Hemispherical Mabé Pearl Formation by Pinctada mazatlanica in a Tropical Estuary: Effects of Culture Duration

The effect of time on mabé pearl formation in the mother-of-pearl oyster Pinctada mazatlanica was evaluated under suspended culture in Bahía de Caráquez, Chone River estuary, Manabí, Ecuador. Oysters measuring 80–90 mm were grafted with three hemispherical nuclei (11 mm in diameter and 6 mm in height): one in the left valve and two in the right valve (left and right sides). Cultivation occurred from September 2023 to January 2024 in lantern nets suspended at a depth of 1–2 m from a floating aquaculture platform located in waters 6–8 m deep. Monthly assessments included survival, nacre deposition on the nuclei, and pearl quality (classified into commercial categories AAA, AA, A, B, and noncommercial-NC). Cumulative survival decreased in the last 2 mo, reaching 80.7% ± 17.95% by the end of the study. Nacre deposition varied significantly, with the highest layer observed in the right valve at the end of the study. Initially, mabé pearl quality was predominantly grade B (>35%) and noncommercial (>30%), followed by grade A (15%–28%), AA (3%–17%), and AAA (0%–7%). At the end of the experiment, the proportion of noncommercial pearls in the right valve significantly decreased, whereas AA (17%) and AAA (7%) categories increased. An association analysis revealed a positive correlation between nacre deposition and AA category pearls. These findings suggest that the nucleus's placement on the right side of the right valve and a minimum cultivation period of 4 mo or more are crucial for producing higher quality pearls and better nacre deposition in Bahía de Caráquez, Chone River estuary.