RED TIDE MANAGEMENT IN BRUNEI DARUSSALAM

Introduction

Red Tide phenomenon is associated with the change in water coloration from normal to a reddish or brownish color due to a sudden bloom of planktonic algae. Red Tide phenomenon was first recorded in the coastal waters of Brunei Darussalam in 1976. Since then the coastal waters of Brunei Darussalam experienced sporadic bloom. The culprit was identified as Pyrodinium bahamense var. compressum. The subsequent red tide events were repeated in 1980 and the last occurrence was in 1988 caused by the same organism.

HISTORY OF RED TIDE OCCURRENCES

The 1976 Red Tide Occurrence

The occurrence was discovered almost by chance by Fisheries Department biologists who were conducting routine scientific work on 11 March 1976. The water and plankton samples were collected and examined. Initially, the culprit was thought as Gonyaulax but eventually identified and confirmed as Pyrodinium bahamense. The red tide event overwhelmed the entire country which had, till then no experience with red tides. Fortunately, no fatalities were reported, although five patients were hospitalised after consuming mackerels (Rastrelliger sp.) and Scads (Selar sp.)

The 1980 Red Tide Occurrence

A second outbreak occurred in early 1980. The outbreak was initially reported in Brunei Bay and the information was obtained from various sources on 28 April 1980. The bloom was confirmed as Pyrodinium bahamense var. compressum. The blooms were more diffused and not visible on most occassions. There was no incident of Paralytic Shellfish Poisoning as a resultt of the cooperation of various agencies such as Navy, Air Force and commercial airlines and the early warnings issued and precautions taken based on the previous experience. In addition, there was the establishment for a regular monitoring of red tide outbreak by the Fisheries Department.

The 1988 Red Tide Occurrence

After the 1980 incident, red tide occurrence subsided. However, the department was on constant alert due to blooms occurring in neighboring Sabah, Malaysia between July 1983 and December 1986. Red tide reappeared in Brunei Darussalam in December 1988 when 40 cats were treated and seven perished at the Government Veterinary Clinic after consuming whole guts, gills etc of  Clupeid fish, Sardinella sp. The causative organisms was similar to that causing red tide incidents in 1976 and 1980.

A ban was enforced on the importation of planktivorous fish and extended to the importation of molluscan shellfish. Unlike previous incidents, no visible blooms are observed despite the high concentration of PSP level in the planktivorous fish and molluscan shellfish.

Red tide-causing organisms are potentially lethal and may lead to death if affected fish or shellfish are consumed by humans. The organism contains toxins which can cause Paralytic Shellfish Poisoning/Paralytic Fish Poisoning (PSP/PFP) and may lead eventually to death. Thus, during red tide occurrences, affected fish and shellfish are normally banned from being harvested. Luckily, no human fatalities were recorded during the local red tide events or as a result of eating contaminated fish from neighbouring countries.

During red tide occurences, small planktivorous fish and molluscan shellfish are known to be affected. Large demersal fish, crustaceans and other molluscs such as squids are not affected.

Role of the Department of Fisheries

Since the first occurrence in 1976, various impacts had been reported in terms of human illness and economic losses. The losses were due to the closures of shellfish farms and the ban in harvesting, importing and selling of shellfish from red tide affected areas. However, various steps had been taken by the relevant authorities to mitigate the negative impacts.

Although Brunei Darussalam had its last experience of red tide in 1988, the country had developed several regular monitoring programmes to monitor the impending red tide occurrences in the coastal waters and established regular contacts with its neighbouring countries for red tide information.

a)            Management of Red Tide at National Level

Water and Plankton Samplings

The  Fisheries Department conducts water and plankton samplings as a routine activity to look out for red tide occurrence. The monitoring is done frequently at every fortnight during a non-red tide event and increases to once every two days during red tide.

Sampling stations for the monitoring activity have been pre identified based on the earlier occurrence of the red tide events. The stations are as in Fig. 1. A total of ten stations are monitored of which five are inshore within the Brunei Bay and the other five offshore.

Water samples will be collected and analysed in the red tide laboratory for the absence or presence of red tide organisms. However, other water quality parameters such as temperature, salinity, dissolved oxygen and visibility are measured in-situ.

The presence of  a high density of red tide organisms indicate the waters are experiencing a red tide occurrence.

Fish Stomach Analysis

Beside routine water and plankton samplings, fish sold in the wet markets are monitored frequently. The fish are collected randomly for analysis of stomach content and gills.  The analysis is done in two steps: qualitative analysis to determine absence or presence of red tide organisms, and quantitative  analysis to measure the level of toxins.

The monitoring of fish samples is done to ensure fish sold to the public is not contaminated with red tide organisms.

Both fish stomach analysis and  water and plankton samplings are done regularly in a routine manner. These activities are the early warning system established by the department to safeguard the public against red tide events. In the case of a red tide event  occurring either locally or in neighbouring countries, the Department of Fisheries will activate the National Red Tide Action Plan.

b)            Management of Red Tide at Regional Level

Because of its huge dependence on imported fish from neighbouring countries, the Department has to be aware on the red tide situation in those countries. Regular contacts are made with the relevant authority. Within ASEAN, Brunei Darussalam is a member of a red tide information network.

