Salmon Paper draft 4

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Effect of rearing practices on physiological characteristics in Landlocked Atlantic Salmon:
A comparative analysis in condition factor and smolt index
Taylor Luneau
December 14, 2012
Saint Michaels College, Burlington VT
Abstract
Variations in hatchery rearing practices may have substantial implications in the
development and maturation of landlocked Atlantic salmon (Salmo salar). As juvenile salmon
develop, they go through a process known as smoltification, which prepares them for
downstream migrations and marine or lake residency. Initiated by environmental cues such as
photoperiod and water temperature, smoltification induces change in several physiological
characteristics such as condition factor and body coloration. Hatchery practices have attempted
to assimilate these physiological characteristics so as to increase survival after release by
decreasing differences in physiology between hatchery reared and wild smolts. Landlocked
Atlantic salmon were sampled over the course of two years, 2011 and 2012 at Eisenhower
National Fish Hatchery (ENFH) and Ed Weed Fish Culture Station (EWFCS) in Vermont and
compared to wild salmon sampled in the Huntington, River, VT. Mean condition factors and
smolt index values were calculated for each sample month and compared with other sampling
locations to assess statistical difference. Fish sampled at ENFH had a statistically lower average
condition factor on each sample month in comparison to EWFCS. Both hatcheries had
significantly higher condition factors in comparison to their wild cohorts, however smolts
sampled at ENFH approached a greater resemblance to that of the wild group. Silvering and fin
darkening values appeared to be higher at EWFCS in 2011, however was significantly greater at
ENFH in 2012. Refined rearing practices, dictated by correspondences in the physiological traits
between hatchery raised and wild salmon, will increase the survival of stocked hatchery fish and
contribute to the regrowth of the salmon population in Vermont’s lakes and rivers.
Introduction

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Indigenous populations of landlocked Atlantic salmon (Salmo salar) have suffered
significant declines in the Lake Champlain basin due to overfishing and habitat degradation
marked by the immense loss of stream cover, the building of dams and furthermore the increase
of siltation and pollution in streams and rivers (Fisheries technical committee, 2009). As a result,
landlocked salmon were deemed extinct by the mid 1800’s in Lake Champlain and it’ tributaries
(Fisheries technical committee, 2009). The loss of this species from the aquatic ecosystems of
Vermont posed serious implications unto those who depended upon its presence. Salmon fill an
integral trophic level in biotic communities as predators and prey, and directly benefit species
such as the Osprey (Pandion haliatus) and American eel (Anguilla rostrata) (Gephard, 2008).
With the confounding loss of the Atlantic salmon from the environment, hatchery
supplementation programs were implemented to secure the effective return of the salmon
population. Current management programs sponsored by the VFWD, NYSDEC and the USFWS
have focused on restoring Atlantic salmon in Lake Champlain to a level of self-sustainability in
order to support a viable sport fishery and the natural reproduction of the native salmon species
(Fisheries technical committee, 2009). While viable, this goal has proven far more difficult than
once thought, as a multitude of factors, ranging from harmful invasive aquatic species, climate
change and spawning habitat degradation, fringe against the regrowth of the Atlantic salmon
population. For these reasons the success of hatchery programs in culturing and stocking
productive salmon has never been more essential to the development of the salmon community
in Vermont waters.
Still, hatchery fish differ from their wild counterparts in varying degrees due partly to
large differences in hatchery and natural rearing environments (Weber, 2003). Hatcheries
typically rear fish in concrete runways with lower current velocities, higher population densities,
different food and feeding regimes and sometimes, variable photoperiods as well as water
temperatures and treatments. Consequently, morphological variance between wild and captive
raised salmon may appear as a result of such variables (Weber, 2003). For instance, some
phenotypic traits expressed by fish in hatchery environments may only exist as local adaptions
and would otherwise be selected against in a wild environment. However to fully comprehend
phenotypic variation appearing between Atlantic salmon hailing from varying natal
environments, it is essential to cultivate an understanding of the complex salmon life cycle.

