Investigation of mortality in Pacific oysters associated with Ostreid herpesvirus-1 μVar in the Republic of Ireland in 2009

High levels of mortality in Pacific oysters Crassostrea gigas in the Republic of Ireland were recorded during the summer of 2009. The new variant of Ostreid herpes 1 (OsHV-1 μVar) which first emerged in France in 2008 was identified from affected stocks. Retrospective data was collected from 70 oyster farmers through an interviewer-administered questionnaire to investigate the distribution and determinants of the mortality. Based on farmer recall, data were recorded at the batch level for cumulative mortality during 2009, start dates and duration of the mortality event and the age of animals affected. Observable mortalities were recorded in 109 out of 346 batches at 47 sites; 104 of the 109 batches were located in bays where OsHV-1 μVar had been detected. The records from bays where OsHV-1 μVar had been detected were analysed to characterize the pattern of mortality and potential risk factors. Batch mortality averaged 37% (18-65% quartiles) but showed a bimodal distribution (half the batches had mortality less than 45%). Mortalities started at the end of May and continued until early August, peaking in early July. On average oysters died over a period of 18 days. Mortality varied considerably both between and within bays. Mortality started in recently introduced batches and occurred later in the summer in established oysters, which is consistent with the introduction of an infectious agent. Mortality was significantly lower in adults compared with other age groups, which supports observations from France. Three variables were significantly (P<0.05) associated, in both bivariate screening and a logistic regression, with high batch-level mortality (>40%): oysters (i) introduced as juveniles, (ii) during or since the winter of 2008/9 and (iii) which spent less than 8h out of water (in a tidal cycle) (compared with oysters introduced as adults before the winter of 2008/9 and spending more than 8h out of water). Twenty-one percent of triploid batches experienced "high" (>40%) mortality compared with 10% for diploid batches which was significant (P<0.05) in the initial bivariate screening but not in the final logistic regression model. Future studies should develop improved methods to assess oyster mortality and follow stocks over time to better determine the influence of management and environmental factors on mortality.     

Biological effects-based sediment quality in ecological risk assessment for European waters

An overview is given of decision making frameworks for Ecological Risk Assessment (ERA) used for sediment in a number of European countries. These frameworks fall into two categories:

An international comparison of pig breeds using a common control stock

In order to compare the genetic merit of different pig stocks a co-operative experiment was carried out in seven different countries. A group of Norwegian Landrace pigs was used as a control population and divided at random into seven samples, one sample being sent to Northern Ireland, the Republic of Ireland, the Federal Republic of Germany, Finland, The Netherlands and Great Britain and one retained in Norway. The sample pigs were used as breeding stock and comparisons made of their progeny in each country, the tests being carried out either in national testing stations or in experimental stations alongside comparable animals from that country. The pigs were fed according to standards prevailing in each country and were slaughtered and measured according to local methods.The results have been used to compare local breeds with the control stock in a great number of performance characteristics. For most traits, the differences between breeds were not found to be large. In general, pigs from the control population of Norwegian Landrace had good growth rates and efficiency of food conversion, and produced carcasses that were long, low in backfat and showed good muscle quality, but were rather poor in area of “eye” muscle and in ham shape. The control population of Norwegian Landrace also differed in performance from that of pigs submitted to Norwegian testing stations and the possible reasons for this and the general problem of making indirect comparisons between countries are discussed.