Abstract
Asian moon scallop, Amusium pleuronectes, is among the most common commercially harvested scallop in the Philippines. This study investigated suitable conditioning methods, induced spawning, and documented scallop larval development at the Marine Fisheries Research and Development Center (MFRDC) Guiuan, Eastern Samar. Scallops held in tanks with flow-through water system without substrate yielded high survival rate of 48.06 ± 5.95%. Optimum water temperature was 28-29°C for maintaining scallops. Isochrysis galbana and Chaetoceros calcitrans were suitable microalgal feed for A. pleuronectes consumed at 7,388,888 cells min-1 per scallop. These significant results were applied in maintaining scallops at the hatchery. As a result, scallops with an average 19.8 mm shell length (SL) reached 37.5 mm SL within four months with a survival rate of 96.57 ± 2.04%, average daily growth rate (ADGR) of 0.13 ± 0.04 mm.day-1, and specific growth rate (SGR) of 3.92 ± 1.31%.d-1. Natural spawning was successful under controlled conditions while induced spawning trial through thermal stimulation, food shock, sexual stimulation, and serotonin injection resulted unsuccessful release of sperm and eggs. The estimated number of fertilized eggs per spawning ranged from 0.22-1.4 million. Fertilized eggs appeared spherical and dark in color with 54.2-62.57 µm in diameter. After nine hours, the larvae developed into trochophore stage with 59.08-84.4 µm in length. D-veliger with 120.37-157.07µm shell length developed after 24 hours. Development of the early umbone stage was reached on day 5; and on day 7, the umbo larvae become well-developed with shell length of 135.45-173.36 µm. On day 9, pedi-veligers were observed in the culture. Spat grew 312.41-509.48 µm on day 16 and survived until four months with final shell length of 4-10 mm. For the larval rearing, stocking density of A. pleuronectes larvae observed highest survival rate of 0.04 ± 0.03% at 200 larvae/L, while no larvae survived at 800 larvae/L due to contamination of protozoans in the culture medium.
Highlights
Amusium pleuronectes is a bivalve species which belongs to the Pectinidae family and commonly known as Asian moon scallop
A. pleuronectes lies recessed in the substrate, the white colored valve positioned lying on the seabed while brown colored valve is on top and the umbonal region is submerged in the substrate (Morton 1980)
Preliminary data and information were presented in the attempt of breeding and larval rearing of Amusium pleuronectes in Guiuan, Eastern Samar
Summary
Amusium pleuronectes is a bivalve species which belongs to the Pectinidae family and commonly known as Asian moon scallop. A. pleuronectes lies recessed in the substrate, the white colored valve positioned lying on the seabed while brown colored valve is on top and the umbonal region is submerged in the substrate (Morton 1980). This species naturally occur in soft substratum such as sandy-mud to muddy bottom at a depth of 18-40 meter (Gabral-Llana 1980; Del Norte 1988) where it feeds on phytoplankton, detritus, and other suspended particulates. The spawning of A. pleuronectes was observed all year round with peaks during the colder months at
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