Journal of Thermal Biology 27 (2002) 433–437

Effect of temperature on spawning of Penaeus merguiensis

Tung Hoanga,*, S.Y. Leea, Clive P. Keenanb, Gay E. Marsdenc

a School of Environmental & Applied Sciences, Griffith University, Qld 9726, Australiab Bribie Island Aquaculture Research Centre, P.O. Box 2066, 144 North Street, Bribie Island, Qld 4507, Australia

c NFIEC, TAFE, Locked Bag 5, Grafton, NSW 2460, Australia

Received 22 September 2001; accepted 1 February 2002

Abstract

The maturation rate and spawning performance of ablated Penaeus merguiensis were significantly (Po0:05) higher at

271C than at 231C. Increasing the temperature from 231C to 271C further improved spawning performance (Po0:05),

whereas reducing the temperature from 271C to 231C impaired spawning. The effect of temperature during the inducing

period was more critical than during the holding period. Prawn growth (% of weight gain), however, was not different

between 231C and 271C over the 60-day experimental period (P > 0:05). r 2002 Elsevier Science Ltd. All rights

reserved.

Keywords: Temperature; Ovarian maturation; Spawning; Penaeus merguiensis; Growth; Prawn

1. Introduction

The banana prawn, Penaeus merguiensis, is an

important species for commercial fisheries in the Indo-

Pacific region (Grey et al., 1983). This species, however,

has been ignored by modern shrimp farmers because it

does not grow as fast as P. monodon, the major culture

species. Thus, information about reproductive biology

of captive P. merguiensis is limited compared with other

culture species. However, the recent shortage of quality

P. monodon post-larvae for grow-out in southeast Asia

and Australia has prompted more farmers to culture P.

merguiensis; and the change has been good (Hoang,

2001). Therefore, further research on its reproductive

biology is needed to aid hatchery production.

Water temperature is one of the environmental factors

that strongly influence prawn reproduction (Muncy,

1984; Primavera, 1985; Staples, 1991; Bray and Lawr-

ence, 1992). In natural context, an increase of tempera-

ture from late winter to spring is believed as one of the

cues that trigger spawning of prawns (Dall et al., 1990;

Yano, 1993). Simultaneously increasing temperature

and day length has been reported to stimulate ovarian

maturation and spawning of P. japonicus (Laubier-

Bonichon and Laubier, 1979, cited by Primavera, 1985),

P. duorarum (Cripe, 1994) and P. stylirostris (Chamber-

lain and Gervais, 1984). Rothlisberg and Jackson (1985),

based on field sampling of larval abundance, suggested

that 291C is optimal for reproduction of P. merguiensis

in the tropical northern Australia. However, the effect of

temperature on reproduction of subtropical P. mer-

guiensis has not been reported. Dredge (1985) reported

the absence of ripe P. merguiensis females during winter

in the central Queensland coast, Australia. This in-

dicates that a low temperature is unsuitable for ovarian

maturation and spawning of this species. Recent study

on the cold tolerance of P. merguiensis suggests that the

species can cope with low temperatures, enabling two

culture crops per year in the subtropical southeast

Queensland, Australia (Hoang et al., 2002). Breeding P.

merguiensis to produce post-larvae for stocking, there-

fore, may require temperature manipulation as this

environmental factor varies seasonally.

In this study, the effect of low and high temperatures

(in the holding and inducing periods) on ovarian

maturation and spawning of P. merguiensis was

*Corresponding author. Present address: Bribie Island

Aquaculture Research Centre, P.O. Box 2066, 144 North

Street, Bribie Island, QLD 4507, Australia. Tel.: +61-7-3400-

2020; fax: +61-7-3408-3535.

E-mail address: tung.hoang@dpi.qld.gov.au (T. Hoang).

0306-4565/02/$ - see front matter r 2002 Elsevier Science Ltd. All rights reserved.

PII: S 0 3 0 6 - 4 5 6 5 ( 0 2 ) 0 0 0 1 3 - X

investigated. The effect of short-term raising and

reducing temperature was also examined. Other envir-

onmental parameters such as photoperiod, light

intensity, salinity and pH were maintained at optimal

levels in order to demonstrate the profound effect of

temperature.

