PRELIMINARY STUDY ON TIlE REPRODUCTION OF RAZOR CLAMS (FAMILY: SOLENIDAE)
Mzalina Binti Ahamad
Bachelor ofScience with Honours S8 (Aquatic Resource Science and Management) 313 2006 A258 2006 Acknowlegdement
Here I would like to thank for kindness and help from my respective supervisor; Dr. Siti
Akmar Khadijah Ab. Rahim, lab assistants; Mr. Zulkifli Ahmad, Mr. Harris Nonnan, Mr.
Zaidi, and all the lecturers in Aquatic Resource Science and Management Programme especially to Dr. Ruhana Hassan, Mr. Samsur Mohamad and Mr. Khairul Adha A. Rahim upon their encouragement and support. Last but not least, to all my beloved family and friends (Siti Najihah Amney Noor, Hadiana Simatzaman, Helen Orang, Felicia May and
Zulkernine) for their understanding and motivation and all the supportive team who helped me within completing this project. , t1R Pu . t Khi T ~ ~ " I /r UNIVERSITI .I Y '!A • 94300 Kota Samarahao
CONTENTS PAGES
Acknowledgement I
List of tables, figures and appendices IV-V
Abstract VI 1.0 Introduction 1-4 2.0 Literature Review 2.1 Systematic arrangement 5 2.2 Artificial induced spawning technique 6 2.3 Reproduction 6-7 2.4 Early development 8 2.5 Larval stages 9 3.0 Materials and Methods 3.1 Field work 10 a) Sources of Razor clam 11 b) Physico-chemical parameter 12 3.2 Laboratory works a) Artificial induced spawning experiment 12 b) Gonadal Condition Index (GCl) 13 c) Maintaining Razor !tam in the laboratory 14 4.0 Results 4.1 Artificial induced spawning experiment 15-16 4.2 Gonadal Condition Index (GCl) 17-25 4.3 Physico-chemical parameter 26-27 4.4 Maintaining Razor clam in the laboratory 4.4.1 First trial 28 4.4.2 Second trial 29
11 5.0 Discussions 5.1 Artificial induced spawning experiment 30-31 5.2 Gonadal Condition Index (GCI) 32 5.3 Maintaining Razor clam in the laboratory 33-34
6.0 Conclusion and recommendation 35-36 7.0 References 37-40 8.0 Appendices 41-67
11l LIST OF TABLES
Table 1. Systematic arrangement of the Solenacea by Cosel (1986).
Table 2. Summary of Bivalvia reproductive patterns (Source: Pechenik, 2000).
Table 3. Sources of Razor clams from the place and date mentioned.
Table 4. Summarized of experimental works on induced spawning trial.
Table 5. Physico-chemical parameters taken in-situ from Asajaya Laut sampling site.
Table 6: Physico-chemical parameters taken in-situ from Buntal and Bako sampling site.
LIST OF FIGURES
Figure 1: Location of the field work.
Figure 2: Measurement for total shell length and shell width.
Figure 3: Gonadal Condition Index of 'Ambal biasa' from Asajaya Laut, lOth October, 2005.
Figure 4: Gonadal Condition Index of 'Ambal biasa' from Asajaya Laut, 20th October, 2005.
Figure 5: Gonadal Condition Index of 'Ambal biasa' from Asajaya Laut, 17th November, 2005.
Figure 6: Gonadal Condition Index of9\mbal biasa' from Asajaya Laut, 5th December, 2005.
Figure 7: Gonadal Condition Index of'Ambal biasa' from Asajaya Laut, 18th December, 2005.
Figure 8: Gonadal Condition Index of'Ambal biasa' from samples of Asajaya Laut, 2nd January, 2005.
Figure 9: Gonadal Condition Index of 'Ambal biasa' from Bako, 6th December, 2005.
Figure 10: Gonadal Condition Index of'Ambal biasa' from samples of Bako, 16th December, 2005.
