No abstract

Crowding conditions in bivalve populations cause intraspecific competition processes, resulting in individual growth reduction. In aquaculture, density is usually maximized to obtain a greater commercial yield. Commercial farms provide an ideal scenario for studying the effect of density on mussel growth in suspended culture systems. In this study, different growth indicators for Mytilus galloprovincialis (growth rates, length and weight growth curves and size frequency distributions) were measured along a cultivation density gradient. Ropes cultured at different densities (220, 370, 500, 570, 700, 800 and 1150 ind/m) were hanged from a commercial raft and growth indicators were monitored monthly over the second phase of traditional culture in Galicia, from thinning-out to harvest (April to October 2008). A negative effect of density on individual growth was observed. Individuals cultured at lower densities presented higher growth rates and consequently reached greater weight and length values at the end of the experimental period than those cultured at higher densities. Differences in growth related to the cultivation density may suggest differences in intraspecific competition for limiting resources (space/food). Effects of density on growth started after 4 months of culture (August) when individuals reached sizes around 66 ± 1.3 mm. The increase in size of individuals in a population implies an increment of their food and space requirements, which in turn intensifies intraspecific competition. This fact should be considered in aquaculture management, since higher densities could be supported without effects on growth performance if cultured mussels are limited to a lower size.

Kreiss et al. Future Socio-Political Scenarios Aquaculture returns, and marketing options as opposed to the direct effect of climate-driven changes in the environment. These results can inform adaptation planning by the European aquaculture sector. Moreover, applying consistent scenarios including societal and economic dimensions, facilitates regional to global comparisons of adaptation advice both within and across Blue Growth sectors.

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We present an on-line early warning system that is operational in Scottish coastal waters to minimize the risk to humans and aquaculture businesses in terms of the human health and economic impacts of harmful algal blooms (HABs) and their associated biotoxins. The system includes both map and time-series based visualization tools. A "traffic light" index approach is used to highlight locations at elevated HAB/biotoxin risk. High resolution mathematical modelling of cell advection, in combination with satellite remote sensing, provides early warning of HABs that advect from offshore waters to the coast. Expert interpretation of HAB, biotoxin and environmental data in light of recent and historical trends is used to provide, on a weekly basis, a forecast of the risk from HABs and their biotoxins to allow mitigation measures to be put in place by aquaculture businesses, should a HAB event be imminent.