Aquaculture 524 (2020) 735267 Contents lists available at ScienceDirect Aquaculture journal homepage: www.elsevier.com/locate/aquaculture Performance of the winged pearl oyster Pteria sterna (GOULD, 1851), implanted for half-pearl (mabé) production in two size groups T ⁎ Luis Freitesa,b, , Franklin Jaraa, María Gregoria, Adrián Márquezc, Pedro E. Saucedod, César Lodeirosb,e a Universidad Estatal de la Península de Santa Elena, Facultad de Ciencias Marinas, Ecuador b Instituto Oceanográfico de Venezuela, Universidad de Oriente, Apartado Postal 245, Cumaná 6101, Venezuela c Escuela Superior Politécnica del Litoral (ESPOL), Centro Nacional de Acuicultura e Investigaciones Marinas (CENAIM), km 30.5 Vía Perimetral, Guayaquil, Ecuador d Centro de Investigaciones Biológicas del Noroeste, S.C. La Paz, Baja California Sur 23000, Mexico e Grupo de Investigación en Biología y Cultivo de Moluscos, Escuela de Acuicultura y Pesquerías, Facultad de Ciencias Veterinarias, Universidad Técnica de Manabí, Bahía de Caráquez, Manabí, Ecuador ARTICLE INFO ABSTRACT Keywords: This study generated baseline information relative to overall performance of the winged pearl oyster Pteria sterna Aquaculture implanted at two groups (small and large) for half-pearl (mabé) production. This is a suitable technology to Growth optimize the pearl production in the tropical coasts of Ecuador. The yield and quality of mabé pearl produced, as Implantation well as oyster condition index, increase in oyster survival, shell size and mass of tissues, and environmental Mabé variables were examined in this study. From 120 oysters used, 65 were of small size (25 nucleated, 25 non- Survival nucleated and 15 for the initial sample; initial average shell length of 64.7 ± 5.3 mm; ~6 months old) and 55 Pearl oyster were of large size (20 nucleated, 20 non-nucleated and 15 for the initial sample; 78.0 ± 5.8 shell length cm; ~10 months old). Hemispherical plastic nuclei (12.5 mm base diameter, 7 mm height) were used. All groups of oysters were anesthetized with 1% Eugenol and cultivated for five months (May through October 2017). At the end of the trials, only one dead oyster occurred in the small size group. A high percentage (29.2%) of adductor muscle over-growth on the nuclei occurred in small oysters, probably caused by the relatively fast growth rate (≥8 mm in 5 months). A lower percentage of muscle over-growth on the nuclei (5.6%), thicker nacre deposition, and higher occurrence of regular-shaped mabé pearls were observed in large oysters, compared to small oysters. This study suggests that large oysters (> 80 mm) should be preferably used for half-pearl production in P. sterna to ensure the highest quality standards for commercialization. 1. Introduction exploited to produce cultured pearls. This process, which has changed little since then, provides the basis for an industry with increasing Pteria sterna (Gould, 1851), commonly known as the rainbow pearl growth and value with different bivalve species (e.g. Pinctada spp., oyster or winged pearl oyster, is a marine bivalve (Pteriidae family) Pteria spp.) and gastropod species (Haliotis spp.). Today, pearl culture inhabiting the subtidal zone (Álamo and Valdivieso, 1997), from the exists as a consolidated or growing industry in countries such as Fiji lowest tide to 23 m depth (Mora, 1990). The species adheres to hard (Kishore et al., 2015), Tonga (Gordon et al., 2018, 2019), Mexico substrates (rocks, gorgonid corals and submerged metallic structures), (Saucedo et al., 1998; Ruiz-Rubio et al., 2006), and Chile (Rojas- coarse sand, and mangroves (Monteforte, 2005; Ordinola et al., 2010). Figueroa et al., 2019). Despite this, the worldwide industry related to Its distribution extends along a wide range of temperate, subtropical, the production, sale, and marketing of cultured pearls has mostly relied and tropical coasts of the Pacific Ocean, from the upper Gulf of Cali- on three pearl oyster species of the genus Pinctada: Pinctada fucata, P. fornia (in Mexico) to Peru (Keen, 1971; Arízpe, 1992; Álamo and margaritifera, and P. maxima (Taylor and Strack, 2008). Although Valdivieso, 1997; Ordinola et al., 2010). Ecuador has high potential for the development of a similar industry Since the 1900s, the ability of mantle tissue of different pearl oyster due to the natural occurrence of P. sterna and mother-of-pearl Pinctada species to secrete prismatic nacre layers has been commercially mazatlanica, there is little local information of their basic ⁎ Corresponding author at: Instituto Oceanográfico de Venezuela, Universidad de Oriente, Apartado Postal 245, Cumaná 6101, Venezuela E-mail address: [email protected] (L. Freites). https://doi.org/10.1016/j.aquaculture.2020.735267 Received 15 November 2019; Received in revised form 15 March 2020; Accepted 18 March 2020 Available online 19 March 2020 0044-8486/ © 2020 Elsevier B.V. All rights reserved. L. Freites, et al. Aquaculture 524 (2020) 