IV Figure 11: Gonadal Condition Index of'Ambal biasa' from samples of Buntal, 3rd December, 2005.
Figure 12: Gonadal Condition Index of'Ambal riong' from samples of Buntal, 3th December, 2005.
Figure 13. Total number of dissected specimens (294 individual) according to species.
Figure 14. Number of individual of 'Ambal biasa' which presence with gonad from the sampling site and date mentioned.
Figure 15. 'Ambal biasa' with gonad.
Figure 16. 'Ambal biasa' without gonad.
Figure 17. Number of dead and live individual in first trial.
Figure 18. Number of dead and live individual in second trial.
LIST OF APPENDIXES
1. Raw data for measurement of shell length, shell width, total weight, dried shell weight, gonad weight and GCI of Razor clam.
2. Table of systematic arrangement of Solenacea by different authors.
3. Figure of 'Ambal biasa', 'Ambaljemang' and 'Ambal riong'.
4. Photos during field works.
v Preliminary Study on the Reproduction of Razor Clams (Family: Solenidae)
Afzalina Binti Ahamad
Aquatic Resource Science and Management Faculty ofResource Science and Technology Universiti Malaysia Sarmvak
Abstract
Thi study is a preliminary study on the reproductive pattern which consist of gonadal condition index (Gel) which being observed monthly. Gonad presences were observed and apply to Gel number. Monthly Gel observations apply only to Asajaya Laut sample. Result of GCI showed that sample on October was the highest number of Gel. Month of November, December and January shows no presence of gonad. Gel observations also apply for sample from Bako and Bunta! which sampling had been done on December. Artificial induced spawning trials also have been made. Trial had been made for sample from Asajaya Laut and Muara Tebas. Experiment showed that none of the sample was producing eggs or sperms. Maintaining samples under laboratory condition was done in two times of trial. From the second trial, razor clam can be rear under laboratory condition for 8 days with brine shrimp as a food source.
Key words: Razor clam, Gonadal Condition Index (Gel), observation, trial
Abstrak
Kajian ini dijalankan sebagai permulaan untuk melihat kepada bentuk pembiakan amba!. Sehubungan dengan itu, pemerhatian kepada keadaan gonad ambal ini dilakukan dalam bentuk indeks (Gel) dan dijalankan pada setiap bulan untuk sampel dari kawasan Asajaya Laut. Hasil doripoda pemerhatian untuk Gel, nilai Gelpada bulan Oktober merupakan nilai yang tertinggi. Tiada pembentukan gonad yang boleh diperhatikan pada bulan November, Disember dan Janllari. Pemerhatian untuk Gel bagi sampel dari Bako dan Buntal turut dijalankan semasa kerja lapangan dilakukan pada bulan Di~er. Selain daripada itu, eksperimen pembiakan arullan juga turut dijalankan. Sampel-sampel yang digunakan untuk tujuan eksperimen ini didapati dari Asajaya Laut dan Muara Tebas. Dua kali percubaan untuk memelihara ambal do/am makmal juga turut dilakukan. Percubaan pada kali kedua menunjukkan bahawa ambal bole" dipelihara selama 8 hari dengan memberikan artemia sebagai sumber makanannya.
Kata kunci: Ambal, Indeks Keadaan Gonad (Gel), pemerhatian, percubaan
VI ,....
1.0 Introduction
Phylum Mollusca consists classes of Gastropoda, Bivalvia, Polyplacophora,
Cephalopoda, Monoplacophora, and Aplacophora. As one of the largest of all animal
phyla, they consist about 50,000 to 110,000 living species. Under the class of Bivalvia
they are over 25,000 species, including clams, scallops, mussels and oysters. Most of the
bivalves are marine with only 10-15 percent can be found in freshwater and no bivalves
are terrestrial (Pechenik, 2000).
