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This article was downloaded by: [Washington State University Libraries ]On: 25 October 2014, At: 00:05Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registeredoffice: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
North American Journal of AquaculturePublication details, including instructions for authors andsubscription information:http://www.tandfonline.com/loi/unaj20
Survival, Growth, and Feed Utilizationof Pre- and Postmetamorphic AmericanShad Exposed to Increasing SalinityYanju Jia a , Qinghua Liu b , Cheryl A. Goudie c & Bill A. Simco da College of Biological Science and Engineering, Hebei Universityof Economics and Business , Shijiazhuang, 050061, People'sRepublic of Chinab Aegis EcoTechnology Development Company, Inc. , Shanghai,201203, People's Republic of Chinac Aegis EcoTechnology Development Company, Inc. and EcologicalResearch Center , University of Memphis , Memphis, Tennessee,38152, USAd Ecological Research Center, University of Memphis , Memphis,Tennessee, 38152, USAPublished online: 09 Jan 2011.
To cite this article: Yanju Jia , Qinghua Liu , Cheryl A. Goudie & Bill A. Simco (2009) Survival,Growth, and Feed Utilization of Pre- and Postmetamorphic American Shad Exposed to IncreasingSalinity, North American Journal of Aquaculture, 71:3, 197-205, DOI: 10.1577/A07-095.1
To link to this article: http://dx.doi.org/10.1577/A07-095.1
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Survival, Growth, and Feed Utilization of Pre- andPostmetamorphic American Shad Exposed to Increasing Salinity
YANJU JIA
College of Biological Science and Engineering, Hebei University of Economics and Business,Shijiazhuang 050061, People’s Republic of China
QINGHUA LIU
Aegis EcoTechnology Development Company, Inc.,Shanghai 201203, People’s Republic of China, and Memphis, Tennessee 38152, USA
CHERYL A. GOUDIE*Aegis EcoTechnology Development Company, Inc., and Ecological Research Center,
University of Memphis, Memphis, Tennessee 38152, USA
BILL A. SIMCO
Ecological Research Center, University of Memphis, Memphis, Tennessee 38152, USA
Abstract.—The American shad Alosa sapidissima is currently an emerging aquaculture species in China,
and establishing conditions required for optimal growth will play a key role in future development of
American shad culture. We evaluated the effects of increasing salinity concentrations on survival, growth, and
feed utilization of American shad in two separate 30-d experiments. In experiment 1, 25-d-old,
premetamorphic fish (mean weight 6 SD ¼ 0.07 6 0.04 g) were exposed to 0, 10, 20, and 30-ppt salinity
(26–298C). In experiment 2, 80-d-old, postmetamorphic fish (1.46 6 0.52 g) were exposed to 0, 5, 10, 20, and
30-ppt salinity (21–268C). Mortality was markedly higher at salinities of 20 ppt (52% and 74%, respectively,
for pre- and postmetamorphic fish) and 30 ppt (100% and 90%, respectively) than at 0 and 5 ppt (,1%).
Specific growth rate (SGR) and feed conversion efficiency (FCE) were highest at 0-ppt salinity for
premetamorphic fish (SGR ¼ 8.81% per day; FCE ¼ 1.12) and at 5-ppt salinity for postmetamorphic fish
(SGR ¼ 4.59% per day; FCE ¼ 0.87). The SGR and FCE were lowest at 30-ppt salinity, and a significant
negative relationship was demonstrated between salinity and SGR and between salinity and FCE. In both
experiments, SGR and FCE were positively correlated. Our observations demonstrate that culture of young
American shad may be possible at salinities up to 10 ppt, but 0–5-ppt salinity produced the best growth.
Salinity is an important environmental factor
affecting fish survival, growth, and distribution, and
its interaction with temperature is complex (Boeuf and
Payan 2001; Schreiber 2001). It is generally accepted
that the energetic cost of osmoregulation is lower in an
isosmotic medium, where the gradients between blood
and water are minimal, and that these energy savings
are substantial enough to increase growth (Brett 1979).