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Hutchings (1985) described migration as the adaptive phenomenon of the Atlantic
salmon life cycle, which increases survivability, reproductive fitness and overall growth. Gravel
beds, prevalent in natal streams, with a moderate velocity and depth, mark the spawning grounds
for adult salmon (McCormick, 1998). Once eggs have developed, fry emerge and tend to remain
in their natal environments until developing into juvenile salmonids known as parr (McCormick,
1998). Typically in late autumn, after 1-2 years, parr move downstream from their summer
habitat to maximize food intake and growth in order to prepare for the high energy demand of
the winter season (McCormick, 1998). In the spring however, parr of a particular size undergo
physiological changes in a period of development known as smoltification (Folmer, 1979).
Now in a stage referred to as presmolt, salmon experience increased olfactory sensitivity
to chemical cues prevalent in their environment (Specker et al., 2000). Ueda (1995) attributes
the imprinting mechanism of the maternal stream on the juvenile salmon to the homing ability of
adults in their return upstream to spawning grounds later in life. Other environmental factors
such as increased photoperiod and water temperature are perceived by the neuroendocrine
system of salmon, which in turn initiate the physiological response known as smolting
(McCormick, 1998). Once the smolting process has begun, presmolts undergo a variety of
intense morphological changes (Hoar, 1988). Characteristically, smolts lose their camouflage
coloration (identified by black bars on the fishes side known as parr marks) becoming a silvery
color with increased black margins on the fins, particularly the caudal and pectorals, and
furthermore gain a streamlining in shape (Hoar, 1988). McCormick (1998) described the shape
changes attributed to smoltification as a larger gain in length than weight, which subsequently
results in the reduction of the condition factor (a descriptive weight to length ratio corresponding
to the age and health of the fish (Calander, 1977)). McCormick (2008) detailed the average
length of smolts to range from 130-180mm. Furthermore, increases in gill Na+, K+-ATPase
activity are prevalent during this stage, which afford the developing salmon with
hypoosmoregulatory abilities, providing increased salinity tolerance (McCormick, 1998; Hoar,
1988). Increases in hypoosmoregulation enable smolts to directly enter highly salinated
environments, such as the ocean, with little ionic disturbance (Hoar, 1988). Once the process of
smoltification has completed, smolts migrate downstream to marine or lake environments where
they take up residency and develop into adults.

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Advances in comprehension of the morphological and physiological variation in the parr-
smolt transformation will afford hatchery workers with the increased ability to determine optimal
stocking rates of Atlantic salmon. Hatchery reared fish are known to make up large proportions
of some stocks, and fish culturist should therefore strive to most effectively propagate fish
similar to those that are naturally spawned (Weber, 2003). Weber (2003) outlines that negligence
in rearing naturally assimilating fish, may result in a variety of negative impacts on wild fish
such as genetic contamination, predator attraction and disease transmission. However the task of
producing fish of close similarity to their wild peers, has historically been no easy task. Gross
(1998) describes captively reared Atlantic salmon in comparison to wild salmon as, “one species
with two biologies.” Hatchery reared salmonids have been described as less energetically
efficient, less capable of assimilating their natural environment through the use of camouflage
and while faster growers are less capable of adapting to increased water velocity (Weber, 2003).
Furthermore, many have speculated that the natal environment may alter morphology, which
directly influences swimming ability, spawning success and overall survivability (Weber, 2003;
Taylor, 1986; Gross, 1998).
It is therefore vital to understand the physical parameters that hatchery reared fish must
assimilate in order to decrease behavioral, morphological and physiological differences from
their wild and stream dwelling peers. Without a thorough comprehension of the developmental
gradients of landlocked Atlantic salmon, it is impossible to ensure the successful management of
this vulnerable species and inevitably, conservation efforts will become fiscally exhausting and
counterproductive. Successful population growth of landlocked Atlantic salmon in Vermont’s
lakes and tributaries is therefore intrinsically associated with providing our states hatcheries with
the proper tools and information to culture more natural resembling fish. This study will analyze
morphological indices of fish cultured at Ed Weed Fish Culture Station (EWFCS) and
Eisenhower National Fish Hatchery (ENFH) in comparison to wild fish sampled in the
Huntington River, VT. Correspondences in morphological and physiological factors of hatchery
and wild fish, will dictate successful rearing practices for hatcheries that strive to minimize
differences between the populations.
Methods:

