Exploitation influences community structure directly through preferential removal of larger-bodied fishes and indirectly because larger-bodied fishes may exert top-down control upon other community members. We consider the direct and indirect effects of subsistence exploitation upon the size structure of coral reef fish communities along an island-scale spatial gradient of fishing intensity. We explored the effect of fishing intensity and sample date (three dates over a year) at six islands and the overall effect of fishing intensity averaged over sample dates at 13 islands. Fishing intensity consistently explained more of the variation in the size metrics than sample date. In response to exploitation, the mean weight of individuals declined by 52%, the weighted average maximum size (L max ) declined by 25%, and slopes of community size spectra steepened. The larger size classes (>26 cm) declined in relative numbers by 63% and relative biomass by 61% in response to exploitation. However, the numbers and biomass of the three smallest size classes (<25 cm) increased by 31% and 9%, respectively, in response to exploitation. This increased abundance is consistent with a weak compensatory response presumably from a reduction in predation upon smaller size classes as an indirect effect of exploiting larger size classes.Résumé : L'exploitation affecte la structure de la communauté directement par le retrait préférentiel des poissons de grande taille et indirectement parce que les poissons de grande taille peuvent exercer un contrôle descendant sur les autres membres de la communauté. Nous avons examiné les effets directs et indirects de l'exploitation de subsistance sur la structure en taille de communautés de poissons de récifs coralliens le long d'un gradient d'intensité de pêche à l'échelle spatiale des îles. Nous avons étudié les effets de l'intensité de la pêche et de la date d'échantillonnage (trois dates au cours d'une année) à six îles, ainsi que l'effet général de l'intensité moyenne (toutes dates confondues) de la pêche à 13 îles. Dans tous les cas, l'intensité de la pêche explique une plus grande proportion de la variation des mé-triques reliées à la taille que la date d'échantillonnage. En réaction à l'exploitation, la masse moyenne individuelle diminue de 52 %, la taille maximale moyenne pondérée (L max ) baisse de 25 % et la pente des spectres de taille de la communauté augmente. En réaction à l'exploitation, les densités relatives des classes de grande taille (>26 cm) diminuent de 63 % et leur biomasse de 61 % . Cependant, les densités et les biomasses des trois classes les plus petites (<25 cm) augmentent respectivement de 31 % et de 9 %. Cette densité accrue s'accorde bien avec l'existence d'une faible réaction compensatoire probablement causée par une réduction de la prédation chez les classes de plus petite taille comme effet indirect de l'exploitation des classes de plus grande taille.[Traduit par la Rédaction] Dulvy et al. 475

Robust tools are needed to prioritise the management of invasive non-native species

N between consumer and diet (usually 3·4‰ for diet-muscle tissue differences) allows inferences to be made about feeding interactions and trophic level in food web studies. However, considerable variability surrounds this constant, which may conceal subtle differences about the trophodynamics of consumers. 2. The feeding ecologies of herbivores and carnivores differ in terms of diet quality (in C : N terms) and food processing mechanisms, which may affect fractionation. 3. We present a new model that explores how consumer feeding rates, excretion rates and diet quality determine the 15 N/ 14 N ratios in the consumer's tissues and hence influence the magnitude of trophic fractionation. 4. Three herbivorous reef fish Acanthurus sohal , Zebrasoma xanthurum and Pomacentrus arabicus were chosen as study organisms. Empirical estimates of diet-tissue stable isotope fractionation were made in the field, and model parameters were derived from feeding observations and literature data. 5. The trophic fractionation values of A. sohal , Z. xanthurum and P. arabicus were 4·69‰, 4·47‰ and 5·25‰, respectively, by empirical measurement, and 4·41‰, 4·30‰ and 5·68‰, respectively, by model, indicating that herbivores have a higher trophic fractionation than the currently accepted value of 3·4‰. 6. The model was most sensitive to the excretion rate, which may differ between herbivores and carnivorous animals. This model is the first to determine stable isotope signatures of a consumer's diet mixture without applying a constant fractionation value.

Earlier treatment with antiviral agents is associated with improved outcomes for pregnant women and further actions are needed in future pandemics to ensure that antiviral agents and vaccines are provided promptly to pregnant women, particularly in the primary care setting. Further research is needed on longer-term outcomes for infants exposed to AH1N1v influenza, antiviral drugs or vaccines during pregnancy.