8-10-2002
Mark Deleray
Fisheries
Biologist
Montana Fish, Wildlife, & Parks
490 North Meridian Road
Kalispell, MT 59901
Barry Hansen
Fisheries Biologist
Confederated Salish and Kootenai Tribes
P.O. Box 278
Pablo, MT 59855
Dear
Mr. Deleray and Mr. Hansen:
As
you both are aware, the Montana Chapter of the American Fisheries Society
(MCAFS) is an organization of professional fisheries scientists and students
from agencies, universities, and the private sector across Montana. Our objectives are: conservation, development, and wise
utilization of Montana�s fisheries; promotion of the educational, scientific,
and technological development and advancement of all branches of fisheries
science and practice; and exchange and dissemination of knowledge about fish,
fisheries, and related subjects.
The
MCAFS would like to take this opportunity to comment and provide information on
development of criteria for secure population levels for bull trout (Salvelinus
confluentus), a threatened species, and westslope cutthroat trout (Oncorhynchus
clarki lewisi), a species of special concern, in the Flathead Lake and River
system. As mandated by the Flathead
Lake and River Fisheries Co-Management Plan (2000), your agencies are
responsible for establishing secure criteria to ensure that bull trout and
westslope cutthroat trout exhibit all life histories and are unlikely to go
extinct. These criteria will
establish a benchmark for conservation and management for these important native
fishes. We believe that development of secure criteria will be an effective tool
for native trout conservation and management in the Flathead system if this
process is conducted in a conservative fashion based on the best available
scientific information.
The
Native Trout Security Levels for the Flathead Systems proposal is well written
and the report does a good job of reviewing the literature and trying to develop
definitions of �secure� levels for bull trout and cutthroat trout. This is a difficult task because this is a new concept with
little previous work to draw upon. The
three criteria used to define security (population trend, geographic
distribution, and genetic diversity) are logical and defendable goals.
The
MCAFS believes that secure levels are not a goal to achieve and maintain, but
are an absolute minimum for persistence of the population.
We believe that the document should more clearly state that your
agencies� goal for the Flathead System bull trout population is substantially
higher than the �secure� level to insure long-term self-sustainability.
We also believe that how your agencies will determine each of these
secure level factors needs further thought and development.
We
feel the document focuses extensively on reasons for defining 300 bull trout
redds as a secure level and does not provide adequate definition of secure
levels for other population monitoring parameters, or how the various monitoring
parameters will be used in concert to direct management actions.
Management actions that will be implemented or considered need to be
identified and linked to hierarchical benchmarks for each criterion.
We
question whether 300 redds basin-wide is a conservative value that will ensure
the long-term persistence (e.g., genetic variation and resistence to stochastic
events) of bull trout populations in the Flathead Basin.
Rieman and Allendorf (2001) reported that an average of 1,000 adults
spawning annually would be necessary to maintain genetic variation indefinitely
for bull trout populations. Based
on this approach using data previously collected in the Flathead System,
designating 300 redds annually as a secure criterion in the Flathead System
produces a value of 960 adult spawners (300 redds X 3.2 fish/redd).
While this calculation appears logical, using 3.2 fish/redd is
questionable due to the age of the data upon which it is based and trophic
changes that have occurred within the Flathead aquatic ecosystem (Brad Shepard,
personal communication), and comparisons to the ratio of adults to redds in
other bull trout populations. Trophic
conditions and relative species abundance in Flathead Lake have changed
substantially in the past 10-15 years, which justifies suspicion of data that
was collected prior to and during those years.
Mr. Shepard suggested that new, additional research is needed to
accurately update this parameter because the studies are outdated (Block 1955
and 1977-1981; Fraley and Shepard 1989). Additionally,
the original estimate was obtained by trapping in just a few tributaries.
We are pleased to see the initiation of the Development of a Protocol for
Monitoring Trajectories of Bull and Westslope Cutthroat Trout Populations Using
Selected Demographic Parameters Through a Probabilistic Framework.
However, we believe that until the results of this study are available
and can be implemented, a more conservative approach to assessing the bull trout
and westslope cutthroat trout populations should be taken.
In a recent study, Baxter and Westover (2000) reported that there were an
estimated 1.4 to 2.1 bull trout adults per redd in the Wigwam River Drainage,
British Columbia, which is located directly northwest of the North Fork Flathead
River. Using an average of 2
adults/redd, for example, would be a more conservative approach based on recent
data in the same geographic area (1000 spawning individuals/ 2 fish/redd = 500
redds annually). If managers desire
a conservative estimate, we recommend that the lower ratio be used.
