Prorocentrum minimum bloom and its possible link to a massive fish kill in Bolinao, Pangasinan, Northern Philippines

Abstract

For the first time, a Prorocentrum minimum bloom at a maximum cell density of 4.7 × 10 5 cells/L was recorded on January 31 to February 4, 2002 at Bolinao, Pangasinan, Northern Philippines where intensive and extensive aquaculture of Chanos chanos (milkfish) in fish pens and cages has been practiced for years now. The fish kill, which lasted almost simultaneously with the bloom of the organism had its peak when the organisms bloom was declining. Lack of oxygen in the cages and pens was the fundamental cause of the fish kill. Losses due to the fish kill were estimated at six million pesos (equivalent to US$ 120,000), which includes only the worth of dead cultivated fish. Lack of oxygen in the cages and pens was the fundamental cause of the fish kill, and toxicity of the Prorocentrum could not be confirmed. The cells had minute spinules equally all over the surface of valves. Intercalary striae were wide with many ridges perpendicular to valve margin. Outline of cells was rounder than typical P. minimum cells and similar to P. balticum. Recommendations for future research on the organism are incorporated together with monitoring and management interventions in order to mitigate or possibly prevent damages in similar future events.