We have applied a Sr/Ca ratio technique of otolith analysis to reconstruct the temperature histories of fall-spawned herring larvae Clupea harengus L. captured in inshore waters of the Gulf of Maine, USA, in order to infer their overwintering distributions. Winter survival of herring larvae is believed to be a determinant of recruitment in the Gulf of Maine, though very little is known about this important phase in their life history. Shortly after hatching in coastal spawning areas, larvae congregate inshore along the Maine coast during fall (September to November). Following this abundance peak, inshore larval densities drop to very low levels in mid-winter (late December and January), before a second group of fall-spawned larvae appears inshore in spring (February through April), thus giving a bimodal abundance distribution with time. We have inferred the overwinteriug distributions of larvae captured in the spring in the Sheepscot hver estuary, Maine, by analyzing changes in the concentrations ratios of strontium to calcium in the otoliths. These ratios vary as a function of temperature and thus act as a biological recorder of water temperatures experienced by an individual larva throughout its life history. Results suggest that the spring peak of herring larvae inshore represents larvae which overwintered offshore in the Gulf of Maine, implying that larvae w h c h enter the inshore nursery areas in the fall do not survive.
The regional variability in earthquake ground-motion amplitudes for a given magnitude and distance in western North American environments was examined using ShakeMap data from small-to-moderate events. The abundance of data for small-tomoderate events in California allows average ground-motion levels, as a function of magnitude and distance, to be resolved with a high level of confidence. Ground-motion amplitudes in northern California are lower on average than those for southern California, for events of the same magnitude, at distances in the range from 120-250 km, over all frequencies. The observed regional variations could be indicative of regional differences in attenuation effects or site effects. An unexpected result of the study is the finding that ground motions for events of M<5.5 in California attenuate more rapidly with distance than predicted by the recent PEER-NGA ground-motion prediction equations for shallow crustal earthquakes in active
Increments in the hard parts of marine organisms (otoliths, skeletons, shells) can provide long-term chronologies of growth analogous to tree rings. For the first time in the Southern Hemisphere, we use a dendrochronological (tree-ring analysis) approach to develop a multidecadal chronology of growth for a temperate reef fish, Girella tricuspidata, from the coast of northern New Zealand. Growth patterns in the otoliths of this species were strongly synchronous among individual fish over a period spanning 27 years . We then compared our otolith chronology to climatic records and found strong positive correlations of growth with sea surface temperature, and weak negative correlations with the multivariate El Nino Southern Oscillation (ENSO) index. Strongest correlations were found between summer sea surface temperature and otolith growth. This relationship was consistent across all years and explained 44 % of the variation (y = -2.0 ? 0.1785 9 temperature, r 2 = 0.4367, P = 0.0002) in the G. tricuspidata growth chronology. Our study illustrates how otolith chronologies provide remarkable records of annual growth patterns over decadal time scales that will be useful for forecasting the likely effects of climate change on marine ecosystems.
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