However, optimal salinities for growth and metabolic
rates are influenced both by species and developmental
status (Morgan and Iwama 1991). Growth increases
can be mediated by direct effects of salinity on food
intake and food conversion efficiency or indirectly by
physiological consequences of salinity exposure
(Boeuf and Payan 2001).
The Reeves shad Tenualosa reevesii is an anadro-
mous herring native to China (Wang and St. Pierre
1997). It historically constituted a significant fishery in
China and has experienced dramatic depletions due to
common factors, such as overfishing and alteration,
degradation, and loss of habitat. The Reeves shad is in
great demand at local markets and commands a high
price due to its scarcity and particularly esteemed value
in Chinese culture (Qiu et al. 1998; Liu et al. 2002;
Wang 2003). The morphologically similar American
shad Alosa sapidissima is considered an emerging
aquaculture species in China (Liu et al. 2006) and
could be a potential alternative to alleviate commercial
pressure on Reeves shad. Establishing the conditions
required for optimal growth of American shad will play
a key role in the development of future aquaculture
efforts.
Although larval American shad naturally live in
freshwater, their growth rate may not be optimal in
freshwater compared with that in a saline environment.
Several studies have reported the effects of salinity on
* Corresponding author: [email protected]
Received November 16, 2007; accepted July 25, 2008Published online May 7, 2009
197
North American Journal of Aquaculture 71:197–205, 2009� Copyright by the American Fisheries Society 2009DOI: 10.1577/A07-095.1
[Article]
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American shad (e.g., Chittenden 1973; Howey 1985;
Shrimpton et al. 2001). However, the contradictory
results of these experiments do not provide enough
information for proper salinity management.
In this study, we evaluated survival, growth, and
feed utilization of American shad exposed for 30 d to
salinity concentrations from 0 to 30 ppt. Two
experiments were conducted: the first began with 25-
d-old American shad that would be undergoing
metamorphic transformation from the larval to juvenile
stage during the experiment (see Zydlewski and
McCormick 1997), and the second began with 80-d-
old, postmetamorphic juveniles that presumably would
have the osmoregulatory capacity for oceanic migra-
tion. Our objective was to identify the optimal salinity
for use during early culture of American shad.
Methods
Experimental fish.—In June 2006, American shad
eggs were obtained from Shanghai Aquaculture
Research Institute, Shanghai, People’s Republic of
China, and were cultured at Aegis EcoTechnology
Company, Ltd. in Shanghai. Hatched larvae were
stocked in circular concrete tanks containing 9 m3 of
freshwater (hardness ¼ 7.40 mg/L; calcium ¼ 90.18
mg/L; pH¼ 6.9). About 20% of the rearing water was
exchanged daily. Larvae were fed rotifers beginning at
3 d posthatch and were gradually converted to a dry
shrimp diet (Shunde Aquatic Feed Company, Guang-
dong, China) beginning at 7 d posthatch. All
experimental fish were randomly selected from this
hatchery population.
The effects of salinity on culture of American shad
were investigated in two separate 30-d periods. In
experiment 1, 25-d-old, premetamorphic fish (mean
weight 6 SD¼ 0.07 6 0.04 g; total length [TL]¼ 23.4
6 2.6 mm) were exposed to 0, 10, 20, and 30-ppt
salinity. During the course of experiment 1, the
metamorphic transition from larvae to juveniles was
completed. In experiment 2, 80-d-old postmetamorphic
fish (1.46 6 0.52 g; 56.3 6 5.0 mm TL) were exposed
to 0, 5, 10, 20, and 30-ppt salinity.
