THREE bay areas in Davao Region are now declared free of the toxic red tide as of May 13, 202, the Bureau of Fisheries and Aquatic Resources (BFAR) - Davao said.
Based on the Shellfish Bulletin No. 09 Series of 2022, BFAR-Davao revealed that the Balite and Pujada Bays in Mati City, Davao Oriental and Malalag Bay that transcends Davao Occidental and Davao del Sur are now off the list of bays with toxic red tide.
BFAR-Davao has previously issued a Local Red Tide Warning in Balite Bay on March 18 for testing positive for Paralytic Shellfish Poison (PSP) that causes red tide. The situation, however, did not escalate into a shellfish ban by the Department of Agriculture (DA)-BFAR.
“March 18, nag bigay kami ng (we issued a) Local Red Tide Warning for precautionary advisory lang. Kasi ang may mandate na mag declare ng shellfish ban is yung central office (Because only the central office has the mandate to declare a shellfish ban),” Sajeda Canobas, Aquaculturist II of BFAR-Davao, told SunStar Davao on Tuesday, May 17.
A shellfish ban may be implemented by DA-Bfar if an area exceeds the regulatory limit of 60 unit grams of toxin per 100 grams of shellfish meat, and may only be declared red tide-free if three consecutive shellfish samples are tested negative for PSP.
During a shellfish ban caused by the red tide event, all kinds of shellfish are prohibited for human consumption and transit to other bay areas as they may infect red tide-free areas.
Examples of these are green mussels or “tahong” found in Malalag Bay, and venus clam and blood cockles found in Balite Bay. But shrimps and crabs are still safe to eat, along with fish and squids - provided they are thoroughly cleaned and cooked.
According to Canobas, red tide events usually come and go, depending on the environmental factors in the area wherein algae species producing paralytic shellfish toxins are present.
“Kasi andoon lang siya (algae) sa area, nag bloom lang siya kapag nagiging preferable sa kanya ang condition ng water (The algae is present in the area. It blooms when the water environment are in preferable conditions),” Canobas said.
“Kapag eutrophicated ang water, meaning mataas ang nutrient level sa water... Pwede rin yung temperature, yung malakas na ulan tas mainit kinabukasan (This happens when the water is eutrophicated or when high nutrient levels are present. It can also be a sudden shift in temperature from cold to hot) .”
Canobas added that this explains why preventing red tide occurrence or predicting when it will happen is difficult to forecast. At the same time, the country’s lack of instrument to treat algal blooms forces the bureau to resort only to consistent monitoring to identify areas with PSP.
“Meron yung ibang countries, nakagawa sila ng way how to treat the algal blooms pero based sa results, mas malaki yung negative impact niya sa environment so hindi pa rin siya magandang gamitin (Other countries have developed a treatment of algal blooms but based on the results, it has a huge negative impact on the environment so it’s still not good to use),” Canobas underscored.
Balite Bay was declared positive for PSP in February 2020 which resulted in a shellfish ban until August 2021 when it was finally tested negative.