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This article was downloaded by: [Washington State University Libraries ] On: 25 October 2014, At: 00:05 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK North American Journal of Aquaculture Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/unaj20 Survival, Growth, and Feed Utilization of Pre- and Postmetamorphic American Shad Exposed to Increasing Salinity Yanju Jia a , Qinghua Liu b , Cheryl A. Goudie c & Bill A. Simco d a College of Biological Science and Engineering, Hebei University of Economics and Business , Shijiazhuang, 050061, People's Republic of China b Aegis EcoTechnology Development Company, Inc. , Shanghai, 201203, People's Republic of China c Aegis EcoTechnology Development Company, Inc. and Ecological Research Center , University of Memphis , Memphis, Tennessee, 38152, USA d Ecological Research Center, University of Memphis , Memphis, Tennessee, 38152, USA Published 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 Increasing Salinity, 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 PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &

Survival, Growth, and Feed Utilization of Pre- and Postmetamorphic American Shad Exposed to Increasing Salinity

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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

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the“Content”) contained in the publications on our platform. However, Taylor & Francis,our agents, and our licensors make no representations or warranties whatsoever as tothe accuracy, completeness, or suitability for any purpose of the Content. Any opinionsand views expressed in this publication are the opinions and views of the authors,and are not the views of or endorsed by Taylor & Francis. The accuracy of the Contentshould not be relied upon and should be independently verified with primary sourcesof information. Taylor and Francis shall not be liable for any losses, actions, claims,proceedings, demands, costs, expenses, damages, and other liabilities whatsoever orhowsoever caused arising directly or indirectly in connection with, in relation to or arisingout of the use of the Content.

This article may be used for research, teaching, and private study purposes. Anysubstantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &

Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions

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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.

204 JIA ET AL.

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