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Hatcheries and Rearing Conditions
Fish were sampled at the Eisenhower National Fish Hatchery (ENFH), the Ed Weed Fish
Culture Station (EWFCS) and the Huntington River in Huntington, VT over several months in
the years of 2011 and 2012. In 2011, fish were collected at ENFH on February 23, March 16 and
April 13 and at EWFCS on February 21, March 21 and April 19. In 2012, fish were sampled at
ENFH on January 25, February 29, April 2, April 24 and May 17 and at EWFCS on December
29 (2011, data substitute for Jan. data), January 30 and March 1. The Huntington River was
sampled only in the month of May in both sampling years. Salmon considered to be of the 2009
year-class were sampled in 2011 while salmon of the 2010 year-class were sampled in 2012.
Hatcheries were both selected for sampling due to rearing landlocked Atlantic salmon,
which would later serve as stock for Lake Champlain and it’s tributaries. However, the
hatcheries vary from each other in rearing methods, providing their fish with different light
exposures, water temperatures and treatments, rearing space and feed. Both hatcheries received
eggs from a broodstock maintained at the Bald Hill Fish Culture Station in Newark, VT.
ENFH, located in Pittsford, VT, is supervised by the U.S. Fish and Wildlife Service and
currently produces 95, 000 Landlocked Atlantic salmon smolts (U.S. Fish and Wildlife Service,
2009). Eggs were received in November and incubated over a period of five months in egg trays
(U.S. Fish and Wildlife Service, 2009). After consuming their egg sack and developing into fry,
they were moved into circular tanks and fed every twenty minutes until becoming one year old
parr (U.S. Fish and Wildlife Service, 2009). Parr were then moved outside into covered raceways
in May, where they continued to develop. Unfiltered water was supplied for the raceways from
the nearby Furnace Brook, which flowed directly through each raceway before being released
back to the brook again. Water temperatures were slightly less than that of EWFCS during this
period and fish were only provided with natural lighting. Between the months of June and
September, fish were kept in raceways with the warmer, summer brook water and fed
continually. Ten concrete outdoor raceways were utilized at ENFH. Each raceway is 30.48m by
2.44 m and 55.88cm in depth and enclosed so as to prevent outside predation or harmful climate
exposure (Shannon, 2011). From October to the following March, water averaging 48-52° F, was
provided via a well near the raceways. Salmon were then stocked in May, almost two years after
first arriving at ENFH.

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Established in 1991, EWFCS is located in Grand Isle, VT and is the newest of five state
run fish culture stations owned and operated by the Vermont Fish and Wildlife Department (VT
Fish and Wildlife Department, 2011). Eggs received in November were incubated in egg trays
until fry had emerged, which were then moved into circular tanks in April. At this point
however, hatchery workers graded the fish with a screen, herding the larger fish and removing
25-30% of the total population. Once parr were observed in May, fish were moved into raceways
and kept on constantly re-circulating water, which was warmer than that of ENFH during this
period. Due to it’s close proximity to Lake Champlain, the lake serves as the principle water
source for each of the raceways (VT Fish and Wildlife Department, 2011). Fish were also
constantly fed at this point and exposed to a continuous 24 hour light regime. Concrete raceways
at EWFCS are comparable to ENFH yet slightly larger, measuring 30.48 m by 2.44m with a
depth of 91cm (Shannon, 2011). Similar to ENFH, lake water used for the raceways became
warmer between the months of July and September however EWFCS fish (no longer on 24 hours
of continuous light) were only fed at sunrise and sunset. Fish remained in the raceways from
October until the following March, however lake water temperature declined to roughly 34-35° F
during this time. Fish were finally stocked out in March, rather than May like the fish from
ENFH.
Sampling the Huntington River
In an attempt to capture out-migrating landlocked Atlantic salmon in the Huntington
River, a rotary screw trap was installed on the river near the corners of Cochran Rd and Wess
White Hill Rd in Huntington, VT. This particular site afforded easy access to and installation of
the trap, as well as healthy river habitat and a close proximity to the Winooski River. The
Huntington empties directly into the Winooski River, which is not only one of Lake Champlain’s
largest tributaries but furthermore supports a large population of fall-migrating landlocked
salmon (USFWS, 2007). The trap functioned as a funnel, sifting the rivers contents into a live
well on the downstream side of the trap. The trap was checked daily and fish were measured and
assessed before being released back into the river. Electo-shocking was also utilized for salmon
collection in the Huntington River. Salmon collected via electro-shocking were sampled
upstream of the trap and above the Huntington River Gorge. Measurement protocols were
analogous to that of samples collected via the smolt trap.