2. Materials and methods

Female prawns were randomly collected from the

grow-out tanks (60 m3 in volume) at Bribie Island

Aquaculture Research Centre, Queensland, Australia

in early spring 2000. Average carapace length (CL) and

weight (W ) at collection time was 22.971.2 mm (SD)

and 7.671.2 g (SD), respectively. Prawns were then

stocked in twelve 1-m3 tanks (fiber glass, painted black,

40 cm water depth) at a density of 5 individuals tank�1.

The experiment used a flow-through system; water used

in the experimental period was continuously exchanged

at a rate of 300% volume day�1. During the experi-

mental period, photoperiod, light intensity, salinity and

pH were maintained at 14L:10D, 2–3 lux, 34.5–35.1 ppt

and 8.0–8.1, respectively. Prawns were fed with 10% of

biomass day�1 by the BIARC maturation diet (a

mixture of fresh frozen green mussel, squid, calf liver

and other essential nutrients; 54.6% crude protein;

Marsden et al., 1997) and 2% of biomass day�1 by

EBI STAR pellets (50% crude protein, Higashimaru,

Japan) at 09:30 and 17:00. The experimental tanks were

cleaned twice a day prior to feeding.

The experiment had two consecutive periods: holding

(39 days) and inducing (21 days). Two levels of water

temperature (high: 271C and low: 231C) were tested in

each period, establishing four combinations of treat-

ments namely: high–high (HH), high–low (HL), low–

low (LL) and low–high (LH). Each treatment had three

replicate tanks. In the HH and LL treatments, water

temperature was maintained at 271C and 231C, respec-

tively, throughout the experimental period. In the HL

treatment, water temperature was 271C during the first

28 days, then reduced to 231C (within 24 h) from day 29

and maintained at this level until the end of the

experiment. In the LH treatment, water temperature

was 231C during the first 28 days, then increased to 271C

(within 24 h) on day 29 and was maintained at this level

until the end of the experiment. To induce spawning, all

the prawns were unilaterally ablated on day 39 (10 days

after the water temperature was increased in the LH

treatment and reduced in the HL treatment).

Ovarian maturation was checked daily at 17:30,

following the descriptions provided by Tuma (1967)

and Primavera (1985). Females with stage-IV ovaries

were then transferred to 150-l spawning tanks and

returned to the corresponding experimental tank early

next morning. Water temperature in the spawning tank

was similar to that in the experimental tank where the

spawner was taken from. Sampling for fecundity was

conducted by vigorously agitating the tank water to

ensure a homogenous suspension of eggs, then quickly

taking 100-ml aliquot samples and counting the number

of eggs in each sample under a stereo microscope.

Data were analyzed with Genstat 4.1 for Windows

(Payne et al., 1993). Analysis of variance (ANOVA) and

least significant difference (LSD) multiple-range proce-

dure were used to detect the statistical difference among

the treatments. The percentage of spawners and the

percentage of prawns reaching stage IV were analyzed

by a generalized linear model (modeling of binomial

proportions by logits) (McCullagh and Nelder, 1989).

Due to the limited number of observations, no statistical

test was conducted for latency period and fecundity.

Means were calculated and presented for only prawns

that spawned. The latency period is defined as the

number of days from eyestalk ablation to the first

spawning of a spawner. The number of spawns

produced by prawn individuals (i.e. number of spawns

female�1) was adjusted by the number of survival days,

presumably capable of spawning.

