Giant freshwater prawn, Macrobrachium rosenbergii is grouped in caridean
crustacean belonging to the family Palaemonidae (Rabanal
and Soesanto, 1985). Indigenous of the Asia-Pacific region, M. rosenbergii
is better known as the giant Malaysian prawn and has become a major globally
cultured species. Over the last decade, its total annual production had doubled
up to 207,749 tons in 2008 which worth USD 1.1 billion (FAO,
2010). China, Thailand and Bangladesh are three main producers of M.
In the South-east Asian regions including Malaysia, the backyard hatcheries
are still the back bone in supplying the M. rosenbergii fry (Angel,
1994). There is a growing trend among the Malaysian prawn hatchery operators
to conduct the larviculture in enclosed buildings to keep the buildings warm
in the evenings as the night rearing water temperature in an open shed could
reach or nearing the lower lethal temperature, 24°C (Tayamen,
In aquaculture, enclosed buildings are used to shelter the production unit
from the environmental factors such as wind, rain, cold, heat, excessive light
and improve the working environment for the workers (Lekang,
2007). However, the main purposes for an enclosed aquaculture building are
to maintain controlled environmental conditions and provide biosecurity by minimising
the infestation of insects dust and spread of pathogens into the culture system
(Correia et al., 2000). Singh
and Marsh (1996) stated that the utilization of temperature-controlled building
or hatchery building is to maintain the inside warm temperature while warding
off cold temperature from entering the building. The enclosed building designs
for the temperate and cold climatic regions may not be suitable for the tropical
regions as the latter main design challenge is to maintain an optimal rearing
temperature for the cultured species and workers thermal comfort by warding
off excessive heat during the day and possible cooling temperature after the
ISO 7730 Standard defines thermal comfort for human as a condition of mind
which expresses satisfaction with the thermal environment (ISO
7730, 1994). While most researchers agree with the definition, the term
cannot be not easily converted into physical parameters (Olesen,
2000). An enclosed environment will cause the human body to exchange heat
by conduction, convection and radiation (Gadi, 2000a).
The temperature difference between the body and the enclosing surfaces were
affected the rate of radiative heat exchange (Gadi, 2000b).
According to De Waal (1993), air movements in a enclosed
building need to be set between 0.1 to 1.5 m sec-1 to provide an
indoor thermal comfort. It because effect from increasing air movements from
0.1 to 0.5 m sec-1 gives an increase in maximum comfort temperature
of some 3°C and further increase to 1.0 m sec-1 results in additional
1°C. However, air movement cannot increase rapidly and if greater than 1.5
m sec-1 become annoying during the day. Maximum air movement during
night is 1.0 m sec-1.
Comfort is a major concern of the Heating Ventilating and Air Conditioning
(HVAC) industry. Three main factors that can affect the human comfort are effective
temperature, moisture content of air (relative humidity) and air motion (Hussein
et al., 2001). American Society of Heating, Refrigerating and Air-conditioning
Engineers, ASHRAE (1993) quantifies parameters of a room
or space for the comfort zone in the summer season as dry bulb temperature of
22-27°C, relative humidity of 30-60% and air motion velocity of about 15
In addition to the above parameters, other factors affecting the human comfort
are heat production and regulation in human body, cold and hot surfaces and
air stratification. The deep human body temperature is about 37°C, whilst
the human skin temperature can vary between 31°C and 34°C under comfort
conditions (Auliciems and Szokolay, 1997). Human occupants
are less sensitive to relative humidity rather than variation of temperature
(Hussein et al. 2001). The knowledge of thermal
comfort behaviour of human and energy utilization behavior of buildings are
important to give the best strategy to develop in a sustainable manner.
The thermal conditions of the enclosed aquaculture buildings in the tropical
conditions especially Malaysia have not been studied. A thermal discomfort condition
in an enclosed building can be easily developed in Malaysia because it is hot
and humid tropical country and has a yearly mean temperature of between 26 to
27°C (Sabarinah, 2006). This research was conducted
to study the thermal conditions and the suitability of the building design of
a small-scaled hatchery building for the Malaysian giant freshwater prawn, M.
rosenbergii. The information gathered would be useful for the designing
of an ideal enclosed hatchery building that can provide better indoor conditions
for the workers and an optimal larval prawn growth (Sandifer
and Smith, 1985).
MATERIALS AND METHODS
Case study: This study was carried out at Annur Hatchery, Bagan Terap, Sungai Besar, Selangor Darul Ehsan, Malaysia (Fig. 1). This hatchery is located at latitude 3°4453.0 N and longitude 101°312.0 E. The orientation of hatchery building is 292.5°C.
The building was 12.1 m wide, 18.2 m long and 3.0 m high. This hatchery building
has a production unit for larval rearing, a small office and a store. The plan
layout of hatchery building are small scale hatchery (Fig. 2-6).