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Fish Measurement and Analysis
Thirty fish were selected randomly, on each sampling date, at each hatchery. Fish were
first anesthetized using a mixture of clove oil and water and then measured for weight (g), length
(mm), and scored on the smolt index. The smolt index is a grading scale used to assess the stage
in development of juvenile salmon based on silvering and fin darkening observations. Scores of
1 in both evaluations would be analogous to a parr while scores of 5 would indicate a fully
evolved smolt (Table 1). Lastly, fish were photographed and scales were removed for use in age
measurement. Fish were then returned to their respective raceways. These methods for
measurement were also used in the analysis of salmon collected from the Huntington River. This
experiment utilized twelve of the randomly selected 30 fish from each sample date at each of the
hatcheries. Fish collected in the Huntington River via electro-shocking were disregarded for
analysis due to expectations of only reaching the parr stage of development. Twelve fish were
randomly selected from samples taken at the Huntington screw trap and utilized as wild smolt
comparisons to that of the hatchery fish.
Table 1: Observational cues used in assessing silvering and fin darkening of fish. Combined
evaluations indicate an overall smolt index score for each fish. A score of 1 in both categories
would be indicative of a fish that is still in the parr stage. Scores of 5 in both categories would
indicate a fully evolved smolt. (SOP provided by USFWS)
Index Silvering Fin Darkening
1
No silvering, dark parr marks and bright pink
spots. No darkening of fin margins.
2
Slight silvering, clearly visible parr marks and
pink spots.
Slight darkening of posterior of fin margins
but no portion of fin margin is solely black.
3
Medium silvering, slightly visible parr marks
and pink spots.
Solid black fin margins in pectoral (<25% fin
length) and caudal (≤1mm).
4
Heavy silvering, parr marks and pink spots
barely visible (only by rotating fish).
Solid black fin margins in pectoral (25-75%
fin length) and caudal (2-4 mm).
5
Complete and very bright silvering, no
visiblbe parr marks or pink spots.
Solid black fin margins in pectoral (>75% fin
length) and caudal (≥5mm).
Once weight and length measurements were assessed, condition factor
(K=(100xweight(g)/ length(mm)^3) was calculated for each fish. The weight of a fish is
correlated to the cube of its length and we can therefore postulate changes in the shape of a fish,

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as we observe influxes in the condition factor (Calander, 1977). Often times the K value is used
to determine the rate at which fish should be stocked into a particular body of water (Barnham,
1998). Hatcheries strive to meet optimum standards in the physiological preparedness of each
fish before stocking. The use of the K value affords a quantitative condition of each fish, which
can be interpreted to assess overall shape and size of each fish (Barnham, 1998). It is important
to note that the K value is strongly influenced by the growth stage of each fish but can
furthermore be an indicator of productivity in the water that fish were reared in (Barnham, 1998).
When considering development in smolts, we note a greater increase in length than overall
weight, which results in decreases in condition factor the further along a particular salmon is in
the smoltification process (McCormick, 1998). Once condition factors were calculated for each
fish a student’s t-test was used to assess statistical difference between monthly samples. A one-
way ANOVA was used to determine significance if statistical difference was expected among all
three groups, or one hatchery over multiple months. Probability levels of less than 0.05 (p<0.05)
were considered significant in each of the t-tests and one-way ANOVAs conducted.
Results:
2009 year class: Condition Factor
Mean condition factors of Landlocked Atlantic Salmon sampled 2011 at ENFH were
significantly less than those of the EWFCS on each month sampled (P<0.01, t-test) (Fig. 1). The
average condition factor of EWFCS (K=0.97) and ENFH (K=0.86) in April, (their final sampling
date) were also significantly greater than those of the wild fish sampled in the Huntington River
in May (K=0.78) (p<<0.001, one-way ANOVA) (Fig. 1). Condition factors of fish at ENFH
declined significantly over the three-month sampling period from February (K=0.94) to April
(K=0.86) (p<0.006, one-way ANOVA). This pattern was not observed in the fish at EWFCS as
condition factors did not significantly decline during the three-month period of February
(K=1.002) to April (K=0.97) (p<0.53, one-way ANOVA). Linear trend lines supported this
finding, showing that EWFCS condition factors declined at an almost non-existent rate over the
three-month sampling period (m= –0.013) (Fig 1). While variation between sampling months in
condition factor at ENFH was significant, the rate of decline was only slightly greater than that
of EWFCS (m=-0.0406).