The bivalves can be divided into three subclasses - Protobranchia, Lamelibranchia and
Septibranchia. Characterized with these major the major characteristics: (1) a hinged
shell, the two valve (left and right side) of which are joined together by a springy
li gament that springs the shell valves apart when the adductor muscles relax; (2) lateral
compression of the body and foot; (3) virtual absence of a head and associated sensory
structures; (4) a spacious mantle cavity, relative to that found in other molluscan classes;
(5) sedentary life-style; and (6) the absence of a radulalodontophore complex (Pechenik,
2000). Oxford Dictionary of Biology (2004), describes Bivalvia as a class of aquatic
I,' molluscs that includes the oysters, mussels, and clams. They were characterized by
laterally flattened body and a shell consisting of two hinged shells (i.e. a bivalved shell).
The enlarged gills were covered with cilia and have the additional function of filtering
microscopic food particles from the water flowing over them. Bivalves live on the sea
bed or lake bottom and are sedentary, so the head and foot were reduced.
I'
l l
Razor clam or ambal as named by local people, is one of the marine bivalve species, under ubclass of Heterodonta, Order of Veneroidea,and in Superfamily of Solenacea which consist family of Solenidea, Solercutidae, Pharellidae, and Cutellidae (Cosel,
1986). It was named razor because its' appearance look like long razor sharp shell. Some parts of the world called it as the 'bamboo shell clams' or 'jackknife clam' as the shell look like a bamboo or a jackknife.
According to Fitch (1953, cited in Lassuy and Simons, 1986) had describe the Razor clam as follows: "elongate shells, thin, flat and smooth; covered with a heavy, glossy, yellowish periostracum, a prominent rib extending from the umbo to the margin on the inside of the valve. Foot large and powerful, never pigmented. Siphon rather short and united except at tips. Umbos nearest anterior than posterior end. Attain a length of seven centimeters. Razor clam was different from the Rosy clam (Solen rosaceus) and Sickle clam (s. sicarius) and the Jack knife clam (Tagelus californianus) by having a heavy, raised rib extending from the umbo to the margin of the shell on the inside". According to
Quayle (1962 cited in Lassuy and Simons, 1986), the Razor clams has thin and brittle; ol ive green in youth, changing to brown with age. Meanwhile Cosel (1986), claimed that there are about 60-65 living species in Family of Solenidae predominantly found near the tropical and subtropical zones with the distribution centre in the Indo-West Pacific and only a fe w species in temperate zones.
2 Hill and Phillips (1981 cited in Loh, 2005), stated that in the west coast of America, species found were namely Silliqua patula, S alta and S sloati while in Scotland, it is of
Ensis spp. (E. ensis, E.minor, E. siliqua, E. directus, and E. arcuatus) and there were two common genera found in Hong Kong that included Solen (S vagina) with its straight shell and Ensis, curved shells and was more temperate in distribution.
Razor clam, as a soft bottom infaunal marine bivalve live burrowing in the sandy beaches at the intertidal zone and feed by filtering freshly deposited alluvial mud and sand for micronutrients and usually feed during high tide. Siphon was used to locate and filter suspended food in the water and also it works as a path to excrete waste like carbon dioxide from the body of Razor clam.
There are three different species of Razor clam (Solenidae) being collected in Sarawak that were known as 'Ambal Biasa', 'Ambal Riong', 'Ambal Jernang' (Pang, 1992; Loh,
2005). Meanwhile, Zulkifli (2000) claimed that those three types of Razor clam which belongs to three different species which are; i) Solen corne us Lamarck, 1818 (Ambal
Biasa), ii) Solen vagina Linne, 1785 (Ambal Riong), iii) Solen sp. (Ambal Jernang which is most probably a new endemic species in Borneo). Pang (1993, cited in Loh, 2005) pointed out that in Sarawak, Razor clams thrive in the intertidal sandy beaches of the
Sarawak and were found abundantly in Kuching and Samarahan district. Collecting season for Razor clam usually starts in August until March the following year. Collection of Razor clam was carried out during low tide, when the intertidal zone was exposed.
3 ,...