We
recommend avoiding the discussion of alternate year spawning, as this discussion
just confuses the issue. Redd
counts are conducted annually, and the intent is to attain at least the secure
level each year. Additionally,
Rieman and Allendorf (2001) assumed that all fish spawn every year when they
made their recommendation of 1,000 adults.
MCAFS
views the secure level of redds annually in the Flathead System as a minimum
level for bull trout. If the
long-term goal of this proposal is to create a higher level of distribution and
abundance for bull trout in order to remove them from the threatened species
list, then accepting the minimal level may be problematic, and will do little to
enhance their status to allow consideration for their removal from the list.
The population dropped to about half this number recently (redd counts
were below this benchmark in five of six years between 1992-1997) and has since
returned to these levels. If the
causes of this decline and rebound are known, they should be presented in the
document, along with any measures that have been implemented to prevent a
recurrence. The population level of
bull trout should be high enough so that in down years, such as 1992-97, the
population does not decrease below the secure level.
Since
the early 1980�s, the overall population trend for bull trout has dramatically
declined in the Flathead System. Examination
of annual redd count data reveals that 300 redds is on the lower end of the
distribution. While there have been
substantial changes to the Flathead ecosystem (e.g., the establishment of Mysis
shrimp and the expansion of the lake trout population), we question whether 300
redds is a conservative value given that the population has declined
significantly from the 1980�s values when the population was stable and
averaged nearly 900 redds basin-wide, is now considered Threatened, and just
recently rebounded to the lower 300 redd threshold. Again, if delisting and long-term security of the Flathead
System population is desired, we feel the secure criterion for redds should be
higher than 300. Setting the
benchmark based on the 1980�s data may be an appropriately conservative
approach to ensuring the long-term genetic diversity of bull trout populations,
especially since the population was stable during that time period.
Further, it is important to remember that 300 redds in the 1980�s is
likely not equivalent to 300 redds today. High
levels of bull trout harvest occurred in the 1980�s.
Current regulations prohibit intentionally fishing for bull trout.
Given that legal angler harvest of bull trout is effectively non-existent
now, it is clear that the number of bull trout in the Flathead Lake system today
is still very far below what it was in the 1980�s, even when 300 redds are
constructed. Again, MCAFS believes
the secure criteria define a minimum population level, and extensive effort
should be undertaken to substantially exceed the secure criteria.
If monitoring shows the secure criteria benchmarks are being approached
on a downward trend, management actions should occur in an effort to reverse the
fall toward the secure criteria. As
an example, using the 300 redd count as the minimum secure level, lake trout
harvest would be liberalized when bull trout redd counts decrease to 350, then
would be removed altogether if the bull trout redd count decreased to 325.
Similar hierarchical actions should be described for each monitoring
activity (for example, implement a sliding scale for lake trout harvest
depending on their gill net catch rates).
The
term �unlikely to go extinct� requires additional information and
quantification. What is the time
frame? What are the probabilities
or likelihood of extinction thresholds? Please
define further.
The
definition of secure assumes no �unforseen changes� to the bull trout
populations. Many of the potential
changes listed (i.e., environmental stochasticity, new species introductions,
habitat degradation etc.) are highly probable within the next 100 years. We view this as strong reasoning to set the goal for the bull
trout population level substantially higher than the secure criteria - to buffer
for �unforeseen changes�.
The
geographic distribution criterion fails to include any commitment to maintaining
local spawning populations at or above a baseline level. For example, under the proposed secure criteria of a
�numeric indicator of wide geographic distribution�, significant declines of
strong populations (i.e., Coal Creek) would not appear to be a concern.
Secure levels need to reflect the status and trends of local populations
to ensure a natural collection of populations large enough to collectively meet
the goals and minimum numbers for the entire system.
Perhaps it is necessary to define population goals (number of spawning
adults, number of redds, juvenile abundance) for each spawning tributary (or at
least index tributaries) with numeric goals set for each, including a minimum
secure level for each. Including a
discussion of actions to reverse the decline in Coal Creek would be informative
to the reader.
Finally,
it is necessary to consider more than genetic variation when determining secure
levels for at-risk populations, such as bull trout in the Flathead System.
The entire secure level document seems based on Rieman and Allendorf�s
(2001) approach to establishing a secure benchmark based on 1,000 adults
spawning annually. Other factors to
consider while developing secure criteria include:
1) changes in the food web ecology in Flathead Lake; 2) local population
thresholds; 3) dispersal and mixing rates; 4) full expression of life history
and phenotypic diversity; and 5) resistance to catastrophic stochastic events
(distribution among diverse habitats), and so on.
