32 MARCH 2017 • WORLD AQUACULTURE • WWW.WAS.ORG (tank 1), 19 percent (tank 2), and 16 percent (tank 3). The first spat are 255-270 µm shell height and have clearly distinguishable gills and muscle, in contrast to an eye spot that is still very small (Fig. 2e). At this stage, the wing is prominent, but the disoconch remains small and thin, particularly near the lateral extreme of the shell (Fig. 2f). A few growth processes are visible. The spat recovered from artificial collectors after a 10-d nursery period are attached to the substrate with very thick byssus threads, forming dense aggregations or clusters that are locally called macoyos (Fig. 3a). Macoyos may be very dense in wild juveniles monitored from culturing devices (Fig. 3b). The spat recovered measure 340-360 µm shell height and have a brownish shell with silver hues forming distinctive peak shapes (Fig. 3c); the disoconch is larger and thicker, as well as the wing that may be one-third of the total size of the shell. At this stage, we recovered an average of about 280,000 healthy spat from each of three culture tanks.. Different from Pteria penguin that is destined to half pearl production through the Indo-Pacific (Haws 2006), Pteria sterna is preferably used in the Eastern Pacific to produce multicolored round pearls with a unique metallic sheen (Kiefert et al. 2004, Fig. 4). The protocols for cultivating Pteria species in hatcheries are the same defined since the 1970s for the three major Pinctada species, which may represent a problem given the clear differences in distribution, habitat, and physiology of both genera (Gervis and Sims 1992, Southgate 2008). Pteria sterna is a subtropical-temperate species found in deeper (30-40 m) and colder (17-25 C) waters, where it usually resides in soft sandy-to-muddy substrates forming dense macoyos (Monteforte et al. 1995). This natural behavior of the species to form clusters led us to increase initial stocking density to 13-14 larvae/mL in the hatchery, which in general yielded very good results. Contrasts with Other Pearl Oyster Species The experiences developed so far with hatchery-reared winged pearl oyster larvae and spat are few and limited to northwestern Mexico (Araya-Nuñez et al. 1991, 1995, McAnally and Valenzuela 1990, Serrano and Salinas 1993). These studies were done with laboratory-conditioned breeders and used similar conditions to feed and raise the larvae: a mixed diet of I. galbana and Chaetoceros sp. and a stocking density from 6-10 larvae/mL. Rearing conditions were similar, but this study relied on ripe wild broodstock collected during FIGURE 2. Development of hatchery-reared Pteria sterna, showing stages of trochophore larvae (a), early veliger larvae (b), umbo larvae (c), late pediveliger larvae (d), recently settled spat (e), and details of the prodisoconch and disoconch (f). Photos: Pedro E. Saucedo. FIGURE 3. Recovery of winged pearl oyster spat from artificial collectors at the hatchery (a) and culturing devices at the wild (b), showing the color, hue, and long wing characteristic of the species (c). Photos: Pedro E. Saucedo. a b c d e f a c b
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