Harmful Algal Blooms in Malaysia: occurrences and monitoring strategies
Choo Poh-Sze
WorldFish Center
PO Box 500 GPO
10670 Penang, Malaysia
ABSTRACT
With globalisation, importing countries often demand greater transparency together with
the need for accredited certification of imported products. Although harmful algal
blooms (HABs) do not pose a serious problem in Malaysia, except for Sabah, steps must
be taken to develop effective monitoring programmes for harmful algae and HAB toxins.
This paper describes the status of HABs in Malaysia and the monitoring programmes
implemented to ensure seafood safety. Measures taken to upgrade and improve HAB
management are also discussed.
Introduction
Harmful algal bloom (HAB) occurrences are believed to be on the rise all over the world
(Anderson 1989, Lam and Ho 1989; Maclean 1989 and Shumway 1995), with an
estimated 2000 cases of human poisoning recorded annually (Hallegraeff 1993). Apart
from human fatalities, HABs also cause huge economic losses both to the natural
fisheries and also to cultured species (Corrales and Maclean 1995; Okaichi 1991;
Shumway 1990; Smayda 1991 and Choo 1996).
Trade in seafood, especially shellfish, has also been subjected to stringent controls by
importing countries in recent years. Limits and regulations on marine phycotoxins exist
in at least 21 countries (van Egmond and van den Top 1991). The European Union, for
example, requires exporting countries to not only adhere to regulations on toxin residues
in seafood but also requires plankton sampling in shellfish culture areas to be conducted.
In 1998, Malaysia exported a total of 20,412.32 tonnes of fish, crustaceans and molluscs
(prepared or preserved) worth RM328,205,992, as well as 47,003.65 tonnes of
crustaceans and molluscs either chilled, frozen, salted or dried, worth RM609,879,144
(Anon. 1998). Countries importing our shellfish, especially molluscs, may require
certification declaring that our seafood does not contain HAB toxins above the level
stipulated in their regulations. In order to sustain a healthy export trade in molluscs and
other seafood, it is important that Malaysia ensures that seafood is regularly monitored
for HAB toxins to ensure it is safe for consumption.
2. Status of harmful algal blooms in Malaysia
Status of HAB blooms in Malaysia has been described by Choo (1994 and 1996) and
Puyong et al. (1999). The following description serves as an update to the situation
previously documented.
2.1 Sabah
Incidences of HAB blooms in the west coast of Sabah remain frequent, occurring mainly
in Sipatang, Kuala Penyu, Binsuluk and Kota Kinabalu. The causative organism is
Pyrodinium bahamense vars. compressum. Molluscs affected by HAB blooms include
Meretrix sp., Perna viridis, Gafrarium sp., Donax sp., Tridacna sp., Anadara granosa,
Crassostrea sp., Atrina sp. Spondylus sp. and Olivia sp. Apart from molluscs,
planktivorous fish, such as Sardinella (sardines, local name selayang/curut) and
Decapterus sp. (round scad, local name tamban) have been reported to accumulate HAB
toxins in the gut and the gills. According to the Annual Fisheries Statistics (Anon.
2001), Sabah has a relatively important sardine fishery; in 1999, 16,145 tonnes of
sardines and 14,973 tonnes of round scad were caught in the coastal waters. At an
average ex-vessel price of RM1.81/kg, the sardine fishery in 1999 was worth
RM29,222,450, and the round scad fishery at an average ex-vessel price of RM1.51/kg
was worth RM22,609,230. The mollusc culture industry in Sabah is relatively
unimportant. Sabah produced only 54.72 tonnes of cockles (Anadara granosa), 49.34
tonnes of mussels (Perna viridis) and 187.34 tonnes of oysters (Crassostrea sp.) in 1999
(Anon 2001).
2.2 Sarawak
No HAB incidences have been reported in Sarawak. A study carried out in Kuching Bay
and Brunei Bay by Pang and Yong (1995) showed the absence of Pyrodinium. Mouse
bioassay conducted for PSP toxins on several species of molluscs gave negative results.