735267 ecophysiological and reproductive biology in relation to pearl produc- Of these, 65 were of small size (64.7 ± 5.3 mm shell length; tion in tropical areas of the Pacific(Serna-Gallo et al., 2014). In Mexico, ~6 months old) and were divided into 25 nucleated, 25 non-nucleated for example, few studies have analyzed the factors influencing the and 15 oysters for the initial sample. The remaining 55 oysters were of production and quality of half pearls in the winged pearl oyster P. sterna large size (78.0 ± 5.8 mm; ~10 months old) and were divided into 20 (Saucedo et al., 1998; Ruiz-Rubio et al., 2006) or free and round pearls nucleated, 20 non-nucleated and 15 for the initial sample. Oysters from (Nava et al., 2000). both groups (small and large) and treatments (nucleated and non-nu- − Half pearls produced from Pteria penguin are traditionally known as cleated) were anesthetized for 15 min in a solution containing 1 mg L 1 ‘mabé’ (Kripa et al., 2008). However, the term mabé is now used gen- Eugenol (clove oil) to facilitate nuclei implantation. Oysters were erically to refer to half pearls produced from a different number of considered completely relaxed when they had no reaction to physical bivalve species (Ruiz-Rubio et al., 2006; Kishore et al., 2015; Gordon stimuli, or when the valves did not close when removed from the re- et al., 2018, 2019). They are the result of a non-surgical procedure in laxant (Mamangkey and Southgate, 2009; Granados-Amores et al., which hemispherical plastic nuclei are cemented on the inner nacreous 2018). side of the shell and further covered by the mantle tissue that gradually One hemispherical plastic nucleus (7 mm height, 12.5 mm base secretes concentric layers of nacre material (Taylor and Strack, 2008). diameter) was cemented on the center of the left valve of each oyster The cultivation of pearl oysters to produce mabé pearls requires a lower using polycyanoacrylate glue (UHU™)(Haws et al., 2006; Ruiz-Rubio financial and technological investment than the cultivation of round et al., 2006; Kripa et al., 2008; Kishore et al., 2015). Oysters were pearls, and local communities can achieve this task by following ade- implanted following standard procedures described by Kishore et al. quate livelihood training programs (Haws et al., 2006; Southgate et al., (2015). Each nucleus was located far from the adductor muscle in a 2006; Kishore et al., 2015). place not affecting the normal closing of the valves. The possible effect For mabé production, the evidence indicates that in young, fast of stress and mortality due to desiccation during implantation was growing oysters the adductor muscle may begin to over-grow the nu- minimized by limiting the process to approximately 3 min per oyster. cleus, leading to its incomplete covering and reducing nacre thickness and lustre (Saucedo et al., 1998; Ruiz-Rubio et al., 2006). In turn, this 2.2. Recovery, cultivation, and monitoring of nucleated oysters effect can significantly reduce the value of resulting pearls. Similarly, nuclei placed too close to the shell edge may be covered with perios- Following nucleus implantation, oysters from the two groups were tracum, favoring a high proportion of asymmetrical, dull, and low- separately placed in two 500-L plastic tanks containing freshly aerated quality mabé. Preliminary studies with P. sterna cultured in equatorial seawater to allow their full recovery for 48 h. All surviving oysters were waters (Lodeiros et al., 2018; Treviño et al., 2019) show that the species then transferred to a cultivation system consisting of a long-line an- can reach the minimum size required for pearl induction (70–80 mm chored at 800 m from the coastline (1°59′12.19”S; 80°45′39.00”O) in shell height) within the first year (7–8 months), due to its high growth Ayangue Bay, Santa Elena Province, Ecuador. The oysters from both rates (> 8 mm/mo). Data describing shell growth rates also provide groups (small and large) and treatments (nucleated and non-nucleated) useful estimates of pearl growth, as shell growth and nacre deposition were cultivated in three-floor baskets, previously described by Freites are positively correlated (Coeroli and Mizuno, 1985; Monteforte and et al. (2019). Seven to eight oysters occupied the first floor or level of Morales-Mulia, 2000; Kishore et al., 2018). This information illustrates each basket, covering 27% and 34% of the bottom. Both groups of the potential of P. sterna for mabé production, as occurs in Bahía de La baskets (small and large) were suspended at 4-m depth. Oysters were Paz, Mexico (Saucedo et al., 1998; Ruiz-Rubio et al., 2006) and Bahía deployed in May 2017 and harvested for mabé grading in October 2017 de Acapulco, Mexico (Serna-Gallo et al., 2014). These results contrast (see below). Oysters were counted on a fortnight basis to determine with the projection of 24 months that Gaytán-Mondragon et al. (1993) survival (%) after being implanted.