FINALLY NUISANCE CONTROLLED

THANKS to El Niño, the invasion of oysters’ territory by blue mussels has stopped enabling fish cage operators in western Pangasinan to finally heave a sigh of relief.

The blue mussels that proliferated inside their fish cages and left no room for oysters to grow on suddenly died due to high salinity intolerance.

Dr. Westly Rosario, center chief of the Bureau of Fisheries and Aquatic Resources (BFAR) in Dagupan City, told The PUNCH that the blue mussels, Mytella Charruana, cannot tolerate salinity higher than 30 parts per liter (ppt).

The blue mussels along the Brazilian and Columbian coasts of South America, that traversed the Panama Canal to become established in the tropical Eastern Pacific, have reached the coastal waters in Pangasinan, based on a DNA test made in the United States of America last year.

He said fish cage operators complained of having to frequently change the nets in their fish structures because of the mushrooming of blue mussels.

“When blue mussels bloomed, they multiplied fast and occupied spaces intended for oyster production causing problems to the fish cage operators,” Rosario said.

He added, “They invaded the oysters’ territory.”

He said the blue mussels impede fish cage operation because it normally takes 15 days before the caretakers change their nets, but with the blue mussels presence, the nets have to be changed every week. Fish traps are also affected.

“The good news is, becasue of El Nino, these blue mussels die because of high salinity intolerance,” Rosario said.

Ashley Salinas, a research assistant/laboratory technician of BFAR here said this was revealed by initial experiments conducted on the salinity tolerance of the blue mussles particularly in the Philippine setting.

In the experiment Salinas conducted, she ran a salinity shock trial where mussel individuals were randomly selected from the holding tanks and were directly transferred to each of the experimental aquarium.

When the tests confirmed that the mussels can survive from 5-30 ppt. but will die at 35 ppt after 5 days, it showed that unwanted proliferation of this invasive species can also be controlled through natural environmental fluctuations such as salinity change.

She added this may explain why some reported that this invasive mussel is slowly experiencing die-out in parts of Bolinao and Anda towns, Pangasinan.

“As El Nino starts to occur, water salinity rises causing Charru mussels to die, giving way for oysters and green mussels to re-emerge,” Salinas said. (Tita Roces)

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