Phenotypic response of a cohort of Ostrea chilensis (Philippi 1845) to differing environmental conditions in three oyster farms in southern Chile

Abstract

Offspring from a mass spawning of the Chilean oyster Ostrea cMensis (Philippi) were reared in three locations, at two depths and three densities along the east coast of Chiloe Island, southern Chile, to test for the presence of genotype-environment interaction for growth rate and the effect of environmental variables on shell growth. Site, density and depth effects and their interactions upon shell length variation at 26 months of age were all statistically significant (P < 0.05). These results indicate that sibling oysters perform differently in different environments, densities and depths. The shell length of 0. cMensis in the three different environments may be limited by food supply when the abiotic variables are in the range of tolerance for the species. Salinity was the most important factor limiting the shell growth of 0. chilensis in the Quempillen estuary. Thus, in breeding programmes, it is recommended that the testing of stocks and their offsprings' performance should be carried out on the farm to ensure that the selection criteria are valid.

Phytoplankton distribution and oyster,Ostrea chilensis(Philippi 1845), growth at Putemún Channel, southern Chile

“…The growth rates obtained during the study period are in accordance with those previous reported for Ostrea chilensis in suspended culture (Toro & Varela 1988;Toro &Newkirk 1991;Toro 1996). There was no apparent effect of salinity or pH on growth rate.…”

“…However, a major difficulty in correlating temperature and growth rate in field populations of bivalves is that the correlation, even if it is significant, may not be causal (Wilson 1977;Page & Hubbard 1987). Water temperature may strongly covary with seasonal phytoplankton abundance and/or chlorophyll a (Kautsky 1982;Toro et al 1995;Toro 1996), thus making it difficult to draw any conclusion about the importance of temperature or chlorophyll abundance in regulating growth rate. Strong positive effects on growth would be expected from an increment in the chlorophyll abundance (Page & Hubbard 1987;Camacho et al 1995).…”

The effects of stressors on the dynamics of Bonamia exitiosus Hine, Cochennec‐Laureau & Berthe, infections in flat oysters Ostrea chilensis (Philippi)

“…Although parasites such as the protozoan Perkinsus marinus may reduce the tolerance of oysters to salinity changes (Paynter, Pierce & Burreson 1995), the prevalence of B. exitiosus at the beginning of the experiment was low (6%), and therefore parasite‐induced salinity intolerance does not explain the mortalities. Similarly, below 18‰, the filtration rate of O. chilensis decreases (Toro 1996) and therefore oysters grown in low salinity may experience reduced nutrition (Winstead 1995). Starvation could be a factor, but this is unlikely as oysters in the filtered water group had the lowest mortality and the lowest B. exitiosus prevalence among surviving oysters.…”