3. Results

Prawns started to spawn 6 days after eyestalk

ablation. More prawns reached full ovarian maturation

(stage IV) and were spawned at 271C, while increasing

the temperature from 231C to 271C further stimulated

ovarian maturation and spawning (Table 1). The

percentage of spawners was significantly (Po0:05)

highest in the LH treatment (73.3%), followed by the

HH (40.0%) and HL (26.7%) treatments, and lowest in

the LL treatment (6.7%) (Table 1). No significant

difference (P > 0:05) in the percentage of spawners was

found between the HH and HL treatments (treatments

that had a high temperature during the holding period),

and between the HL and LL treatments (treatments that

had a low temperature during the inducing period). The

numbers of spawns female�1 in the LH and HH

treatments was significantly (Po0.05) higher than the

HL and LL treatments, averaging at 0.061 and 0.048

spawns day�1, respectively (Table 1). Prawns in the HL

and LL treatments produced only 0.017 and 0.003

spawns day�1 on average, respectively. The total

number of eggs produced female�1 averaged at 63,137

in the LH and 42,870 in the HH treatments; significantly

(P > 0:05) higher than the HL and LL treatments.

Overall, the LH and HH treatments each produced

almost a million eggs during 21 days, while the HL and

LL treatments produced only 164,450 and 18,200 eggs,

respectively.

For prawns that spawned, the latency period was

similar among the HH, HL and LH treatments with

T. Hoang et al. / Journal of Thermal Biology 27 (2002) 433–437434

mean values of 12.0–13.8 days. Only one prawn spawned

in the LL treatment 17 days after eyestalk ablation

(Table 1). This prawn produced 18,200 eggs. Mean

fecundity of spawners was higher in other treatments,

ranging from 32,175 to 42,945 eggs spawn�1.

The interval between two successive spawns was usually

3 days within an intermoult period; and was extended to

5–8 days if moulting occurred between two successive

spawns.

Growth of prawns (% of weight gain) was not

significantly different (P > 0:05) among the treatments

(Table 1). However, there was a trend of reducing

growth in treatments with the lower temperature (231C).

Growth of prawns in the LH treatment was likely to be

affected by high spawning rate. Survival was high in all

the treatments: 86.7%, 93.3%, 93.3% and 100% in the

LL, LH, HH and HL treatments, respectively.

4. Discussion

From the results of this study, it is clear that water

temperature has a strong effect on ovarian maturation

and spawning of P. merguiensis. The percentage of

spawners, number of spawns female�1 and total eggs

produced female�1 were all significantly higher

(Po0:05) in treatments with the higher water tempera-

ture (271C) during the period that prawns were induced

to spawn, i.e. during ovarian maturation. The formation

of oocytes during ovarian maturation requires a

substantial mobilization of nutrients from other tissues,

e.g. hepatopancreas and food intake for the synthesis of

new materials, e.g. vitellogenin (Harrison, 1990; Wou-

ters et al., 2001), which is regulated by hormones (Yano,

1998; Huberman, 2000). The lower temperature (231C)

in this study may have retarded these processes, thus

compromising the completion of ovarian maturation or

reducing fecundity. Although photoperiod, light inten-

sity, salinity and pH were generally optimal for penaeid

reproduction (Primavera, 1985; Bray and Lawrence,

1992), spawning performance of prawns was poor in

treatments that had lower water temperature (231C)

during the inducing period. This may indicate that the

effect of temperature can override those aforementioned

environmental factors. Alternatively, ovarian maturation

can be induced by eyestalk ablation, but a suitable

temperature is still a requisite for the success of the

process and spawning. This finding is in agreement with

previous studies on penaeid species. Rothlisberg et al.

(1987) suggested that temperature might be the factor that

controls spawning pattern of penaeid prawns in natural

conditions. During winter ripe P. merguiensis females were

absent in the central Queensland coast (Dredge, 1985) and

were significantly reduced in number in the Gulf of

Carpentaria, northern Australia (Crocos and Kerr, 1983).

Similarly, Penn (1980) reported neither maturation nor

spawning of P. latisulcatus in Cockburn Sound when

water temperatures were o171C. In laboratory condi-

tions, high maturation and spawning rate of P. esculentus

were achieved at 261C, while only a few spawnings were

achieved at 201C (Crocos and Kerr, 1986).