2.3 Peninsular Malaysia
In Peninsular Malaysia, HAB blooms remain sporadic. Since the first report of a
paralytic shellfish poisoning (PSP) incidence in Melaka in November 1993, there has
been no recurrence of another outbreak in this locality. The culture of mussel in Melaka
has since picked up, after the setback experienced in 1993. In 1999, Melaka produced
329.29 tonnes of mussels (Anon. 2001) versus the 1993 production of 58.1 tonnes
(Anon. 1994). In September 2001, the first PSP incidence was reported in the east coast
of Peninsular Malaysia, in Tumpat, Kelantan. The causative organism was Alexandrium
minutum with another species, Alexandrium sp. yet to be identified (Lim et al. 2001).
One fatality and one hospitalized case were reported after a meal of the clam,
Polymesoda sp. locally known as the lokan, which was collected from the wild.
3. Monitoring Programmes
3.1 Sabah
Sabah has a regular sampling programme for PSP toxins in shellfish and fish, and for the
dinoflagellate, Pyrodinium bahamense var. compressum, due to the frequent occurrences
of HAB in the west coast of Sabah. Shellfish, fish and plankton samples are collected
fortnightly in at least 12 districts throughout Sabah, and for areas in Kota Kinabalu
samples are collected weekly (Puyong et al. 1999). A public warning is issued when
toxin levels reach 80 µg/100g or the density of Pyrodinium cells reach 7,000 cells/litre.
Results from more than 25 years of monitoring indicate that PSP levels vary widely for
different locations, at different times of the year and for different HAB species.
3.2 Sarawak
Monitoring for harmful algae is carried out in Kuching Bay and Brunei Bay. Monitoring
in some penaeid shrimp culture ponds is also carried out. Presently Sarawak has not
developed its facilities and capability to conduct mouse bioassay tests.
3.3 Peninsular Malaysia
Plankton monitoring and mouse bioassay tests conducted on various molluscs for PSP
toxins are regularly carried out by the Fisheries Research Institute in various culture sites
such as at the mussel farms in the Jasin district, Melaka and at the oyster culture area in
Batu Lintang, Kedah, as well as around the coastal areas in Tumpat, Kelantan after the
recent HAB outbreak in this area. The Food Inspection and Quality Control Unit of the
Department of Fisheries will conduct more regular and widespread sampling in the near
future, especially in important mollusc culture sites in the coastal areas throughout
Malaysia.
4. Discussion
With globalisation, trade issues need to be more transparent and it is important that
Malaysia develops effective monitoring programmes to ensure that seafood exported will
meet the standards imposed by importing countries. Sabah, which experiences annual
HAB outbreaks will benefit from the development of HAB models which can predict the
occurrence and seriousness of an impending bloom.
Technicians and scientists managing regulatory laboratories should be provided with new
skills to enable them to conduct more sophisticated analytical methods for regulatory
purposes. Some countries have already enforced a ban on the use of mice for toxin
testing, and technicians must also keep ahead with laboratory technology that does not
require the use of animals.
Understanding and controlling HABs involve various specialised fields of science. HABs
impact on various aspects of human society, including the economy of the country and
health of people. The development of knowledgebases like FishBase
(http://www.fishbase.org) and ReefBase (http://www. reefbase.org) developed by
WorldFish Center can be of immense help in bringing scattered information together,
acting like an electronic encyclopedia to allow easy and rapid information access on a
wide range of topics. Topics compiled can include harmful algal taxonomy, GIS maps
for HAB areas with hydrographic data, analytical methods for toxin analyses, medical
treatment for persons who have ingested toxic shellfish and contact information on
regulatory authorities and standards and regulations for HAB toxins in various countries.
Above all, the cooperation and understanding between importing and exporting countries
especially during a HAB occurrence are critical in order to ensure food safety and also to
ensure that the exporting country does not suffer unnecessary economic loss. The ban on
seafood exports must be carried out rationally and there should not be any ban on seafood
that is not affected by the HABs (see Choo 2002).
5. Conclusions
In order to ensure that seafood trade in Malaysia is not adversely affected by HABs, it is
important that effective monitoring programmes are developed. The monitoring
strategies applied are dependent on the frequency and the intensity of the blooms.
Scientists and technicians in regulatory laboratories who are familiar with only the mouse
bioassay technique should be trained and be kept abreast with other analytical methods.
The development of knowledgebases to ensure easy and rapid information access should
be given priority since understanding and controlling HABs often call upon knowledge
from many disciplines.
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