Cadmium and lead concentrations in the dorsal muscles of spotted knifefish (Chitala ornata Gray) from Laguna de Bay, Philippines.

Laguna de Bay is the largest freshwater lake in the Philippines and has become a major source of agricultural food supply, housing 33 fish species. Previous studies have shown that fish in the lake are significantly impacted by pollution, including heavy metals, which can have harmful effects on humans when consumed. Invasive spotted knifefishes were randomly collected from Binangonan, Cardona, and Sta. Rosa, which represents the West Bay, Central Bay, and South West Bay of Laguna de Bay, respectively. The length and weight of the samples were measured before obtaining the dorsal muscle from each fish. The muscles were oven-dried, furnaced, and dissolved in concentrated nitric acid and deionized water before being subjected to cadmium and lead analysis using AA-6300 Atomic Absorption Spectrophotometer. Spotted knifefish samples from Binangonan, Cardona, and Sta. Rosa sites had similar mean cadmium concentrations of 0.296, 0.287, and 0.296 mg/kg (d.w.), respectively. The mean concentration of lead in samples collected from Binangonan, Cardona, and Sta. Rosa was 0.322 mg/kg, 0.489 mg/kg, and 0.764 mg/kg (d.w.), respectively. All cadmium and lead (w.w.) not significantly exceeded the maximum permissible limits of all local and international standards. The cadmium and lead levels from Binangonan were similar, while the lead levels from Cardona and Sta. Rosa were higher than the cadmium levels. There was no significant correlation between all sites' cadmium concentrations with body weight and length while a significant correlation observed between lead levels from Sta. Rosa and body weight and length. The utilization of knifefish as bioindicator transforms a major ecological pest into a vital diagnostic tool to reveal both heavy metal contamination in lakes and specific industrial hotspots like the Southwest Bay. This study directs future management toward continuous and longitudinal surveillance to ensure that efforts to control the invasive population also strictly safeguard regional food security.