This hatchery represented a typical small scale backyard prawn hatchery in Malaysia
and was constructed mainly from recycled building materials such as used metal
and non-asbestos fiber sheets for the roof and walls and used planks for the
walls of the office and store. The wall and roofs were not insulated against
heat transmission. A portion of the roof was made transparent using acrylic
sheets. The hatchery building are constructed with complete materials with different
thickness (Table 1).
|| A small-scale giant freshwater prawn hatchery at Sungai Besar,
|| Construction materials and thickness
|aConstruction materials provided in the simulation
|| Hatchery building model (Axonometric, 3D view)
|| Front elevation of the building
||Side elevation of the building
Field measurement: The data measurements were collected for 12 days from 25 November to 6 December 2007. During the measurement, all doors and windows in the production unit remained closed. Typography measurement and in situ indoor, outdoor and water parameters (temperature, relative humidity, light intensity) were recorded using Hobo multi-data loggers (Onset, USA). The multi-data loggers were placed at selected locations in the hatchery (Hobo U12) and culture tanks (HOBO® Temperature/Light Waterproof Pendant). In the production unit there were 10 rectangular fiberglass tanks with size 2.5 m wide, 7 m long and 4 m high.
Simulation: Beside the in situ measurements, the thermal conditions in the building were also simulated using Integrated Environmental Solutions (IES) Virtual Environment version 5.6 (Integrated Environmental Solutions (IES) Limited, 1994). The construction properties are:
||Alesorptance for solar radiation: 0.55
||Emissivity: Both for inside and outside of opaque surface: 0.90
||Air infiltration: 1 ach
||Cooling mechanism: Natural ventilation
||Incoming of air: Natural (external air)
||Building orientation: 292.5°
|| Top elevation of the building
||Floor plan of the hatchery building. a: Office, b: Hallway,
c: Store room, d: Culture (no wall), e: culture room
The building operated 7 days per week at 12 h per day (0700 to 1900 h). The
internal gain of the building was from two workers:
|Max. sensible gain
|| 90 W per person (90 Wx2 person = 180 W)
|Max. latent gain
||60 W per person (60 Wx2 person = 120 W)
The simulations were performed using the nearest climatic data, Kuala Lumpur,
Malaysia provided by ASHRAE.
In situ measurement: The profiles of measured indoor and outdoor
temperature in the hatchery building and water temperature in the larviculture
tanks (Fig. 7-8). The indoor and outdoor
and water temperature fluctuated during the study within 23.55-41.24°C,
23.63-35.49°C and 25.71-32.74°C, respectively.
|| Measured temperature (outdoor, indoor and water)
|| Average daily measured temperature
The highest indoor temperature recorded was 41.24°C on 2nd Dec at 16:00
h while the highest water temperature of 32.74°C was seen on 1st Dec. at
1345 h. The average daily indoor, outdoor and water temperature ranged 25.06-37.52°C,
25.43-33.48°C and 26.78-30.98°C, respectively.
The hatchery operated from 07:00 to 19:00 h daily. Generally, the indoor air
temperature was significantly higher than outdoor temperature almost 0.39% of
the working hour. The indoor and outdoor relative humidity (RH) ranged 43.51-82.25
and 50.01-79.21%, respectively (Fig. 9, 10).
The average RH was lower than outdoor RH in hatchery building during most of
the daytime and became higher than the outdoor RH at nighttime. Indoor RH ranged
43.51-82.15% during the daytime.
The average indoor Light Intensity (LI) was measured during the study (Fig. 10). The daytime indoor LI ranged between 34 to 5567.42 lux observed at 1415 h. The daytime water LI ranged 293.26-4066.14 lux and was always lower than indoor LI.
The indoor air temperature with tank water temperature of hatchery building
showed the correlation (Fig. 11). The rising and cooling
indoor air temperature occured between 0645 to 1415 h and 1415 to 0645 h, respectively.
A similar pattern was observed in the water temperature with a 0.5h delay from
the indoor air temperature. When these delayed rising and cooling temperatures
were plotted against the indoor air temperature (Fig. 12,
13), the following linear equations were obtained.
|| Average daily measured relative humidity
|| Average daily measured light intensity
|| Average daily indoor air temperature and eater temperature
|| Average daily indoor air temperature and water temperature
|| Correlation for rising temperature pattern of indoor air
temperature vs. water temperature
||Measured and simulated indoor air temperature (25 Nov. to
6 Dec. 2007)
||Simulated indoor air temperature on hottest (March) and coolest
||Simulated indoor air temperature on hottest (March) and coolest
||0.2717 Ti+20.749 (R2 = 0.7830)
||0.2531 Ti+21.308 (R2 = 0.7665)
||tank water temperature and Ti = indoor air temperature
Simulation: The thermal conditions of hatchery building were simulated
for hottest (March) and coolest (December) months. The profiles of measured
and simulated indoor air temperature are shown for verification and comparison
(Fig. 14). The simulated indoor air temperature were similar
with measured temperature for most of the days except on 29th November.
The simulated indoor air temperature and tank water temperature were obtained
on hottest and coolest month (Fig. 15, 16).
