ALBERT

Description: SUMMARYTrade in ornamental marine species in Australia, a country with relatively stringent import controls, was investigated using a telephone survey of wholesalers and retailers, and a desktop review of internet import databases and hobbyist trading websites. Information on the regulatory framework was obtained from government and other published or online sources, and from staff of regulatory agencies. Although the trade is small relative to that in the USA, Europe and parts of Asia, Australia imports significant numbers of marine fish each year for the aquarium trade. Many of the more than 200 species imported have the potential to become environmental and/or economic pests. Imported individuals of native species could act as vectors of disease or affect the genetic diversity of native populations if they were released into the wild. Regulatory measures include the use of lists of permitted species of plants and animals, a case-by-case risk assessment process for species not on these lists, and requirements for health certification and quarantining of imported stock. Once within Australia, however, translocation is less rigorously controlled, being managed by individual states and based largely on lists of prohibited species, though generally with scope for case-by-case assessment and refusal of permits for unwanted species, such as recognized pests. Wholesalers and retailers interviewed generally showed a responsible attitude to the disposal of dead or unwanted stock, but awareness and understanding of the potential pest risk of ornamental marine species was generally poor. The importance of raising public awareness of the pest potential of ornamental marine species is likely to increase with the growing importance of mail-order and internet trade.

Description: Losses due to predation are recognized as an important factor affecting shellfish stocks, restoration efforts and aquaculture production. Managing and mitigating the impact of predators require information on the population dynamics and functional responses to prey availability under varying environmental conditions. Asterias spp. are well-known keystone predators with the capacity to exert a top down control on shellfish populations. Asterias spp. populations are extremely plastic, booming fast when prey is abundant and exhibiting a remarkable individual resilience to starvation and adverse environmental conditions. These aspects have led Asterias spp. to be considered pests by shellfish producers and fishers and to be catalogued among the most devastating invasive species. Assessment and mitigation of the impact of Asterias rubens in northern Europe have been the objective of several projects. However, there is still a limited understanding of the processes behind A. rubens population plasticity and how environmental conditions affect individual growth and predation. Under these circumstances a comprehensive eco-physiological model becomes necessary. These models can integrate available information on biology and eco-physiology to gain understanding of the effect of the environmental conditions on the impact of A. rubens.In this work, we performed a number of eco-physiological experiments and combined them with field data from a Danish estuary to estimate and validate the parameters of a dynamic energy budget (DEB) model for the whole life cycle of A. rubens. DEB models can be used to assess the effects of environmental variability on the life cycle and key population traits allowing the prediction of the performance, abundance, resource requirements and potential distribution of individuals and populations under dynamic environments. As such the DEB model presented in this study aims to become a tool to be used to assess and manage the impact of A. rubens in cultured and natural shellfish populations. The successfully parameterised DEB model describes A. rubens as a plastic species, an efficient predator with low maintenance costs and, at least while feeding on mussels, a high energy yield from its prey. The model validation against independent data resulted in the model being capable to assess growth, food demand, reproductive output and reserves dynamics of A. rubens under experimental and natural conditions. Moreover, application of the model to the Limfjorden seastar fishery is used to further discuss the use of the model to understand biology and ecology of this pest species in the context with the management of shellfish stocks and impact mitigation.

Description: Fouling organisms in bivalve aquaculture cause significant economic losses for the industry. Husbandry strategies to reduce biofouling can involve avoidance, prevention, and treatment. In this way, the type of rope used to collect spat or grow bivalves may prevent or reduce fouling by particularly harmful species but remains largely untested. Further, while a range of eco-friendly control methods exist, their effect on widespread, common biofoulers is poorly known. We tested biofouling accumulation and spat collection for seven commercially used ropes, and evaluated treatments of ambient and heated seawater, acetic and citric acid, and combinations of both applied across a range of exposure times to two commercially grown shellfish (Mytilus galloprovincialis and Ostrea angasi) and three biofouling species (Ectopleura crocea, Ciona intestinalis and Styela clava). Rope types differed significantly in terms of fouling rates and spat collection, with specific rope types clearly advantageous, despite not being used commercially in our study area. Treatments proved variably successful, with E. crocea highly susceptible to all treatments, Ciona intestinalis moderately susceptible, and Styela clava relatively resistant. Excluding S. clava, efficacious treatments were attainable that did not adversely affect shellfish. Combining heat and acid treatments were more successful than individual treatments and provide a useful avenue for further trials. This study provides baseline evidence for treatment efficacy that will tailor longer-term, field trials to validate and streamline biofouling treatments in shellfish aquaculture.