SummaryFishery observers recorded incidental capture of seabirds during 785 days on Japanese bluefin tuna longline vessels around New Zealand between April and August each year, 1988-1992. High numbers of albatrosses Diomedea spp. and petrels Procellaria spp. were caught on longline hooks during setting and drowned. Twelve seabird taxa were recorded, six of them breeding only in New Zealand. Most were breeding adults, except for Grey-headed and Black-browed Albatrosses. No bias in sex ratio was evident except for Grey Petrels, of which nearly all were female. Winter-breeding species were most often caught. Birds were not caught randomly, but in a highly aggregated fashion suggestive of complex behavioural interactions with the fishery. Most albatrosses were caught by day in the south whereas most petrels were caught by night north-east of New Zealand. Highest capture rates occurred at dawn and dusk off north-east New Zealand in June-August. Very large catches at specific sites contributed disproportionately to the overall catch rate. The estimated minimum number of total seabirds caught in New Zealand waters declined from 3,652 in 1988 to 360 in 1992, probably as a result of mitigation measures introduced progressively by the industry and by government regulation. Use of tori lines to prevent birds seizing baits had an effect, as did setting in total darkness in the south. Considerably more work needs to be done on the development of improved mitigation measures. Greater observer coverage is required to measure accurately the mortality of individual seabird species on tuna longlines throughout the Southern Ocean and to determine the effectiveness of mitigation measures.

Mercury, cadmium, zinc and copper concentrations were analysed in the liver and ludney tissues of 14 species of albatross and petrel. These birds were obtained as by-catch of the long-line tuna fishing industry in New Zealand waters, and provided a unique opportunity to compare heavy metal accumulation in a group of closely related species. Mercury levels in the liver of the wandering and royal albatrosses were among the highest recorded for free-living birds. In multiple regression analyses, much of the inter-specific variation in cadmium and mercury levels was related to the importance of Crustacea in the diet, to phylogeny, or to the duration of the moult cycle. Species in which crustacea constituted >33% of the diet had significantly lower cadmium concentrations in liver tissues, and mercury concentrations in both liver and kidney tissues, than those in which birds consumed mainly or entirely squid and fish. Thls accords reasonably well with information on relative mercury and cadmium content of prey species. After accounting for dietary variation, Procellariidae (petrels, shearwaters and prions) and Hydrobatidae (storm petrels) still exhibited higher cadrmum concentrations in the liver than Diomedeidae (albatrosses). In addition, albatrosses which took more than a year to moult accumulated higher mercury concentrations in their livers, probably because of a restricted ability to excrete mercury into growing feathers.

The political 'centre' is often discussed in debates about public policy and analyses of party strategies and election outcomes. Yet, to date, there has been little effort to estimate the political centre outside the United States. This article outlines a method of estimating the political centre using public opinion data collected for the period between 1950 and 2005. It is demonstrated that it is possible to measure the centre in Britain, that it moves over time, that it shifts in response to government activity and, furthermore, that it has an observable association with general election outcomes.The fundamental driving forces in democracy are the preferences of citizens across a wide range of issues. These preferences, together with other factors, influence the decisions of individual voters. Elections aggregate those individual preferences, however imperfectly, into collective choices. The aggregation of preferences across issues and across individuals, therefore, lies at the very heart of the democratic process.1 And since electoral choices are structured by political parties that tend to compete primarily along a single left-right dimension relating to the scope of government activity, it is just a small step to arguing that these preferences can be summarized by a measure of central tendency such as the 'typical', 'average', 'mean', 'median' or 'political centre'. 2The political centre is a concept of enormous political importance. Political theorists maintain that, if politics is unidimensional, the median voter is the 'Condorcet winner' in the sense that a policy package that suits this individual would defeat all others in a * Department of Government, University of Essex (email: jbartl@essex.ac.uk); School of Politics, University College Dublin; and Department of Political Science, University of North Carolina, Chapel Hill, respectively. The authors would like to thank Hershbinder Mann for collecting much of the early Gallup data. This project was funded by ESRC award number 00-22-2053. Earlier versions of this article were presented at the ECPR General Conference, Pisa, 2007 and the MPSA, Chicago, 2008. The authors also thank James Adams, Judith Bara, Malcolm Brynin, Evelyn Bytzek, Ian Budge, Lawrence Ezrow, Jane Green, Samantha Laycock, Anthony McGann, Hershbinder Mann, Samuel Merrill, Thomas J. Quinn, David Sanders, Elinor Scarbrough, Thomas J. Scotto, Stuart Soroka, Vera Troeger, Hugh Ward, Paul Whiteley and Chris Wlezien for their helpful comments and suggestions, and are particularly grateful to Frances Lynch of the University of Westminster for generously supplying data on average income tax levels.1 Philip E. Converse, 'Popular Representation and the distribution of information', in John A.

SummaryFisheries observers recorded incidental capture of seabirds during 338 days on Soviet squid trawlers in New Zealand subantarctic shelf waters around the Snares and Auckland Islands in 1990. Seven species were recorded entangled in fishing gear, including very high numbers of breeding adult White-capped Albatrosses Diomedea cauta steadi. The actual level of White-capped Albatross mortality was estimated at 2,300 birds in 1990, and is not considered sustainable. Nearly all albatrosses were killed by collision with the netsonde monitor cable. In New Zealand waters this equipment is carried only by Soviet trawlers, and is considered obsolete. Replacement of this cable by discrete netsonde transducers on Soviet trawlers should be a global seabird conservation priority.

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