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Crassostrea iredalei:   (click for more)

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FAO Names
En - Slipper cupped oyster, Fr - Huître creuse chausson, Sp - .
3Alpha Code: CSI     Taxonomic Code: 3160700811
Diagnostic Features
Shell medium sized, usually poorly sculptured, very variable in shape but generally higher than long, roughly rounded, oblique triangular or elongate ovate in outline. Left (lower) valve rather thick but lighweighted, more convex and larger than right (upper) valve, with small to large attachment area.  Surface of left valve somewhat lamellate, with a few shallow to indistinct radial furrows that fainly scallop the commissure of valves. Right valve flattish, concentrically lamellate or nearly smooth. A moderately small umbonal cavity present under the hinge of left valve. Adductor muscle scar large, kidney-shaped, somewhat concave anterodorsally and a little nearer to ventral margin than to the hinge. Chomata completely absent from internal margins.  Colour outside of shell dirty white, often flushed with pale greyish brown. Right valve frequently with a few darker purplish grey radial bands in early syages of growth. Interior of valves whitish and shiny, often with irregular areas of chalky white, deep purple-brown on posterior adductor scar. 
Geographical Distribution
Restricted to the Philippine Archipelago and Malaysia.
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Habitat and Biology
Attached to hard objects or growing in bunches, on various soft bottoms, especially in bays and estuaries with somewhat reduced salinity. Intertidal and shallow subtidal water.Suspension-feeding (Hawkins et al. 1998).This brackishwater species is noted for its tasty creamy flesh and its culture requires a salinity range of 15-25 ppt. (Devakie & Ali, 2000). 
Size
Maximum shell height 15 cm, commontly to 8 cm.
Interest to Fisheries
This is an important commercial species in the Philippines, produced from both wild stocks and aquaculture. FAO's Yearbook of Fishery Statistics reports a range of yearly production from around 324 mt in 1995 to 95 mt in 1999 in Philippines. In the same period, the yearly aquaculture production ranged of from around 11874 mt in 1995 to 13698 mt in 1999. To date, some 192 small-scale fisherfolk are engaged in the culture of C. iredalei, involving an area of 101,416 m2 in Malaysia (Anonymous, 1996). Although, the spat supply of this species is only confined to the east coast of Peninsular Malaysia, culture operations have been very successful on the west coast through spat transplantation programs. Culturists on the west coast are thus solely dependent on spat supply from the east coast, which takes more than 24 h by road. However, spat collection (peak seasons being April to June and October to December) on the east coast are hindered by monsoons which often result in total mortality of spat (salinity often reaching 0 ppt) during the November to January period. When the spat supply was disrupted for farms on the west coast, the culturists would then resort to importing oyster spat from southern Thailand (Devakie & Ali, 2000).
Bibliography
Anonymous - 1996. Annual Malaysian Fisheries Statistics, vol. 1. Depart. Fish. Malaysia, Min. of Agric., Kuala Lumpur, Malaysia. . 
Devakie, MN & Ali, AB - 2000. Effects of storage temperature and duration on the setting and post-set spat survival of the tropical oyster, Crassostrea iredalei (Faustino). Aquaculture. .  vol. 190, no. 3-4, pp. 369-376 ..
Hawkins, AJS, Smith, RFM, Tan, SH & Yasin, ZB - 1998. Suspension-feeding behaviour in tropical bivalve molluscs: Perna viridis, Crassostrea belcheri, Crassostrea iradelei, Saccostrea cucculata and Pinctada margarifera. Mar. Ecol. Prog. Ser. .  vol. 166, pp. 173-185 ..
Poutiers, J. M. - 1998. Bivalves (Acephala, Lamellibranchia: Pellecypoda). In: The living Marine Resources of the Western Central Pacific. Volume 1. Seaweeds, corals, bivalves and gastropods. (Carpentier, K. E., Niem, V. H. eds) FAO, Rome, Italy . 
 
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