• Environmental factors associated with invasion: modeling occurrence data from a coordinated sampling programme for Pacific oysters

      Kochmann, J.; O’Beirn, F.X.; Yearsley, J.; Crowe, T.P. (Springer Netherlands, 2013)
      Documenting establishment and spread of invasive species requires extensive co-ordinated sampling programmes. Identifying the factors promoting or inhibiting local establishment of an invasive species can improve capacity to predict further spread and underpin strategies to limit spread. Here, a structured sampling programme was used to assess the current distribution of feral populations of Pacific oysters, Crassostrea gigas, in Ireland. Sixty-nine sites were sampled using a standardised protocol combining semi-quantitative and quantitative approaches. Sites were chosen to represent variation in proximity to aquaculture and a range of environmental variables. Oyster populations were found at 18 locations, with densities ranging from single individuals to nine individuals per m2. The broad size range of oysters found is indicative of more than one recruitment event. Logistic regression indicated that feral oysters were positively associated with the presence of hard substrata or biogenic reef, long residence times of embayments and large intertidal areas. There was also a tendency for oysters to occur disproportionately in bays with aquaculture, but >500 m from it. Small-scale analysis within sites showed that oysters were almost exclusively attached to hard substrata and mussel shell. The approach taken here provides a rigorous repeatable methodology for future monitoring and a detailed basis for the prediction of further spread.
    • Growth and survival of Spisula solidissima similis larvae fed different rations of Tahitian strain Isochrysis species

      Hurley, D.H.; Walker, R.L.; O'Beirn, F.X. (National Shellfisheries Association, 1997)
      Laboratory-spawned veliger-stage larvae of the southern Atlantic surfclam, Spisula solidissima similis (Say 1822), were reared to late pediveliger stage on five different cell concentrations of Tahitian strain Isochrysis species (T-Iso) to determine an optimal food ration for this subspecies. Larvae were fed daily 0, 50,000, 100,000, 200,000, or 300,000 cells/mL of T-Iso. Day-old veliger larvae were stocked in 150 (1-L) replicate flasks at mean densities of 0.7 or 0.8 larvae/mL for trials A and B, respectively. Larval growth and survival were assessed every 2 days over the 14-day trial penods. Significantly greater growth and survival of larvae occurred in both trials in the lower food rations of 50,000 and 100,000 cells/mL. A reduction in larval growth rate and survival was observed at the higher ration treatments. A decline in overall larval health may be associated with the deliterious effects of surplus ration degradation.
    • Modelling origin and spread of Infectious Pancreatic Necrosis Virus in the Irish salmon farming industry: the role of inputs

      Ruane, N.M.; Murray, A.G.; Geoghegan, F.; Raynard, R.S. (Elsevier, 2009)
      Observed emergence of IPNV in farmed Irish salmon is simulated using a model originally developed to analyse the spread of the virus in Scotland [Murray, A.G., 2006a. A model of the spread of infectious pancreatic necrosis virus in Scottish salmon farms 1996–2003. Ecol. Model. 199, 64–72]. IPNV appears to have become established relatively recently in Ireland and the model is altered to explicitly simulate the origin of the spread of the virus. Input to freshwater farms was key to initiation of infection, but modelling suggests that endogenous spread was responsible for much of the subsequent increase in prevalence of IPNV. From the modelling, it is unlikely that direct imports accounted for most IPNV cases. If this is the case, cessation of imports, without a substantial improvement in biosecurity, would be likely to be of only limited effect in controlling IPNV. Marine IPNV prevalence appears to be insensitive to direct interventions in the marine environment (as in the Scottish model). A multi-element control strategy, targeting both endogenous spread and external input of infection and prioritising freshwater sites, but extending to marine sites, would probably now be required to eradicate IPNV from Ireland.
    • The occurrence of DSP toxicity in Ireland

      Jackson, D.; Silke, J.; Doyle, J.; Nixon, E.; Taaffe, B. (ICES, 1993)
      The geographical and temporal variations in the occurrence of DSP in Ireland are presented and the implications of the resulting closures on aquaculture operations and fisheries are discussed. Prior to 1992 DSP toxicity had been confined to the southwest and south coasts but in 1992 a protracted occurrence of DSP was recorded in Killary Harbour on the west coast.
    • Organisms associated with oysters cultured in floating systems in Virginia, USA

      O'Beirn, F.X.; Ross, P.G.; Luckenbach, M.W. (National Shellfisheries Association, 2004)
      The number and abundance of macro-fauna! taxa was estimated from six floating structures (floats) used to culture the Eastern oyster (Crassostrea virginica) near Chincoteague Island, Virginia, USA. After a 10-mo grow-out period, all organisms found among and attached to the cultured oysters were counted. The final mean size of oysters was 80.5 (14.7 SD) mm. Overall, 45 species of macrofauna were recorded with the number of species in the floats ranging from 24 to 36. There was no relationship between the number of taxa and the density of oysters in the floats. Total abundances of associated organisms were estimated at 12,746/float to 92,602/float. These findings highlight the diverse (taxonomic and trophic) and abundant nature of communities associated with cultured oysters. They also provide a baseline set of information that may help more clearly define the interactions between oyster culture and the environment.
    • Phylogenetic analysis of infectious pancreatic necrosis virus in Ireland reveals the spread of a virulent genogroup 5 subtype previously associated with imports

      Ruane, N.M.; McCleary, S.J.; McCarthy, L.J.; Henshilwood, K. (Springer Verlag, 2015)
      Infectious pancreatic necrosis is a significant disease of farmed salmonids resulting in direct economic losses due to high mortality and disease-management costs. Significant outbreaks of the disease occurred in farmed Atlantic salmon in Ireland between 2003 and 2007, associated with imported ova and smolts. As the virus was known to occur in the country since the development of aquaculture in the 1980s, this study examined archived samples to determine whether these older isolates were associated with virulent forms. The study showed that two genotypes of IPNV were present in the 1990s, genotype 3 and genotype 5. A more virulent subtype of the virus first appeared in 2003 associated with clinical outbreaks of IPN, and this subtype is now the most prevalent form of IPNV found in the country. The data also indicated that IPNV in Ireland is more closely related to Scottish and continental European isolates than to Norwegian, Chilean and Australasian genogroup 5 isolates.