1

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

2

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.

3

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.

4

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:

5

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.

6

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.

7

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,

8

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).

9

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

Ave

rage

Co

nd

itio

n F

acto

r (K

)

EWFCS

ENFH

Huntington

Jan Feb Mar Apr May

10

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).

11

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

Ave

rgae

Co

nd

itio

n f

acto

r (K

)

EWFCS

ENFH

Huntington

Jan Feb Mar Apr May

12

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

Silve

rin

g

1.5

2

2.5

3

3.5

4

4.5

�Feb �Mar �Apr �May

Fin

Dark

enin

g

2

2.5

3

3.5

4

4.5

�Jan �Feb �Mar �Apr �May

Silveri

ng

1

1.5

2

2.5

3

3.5

4

4.5

5

�Jan �Feb �Mar �Apr �May

Fin

Dark

enin

g

13

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

Works Cited Barnham, C. 1998. "Condition Factor, K, for Salmonid Fish." Fisheries Notes: State of Victoria,

Department of Primary Industries.

Calander, K. 1977. Ponderal Indexes or Condition Factors. Handbook of Freshwater Fishery Biology. 2. Iowa: Iowa State University.

Duston, J., Saunders, R.L. 1995. Advancing smolting to autumn in age 0+ Atlantic salmon by

photoperiod, and long-term performance in sea water. Aquaculture, 135: 295–309. Duncan, Neil J., Niall Bromage. 1998. "The effect of different periods of constant short days on

smoltification in juvenile Atlantic salmon (Salmo salar)." Aquaculture 168.1: 369-386.

Eriksson, L.-O., Lundqvist, H. 1982. Circannual rhythms and photoperiod regulation of growth and smolting in Baltic salmon (Salmo salar L.). Aquaculture, 28: 113-121.

Essex Junction, VT: Lake Champlain Fish and Wildlife Management Cooperative.

Fisheries Technical Committee. 2009. Strategic plan for Lake Champlain fisheries.

Folmar, Leroy C., Walton W. Dickhoff. "The parr-Smolt transformation (smoltification) and seawater adaptation in salmonids: A review of selected literature." Aquaculture 21.1 (1980): 1-37.

Gephard, S. 2008. Restoring Atlantic salmon (Salmo salar) to New England.

In Askins, R.A.,G.D. Dreyer, G.R. Visgilio, and D.M. Whitelaw (Ed.), Saving Biological Diversity:

Balancing Protection of Endangered Species and Ecosystems. New York, NY: Springer.

Handeland, S.O., Wilkinson E., Sveinsb B., McCormick S.D., Stefansson S.O. 2004.Temperature influence on the development and loss of seawater tolerance in two fast growing strains of Atlantic

salmon. Aquaculture 233: 513-529.

Hansen, L.P. 1987. Growth, migration and survival of lake reared juvenile anadromous Atlantic salmon Salmo salar L. Fauna Norv. Ser. A, 8: 29–34.

Herbinger, C. M., and G. W. Friars. "Correlation between condition factor and total lipid content in Atlantic salmon, Salmo salar L., parr." Aquaculture Research 22.4 (1991): 527-529.

Hoar, W.S. Fish Physiology: Viviparity and Posthatching Juveniles. 11. London: Academic Press, INC.,

1988. 275-317.

19

Hutchings, Jeffrey A. "Lakeward migrations by juvenile Atlantic salmon, Salmo salar." Canadian Journal of Fisheries and Aquatic Sciences 43.4 (1986): 732-741.

Jonsson, Nina, Bror Jonsson, and Lars Petter Hansen. "The marine survival and growth of wild and

hatchery‐ reared Atlantic salmon." Journal of Applied Ecology 40.5 (2003): 900-911.

Rohlf, F.J. 2001. TpsRelw: relative warps analysis. State University of New York, Department of Ecology and Evolution, Stony Brook. Available at: http://life.bio.sunysb.edu.

Shannon, Virginia. "Restoring Landlocked Atlantic Salmon to Lake Champlain." BS thesis. Middlebury College, 2011.

Shrimpton, J. Mark, Björn Thrandur Björnsson, and Stephen D. McCormick. "Can Atlantic salmon smolt twice? Endocrine and biochemical changes during smolting." Can. J. Fish. Aquat. Sci 57 (2000):

1969-1976

Specker, Jennifer L., et al. 2000. "Parr-smolt transformation in Atlantic salmon: Thyroid hormone

deiodination in liver and brain and endocrine correlates of change in rheotactic behavior." Canadian journal of zoology 78.5: 696-705.

Solbakken, Viktor A., Tom Hansen, and Sigurd O. Stefansson. 1994. "Effects of photoperiod and temperature on growth and parr-smolt transformation in Atlantic salmon (Salmo salar ) and subsequent

performance in seawater." Aquaculture 121.1: 13-27.

McCormick, Stephan., Lars P Hansen, Thomas P Quinn, Richard L Saunders. 1998. Movement, migration, and smolting of Atlantic salmon (Salmo salar). Canadian Journal of Fisheries and Aquatic Sciences, Volume 55, Pages 77-92.

McCormick, Stephan. 2008. "The Biology of Salmon Smolts." McCormick Laboratory Fish Physiology.

<http://www.bio.umass.edu/biology/mccormick/Smolts.html>.

McCormick, Stephan D. "Fin development in stream-and hatchery-reared Atlantic salmon." Aquaculture

220.1 (2003): 525-536.

McDonald, D. G., et al. "Condition and performance of juvenile Atlantic salmon (Salmo salar): effects of rearing practices on hatchery fish and comparison with wild fish." Canadian Journal of Fisheries and Aquatic Sciences 55.5 (1998): 1208-1219.

Taylor, Eric B. "Differences in morphology between wild and hatchery populations of juvenile coho

salmon." The Progressive Fish-Culturist 48.3 (1986): 171-176.

20

Ueda, Hiroshi. 1995. "Biochemistry of Fish migration." Biochemistry and molecular biology of fishes. P.W. Hochachka. 5. Amsterdam: Elsevier Science B.V., 265-281.

U.S. Fish and Wildlife Service. 2007. "LAKE CHAMPLAIN OFFICE CONDUCTS LANDLOCKED

SALMON SMOLT TRAPPING." US Fish and Wildlife Service: Field Notes. <http://www.fws.gov/FieldNotes/regmap.cfm?arskey=21367>.

U.S. Fish and Wildlife Service. 2009. Dwight D. Eisenhower National Fish Hatchery. Retrieved from http://www.fws.gov/ddenfh/aboutus.html

Vermont Fish and Wildlife Department. 2011. Fisheries Program. Retrieved from

http://www.vtfishandwildlife.com/fisheries_hatcheries.cfm.

Virtanen, E., et al. 1991. "Effect of physiological condition and smoltification status at smolt release on

subsequent catches of adult salmon." Aquaculture 97.2: 231-257.

Wagner, H. H. 1974. The parr-smolt metamorphosis in steelhead trout as affected by photo- period and

temperature. Ph.D Thesis, Oreg. State Univ., Corvallis, 211 p.

Weber, Edward D., Kurt D. Fausch. 2003. "Interactions between hatchery and wild salmonids in streams: differences in biology and evidence for competition." Canadian Journal of Fisheries and Aquatic Sciences 60.8: 1018-1036.

Wedemeyer, G.A., Saunders, R.L., Clarke, W.C. 1980. Envi- ronmental factors affecting smoltification

and early marine sur- vival of anadromous salmonids. Mar. Fish. Rev. 42: 1–14.

.