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2009 year class: Smolt Index
Mean silvering and fin darkening scores were higher at EWFCS in all months sampled in
2011(Fig. 3). However, silvering was only significantly greater at EWFCS in the month of
March (p<<0.0001, one-way ANOVA). Furthermore, no statistical difference in silvering was
determined between hatchery samples in April when compared to samples from the Huntington
River (p<0.21, one-way ANOVA). While the April sample at EWFCS was also not statistically
different in fin darkening from Huntington, fish sampled at ENFH in April were (p<0.007, one-
way ANOVA). Fish sampled at EWFCS were observed to have the greatest changes in silvering
between the months of February and March, however little change in fin darkening was observed
over the three-month sampling period (Fig. 3). ENFH fish showed fairly constant smolt index
scores between February and March however large increase in both silvering and fin darkening
were observed between March and April (Fig. 3).
Figure 1. Monthly change in condition factor in Landlocked Atlantic Salmon (yc 2009) sampled
at ENFH, EWFCS and the Huntington River in 2011. Averages were attained from random
sample of twelve fish collected on each sampling date. Values are means ± 1 SEM. K=(((weight
grams)*10))/(Length mm^3)).
0.7
0.75
0.8
0.85
0.9
0.95
1
1.05
0 1 2 3 4
AverageConditionFactor(K)
EWFCS
ENFH
Huntington
Jan Feb Mar Apr May

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2010 year class: Condition Factor
Hatcheries sampled in 2012, displayed similar average condition factors in January, the
first sampling month (ENFH and EWFCS K=1.03) (Fig. 1). However, mean condition factors of
fish sampled at ENFH were significantly less then EWFCS in both February (ENFH K=1.004;
EWFCS K=1.06; p<0.04, t-test) and March (ENFH K=0.95; EWFCS K=1.03; p<0.0043, t-test)
(Fig. 2). It is also important to note that no significant changes in condition factors of fish at
EWFCS were observed over the three-month sampling period (p<0.62, one-way ANOVA).
Linear trend lines showed that condition factors stayed relatively the same over time at the
EWFCS (m=0.004). This anomaly was not observed at ENFH, which expressed significant
differences between the sample dates of January to March (p<0.0091, one-way ANOVA).
Significant declines in average condition factor were also observed between the months of
March and April at ENFH (p<<0.0001, t-test). This trend did not continue however, as no
statistical difference was found between condition factors of fish sampled in April and May at
ENFH (p<0.07, t-test) (Fig. 2). Fish sampled in the Huntington River had an average condition
factor (K=0.78) much lower than those of the hatcheries on their final sampling dates (Fig. 2).
2010 year class: Smolt Index
Smolt index scores were lower at ENFH in both January and February in comparison to
EWFCS, however increased to a level higher than EWFCS by the month of March (Fig. 3).
While silvering was observed to constantly increase between January and March at ENFH,
silvering in fish sampled at EWFCS constantly decreased over the three-month sampling period.
A similar observation was made of fin darkening in fish sampled at EWFCS, which also
decreased over the three months sampled (Fig. 3). Fin darkening stayed mostly constant in fish
sampled at ENFH between January and February, however significantly increased from February
to March (p<0.0003, one-way ANOVA). No statistical change in silvering was observed in fish
sampled at ENFH from March to May (P<0.55, one-way ANOVA). There was also no statistical
difference observed in fin darkening of fish sampled in March at EWFCS when compared to
Huntington, however fin darkening was significantly higher in fish sampled at ENFH in May
when compared to the Huntington sample (p<<0.0001, one-way ANOVA). Average fin
darkening observed in the Huntington River was also much lower in 2012 (M=1.91) when
considering the greater prevalence of fin darkening in the Huntington sample of 2011 (M=4.08).