Furthermore, the water temperatures in which the

prawns had been held previously (before spawning was

induced) and its patterns (increasing or reducing) also

influenced the spawning performance of prawns. The

HL treatment had a favorable result compared to the

LL treatment, suggesting that the higher temperature

during the first 28 days (holding period) in this treatment

was beneficial to ovarian maturation and spawning

performance of the prawns later. However, when

compared with the HH treatment, it is clear that

reducing the temperature from 271C to 231C severely

affected spawning performance of prawns. In contrast,

despite the fact that prawns were held in 231C during the

first 28 days, increasing the temperature from 231C to

271C in the LH treatment significantly improved the

Table 1

Maturation and spawning performance of prawns

Variables Treatment

HH HL LL LH

Percentage of prawns reaching stage IV 6079.1 ab 33.378.7 bc 13.376.3 c 8077.4 a

Percentage of spawners 4078.6 b 26.777.7 bc 6.774.4 c 73.377.7 a

Latency period (days)a 12.070.9 13.870.4 17.0 12.871.6

Number of spawns female�1 day�1 0.04870.005 a 0.01770.003 b 0.003 b 0.06170.006 a

Fecunditya 40,17173962 32,17575461 18,200 42,94577750

Total eggs produced female�1 42,87078726 a 10,96373337 b 1213 b 63,137712,186 a

Total eggs produced treatment�1 899,050 164,450 18,200 947,050

Weight gain (%) 129730.8 127724.4 119711.7 105719.8

Data are means7SE; within rows; means with different alphabets are significantly different (Po0:05).a No statistical test was conducted due to the limited number of observations. Means were calculated only for prawns that spawned.

Only one spawn was recorded in the LL treatment.

T. Hoang et al. / Journal of Thermal Biology 27 (2002) 433–437 435

percentage of spawners and spawning performance of

prawns; it even appeared better than the HH treatment.

This somehow suggests that the varying pattern of

temperature may be as important as, if not more

important than, its static levels (high or low) on

spawning of P. merguiensis. Furthermore, the results

of this study suggest that the effect of temperature

during the inducing period is more important than the

holding period.

Similar results have been reported for other penaeid

species. Simultaneously increasing temperature and

day length resulted in ovarian maturation of P. japonicus

(from 151C to 281C; Laubier–Bonichon and Laubier,

1979, cited by Primavera, 1985), P. stylirostris

(from 181C to 281C; Chamberlain and Gervais, 1984)

and P. duorarum (from 211C to 281C; Cripe, 1994).

Increasing the temperature from 201C to 281C alone

stimulated mating in P. stylirostris (Robertson et al.,

1991).

Therefore, the induction of spawning in P. merguien-

sis should involve raising water temperature to assist

eyestalk ablation; and must be maintained at a favorable

level for high ovarian maturation and spawning rate.

Field survey in the tropical northern Australia suggests

the optimal temperature for spawning and larval

development of P. merguiensis is 291C (Rothlisberg

and Jackson, 1985). Success in breeding P. merguiensis

in tropical areas was also reported at 25–311C (Beard

et al., 1977); 26–301C (Nurjana and Yang, 1976). In

subtropical areas natural water temperature is rarely

over 271C. Our observations show that ablated P.

merguiensis had a higher mortality when maintained at

29–301C. Therefore, 271C is more suitable for breeding

this species in subtropical areas.

Within the range of temperature from 231C to 271C in

this study, prawn growth was not significantly (P > 0:05)

different among the treatments although there was a

trend of reducing growth in treatments with the lower

temperature (231C). It is probable that, for P. merguien-

sis in subtropical areas, 231C might not adversely affect

prawn growth. Staples and Heales (1991) also reported

that a combination of 201C and 20 ppt resulted in

highest survival and greatest biomass increases of P.

merguiensis juveniles. In this present study, low growth

rate of prawns in the LH treatment appeared to be a

combined result of a lower temperature during the first

28 days and their higher spawning rate later on. With an

interval between two successive spawns as short as 3

days, prawn spawners are believed to mobilize their own

energy more than from daily intake for reproduction

(Harrison, 1990). Higher spawning rate, therefore, is

likely to result in depressed growth. Since prawn growth

was not affected at 231C, this may facilitate holding

prawn broodstock at this level before raising tempera-

ture up to 271C to stimulate spawning of ablated P.

merguiensis.

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