Razor clam has a great commercial value in the market with selling price ranging from
RM 12.00 to RM 20.00 per kilogram, depending on the demand. Razor clam was well
known as a un ique delicacy in Sarawak. People come from different places to have a taste
of it in many famous seafood restaurants in Sarawak, especially in Kuching and Buntal
area. The main sources of Razor clams which came from Kuching bay were transported
over Sarawak to fulfill the demand. In return, it also provided an extra income for local
people who harvest the Razor clam ranging from RM 7.00 to RM12.00 per kilogram of
Razor clams. Middleman usually will get more income since some of them also provided
[! transportation for the local people to get on the beach.
Razor clam in Sarawak had been reported facing over-fishing problem and depletion of
stocks in the natural resources. Moreover, less information were known about this species
and no detail study on the life cycle, especiaUy on the larval stages. This study was
designated to gather preliminary data related to the gonadal condition as it will be useful
for setting the larval culture in the laboratory and artificial spawning technique at
laboratory scale.
Many attempts had been done on many marine invertebrates to be spawned artificially in
the laboratory, and in such cases they are induced to spawn (Toonen, 1996). Induced
spawning can be triggered by temperature, abundance of food, effects of photoperiod,
and usage of chemical such as ammonia and sodium chloride.
4 2.0 Literature review
2.1 Systematic arrangement
The systematic arrangement that describe in Table I is based on R. von Cosel
(1986) in his paper of'An Introduction to the Razor Shells (Bivalvia: Solenacea),.
Table I. Systematic arrangement of the Solenacea by Cosel (1986). Solenacea Solenidae Lamarck, 1809 Solen Linne, 1758 Solen Ensisolen Habe, 1977 ?Neosolen Ghosh, 1920 Solena T. Browne, 1789 Solena +Eosolen Stewart, 1930 +Plectosolen Conrad, 1866 Pharidae H. and A. Adams, 1858 (= Cultellidae) Pharinae H. and A. Adams, 1858 Pharus Leach in T. Brown, 1844 Cultellinae Davies, 1935 Cultellus Schumacher, 1817 Ensis Schumacher, 1817 Phaxas Leach in Gray, 1852 Phaxas Ensiculus H. Adams, 1860 Si/iqua Muhlfeld, 1811 S"'t~'ua
Neosiliqua Habe, 1965 Pharella Gray, 1854 Orbicularia Deshayes, 1850 Sinonovacula Prashad, 1924
+Leptosolen Conrad, 1865 +Ospriasolen Conrad, 1868
5 I
2.2 Artificial induced spawning techniques
Fertilizatjon of the Razor clam gametes occurs externally in the surrounding
seawater. According to Toonen (1996), many marine invertebrates have yet to be
spawned under imitated "natural" conditions in the lab, and in such cases they
were induced to spawn, or are "artificially spawned". There were numbers of
methods to induce "natural" spawning in ripe specimens, includes (after Toonen,
1996):
a) strong mechanical agitation
b) thermal shock method
c) photoperiod changes
d) abundance of food resources
e) current changes
t) electric-shock method
g) using chemical treatment
2.3 Reproduction
Reproduction among bivalves is sexual and most species are dioecious, though
hermaphroditic representatives are not uncommon (Thorson, 1936; Cae, 1943;
Allen, 1961; Chanley and Chanley, 1980; Campos and Ramorino, 1981 ;
Strathmann, 1987; cited in Zardus and Martel, 2002). Clams are dioecious
(separate sexes) with external fertilization which enables the zygote to develop
into free-swimming trochophore and veliger larvae that will metamorphose into
adults. Clam can reach sexual maturity at a very early age. Menzel (1971) and
6
l Eversole et al. (1980) discovered that motile sperm and mature ova in M mercenaria aged less than a year old with size less than 20 mm. In suitable condition environment, sexually mature clam will release gametes to the surrounding water and the zygotes develop into veliger within 24-48 hours.
Veliger will trans locate primarily through tidal and wind-generated currents.
