A flow-through rearing system for ecophysiological studies of Pacific oyster Crassostrea gigas larvae

Abstract

While literature is relatively abundant on adult shellfish, ecophysiological studies at the larval stage are scarce because of both technical difficulties and inadequate methodology. A tool dedicated to provide basic information for larval ecophysiology was accordingly developed. Two steps were followed: first a flow-through method of Crassostrea gigas larval culture was perfected during a set of experiments in which rearing systems and larval density were assessed. Then a continuous hydrobiological data recorder was adapted with modifications to comply with our experimental aim. SILO (Système d'Instrumentation des Larves en flux Ouvert) allowed the successive acquisition of hydrobiological parameters in ten 150 l larval tanks in which larvae were reared using flow-through techniques under controlled environmental conditions. An automated system enabled sequential measurement of hydrobiological parameters from one larval culture to the next. A chamber system contained several probes for measurement of temperature, salinity, pH and fluorescence. The electronic system allowed real time acquisition, storage and transfer of data. SILO was successful as a larval rearing device, reducing larval disturbance that could result from transfer and handling for measurement. It was also efficient as a tool to provide basic information for larval ecophysiology research. The effect of temperature (17, 22, 25, 27, 32°C) on growth and ingestion of microalgae was studied to test SILO. Maximum growth occurred at 27 °C (16 ± 2 µm d-1) and 32 °C (15 ± 3 µm d-1) whereas larvae reared at 22 and 25°C showed lower development (8.6 ± 3.1 and 11.7 ± 2.5 µm d-1, respectively). Moreover, metamorphosis exhibited no significant difference at 27 or 32 °C with 87.5 ± 7.1 and 85.9 ± 9.6% respectively, while at 22 or 25 °C lower metamorphosis was recorded with 55.2 ± 8.3 and 57.6 ± 9.6%, respectively. The lowest temperature (17 °C) strongly inhibited ingestion whereas the highest temperature (32 °C) stimulated maximum feeding activity over the whole larval rearing period.

Factors influencing disease-induced mortality of Pacific oysters Crassostrea gigas

“…Once the oysters were reproductively mature, gametes from 30 individuals (1/3 males, 2/3 females), obtained by stripping, were mixed in a 5 l jar at 50 spermatozoids per oocyte. The fertilized oocytes completed their embryonic development in 150 l tanks filled with 1 µm filtered and UV-treated seawater at 21°C for 24 h. The D-larvae were then collected and reared in flow-through rearing systems at 25°C (Rico-Villa et al 2008). At the end of the pelagic phase (12 d), competent larvae were collected on a 225 µm sieve and allowed to settle on cultch.…”

Impacts of rearing techniques on growth, survival and bacterial microbiota of carpet shell clam (Ruditapes decussatus) larvae

“…Sarkis et al (2006) showed that calico scallop growth for FT-reared larvae was comparable or significantly higher than in the static system, which corroborate with our findings. Similarly, Rico-Villa et al (2008) reported significant growth and competence improvements in Crassostria gigas larvae reared in the flow-through system compared to static system. These authors also revealed that the use of FTS with constant flows of highquality water and a daily cleaning of the sieve clogs facilitated the circulation in the rearing tank and removal of metabolic waste products providing favorable conditions for larval development.…”

“…These authors also revealed that the use of FTS with constant flows of highquality water and a daily cleaning of the sieve clogs facilitated the circulation in the rearing tank and removal of metabolic waste products providing favorable conditions for larval development. Several studies suggested an association between the stocking density and the water exchange rate (Magnesen et al 2006;Rico-Villa et al 2008). Furthermore, Andersen et al (2000) and Sarkis et al (2006) reported a reduction in growth performance at high stocking density when they reared scallop (Pecten maximus) and oyster (C. gigas) larvae in FTS.…”

“…The FTS is based on regular water exchange in order to reduce bacteria as well as toxic substances, which accumulate in the rearing water (New and Valenti 2000). This method has been successfully used in the nursery culture of oysters, scallops, clams, mussels and in numerous fish hatcheries (Andersen et al 2000;Ritar 2001;Tieman and Goodwin 2001;Otoshi et al 2003;Sarkis et al 2006;Rico-Villa et al 2008). Recirculating systems operate by water undergoing treatment, allowing to the hatcheries production system's waters to be partially reused (Rosenthal et al 1986).…”

Hatchery-scale trials using cryopreserved spermatozoa of black-lip pearl oyster,Pinctada margaritifera

“…Twentyfour hours later, the incubator tank was drained onto a 35 µm sieve and D-shaped larvae were concentrated in a 5 L graduated cylinder. D-shaped larvae were counted (3 × 20 µl) and then reared in a through-flow culture system (Magnesen et al 2006;Rico-Villa et al 2008;Sarkis et al 2006) in 4 replicates. D-shaped larvae were fed using three tropical species of micro-algae: Isochrysis clone T-Iso, Chaetoceros minus and Chaetoceros gracilis.…”