Rieman and Allendorf (2001) suggest that �Mitigation of extinction
threats associated with demographic processes may require larger population
sizes regardless of genetic issues�.� and �Maintenance of genetic
diversity is essential, but not necessarily sufficient for effective
conservation�. We urge your
agencies to consider all necessary factors when determining secure levels for
bull trout in the Flathead system.
A potentially significant issue with the document is that it applies recommendations meant for individual populations to a metapopulation.
What
is the definition of a population? The
term population is used in the document to mean two different things: the group
of fish that interbreed (such as within an individual tributary) and the whole
collection of fish that utilize Flathead Lake at some point in their life
history. The term is used
interchangeably throughout the document to refer to these two very different
scales, which leads to confusion and potential error.
In
the section on genetic threats, the document states, �there is little genetic
variation within populations and high levels of differentiation between
populations (Leary et al. 1993).� Thus,
in order to maintain genetic diversity of bull trout in the Flathead system,
�all distinct populations (each tributary) must be maintained.� Rieman and Allendorf (2001) recommended that an average of
1,000 adults spawning annually would be necessary to maintain genetic variation
of a population indefinitely. Rieman
and Allendorf (2001) are rather clearly using the term population to refer to a
group of fish that breed with one another.
However, the secure redd criterion is based on the total number of redds
of all spawning populations (individual tributaries) combined.
Regardless of the ratio of spawners/redd and the subsequent secure number
of redds, The Native Trout Security Levels for the Flathead System sets the
secure number of adult bull trout at 1,000 adults spawning annually.
This is the total number for the entire Flathead Lake System
metapopulation. This is clearly not
what Rieman and Allendorf (2001) were talking about when then were using the
term �population�. In fact,
Rieman and Allendorf (2001) say, �At present, no simple rules guide
consideration of the effective size of a metapopulation and simulating
metapopulation processes to generate estimates for bull trout would be highly
speculative.� MCAFS again
emphasizes we believe 1,000 adult bull trout spawning annually is an absolute
minimum level for the overall system, and that the spawning tributaries should
each have their own population goals and secure criteria.
The document lacks clarity and detail regarding what future monitoring plans and analysis methods will be.
On
numerous occasions, the words �can� and �could� are used, rather than
�will� and �would�. While
this may just be semantics, it leaves the reader uncertain about what will
actually be done in the future. For
example, regarding cutthroat, it is stated that, �we could add new stream
sections into our annual juvenile abundance monitoring�� and �we could use
a lower significance level to detect changes�.
Rather, the document should identify if managers will add new stream
sections, and if a lower significance level will be used, or at least the
conditions that would require addition of more monitoring segments or lower
significance levels. We look to the
Development of a Protocol for Monitoring Trajectories of Bull and Westslope
Cutthroat Trout Populations Using Selected Demographic Parameters Through a
Probabilistic Framework to provide such information, but also would like to see
a definitive plan for action in the interim.
The
description of how other tools for monitoring trends will be used needs to be
fleshed out in greater detail. Secure
goals and numeric benchmarks are provided only for redd counts, and then only
for the entire basin, not for individual spawning streams or even forks of the
river drainage. Secure goals for
any other criteria listed lack the measurable objectives needed to determine if
the goals have indeed been met. Again,
reliance on redd counts is overemphasized and the other criteria, including
juvenile abundance, habitat quality, angler and gill net catch rates in the
lake, and lake trout gill net catch rates in the lake are underemphasized and
lack detailed descriptions. For
each criterion, whether it is juvenile abundance, gill net or angler catches, or
any other, there should be trigger points that define the population goal and
the secure level. As previously
stated, we recommend management actions that will be implemented or considered
need to be identified and linked to hierarchical benchmarks for each criterion,
along with a description of how those monitoring parameter benchmarks will be
used in concert with one another to direct management actions.
There
is inherent danger in relying on spawning health as an indicator of a population
status, especially with long-lived species.
With a 3-5 year lag time between juvenile population status and the
number of redds those juveniles will ultimately construct, the populations could
be in serious trouble well before redd counts show the decrease. Sturgeon and Missouri River rainbow trout are some examples
of populations that would be classified as �healthy� under the criterion of
spawning, but other criteria show a very poor reproductive success, arguing for
diverse measurement of population status.