Experimental conditions.—Fish were exposed to
each salinity treatment in independent recirculating
water systems. Each salinity treatment was conducted
in duplicate, so there were eight systems in experiment
1 and 10 systems in experiment 2. Each independent
recirculating system contained one circular concrete
tank (2 m2) with a water depth of 50 cm for rearing fish
and one silo tank for upwelling filtration. Water flow
rate in each system was 9 L/min. Salinity concentra-
tions (measured with a YSI Model 85 salinity meter;
Yellow Springs Instruments, Yellow Springs, Ohio)
were gradually obtained over a period of 2 d by
addition of commercial artificial ocean salts. Water
temperatures ranged from 268C to 298C in experiment
1 and from 218C to 268C in experiment 2. Dissolved
oxygen was measured daily and remained above 5 mg/
L throughout the two experimental periods. Density in
each rearing tank was 1,000 fish/m3 in experiment 1
and 260 fish/m3 in experiment 2.
Feeding.—The same person fed fish throughout both
experiments for consistency in diet application. Fish
were fed to apparent satiation four times per day.
Initially, a small amount of diet was offered during the
feeding, but as more fish assembled at the feeding
location more food was offered. As fish that were fed
to satiation dispersed from the feeding location, the
amount of diet offered was gradually decreased. Diet
offering ceased when fish stopped eating. Total weight
of food offered daily was recorded as feed intake (FI).
Experiment 1 was terminated after 27 d due to 100%mortality in both replicates of 30-ppt salinity. Thirty
fingerlings from each tank were individually weighed
(nearest 0.01 g) and measured for TL (nearest 0.1 mm)
on days 0, 10, 20, and 27 (for experiment 1) or 30 (for
experiment 2).
Data analyses.—Condition factor (K) was calculated
as:
K ¼ 105 3½ðbody weight; gÞ=ðTL; mmÞ�:
Dead fish were removed and counted from each tank
daily, and cumulative mortality was calculated as:
Cumulative mortality ð%Þ ¼ 100
3total number of dead fish
initial number of fish
� �:
Feeding rate (FR, %), specific growth rate (SGR, % per
day), and feed conversion efficiency (FCE) were
calculated as:
FR ¼ 100 3 ðFI 3 2Þ=½t 3ðWt þW0Þ�f g;SGR ¼ 100 3½ðlogeWt � logeW0Þ=t�;
and
FCE ¼ ðWt �W0Þ=FI;
where FI is total feed intake (g), t is the duration of the
experiment (d), Wtis the final wet body weight (g), and
W0
is the initial wet body weight.
Statistical analyses were performed using STATIS-
TICA version 6.0 (StatSoft, Inc.). One-way analysis of
variance (ANOVA) was used to evaluate the effect of
salinity on mortality, and repeated-measures ANOVA
was used to assess the effect of salinity on body weight
and K. Differences among treatment means were
identified using Duncan’s multiple comparison tests.
Linear regression was used to analyze the relationships
198 JIA ET AL.
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TABLE 1.—Body weight (g) and condition factor of pre- and postmetamorphic American shad exposed to different salinities
(0–30ppt) for up to 30 d. Values represent the mean (6SD) of two replicates at each salinity level; 30 fish from each replicate
were sampled on each date. Within a row, means followed by different letters are significantly different (P , 0.05).
