapted to the present
conditions. An example of this is between two cold water species that the rainbow trout could
outperform the brook trout in the warming conditions (Rahel et al 2008). Some of the irony in
this is that the brook trout may be endangered from climate change but it to is also
endangering species itself. In the western United States brook trout were introduced and are
actually considered an invasive species and outcompete native cutthroat trout (Rahel et al
2008). In the brook trout’s native range it is considered but across the same country it is acting
as an invasive pressuring other salminoids. These fish even being closely related seem to
reiterate how a difference in temperature tolerance can make the difference on a species
ability to compete. This competition often driving one species to new territory in order to avoid
competition and in (Figure 3) illustrates these kinds of pressures.
(Figure 3) –
Illustrates the
change in
distribution of a
species in the
presence of climate
change (b)
representing any
species being out
competed by a
species represented
by (a).
The effect of invasives not only through competition of food sources or reproduction nest as
mentioned earlier but the direct predation on the species will also greatly effect native
populations. In a study of the Columbian River it is estimated that between the two invasive
species of small mouth bass and walleye it could have a potential increase in salmonid
consumption of 4% to 6% per capita (Rahel et al 2008). Other aspects of warming climate are
often the spread of disease or the appearance of a new disease in populations. These diseases
only adding to the stress in the often suboptimal environment also encouraging the spread of
disease. One example of this is from a disease causing protozoan that causes whirling disease
that destroys cartilage in young fish, this disease like others is temperature dependent (Rahel
2008). In a study done to determine the effects of whirling disease an experimental infection of
the disease resulting in a rate of mortality in juvenile fish of 89%. It would seem that through
the events of the changing habitat it is easy to see that species encroaching on another’s
habitat just one of many problems species face in the future of global warming. That each of
these problems seems to compound on each other and ultimately may drive some species to go
locally or even globally extinct. It seems to be a very bleak future for the fish that depend on
these cold to temperate waters.
Management
Often these temperate or cool waters often are altered by human activity through
agriculture, logging, urbanization and mining (Siitari et al. 2011). Researchers created a model
to take a look at different habitats and to determine if the habitat is suitable for brook trout
depending on area in the watershed. The model looked at 5 core contributors to what
determined suitable habitat but the two that seemed to have the most effect was forest cover
as a positive to brook trout populations and agriculture as a negative (Siitari et al. 2011). The
other core contributors included road density, mixed forest stands in the corridor and sulfate
and nitrate in the watershed. It was generally shown that his model was accurate but
something that came up that did not predict for was ground water discharge that provided cold
clean water. It was shown even areas that were predominantly agriculture in the watershed
was still able to support brook trout populations. Perhaps looking at these areas with great
ground water discharge could serve as a sanctuary for brook trout and other trout species.
That these areas could perhaps serve as preserves for brook trout and could be improved upon
in cases were the surrounding watershed is mostly agriculture.
Some of these improvements could be to either preserve riparian forests or the
planting of new riparian forests that will help shade the water body (Rahel et al 2008). An
organization called the Eastern Brook Trout Joint Venture often implicates stratagies as
mentioned. The EBTJV also tries to relocate brook trout to previously lossed habitat and do try
to improve upon the habitat in other ways of decreasing habitat fragmentation. Other studies
have suggested the use of cold water storage to help alleviate high temperatures in rivers (Isaak
et al 2012).As mentioned in forest cover in the general area of the water shed has been shown
to positively correlate to brook trout populations (Siitari et al. 2011). Another issue with brook
trout and this could eventually be a problem for the suggested sanctuary is in the face of ever
increasing temperatures the ability of the brook trout to migrate may prove invaluable, the
problem of temperature rising and conservation seems to be lacking in the EBTJV plans to help
brook trout in their native range. Habitat fragmentation is a major obstacle to this and is often
related to road densities as was looked at in the model for the watersheds. Roads often cut off
streams preventing brook trout the opportunity to move from a less suitable thermal habitat to
another. One way to prevent this is to use culverts that have been placed so that they do not
alter flow and still allow a passage. In a recent study looking at the Cheat River basin in West
Virginian surveyed 120 culverts only 3 were completely passable, 34 partially and 83 were
completely impassable (Poplar-Jeffers et al. 2009). From an undisclosed source there are over
five million culverts in the United States which could lead one to think this could be a major
contributor to decline in brook trout. Another effect of having culverts is that during floods it
could potentially push fish from existing habitat and if the culvert or whatever is restricting
movement could increase habitat loss (Roghair et al 2002).
Other suggestions to help preserve species of concern is through assisted migration or
the act of physically intervening by moving the species to a new habit that is now suitable from
climate change (Rahel et al 2008). Assisted migration may save a species but it could potential
cause the same sort of problems for the species in the new environment. The act of moving an
organism in that fashion could also transmit diseases to a new error that could have unforeseen
consequences. Rahel et al (2008) also suggest a more active approach that seems to create in
streams an active management to put of some kind of barrier that excludes invasive. It also
incorporates assisted migration with habitat manipulation an almost holistic approach to
management. It also includes the facilitation of migration by the target species that can be
seen in (Figure 4).
(Figure 4) – The difference between
a passive management strategy on
the left and an active approach on
the right.
Conclusion
In the face of rapid global warming it is without a doubt that brook trout and others in
the family Salmonidea will have great challenge to survive. The challenges being mentioned
earlier from habitat loss the physiological effects in the less ideal habitats, the competition from
invasive species from habitat shifts, and the changing of the seasonality that so many
Salmonidea species seem to be in tune to. That it could come down to ultimately changing the
way human activities are conducted in order to preserve these species. It may also take a more
expensive active manage approach as suggested by Rahel et al (2008). It seems that only
through a multi approach solution could help minimize trout habitat loss and preserve what is
left. The implications of climate change do not seem to have been addressed in the
conservation of the brook trout and more than likely many other species. The lack of research
in new ways to help conserve species of interest is going to be very important in the coming
years of climate change, to make a conservation plan that does not take this into account could
would be disastrous. The need to develop a more dynamic approach to addressing the issue of
conservation in the presence of climate change has to be made, for future success in
conservation. With a static approach to conservation it seems doomed to fail in a new era of
species native ranges fluctuating, making isolated preserves for species of concern more a trap
then a sanctuary. So in the end with respect to brook trout and other cold water species great
changes will lead to great challenges to preserve these creatures.
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