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Figure 2. Monthly change in condition factor in Landlocked Atlantic Salmon (yc 2010) sampled
at ENFH, EWFCS and the Huntington River in 2012. Averages were attained from random
sample of twelve fish collected on each sampling date. Values are means ± 1 SEM. K=(((weight
grams)*10))/(Length mm^3)).
0.75
0.8
0.85
0.9
0.95
1
1.05
1.1
1.15
J J J J J
AvergaeConditionfactor(K)
EWFCS
ENFH
Huntington
Jan Feb Mar Apr May

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Year
Class
Silvering Fin Darkening
2009
2010
Figure 3. Fin Darkening and Silvering scores, based on the smolt index, for the 2009 and 2010
year classes are expressed for each sampling group over time. The smolt index indicates the
location in physiological development of each salmon during the smoltification process. A score
of 1 in both silvering and fin darkening within the index would be indicative of a parr while a 5
would represent a fully evolved smolt. Values are Means ± 1 SEM. EWFCS=circle,
ENFH=square, Huntington=triangle.
Discussion
Comparison of hatchery rearing practices utilized at Eisenhower National Fish Hatchery
(ENFH) and Ed Weed Fish Culture Station (EWFCS) revealed large differences in Atlantic
salmon smolt production. While the physiological criteria utilized in this study provided a good
basis in the evaluation of smolt quality, condition factor as well as body and fin coloration are
2.9
3.1
3.3
3.5
3.7
3.9
4.1
4.3
4.5
Feb Mar Apr May
Silvering
1.5
2
2.5
3
3.5
4
4.5
Feb Mar Apr May
FinDarkening
2
2.5
3
3.5
4
4.5
Jan Feb Mar Apr May
Silvering
1
1.5
2
2.5
3
3.5
4
4.5
5
Jan Feb Mar Apr May
FinDarkening

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only some of the many indicators needed to competently predict smolt survival after release.
These physiological characteristics are currently used at several hatcheries in the United States
yet many have noted poor survival rates of hatchery-reared smolts in comparison to that of wild
smolts (Jonsson et al, 2003; Weber, 2003; McCormick, 1998). This, as suggested by Weber
(2003) is most likely due to variations in hatchery rearing conditions when compared to natural
environments. Such variations may include differences in water current velocities, foods and
feeding regimes, photoperiod, water temperature and over-crowding in raceways (Weber, 2003;
McDonald, 1997). It is therefore important to not over estimate the productivity of a smolt based
solely on its external appearance. That said, the evidence provided by this study has shown
salmon smolts reared at ENFH to assimilate their wild counterparts more significantly than those
of EWFCS.
As put forth by McCormick (1998), shape changes attributed to smoltification result in a
streamlining of fish, which in turn strongly decreases the condition factor. Strong correlations
have been found between condition factor and the hypo-osmo-regulatory ability and total lipid
content of juvenile Atlantic salmon (Solbakken et al., 1994; Herbinger, 1991). Condition factor
can therefor be used as an efficient and non-lethal sampling method in determining physiological
preparedness of salmon for maximizing downstream migration and survival. Average condition
factor at ENFH was consistently lower than EWFCS in both 2011 and 2012 sample years (Fig. 1,
Fig. 2). Landlocked salmon reared at ENFH may therefore be further along in the smoltification
process than those from EWFCS at the point of stocking into Vermont’s rivers.
However it is important to note that very few changes occur in condition factor at
EWFCS in both years over the three-month sampling period. Potential reasoning for this may be
attributed to the rate of smoltification occurring in earlier months, which in this study are un-
observed. Specifically, large measures are taken at EWFCS to progress juvenile salmon through
the developmental process earlier in time. The technique of grading, which is utilized only by
EWFCS, culls the population by 25-30%, creating more space for the remaining larger fish.
Furthermore, once parr are moved to raceways at EWFCS in March of their first year, they are
exposed to warmer water, are constantly fed and subjected to a 24hr continuous light exposure.
These conditions are not provided to salmon at ENFH who are exposed to the cooler water of
Furnace Brook and a natural photoperiod regime. Strong differences also exist in the over winter