The highest indoor and water temperature in the hottest month were 48.54°C
and 33.80°C, respectively while the temperature in the coolest month were
40.77°C and 31.81°C, respectively. The indoor and water temperature
on the peak days in the hottest month on 2nd March and coolest month on 6th
December (Fig. 17). The average simulated indoor and water
temperature were obtained in hottest and coolest months (Fig.
|| Peak day simulation on hottest (March) and coolest (Dec.)
|| Average day simulation on hottest (March) and cooles (Dec.)
The indoor air temperature on hottest and coolest months ranged 24.07-41.46°C
and 23.79-38.11°C, respectively. The average water temperature in hottest
and coolest months ranged 27.29-32.01°C and 27.21-31.10°C, respectively.
ASHRAE (1993) recommended that thermal comfort indoor
conditions in a tropical building should fall within 30 to 60% for RH and 22
to 27°C for temperature. However, in general, the daytime indoor air temperature
and relative humidity in the naturally ventilated studied building were much
higher than ASHRAE recommended levels. The daytime indoor air temperature also
remained above the upper comfort limit (28.6°C) for human (Sabarinah,
2006) and even reached higher than 40°C for 6.25% of the working hours.
Zainal and Keong (1996) reported that Malaysian factory
workers can tolerate up to 26°C indoor air temperature while.Sabarinah
(2006) found that the neutrality temperature for naturally ventilated buildings
in Malaysia is 26.1°C while Abdul Rahman and Kannan (1997) reported a higher
neutrality temperature (27.4°C). Unfavorable thermal conditions in a hatchery
cause thermal discomfort amongst the workers which leads to lower productivity
(Lan et al., 2009). An indoor temperature above
40°C creates an unhealthy environment to the workers (Auliciems
and Szokolay, 1997) while prolonged exposure to high indoor temperature
will cause extreme thermal discomfort and may lead to heat stroke when the body
temperature reaches about 40°C (Auliciems and Szokolay,
The optimal water temperature for M. rosenbergii larviculture is 28-30°C
(Tayamen, 2001). At night, the water temperature in the
studied hatchery could drop to 25.71°C and remained under 28°C between
0115-0915 h. During the day, the water temperature remained above 30°C between
1115-1730 h and even reached 32.74°C which was nearing the upper lethal
temperature limit for the prawn larvae (Tayamen, 2001).
The occasional unexplained high mortality or total larval loss reported by the
hatchery operator could be related to the upper lethal temperature limit of
the larval prawns being compromised.
An indoor light intensity of 2500 to 6500 lux is needed in a green water prawn
larviculture system to promote beneficial algal growth in the tanks (Tayamen,
2001). The algae play an important role to keep toxic ammonia in the water
at a low and safe level. Sufficient sunlight penetrated the hatchery production
area through transparent portions of the roof which a common and typical feature
of prawn hatcheries (Hsieh et al., 1989). The
transparent roof portions were made of acrylic without heat or UV blocking feature.
The roof combination of non heat blocking transparent acrylic and uninsulated
metal sheets worsened the indoor thermal conditions of the hatchery as excessive
solar radiation and light produce excessive heat especially during warmer months
(Valenti and Daniels, 2000). In the Indian hatcheries,
silpaulin are commonly used as the roof material (Raju and
This study showed that the design of the building failed to provide comfortable
indoor conditions for workers and optimal larviculture conditions for the prawn.
Specifying the right materials for building construction is one of the important
aspects in designing thermal comfort buildings. The internal thermal condition
of the building can be directly determined through the thermal conductivity
of the materials. Mutaf et al. (2004) focused their research on the effects
of summer and winter natural ventilation air exchange on psychromatic of closed
and open type poultry houses. To increase the efficiency of natural ventilation,
they proposed the roof of the enclosed building to be fitted with slope of not
less than 20-30° and the ridge fitted with continuous capped ventilation
which remains open. The ridge should not be less than 4-5 m high while the building
width should not exceed 12 m. However, these recommendations may not be suitable
for a prawn hatchery as some light penetration is needed for the larviculture
while prawns are poikilothermic animals which do not generate heat.
Jayasinghe et al. (2003) reported that the use
of appropriate roofing materials and insulation can reduce the excessive heat
transferred through the roof and enhance the indoor thermal comfort. However,
they found that the building orientation provide no significant effect on the
thermal performance of the building. A further study exploring the use of roofing
materials and insulation through simulation should be conducted to improve the
indoor thermal conditions of the hatchery for the workers and prawn larviculture.
This study showed that simulation can be used as a tool to assess the indoor thermal conditions of a prawn hatchery as its results were comparable to measured data. The results showed the hatchery failed to provide the optimal thermal rearing conditions for the prawn larvae. In addition, the building could not sufficiently provide thermal comfort conditions for the workers during the working hours.
The authors wish to thank Ministry of Science, Technology and Innovation (MOSTI) for funding this project under the project number 03-01-01-SF007 and to En Nordin Salimin, the owners of the Annur Hatchery for the cooperation.