Day of experiment(d posthatch)
Salinity (ppt)
0 5 10 20 30
Experiment 1 (premetamorphic fish): duplicate tanks, 1,000 fish/m3
Body weight
0 (25) 0.07 6 0.04 0.07 6 0.04 0.07 6 0.04 0.07 6 0.0410 (35) 0.39 6 0.10 0.29 6 0.05 0.32 6 0.07 0.23 6 0.0720 (45) 0.90 6 0.05 0.66 6 0.07 0.74a 0.35a
27 (52)b 1.47 6 0.21 1.05 6 0.15 0.90a 0.52a
Condition factor
0 (25) 0.52 6 0.15 0.52 6 0.15 0.52 6 0.15 0.52 6 0.1510 (35) 0.77 6 0.03 0.72 6 0.02 0.73 6 0.06 0.67 6 0.0020 (45) 0.90 6 0.00 0.78 6 0.01 0.84a 0.76a
27 (52)b 0.89 6 0.01 0.86 6 0.02 0.73a 0.70a
Experiment 2 (postmetamorphic fish): duplicate tanks, 260 fish/m3
Body weight
0 (80) 1.46 6 0.52 1.46 6 0.52 1.46 6 0.52 1.46 6 0.52 1.46 6 0.5210 (90) 2.84 6 0.10 2.64 6 0.21 2.32 6 0.15 2.23 6 0.48 2.09 6 0.3120 (100) 3.90 6 0.30 3.99 6 0.11 2.69 6 0.73 2.86a 1.85a
30 (110) 5.15 6 0.54 z 5.54 6 0.48 z 2.61 6 0.46 y 2.70a y 2.15a y
Condition factor
0 (80) 0.79 6 0.17 0.79 6 0.17 0.79 6 0.17 0.79 6 0.17 0.79 6 0.1710 (90) 1.00 6 0.00 0.97 6 0.02 0.92 6 0.02 0.86 6 0.16 0.87 6 0.0420 (100) 0.91 6 0.04 0.97 6 0.02 0.81 6 0.03 0.85a 0.78a
30 (110) 1.00 6 0.04 z 0.98 6 0.04 z 0.83 6 0.01 y 0.75a y 0.77a y
a Values represent data from a single replicate due to 100% mortality in the second replicate.b Experiment 1 was terminated early due to 100% mortality of both replicates at 30-ppt salinity.
FIGURE 1.—Cumulative mortalities (%) of pre- and postmetamorphic American shad exposed to different salinities (0–30%[ppt]) for up to 30 d. Values represent the mean of two replicates for each salinity level. Experiment 1 was terminated after 27 d
due to 100% mortality in both replicates of 30% salinity.
SALINITY EFFECTS ON AMERICAN SHAD 199
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between salinity and FR, SGR, and FCE, and between
growth rate and FCE. Significance was accepted at P-
values less than 0.05.
Results
Mortality
Heavy mortality began in one replicate of 20- and
30-ppt salinity on day 10 of both experiments, and all
fish in these replicates were dead by day 20. No known
explanation is apparent for the differential mortality
between replicates, as water quality remained similar
throughout the experimental periods. Experiment 1 was
prematurely terminated on day 27 due to 100%mortality of fish in the second replicate of 30-ppt
salinity. A Saprolegnia fungal infestation (identified by
a local aquaculture disease researcher) began on day 13
at 10-ppt salinity in experiment 2.
Cumulative mortality of pre- or postmetamorphic
American shad was less than 1% at 0-, 5-, and 10-ppt
salinity (Figure 1). All treatment groups had low
mortality during the first 10 d of the experiment, but
mortality increased sharply for the groups at 20- and
30-ppt salinity as the experiment progressed. Mortality
averaged 52% and 100% at 20- and 30-ppt salinity,
respectively, for premetamorphic fish by the end of
experiment 1. Average mortality was 74% and 90% at
20- and 30-ppt salinity, respectively, for postmetamor-
phic fish by the end of experiment 2. Significant
differences in mortality were not evident in premeta-
morphic (F3,4¼ 3.93, P ¼ 0.11) or postmetamorphic
(F4,5¼ 2.80, P ¼ 0.14) fish exposed to different
salinities.
Growth
Salinity did not significantly affect body weight (P¼0.14) or K (P¼ 0.05) of premetamorphic fish, although
time (P¼ 0.00 for both weight and K) and the time 3
salinity interaction (P ¼ 0.03 and P ¼ 0.01 for weight
and K, respectively) were significant. By the end of
experiment 1, fish weight increased to 21, 15, 13, and 7
times the initial weights in 0-, 10-, 20-, and 30-ppt
salinity treatment groups, respectively (Table 1). Fish
in the 0-ppt salinity group were nearly three times
heavier (1.47 g) than fish in the 30-ppt salinity group
(0.52 g). The K-value increased by 73% for fish held at
0-ppt salinity compared with only a 30% increase in K
FIGURE 2.—Specific growth rates (SGR, % per day) of pre- and postmetamorphic American shad exposed to different salinities
(S, 0–30% [ppt]) for up to 30 d. Each point represents the value of one replicate (30 fish/replicate were sampled at the end of
each experiment). Experiment 1 was terminated after 27 d due to 100% mortality in both replicates of 30% salinity. Trends were
evaluated using linear regression analysis (significance at P , 0.05).