Razor clam sexes can only be identified during the spawning season when the reproduction organs are ripe and can be distinguished easily.
Histotogkal of Razor clam reproduction systems shows that gonad of the male usually appears milky-white with smooth surface, while the female organ has a rough surface, granular in appearance and beige in colour (Lassuy and Simons,
1989). Morphologically, the ovaries lie in the visceral mass. Ducts are short and may lead to the kidneys or into the mantle chamber direct, while the males possessing paired testis with short genital ducts joining the nephridia on each side
(Nayar, 1977). Reproduction of other Solenidae species such as Ensis minor,
Solen marginatus, Ensis siliqua, and Ensis macha have been made by other researchers (Dariba et at. 2004). Table 2 summerized the bivalve reproduction pattern.
Table 2 S ummary 0 fB'Iva I'vIa repro ductlve patterns (Source: P echem'k, 2000). SU BJECT PATTERNS. Reproductive Mode Sexual Spermathopore Absent Sexuality Dioecious, Hermaphorditic Larval Stage Trochophore, Veliger Ferti lization External, Internal (rare)
7 ,... I
2.4 Early development
Reproduction may compete with somatic growth for limited resources. The most
widespread form of reproduction involves specialized cells- the gametes (Calow,
1981). He also added that, in the case of gamete formation there may be a trade
off between the size and number of gametes produced from the limited resources
made available by the parent and between the extent to which a parent invest
resources in reproduction and in its own soma. Morse and Zardus (1997)
expressed that eggs were fertilized as primary oocytes, and polar bodies were
released at the onset of cleavage (cited in Zardus and Martel, 2002). In addition,
Wada (1968) explained that cell cleavage is spiral determinate with the first few
divisions being total, asynchronous and unequal, resulting in a large D-cell (cited
in Martel and Zardus, 2002). Fioroni (1982) said that, the D-cell and its
descendants displace the regular arrangement of smaller cells, making cell
lineages difficult to follow in bivalves. Embryogenesis proceeds through blastula,
gastrula, and trochophore stages (cited in Zardus and Martel, 2002).
Gastrulation occurs through invagination with epiboly producing a laterally
positioned blastopore which, as in all protostomes, becomes the larval mouth.
Once cilia are functional, the embryos of most species rotating within the
fertilization membrane and soon escape it and develop as free-swimming
trochophore larvae (Zardus and Martel, 2002).
8
l ,...... 1
2.5 Larval stages
Planktonic Razor clam larvae encountered a very different environment from their
benthic adult. The success of recruitment for most species depends on the abilities
of their planktonic larvae to develop, disperse and find a suitable benthic habitat.
Some developmental form are adapted for trans-oceanic or teleplanic (long-lives
cycle or metamorphosis) distribution and others for restricted or aplanic (directly
developing) dispersal (Scheltema, 1971 a,b; cited in Zardus and Martel, 2002).
Three primary sexual developmental modes of marine invertebrates were caJled
planktotrophic, lecithotropic and nonpelagic or direct development. Nyabakken
(1993). defined that terms of:
a) Planktotrophic - produced a great number of small eggs, hatch quickly, free
swimming in the plankton because so little yolk was put into each egg, the
larvae would depend for nutrition on the plankton.
b) Lecithotrophic - produced fewer eggs and endow each with somewhat more
energy in the form of yolk, hatch into larvae, have yolk reserve and not feed in
the plankton period, spend less time in the plankton period before settling, use
the plankton phase mainly for dispersal.
c) Nonpelagic or direct development - produces few eggs, each with a very large
amount of yolk, undergo a long development of egg without additional energy
sources, pass through the larval stages in the eggs and hatch as juvenile.
9
l 3.0 Materials and methods
3.1 Field work
N
SOUTH CHINA SEA T
Figure I. Location of the field work.
10 a) Sources of Razor clams
The brood stocks of Razor clam were obtained for two main purposes which were sources for: a) artificial spawning trial (consist samples from August, September, and
October). b) GonadaJ Condition Index (GCI) study (consist samples from October,
November, December and January).
