Laboratory study of the impact of repetitive electrical and mechanical stimulation on brown shrimp Crangon crangon

Pulse trawling is currently the best available alternative to beam trawling in the brown shrimp Crangon crangon and Sole Solea solea (also known as Solea vulgaris) fisheries. To evaluate the effect of repetitive exposure to electrical fields, brown shrimp were exposed to the commercial electrodes and pulse settings used to catch brown shrimp (shrimp startle pulse) or Sole (Sole cramp pulse) 20 times in 4 d and monitored for up to 14 d after the first exposure. Survival, egg loss, molting, and the degree of intranuclear bacilliform virus (IBV) infection were evaluated and compared with those in stressed but not electrically exposed (procedural control) and nonstressed, nonexposed (control) brown shrimp as well as brown shrimp exposed to mechanical stimuli. The lowest survival at 14 d (57.3%) occurred in the Sole cramp pulse treatment, and this was significantly lower than in the group with the highest survival, the procedural control (70.3%). No effect of electrical stimulation on the severity of IBV infection was found. The lowest percentage of molts occurred in the repetitive mechanical stimulation treatment (14.0%), and this was significantly lower than in the group with the highest percentage of molts, the procedural control (21.7%). Additionally, the mechanically stimulated brown shrimp that died during the experiment had a significantly larger size than the surviving individuals. Finally, no effect of the shrimp startle pulse was found. Therefore, it can be concluded that repetitive exposure to a cramp stimulus and mechanical stimulation may have negative effects on the growth and/or survival of brown shrimp. However, there is no evidence that electrical stimulation during electrotrawls would have a larger negative impact on brown shrimp stocks than mechanical stimulation during conventional beam trawling

Ontwikkeling en stabiliteit van sublitorale mosselbanken, samenvattend eindrapport

Dit rapport is een verslag over onderzoek naar factoren die van belang zijn voor de stabiliteit van wilde sublitorale mosselbanken. Stabiliteit is gedefinieerd als de kans die eenmaal gevestigde wilde mosselbanken hebben om meerdere winters te overleven. In 2005 is op basis van ervaring een stabiliteitskaart opgesteld voor mosselbanken in de westelijke Waddenzee. Het habitatmodel is gericht op het verband tussen het voorkomen van (wilde) mosselen en de abiotische omstandigheden zoals zoutgehalte, diepte, stroming en slibgehalte van de bodem op de locaties waar mosselen werden aangetroffen. Een factor die moeilijk voorspelbaar is, maar die in de praktijk van groot belang kan zijn, is het wegspoelen van mosselen tijdens stormen

An Integrated Ecosystem Approach for Assessing the Potential Role of Cultivated Bivalve Shells as Part of the Carbon Trading System

The role of bivalve mariculture in the CO2 cycle has been commonly evaluated as the balance between respiration, shell calcium carbonate sequestration and CO2 release during biogenic calcification. However, this approach neglects the ecosystem implications of cultivating bivalves at high densities, e.g. the impact on phytoplankton dynamics and benthic-pelagic coupling, which can significantly contribute to the CO2 cycle. Therefore, an ecosystem approach that accounts for the trophic interactions of bivalve aquaculture, including dissolved and particulate organic and inorganic carbon cycling, is needed to provide a rigorous assessment of the role of bivalve mariculture in the CO2 cycle. On the other hand, the discussion about the inclusion of shells of cultured bivalves into the carbon trading system should be framed within the context of ecosystem goods and services. Humans culture bivalves with the aim of producing food, not sequestering CO2 in their shells, therefore the main ecosystem good provided by bivalve aquaculture is meat production, and shells should be considered as by-products of this human activity. This reasoning provides justification for dividing up respired CO2 between meat and shell when constructing a specific bivalve CO2 budget for potential use of bivalve shells in the carbon trading system. Thus, an integrated ecosystem approach, as well as an understanding of the ecosystems goods and services of bivalve aquaculture, are 2 essential requisites for providing a reliable assessment of the role of bivalve shells in the CO2 cycle

Effects of external nutrient sources and extreme weather events on the nutrient budget of a Southern European coastal lagoon

The seasonal and annual nitrogen (N), phosphorus (P), and carbon (C) budgets of the mesotidal Ria Formosa lagoon, southern Portugal, were estimated to reveal the main inputs and outputs, the seasonal patterns, and how they may influence the ecological functioning of the system. The effects of extreme weather events such as long-lasting strong winds causing upwelling and strong rainfall were assessed. External nutrient inputs were quantified; ocean exchange was assessed in 24-h sampling campaigns, and final calculations were made using a hydrodynamic model of the lagoon. Rain and stream inputs were the main freshwater sources to the lagoon. However, wastewater treatment plant and groundwater discharges dominated nutrient input, together accounting for 98, 96, and 88 % of total C, N, and P input, respectively. Organic matter and nutrients were continuously exported to the ocean. This pattern was reversed following extreme events, such as strong winds in early summer that caused upwelling and after a period of heavy rainfall in late autumn. A principal component analysis (PCA) revealed that ammonium and organic N and C exchange were positively associated with temperature as opposed to pH and nitrate. These variables reflected mostly the benthic lagoon metabolism, whereas particulate P exchange was correlated to Chl a, indicating that this was more related to phytoplankton dynamics. The increase of stochastic events, as expected in climate change scenarios, may have strong effects on the ecological functioning of coastal lagoons, altering the C and nutrient budgets.Portuguese Science and Technology Foundation (FCT) [POCI/MAR/58427/2004, PPCDT/MAR/58427/2004]; Portuguese Science and Technology Foundation (FCT

Subtypes of children with attention disabilities.

Subtypes of children with attentional problems were investigated using cluster analysis. Subjects were 9-year-old-elementary school children (N = 443). The test battery administered to these children comprised a comprehensive set of common attention tests, covering different aspects of attentional functioning, and a test of reading comprehension. Cluster analysis of these data yielded eight stable and reproducible clus¬ters. The test profiles of two subgroups were indicative of distinct attentional problems. One group ap¬peared deficient in speed of processing, the other in attentional control. A third subgroup showed a reading deficit. Two additional clusters had very poor and excellent performance on the whole battery, respec¬tively. Finally, three clusters were found with minor variations approximating average performance. The internal validity, that is, the adequacy and stability of the cluster solution, appeared to be reasonably good, as indicated by a variety of measures. The long-term stability over an 18-month period was also checked and found to be satisfactory