14
care of salmon at each facility. EWFCS utilizes cold lake water (approximately 34-35° F) from
Lake Champlain while ENFH switches from brook to well water ranging around 48-52° F.
Eriksson and Lundqvist (1982) observed that patterns in condition factor, silvering and fin
darkening typical of a smolt, run circanually when salmon are kept under consistent photoperiod
and temperature. Alterations in such conditions at each hatchery most likely attribute to variation
in the final smolt production.
Wedemeyer (1976) notes that elevated water temperatures are sometimes utilized to
accelerate growth and shorten the period of time needed to produce smolts. Researchers have
concluded that increases in gill Na+K+-ATPase is correlated with the onset and completion of
the smoltification process (McCormick, 1998). Handeland et al. (2004) noticed such increases in
gill Na+K+-ATPase in Atlantic salmon who were exposed to increases in water temperature such
as those indicative of early spring. Thusly increasing the water temperature at EWFCS during
early rearing phases would most likely increase the overall growth of the salmon at the facility.
However, increased artificial temperature regimes can not only influence the early onset of
smoltification, but also hasten the desmoltification process (Wedemeyer, 1980). Shrimpton
(2000) observed the potential for 1-year-old salmon smolts to revert to parr and undergo the parr-
smolt transformation again in the following season. This he attributed to the denied access of
salmon smolts to enter seawater after physiologically preparedness is met in their first season.
Suspicions of possible reversion of smolts to parr at EWFCS, would be supported by the
declining silvering and fin darkening values observed in 2012 (Fig. 3). While differentiations in
the smolt index may simply be explained through the subjectivity of the test, it is important to
note the possible indication of these signs as early onset of reversed smoltification.
Furthermore, while EWFCS utilizes a 24hr light exposure during a period of the first
summer, salmon at ENFH are only provided natural photoperiods. Wagner (1971) noted that
differentiations in photoperiod could influence the development of smolt like characteristics and
the migratory behavior of steelhead trout. Out of season light regimes have been used to
circumvent short day lengths and increase the smolting process by a matter of months (Dustin
and Saunders, 1995). McCormick (1998) defines photoperiod as having one of the greatest
influences on the smoltification process, but adds that increased day length may have limited
utility when combined with colder water temperatures. Therefore, it is necessary for EWFCS to

15
increase both of these factors so as to successfully stimulate increased growth patterns in salmon.
Still, evidence provided by Duncan (1998) shows that photoperiod manipulation might result in
the de-synchronization of the various developmental processes involved in smoltification. Under
natural photoperiods however, condition factor as well as coloration are synchronized with the
environment by seasonal cues (Eriksson, 1982). While alterations to important environmental
factors like photoperiod may increase the rate of the smoltification process, it is unclear if some
physiological traits are more influenced than others and furthermore if it will be possible to
synchronize said traits again.
Still, mean condition factors of hatchery groups in their final sample months were all
statistically higher from the model wild smolts of the Huntington River. One could predict
however, that ENFH is approaching a stronger level of similarity to the wild population as can be
observed between sample groups in May of 2012 (Fig. 2). Smolt Index values further support the
similarity between salmon sampled at ENFH and those from the Huntington River. While
silvering and fin darkening values were higher for fish at EWFCS in 2011, increases in these
indexes were not observed in ENFH until March. Additionally, the rate of increase in both
indexes is greater at ENFH than it is at EWFCS between the months of March and April,
suggesting the possibility for ENFH fish to surpass those of EWFCS when they are stocked a
month later in May. However, further research is necessary to be certain. In 2012 silvering and
fin darkening indexes were higher at ENFH on its last sampling dat when compared to all other
locations. The possible regression in silvering and fin darkening observed in fish at EWFCS may
be attributed to, as noted earlier, a reversal in the parr-smolt transformation. Fin darkening in the
Huntington sample of 2012 is of particular interest as it is significantly lower than that of 2011
(Fig. 3). This may be due to water level and velocities in the previous growing season. Schneider
(1980) notes that fin erosion is typical of late fall as water temperatures decline and ambient
temperatures increase. Low fin darkening values expressed in the Huntington sample may also
be attributed to previous flood events, such as Hurricane Irene, which had an extremely
damaging impact on Vermont streams and rivers. Flood events such as this, may have had
particularly damaging effects on wild smolt physiology as natal stream an d rivers increased
sedimentation and velocities.