The
secure criteria for westslope cutthroat are weak and lack quantitative
standards.
While
The Native Trout Security Levels for the Flathead System document recognizes the
commitment of the agencies to the goals of the Memorandum of Understanding and
Conservation Agreement for Westslope Cutthroat Trout in Montana, it does not
define criteria that will be used for cutthroat abundance trends or
distribution. It is not clear what
actions will be implemented to improve monitoring. There are no numeric standards of any kind throughout the
document applied to cutthroat. Numeric
criteria are needed to set a benchmark based on the best available data.
Otherwise, this document pertains only to bull trout conservation and
fails to establish secure criteria for westslope cutthroat trout.
Because cutthroat have been petitioned for listing under the ESA, the
co-managers should consider developing benchmarks that will lead to population
maintenance and recovery, and thus preclude listing in the future.
Perhaps using both genetics and abundance data to identify benchmarks
would provide a biologically meaningful standard to ensure the long-term
viability of cutthroat populations. We
believe all upper Flathead Basin river drainages should be considered and
included in such an analysis, including those which may suffer connectivity
problems, such as the Stillwater and Whitefish drainages, and measures
identified that would restore their connectivity.
The
document fails to clearly define how secure level benchmarks will be used for
future management of the lake-river system.
The
purpose for establishing the secure criteria is vague.
The document states �regardless of what these [secure criteria] levels
are, managers will try to increase native trout numbers from current levels.�
While bull trout currently meet the secure criteria level as proposed, we
are pleased to see the commitment to increase native trout numbers beyond their
current level. We advocate
implementation of measures to protect and improve habitat, control harvest, and
suppress populations of non-native species that exert deleterious effects on the
native fish of the Flathead.
Conversely,
if bull trout numbers do not meet the secure level, then what will managers do
to reduce negative non-native species interactions in Flathead Lake?
The report states, �if a criterion is not met we will search for
corroborating monitoring indices in an effort to verify population status�.
MCAFS advocates action (or non-action) based on sound and thorough
monitoring. As described previously
in these comments, the plan should identify progressive, hierarchical management
actions that will be employed as monitoring indicates the population(s) is
decreasing toward or falling below the secure level threshold, or by definition,
extinction is �likely� in the foreseeable future.
The
main body of the document contains no discussion of how these criteria relate to
potential future harvest. The
executive summary states, �Secure populations cannot necessarily sustain
fishing harvest.� and �However, if a population meets these criteria, then
fishing opportunities may exist.� MCAFS
supports restoring and sustaining populations to harvestable levels.
However, we believe the Flathead System native fish populations must be
restored to levels higher than the secure criteria indicated in the document and
sustained at those levels for several consecutive generations prior to allowing
harvest of bull trout or increasing harvest of cutthroat.
Doing so will allow adequate time to conduct monitoring to insure the
secure criteria are actually working and are sustainable.
The
bull trout in the South Fork of the Flathead drainage above Hungry Horse Dam are
discussed in the document, but the relevance of this discussion is not clear.
The
authors state, �when discussing conservation of Flathead Lake native trout
genetic variation, the South Fork populations require consideration and
conservation.� Hungry Horse Dam,
completed in 1953, isolates the South Fork populations from the Flathead
Lake-River system. The South Fork
populations appear to be stable and �secure�.
Both the South Fork and Flathead Lake-River system bull trout populations
represent some of the last remaining bull trout strongholds throughout their
range. Population goals and secure
level criteria should be established for each because these are functionally
separate metapopulations that are both critical to the persistence of bull trout
throughout their range and in the Flathead River Drainage.
Hungry
Horse Dam is also discussed in the section on Habitat Connectivity and Quality.
It is stated that managers are not advocating fish passage at Hungry
Horse Dam. We agree with that
assessment at this time because we do not believe that the South Fork population
should be counted on as a �genebank� for the remainder of the Flathead
System, nor should passage of bull trout or cutthroat trout past Hungry Horse
Dam be considered until the potential for disease transmission, hybridization,
and other necessarily considered factors are understood.
In
summary, the Flathead Lake and River native trout populations are a valued
cultural and economic heritage in Montana.
Management decisions made today represent an opportunity to sustain our
natural heritage for future generations to enjoy and appreciate.
We urge your agencies to use more defined and conservative benchmarks for
securing the Flathead System bull trout and westslope cutthroat trout
populations, and to set a goal of sustaining them at substantially higher
population levels than the secure criteria.
We thank you for considering our concerns and comments.
Sincerely,
Pat
Clancey
MCAFS
President
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