Locations of sampling were situated at the intertidal sandy beaches or sandy bars of western part of Sarawak. Sampling of Razor clam held from August, 2005 to
January, 2006 which is within the harvesting season of Razor clam in Sarawak.
Live Razor clams were bought from local people when they were harvesting on the beaches at various location (Table 3). Samples for observation on the GCI were obtained monthly from Asajaya Laut area, and in December, samples were also obtained from Buntal and Bako. Samples were placed in a cooler box to avoid the extreme heat during the transportation to the laboratory, to lower metabolic activity and also to avoid spontaneous spawning.
Table 3. Sources of Razor clams from the place and date mentioned. Location Date of sampling Muara Tebas 21 s1 of August, 2005 Asajaya 81n and 191n of September, 2005 I Olh and 20th October, 2005 Asajaya lOIn and 20m October, 2005 171h November, 2005 181h December, 2005 I SI January, 2006 Buntal 3.0 December,200S 1n 10 Bako 6 and 16 December,200S
II b) Pbysico-chemical parameter
Data on physico-chemical properties at each location were measured during
monthly sampling in Asajaya Laut and one-off sampling at Bako and Buntal
areas. Temperature and dissolved oxygen were taken using Cyberscan meter
(model DO 300/3 10 series), meanwhile salinity was measured using refractometer
(model Atago -28) and pH meter (model Jenway 30T) was used for pH reading.
Hanna instrument (model HI 9835) also had been used to measure the physico
chemical parameter which were also apply to determine the salinity and dissolved
oxygen.
3.2 Laboratory works
a) Artificial induced spawning experiment
For the first experiment, a modified technique that is used to induce spawning in
mussel had been applied in this study. This technique used the principles of
thermo shocking condition. Artificial induced spawning experiment was done by
the following steps:
I. Live sample of razor clam were chilled with ice overnight.
2. First step to induce spawning, 5 specimens (or more) were transferred into
a container filled with 5 liter of filtered seawater (room temperature).
3. Individual that start to spawn will be separated immediately from the
group and placed in a 500 ml beaker filled with filtered seawater.
4. The eggs and sperms will be mixed in a 2-litre beaker containing filtered
sea water.
12 b) Gonadal Condition Index (Gel)
Thirty samples were used for each batch of samples to determine the gonadal
condition index (GCI). Prior to dissection, the wet weight (total weight with both valves), and total shell length and shell width of every specimen were measured.
Then, dissection of clam was done to obtain the gonad tissue. Dissected clams were observed under the stereo microscope in order to observe the gonad tissue.
Later, the gonad was taken out, placed on a piece of aluminum foil and weighted ofthe gonad were recorded (gonad tissues weight - weight of aluminum foil). The weight of shells of respective clams was measured after being dried in oven for 3 hours at 60°C. The GCI was determined as being described by Dariba et al.
(2004) starting from sample obtained on 10th of October 2005, onward. The total shell length and shell width were measured using a digital vernier caliper
(Mitutoyo model CD-6"B) and the total weight, gonad weight and dried shell weight of specimens was taken utilizing the digital balance (model Ohaus CT
2oo-s).
GCI = Gonad Tissue Fresh Weight
ShelJllDry Weight
Total Shell Length
Shell width
Figure 2. Measurement for total shell length and shell width.