200 JIA ET AL.
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at 30-ppt salinity. Condition factor of premetamorphic
fish ranged from 0.89 at 0- and 10-ppt salinity to 0.70
at 30-ppt salinity.
Salinity, time, and the salinity 3 time interaction
significantly affected body weight and K of postmeta-
morphic fish (Table 2). By the end of experiment 2,
fish held at 0- (5.15 g) and 5-ppt (5.54 g) salinity
weighed about twice as much as fish held at salinity
levels of 10 (2.61 g), 20 (2.70 g), and 30 ppt (2.15 g;
Table 1). Fish in 0- and 5-ppt salinity treatment groups
also increased their weight about 3.5 times over initial
weight compared with increases of 1.5–1.8 times for
fish held at higher salinities. Condition factors of
postmetamorphic fish held at 0- (1.00) and 5-ppt (0.98)
salinity were significantly higher than those of fish held
at 10- (0.83), 20- (0.75), and 30-ppt (0.77) salinity.
The SGR of pre- and postmetamorphic American
shad decreased with increasing salinity (Figure 2). The
significant inverse relationship was characterized by
the linear equation SGR¼ 8.8435� (0.0930 3 salinity)
(n ¼ 6, r ¼ �0.95, r2 ¼ 0.89, P ¼ 0.00) for
premetamorphic fish and SGR ¼ 4.3364 � (0.1133 3
salinity) (n ¼ 8, r ¼�0.84, r2 ¼ 0.70, P ¼ 0.01) for
postmetamorphic fish.
Feed Utilization
The FR of premetamorphic American shad increased
with salinity in experiment 1 (Figure 3). Fish at higher
salinities consumed more feed, resulting in a positive
linear relationship (FR¼ 7.1474þ [0.0714 3 salinity];
n ¼ 6, r ¼ 0.90, r2 ¼ 0.89, P ¼ 0.01). Although FI
increased at higher salinities, FCE decreased with
increasing salinity (Figure 4), resulting in a negative
linear relationship (FCE ¼ 1.1353 � [0.0156 3
salinity]; n ¼ 6, r ¼�0.95, r2 ¼ 0.90, P ¼ 0.00).
For postmetamorphic American shad, no significant
linear relationship existed between FR and salinity (FR
¼ 4.6091 þ [0.0135 3 salinity]; n ¼ 8, r ¼ 0.36, r2 ¼0.13, P¼ 0.39; Figure 3). However, as was found with
premetamorphic fish, a negative linear relationship was
expressed between FCE and salinity (FCE¼ 0.8246�[0.0203 3 salinity]; n ¼ 8, r ¼�0.89, r2 ¼ 0.79, P ¼0.00; Figure 4).
Increased FCE translated into increased growth in
both experimental exposures of American shad to
FIGURE 3.—Feeding rates (FR, %) of pre- and postmetamorphic American shad exposed to different salinities (S, 0–30% [ppt])
for up to 30 d. Each point represents the value of one replicate (30 fish/replicate were sampled at the end of each experiment).
Experiment 1 was terminated after 27 d due to 100% mortality in both replicates of 30% salinity. Trends were evaluated using
linear regression analysis (significance at P , 0.05).
SALINITY EFFECTS ON AMERICAN SHAD 201
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different salinities (Figure 5). Linear equations of SGR
¼ 2.9878þ (5.0059 3 FCE) (n¼ 6, r¼ 0.84, r2¼ 0.71,
P¼ 0.04) and SGR¼�0.3850þ (5.7767 3 FCE) (n¼8, r ¼ 0.98, r2 ¼ 0.96, P ¼ 0.00) expressed positive
relationships for pre- and postmetamorphic fish,
respectively.