16
Based on the evidence presented in this research, rearing practices utilized by ENFH
produces fish that more closely assimilate the wild smolts observed in the Huntington River.
While EWFCS may develop smolts earlier in the developmental process, it would appear that
fish from this facility might be undergoing the smoltification process twice. However, data
consistent with this prediction is needed from earlier phases to fully support the potential of
multiple parr-smolt transformations. EWFCS attempts to grow fish larger at an earlier phase and
then essentially halt the growth process by reducing water temperature to near freezing during
the fishes second winter of development. While this practice tends to generate a plumper smolt,
the fish observed at ENFH tend to more accurately assimilate the physiological characteristics of
the wild fish from Huntington. While these indicators are strong external cues in the prediction
of smolt status, Virtanen (1991) suggests that the singular use of condition factors and body
coloration may be inadequate in the evaluation of smolt status. It is therefore necessary to
continue observation of developmental variation between hatcheries through the comparison of
not only physiological characteristics but furthermore morphological and biochemical
characteristics.
Measurements in Gill Na+K+-ATPase as well as osmololity, total lipid content and mark
and recapture indices may also aid in understanding further differences between hatchery fish
and their wild cohorts. Furthermore, the use of morphometric analysis programs such as those
generated by James Rolf (2001) would further delineate differences in morphological traits
between sample groups. Morphology related variables could be analyzed through the generation
of a truss network, which would be based upon a certain parameter of landmarks, assigned to a
set of distinct shape indicators on salmon. Shape configurations for each sample could then be
utilized in determining the level of differentiation between smolts hailing from various rearing
practices.
Lastly, one might suggest the necessity of EWFCS to retain a selection of their smolt
crop for an extended period of time. This may allow mean condition factors to decrease such as
those observed at ENFH during the months of April and May. Hansen (1987) noted the
importance in timing of the salmon migration to the overall survivability of the fish. McCormick
(1998) builds on this observation, adding that a strong correlation exists between the timing of
migration and the overall physiological preparedness of salmon to increase survival after release.

17
EWFCS may therefore hope to draw closer similarities in physiological traits to the wild fish
sampled and furthermore stock their fish later in the season with other observed migrating
salmon. Through further comparison however, researchers will successfully decrease the
behavioral, morphological and physiological differentiations that exist between hatchery and
wild produced salmon. Whether we hope to create a self-sustainable sports fishery or a
population of landlocked Atlantic salmon hailing from natural reproduction, further insight is
necessary to fully determine the physiological preparedness of stocking fish produced through
captive means.
Acknowledgements
The author would like to thank Professor Facey for his support in developing the
experimental design of the proposed study and furthermore for his aid in the statistical analysis
and interpretation of the results. His careful attention to detail and extensive review enabled the
authors of this study to communicate their observations in the most complete of manners. The
author would also like to thank Bill Ardren and Nick Staats of the US Fish and Wildlife for their
time and expertise in the collection and assessment of Atlantic salmon. The success of this study
heavily relied upon their input and interpretations. Data utilize in the analysis of hatchery rearing
practices was collected and supplied by Bill Ardren and Nick Staats. The author owes them both
a great deal of thanks in their support of this project. Lastly, thanks are owed to Saint Michael’s
College for providing their laboratory and research equipment for analysis.

18
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