Biotransformation enzyme activities and PCDD/PCDF levels in pike caught in a Swedish Lake

Recently, analysis of organochlorines in sediment and in pike from Lake Vänern, Sweden, showed a north-south gradient of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). In the present study, good correlations were found between muscle 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) equivalents and liver ethoxyresorufin-O-deethylase (EROD) activities (and P4501A levels) in pike caught at three sampling sites along the north-south gradient in the lake. This comparison between tissue levels of PCDD/PCDF and EROD activity (and P4501A) may indicate that TCDD or structural analogs could be responsible for the observed induction of the pike P450 system. It must, however, be taken into account that the analysed contaminants often do not appear alone but are, rather, accompanied by a range of other substances which may be inducers or antagonists.     

Lagged social-ecological responses to climate and range shifts in fisheries

While previous research has documented marine fish and invertebrates shifting poleward in response to warming climates, less is known about the response of fisheries to these changes. By examining fisheries in the northeastern United States over the last four decades of warming temperatures, we show that northward shifts in species distributions were matched by corresponding northward shifts in fisheries. The proportion of warm-water species caught in most states also increased through time. Most importantly, however, fisheries shifted only 10–30 % as much as their target species, and evidence suggested that economic and regulatory constraints played important roles in creating these lags. These lags may lead to overfishing and population declines if not accounted for in fisheries management and climate adaptation. In coupled natural-human systems such as fisheries, human actions play important roles in determining the sustainability of the system and, therefore, future conservation and climate mitigation planning will need to consider not only biophysical changes, but also human responses to these changes and the feedbacks that these responses have on ecosystems.     

Astrometry of Southern radio sources

An overview is presented of a number of astrometry and astrophysics programs based on radio sources from the Parkes 2.7 GHz catalogues. The programs cover the optical identification and spectroscopy of flat-spectrum Parkes sources and the determination of their milliarc-second radio structures and positions. Work is also in progress to tie together the radio and Hipparcos positional reference frames. A parallel program of radio and optical astrometry of southern radio stars is also under way.     

A reassessment of the non-stoichiometry of fayalite

The thermogravimetric measurements on fayalite reported by Nakamura and Schmalzried (1983) have been reassessed using the compound-energy model and computer calculations which eliminate much mathematical manipulation and subjective choice. The calculated phase field for fayalite differs somewhat from the one obtained by Nakamura and Schmalzried (1983) but there is satisfactory agreement in the experimental range.