Seite - 26 - in options, Band winter 2014/2015

europe 26 options + winter 2014/2015 www.iiasa.ac.at regional focus Optimal fisheries management depends on understanding fish reproduction, growth, and mortality. IIASA research published in February 2014 sheds new light on sexual maturation of the European fresh- water whitefish Coregonus lavaretus, an important commercial and recreational fish. IIASA scientists studied C. lavaretus living in the Austrian pre-alpine Lake Irrsee, assessing, for the first time in this species, the probability that a fish matures at a certain age and length (the so-called probabilistic maturation reaction norm or PMRN). Since 2000 the Lake Irrsee whitefish population has been sampled every October prior to the spawning season, determining the total length, age, sex, and maturity status of 2,000 individuals. Each individual’s age was identified by scrutinizing its scales, which bear patterns akin to tree rings. By disentangling the effects of maturation from those of survival and growth, the researchers showed fish length to be the only relevant determinant of maturation probability, irrespective of age. This is surprising, since older fish tend to mature at larger sizes in almost every other species for which PMRNs have so far been estimated. More accurate stock predictions in Lake  Irrsee are enabled by these findings. KP Further info Ficker H, Mazzucco R, Gassner H, Wanzenböck J, Dieckmann U (2014). Fish length exclusively determines sexual maturation in the European whitefish Coregonus lavaretus species complex. Journal of Fish Biology 84(4):1164–1170 [doi:10.1111/jfb.12301]. Rupert Mazzucco mazzucco@iiasa.ac.at Ulf Dieckmann dieckmann@iiasa.ac.at Fisheries research tips the scales Paris to breathe easier in 2050 IIASA scientists, together with experts from Airparif, which monitors air quality for the French Environment Ministry, used the CHIMERE model to downscale pollution data to a 4 km-resolution grid to investigate local-scale air pollution over the city of Paris for 2045–2054. CHIMERE, a regional atmospheric composition model, assessed pollution relative to present-day emissions under a business-as-usual (BAU) scenario and a climate mitigation scenario (consistent with the RCP 2.6). Scientists from the French CNRS and INERIS research institutes led the project, and the long-term scenarios drew on IIASA’s Global Energy Assessment. This was the first time a study of a 10-year air-quality projection for the mid-21st century under climate and city-level emission changes has been conducted over a large European agglomeration at such fine scale. Former atmospheric pollutant studies had only a few hundred kilometers resolution and thus did not capture the high spatial variability of short-lived pollutants like ozone (photochemical smog) and fine breathable particles (dust, soot) or their sharp horizontal gradients over urban areas. While previous regional-scale, lower-resolution studies had found 2050 maximum ozone decreasing under both scenarios, this study found projections differing substantially from present data values: +7 parts per billion (ppb) under BAU and a moderate decrease of −3.5 ppb under the “low emissions” climate mitigation scenario. Interestingly, concentrations of fine particulate matter (PM2.5) decreased by 78% and 89% under the BAU and mitigation scenarios, respectively. The reduction was much more prominent over the urban part of the region because of the effective particle reduction from road transport and residential emissions by 2050. KP Further info Markakis K, Valari M, Colette A, Sanchez O, Perrussel O, Honore C, Vautard R, Klimont Z, Rao S (2014). Air quality in the mid-21st century for the city of Paris under two climate scenarios; from the regional to local scale. Atmospheric Chemistry and Physics 14(14):7323–7340 [doi:10.5194/acp-14-7323-2014]. Zbigniew Klimont klimont@iiasa.ac.at