Brunei Darussalam has also set up a communication network with the Department of Fisheries in Sabah, Malaysia since the occurrence of red tide locally. This communication network has been regular in exchanging information on red tide events in respective countries.

c)             National Red Tide Action Plan

In addition to regular monitoring and surveillance, a National Red Tide Action Plan (NRTAP) was developed in 1992. The NRTAP is executed by a team of officers from Fisheries Department (Chairman), Health Services Department, Municipal Board and the District Office. The team is aptly called the  National Red Tide Response Team (NRTRT).

The objectives of the NRTAP is to provide timely and adequate responses to safeguard public health and to minimise economic losses during red tide occurrences. It establishes the procedures and responsibilities so that the response time can be reduce to a minimum during red tide occurrences and aims to :

  • Safeguard public health against Paralytic Shellfish Poisoning (PSP);
  • Provide advance warning of impending red tides by regular monitoring;
  • Reduce the response time in case of red tide occurrences;
  • Provide accurate information to the public;
  • Build up public confidence in the ability of the authorities to mitigate the effects of red tide.

The procedures of the NRTAP in case of red tide occurrence involve four phases as follows :

Any information on actual or suspected red tides should be immediately conveyed to the Chairman/Deputy Chairman of the NRTRT. The Chairman/Deputy Chairman will alert all other members of the NRTRT. The following action will then be carried out:

Phase I - Confirmation Of Red Tide Occurrence

  1. The Quality Control Section of the Department of Fisheries will proceed immediately to confirm the report and provide feedback to the NRTRT;
  2. Reports of water discoloration in the coastal waters outside the range of small boats to be investigated by helicopter;
  3. Detection of unusual numbers of Pyrodinium in vertical plankton haul samples or in the gut contents of planktivorous fish to be followed by immediate PSP toxin assays;
  4. In the case of suspected Paralytic Shellfish Poisoning (PSP); where possible, samples of cooked/uncooked food and if traceable, samples from market outlet of suspected fish/shellfish should be tested for the presence of PSP toxins;
  5. Although PSP toxin level of 80 ug/100 gm of fish flesh is generally accepted as hazardous to human health, the presence of detectable levels of PSP toxins in fish/shellfish will be taken as sufficient evidence of an occurrence of red tide;
  6. The Department of Health Services will alert all hospitals and clinics to be on the look out for patients with possible symptoms and Paralytic Shellfish Poisoning;

The Royal Brunei Air Force, Royal Brunei Airlines, the Marine Department, Brunei Shell Company Sdn. Bhd. are to be requested to report any unusual water discoloration in the coastal waters.

Phase II - Steps to be Taken on Confirmation of a Red Tide Occurrence

The procedures will depend on the extent and severity of the red tide incident and whether it is in Brunei Darussalam or in neighbouring countries.

  1. Warning of prevailing red tides and safeguards that need to be taken, such as not consuming affected fish and shellfish, is to be given to the public through radio, television, newspapers, posters and notice boards;
  2. The Department of Fisheries will issue orders banning the harvesting/importation of molluscan shellfish and if necessary of planktivorous fish and other affected organisms;
  3. The Department of Fisheries, the Municipal Board and the District Office are to keep surveillance over markets and other sales outlets to see that no banned fish/molluscan shellfish are sold;
  4. The Quality Control Section of the Department of Fisheries is to reduce the interval of monitoring for :
    • Red tide sampling to every alternate days instead of the usual once a fortnight;
    • Fish gill and gut analyses every day instead of once in a week;
    • Paralytic Shellfish Poisoning (PSP) toxin analysis every once a week or when necessary;
  5. Increase monitoring stations to cover Tutong, Belait and Temburong Districts;
  6. The Quality Control Section to maintain close contact with the Fisheries Department of the East Malaysian States of Sabah and Sarawak with respect to the red tide situation.

Phase III - End of a Red Tide Occurrence

Recurrent negative results for PSP toxins in test shellfish for at least THREE MONTHS together with only the occasional occurrence of a few cells of Pyrodinium bahamense var. compressum in plankton haul samples over the same period of time can be taken to signal the end of red tide occurrence. The following action are to be taken :

  1. The NRTRT should make a public announcement that the red tide alert is lifted. The same media utilised to warn the public of a red tide occurrence should be used for the purpose;
  2. All posters and boards put up to warn the public regarding a red tide occurrence should be removed unless they were put up for the purposes of public education or awareness on red tides. Particular attention should be given to boards banning the harvesting of shellfish from specific locations;
  3. The Quality Control Section to revert back to normal monitoring and surveillance procedures.

Phase IV - Review of the Red Tide Action Plan

A review of the National Red Tide Action Plan is necessary after the occurrence of a red tide incident to strengthen areas of weakness or updating of contact numbers. Further, at least an annual review needs to be made to maintain the accuracy of the following :

  • Emergency contact addresses;
  • Telephone numbers;
  • Updating of detection techniques for PSP toxins and the red tide organisms would be necessary because of the rapid progress being made in these areas.

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