13 c) Maintaining Razor clam in the laboratory
Razor clam brood stocks were kept in laboratory inside glass tank (39.5 cm
[length] x 29 cm [width] x 30 [height]) and also plastic container (56 cm [length]
x 36 cm [width] x 32 cm [height]) containing seawater with salinity ranges from
29 to 30 Practical Salinity Unit (PSU), taken from Research Centre of Lembaga
Kemajuan Ikan Malaysia (LKIM), Telaga Air. Aeration was given during the
observation period and time frame for the observation was not limited or until all
samples died. Two trials were carried out using samples taken from Asajaya Laut
which consist of 'ambal biasa'. Number of dead and live individuals was recorded
everyday. Room temperature was controlled between 24°C to 25°C. Seawater
was exchange daily. Forty-four individuals were placed in one glass tank in the
first trial witbout sediment and food was not given. Meanwhile for the second trial
(219 total number of individual in this trial), 2 glass tank (labeled as A and B) and
2 plastic containers (labeled as C and D) were used to keep the samples with
random number of individual of samples. Stocking density for each tank as
followed:
a) tank A was kept with 60 individual
b) tank B with 45 individual
c) container C with 95 individual
d) container 0 with 19 individual.
Those trials in the glass tank were filled with sieved sand (10 cm deep in based on
height of tank) and all of the samples were treated with 50 ml of brine shrimps as source of food which contain 800 individual of brine shrimps.
14 I
Maklumat AkademlA ('usnt Khidmat .. , AYSIA SARAWA'J UNIVERSlTl M~ __h ..... lJl 94300 Kota SanllSl
4.0 Results
4.1 Artificial induced spawning experiment
Table 4 summarized the result of induced spawning experiment that had been
done with the time mentioned. Number of sample for this experiment begins with
6 individuals, and addition number of individual was applied for onward
experiment. In the first trial, individual with various sizes of total shell length
were chosen, but starting on 20th of September, sample with shell length more
than 4 cm was used since dissection showed that sizes below that the gonad of
small sample was not developed yet.
All 5 trials using the thermal-shocking failed to produce any egg or sperm. During
the experiment most of the samples were very weak with only several ind ividual
were responding actively (physical movement) such as moving its foot as part of
burrowing behaviour, or using its foot to attach with the container base and try to
be in vertical position. Meanwhile some were just floating or lying down at the
bottom ofthe container.
15
J Table 4. Summarized ofexperimental works on induced spawning trial. Sources of Razor clams are indicated in brackets.
Date Seawater Chilled Temperature Total number Total number Total number Remarks temperature temperature differences ofsample for ofsample ofsample each trial that produce that produce eggs sperm
06.09.2005 a) 11.0 a) 14.5 6 none none a)samp le kept overnight in cooler box contain ing ice and (Muara 25.5 aerated Tebas) b)S.O b)20.S 6 none none b)sample kept in fridge overnight.
09.09.05 a) 12.e• a)12.S 9 none none a) sample wrapped in damp newspaper (Asajaya) 24.5 b) sample kept with sediment b)8.0 b)16.S 10 none none (both are in cooler box with ice packed and aerated)
20.09.2005 28.0 11.5 16.5 6 none none Sample were kept in cooler box with ice packed and no (Asajaya) sediment apply (aerated)
11.10.2005 23 .0 12.0 11.0 10 none none Sample kept in cooler box with sediment and ice packed (Asajaya) (aerated)
21.10.2005 25.0 5.0 20.0 20 none none Sample kept in cooler box with sediment and ice packed (Asajaya) (aerated)
16 4.2 Gonadal Condition Index (GCI)
Figure 3 to 8 showed the pattern of Gel for' Ambal biasa' of Asajaya Laut. Gel
value dated on 10111 of October, 2005 (Figure 3) was the highest value of Gel for
the monthly observation.
Figure 5,6,7 and 8 was the lowest Gel which presented there were no
development of gonad for Razor clam during the date mentioned.
Meanwhile, Figure 9 to 12 were additional observation of Gel value from Bako
and Buntal area. Figure 11 was presenting Gel value sample from Buntal which
were consist species of'Ambal riong'.
Only few individuals (less than 3 individuals) of 'Ambal biasa' from Bako
(Figure 9 and 8) were presence with development of gonad but there were no
development of gonad for 'Ambal biasa' from Buntal (Figure I 1). On the other
hand for 'Ambal riong' from Buntal (Figure 12) there were nine individuals
showed development of gonad on the date mentioned.
17