Discussion
American shad fingerlings in our experiments
survived and grew in salinity levels of up to 30 ppt
for about 10 d, but high mortalities appeared in
salinities of 20 and 30 ppt and mortality reached 100%
as the experimental period progressed. Negative
relationships also existed between increasing salinity
and SGR and FCE in pre- and postmetamorphic
juveniles. The issue of salinity use in culture of
American shad is confusing, as both positive and
negative effects of salinity on survival and growth have
been reported (Tagatz 1961; Limburg and Ross 1995;
Zydlewski and McCormick 1997; Shrimpton et al.
2001). Inconsistent outcomes in these studies may
result from confounding factors, including the age of
the fish used (i.e., whether pre- or postmetamorphic),
the duration of the exposure to salinity, and prior
acclimation to saltwater. Also, the extremely high
sensitivity of American shad to handling and confine-
ment cannot be overlooked as a complicating factor
when trying to determine salinity tolerance of this
species (Chittenden 1971; Backman and Ross 1990).
Zydlewski and McCormick (1997) found that
Connecticut River American shad could not survive
direct transfer from freshwater to 35-ppt salinity until
they were at least 36 d posthatch (i.e., premetamorphic
fish) and that survival increased dramatically up to
nearly 100% from 45 to 127 d posthatch (i.e.,
postmetamorphic fish). We did not see this early
mortality pattern, but our fish were acclimated to the
desired salinity over a 2-d period and were exposed
consistently from 25 or 80 d posthatch. American shad
taken from brackish water also were found to tolerate
salinity increases, both abrupt and gradual, up to full-
strength seawater (Chittenden 1973). Prior acclimation
to salt water may reduce the stress response of
American shad fingerlings to salinity.
Limburg and Ross (1995) evaluated early (16 d old,
originating from the Hudson River) and late (35 d old,
FIGURE 4.—Feed conversion efficiency (FCE) of pre- and postmetamorphic American shad exposed to different salinities (S,
0–30% [ppt]) for up to 30 d. Each point represents the value of one replicate (30 fish/replicate were sampled at the end of each
experiment). Experiment 1 was terminated after 27 d due to 100% mortality in both replicates of 30% salinity. Trends were
evaluated using linear regression analysis (significance at P , 0.05).
202 JIA ET AL.
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originating from the Delaware River) premetamorphic
fish exposed to low (0–1 ppt), medium (9–11 ppt), or
high (19–20 ppt) salinity. Their experiments lasted 8
and 9 d, and they found that neither mortality nor
growth of American shad was adversely affected by
medium or high salinity compared with freshwater. We
observed similar results in our pre- and postmetamor-
phic fish up to the 10th day of exposure, but significant
mortality and decreased growth were evident at 20- and
30-ppt salinity during the remainder of the study.
Zydlewski and McCormick (1997) found that 24-h
survival in 35-ppt salinity was a good indicator of long-
term survival and growth in postmetamorphic (45-d-
old) American shad, but their long-term experiment
lasted only 7 d. Negative effects of salinity on the
survival and growth of American shad juveniles may
have a delay or lag phase; thus, short-term exposures
may not be entirely reliable for long-term survival
estimates.
The most extensive study of American shad cultured
in freshwater (from fertilized egg to 250 d posthatch)
was conducted by Howey (1985). Howey (1985)
reported that the early growth phases of American
shad mimicked those of natural populations but that
hatchery-reared fish did not reach the size typical for
the onset of metamorphosis until they were 6–11 weeks
posthatch compared with 3 weeks posthatch for wild
fish. Our experiments on premetamorphic and post-
metamorphic American shad followed those reported
growth phases very closely; however, the actual weight
of fish in our study matched those of wild fish more
closely than the hatchery-reared fish in Howey’s
(1985) experiment. Warmer temperatures in our
experiments (21–298C) compared with those of Howey
(1985; 16–188C) may account for the observed
differences in growth rates.
