The challenge of reducing the fecal indicator bacteria load and preventing spawning during depuration of Perna perna mussels

Abstract

Perna perna mussels commonly spawn during depuration under water temperatures above 18°C. A previous study conducted under experimental conditions (15L aquariums) has suggested reducing the temperature to decrease the odds of spawning. This study monitored the concentrations of Escherichia coli in mussels during three 48-hour and two 72-hour depuration cycles conducted in a small (600L) commercial depuration unit, under temperatures of 14°C and 17°C. The protocol prevented mussels from spawning, as this behavior was observed only in a few mussels in one out of the four depuration cycles. The reduction of fecal indicator bacteria loads, in turn, was unsatisfactory in all depuration cycles, with at least 67% of the samples from cycles 1, 3, 4, and 5 presenting E. coli concentrations above the end product testing limit (230MPN 100g⁻¹) after 48 hours of depuration. Moreover, none of the sample cycles showed bacterial concentrations below that limit, even after 72 hours of depuration.