Feeding and respiratory time activities in the cupped oysters Crassostrea gigas, Crassostrea angulata and their hybrids

Field clearance of an intertidal bivalve bed: relative significance of the co-occurring blue mussel Mytilus edulis and Pacific oyster Crassostrea gigas

“…This is in good accordance with the mean feeding time activity of 73% observed by Haure et al (2003).…”

“…), Dolmer (2000b) observed that 33 to 75% of an M. edulis population was actively clearing the water. For populations of Crassostrea gigas, a mean feeding time activity of 73% and a mean respiratory time activity of 97% have been reported by Haure et al (2003), and an in situ respiratory time activity in the range of 44 to 82% has been found by Bougrier et al (1998). Under the assumption that (1) clearance rates found in literature for the 2 species represent individual maximal rates and (2) active specimens clear the water at the maximal rate (sensu Jørgensen 1996), the active proportion of the populations in the present study can be estimated.…”

“…edulis has a dry weight-specific clearance rate of about 7.5 l h −1 g −1 (at 10 to 15°C) . The dry weight-specific clearance rate of C. gigas is in the range of 3 to 6 l h −1 g −1 at water temperatures of 15 to 19°C (Bougrier et al 1995, Haure et al 2003 and 12 to 17 l h −1 g −1 at 25°C (Dupuy et al 2000). Walne (1972) found the dry weight-specific clearance rate (≈21°C) of C. gigas and M. edulis to be 9.1 and 3.7 l h −1 g −1…”

Natural hybridization between genetically differentiated populations of Crassostrea gigas and C. angulata highlighted by sequence variation in flanking regions of a microsatellite locus

“…For example, natural selection between close species of mussels in the Baltic zone was found to explain the discordant patterns of allozyme and non-allozyme loci (Riginos et al 2002). Selective pressure in the present study could involve the presence or absence of the iridovirus that affected C. angulata populations in the late 1960s and/ or taxa-specific preferential environmental conditions (Haure et al 2003). However, this second hypothetical selective factor is unlikely to be major, as C. angulata was massively present along the French coasts until the late 1960s, where only C. gigas is found today.…”

“…C. gigas shows a superior production yield in the natural environment in France (Bougrier et al 1986, Héral 1986, Parache 1989, Soletchnick et al 2002, as its growth is twice that of the Portuguese oyster (Bougrier et al 1986). Differences were also shown in terms of their ecophysiological characteristics (His 1972, Goulletquer et al 1999, Haure et al 2003. Furthermore, genetic differences have now been observed on several levels.…”