Although high salinity is stressful and detrimental to
American shad, freshwater may not be optimal. Millard
et al. (2001) reported that American shad broodfish held
for 7 d had higher survival in 2–4-ppt salinity than in
freshwater. Also, Fletcher and Millard (2002) reported
that broodfish survival, egg production, and egg
viability were greater in 3-ppt salinity than in freshwater
and that American shad held in freshwater exhibited
greater postspawn stress than those held at 3-ppt
salinity. Our lowest experimental salinity had analogous
FIGURE 5.—Relationship between specific growth rate (SGR, %/d) and feed conversion efficiency (FCE) of pre- and
postmetamorphic American shad exposed to different salinities (S, 0–30% [ppt]) for up to 30 d. Each point represents the value
of one replicate (30 fish/replicate were sampled at the end of each experiment). Experiment 1 was terminated after 27 d due to
100% mortality in both replicates of 30% salinity. Trends were evaluated using linear regression analysis (significance at P ,
0.05).
SALINITY EFFECTS ON AMERICAN SHAD 203
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results in juveniles, where mortality, growth, and FCE
in freshwater and 5-ppt salinity were similar after 30 d.
To our knowledge, this is the first report of salinity
effects on FCE in American shad. As was observed for
Atlantic cod Gadus morhua (Lambert et al. 1994) and
the striped catfish Mystus vittatus (a freshwater species;
Arunachalam and Reddy 1979), FCE was highest at the
lowest salinity and showed a decreasing trend as
salinity increased. Osmoregulatory processes are con-
sidered to have an energetic cost, and the energy used
for osmoregulation is not available for growth (Brett
1979; Wootton 1990). Increase in assignment of energy
consumed to osmoregulation may result in the decrease
in feed utilization at high salinity. In addition, a high
linear correlation (r2 ¼ 0.71 and 0.93 for pre- and
postmetamorphic fish, respectively) was shown be-
tween growth rate and FCE. The inhibitory effect of
high salinity on growth of American shad fingerlings
may work by decreasing food utilization efficiency.
Our results describing salinity effects on survival of
American shad were not definitive, although the trend
was high mortality at the highest salinities (20 and 30
ppt) for both pre- and postmetamorphic fish compared
with high survival at 0–10-ppt salinity. Growth rate
was higher at 0-ppt salinity for premetamorphic fish
and at 0- and 5-ppt salinity for postmetamorphic fish
compared with higher salinities due to the inhibitory
effect of high salinity on FCE. These results demon-
strate that successful culture of pre- and postmetamor-
phic American shad is possible in salinities up to 10
ppt, but the optimal salinity level is probably between 0
and 5 ppt.
Acknowledgments
Funds for this study were provided by the Shanghai
Agriculture Technology Promotion Project (HNKT
2004-163).
TABLE 2.—Results of repeated-measures analysis of variance comparing changes in body weight (g) and condition factor of
pre- and postmetamorphic American shad exposed to different salinities (0–30ppt) for up to 30 d (2 tanks/salinity level).
Significance was accepted at P-values less than 0.05.
Source of variation Mean square df F P
Experiment 1 (premetamorphic fish)a
Body weight
Between salinity treatments:Salinity 0.2191 3 6.532 0.14Error 0.0335 2
Within subjects:Time 0.6287 2 141.3 0.00Time 3 salinity 0.0369 6 8.298 0.03Error 0.0178 4
Condition factor
Between tanks:Salinity 0.0147 3 19.03 0.05Error 0.0008 2
Within tanks:Time 0.0103 2 46.67 0.00Time 3 salinity 0.0037 6 14.26 0.01Error 0.0002 4
Experiment 2 (postmetamorphic fish)
Body weight
Between tanks:Salinity 14.823 4 11.12 0.04Error 0.9992 3
Within subjects:Time 2.1398 2 28.876 0.00Time 3 salinity 0.8225 8 11.099 0.00Error 0.0741 6
Condition factor
Between tanks:Salinity 0.0242 4 20.88 0.02Error 0.0035 3
Within tanks:Time 0.0373 2 31.37 0.00Time 3 salinity 0.0319 8 6.72 0.02Error 0.0036 6 0.00
a Experiment 1 was terminated after 27 d due to 100% mortality in both replicates of 30-ppt salinity.
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