Use of moored acoustic instruments to measure short-term variability in abundance of Antarctic krill

first_imgUpward-looking acoustic Doppler current profilers (ADCPs) (300 kHz) and echosounders (125 kHz) were deployed on moorings at South Georgia to measure abundance of Antarctic krill continuously over several months. Echoes from krill were identified using the theoretical difference in echo intensity at 300 and 125 kHz and scaled to krill density using target strengths appropriate for krill in the region: krill size was determined from diet samples from fur seals and penguins foraging near the moorings. A method using water flow past the moorings was developed to convert time-based acoustic observations of krill to area-based abundance estimates. Flow past the stationary moorings was treated analogously to motion along-track of a research vessel through a nominally stationary body of water during a conventional survey. The moorings thus provide a Eulerian view of variation in krill abundance. This is ecologically instructive for South Georgia, where krill are generally passive drifters on currents and where temporal fluctuations in abundance have significant consequences for krill-dependent predators. Moorings were positioned on routine research vessel survey transects, and validity of the mooring method was assessed by comparison of mooring and vessel observations. Krill density estimates from the moorings were not statistically different from vessel estimates in adjacent time periods. A time series of krill density from a mooring revealed step-changes that were not seen during short-term vessel surveys. Moorings deliver data over time scales that cannot be achieved from research vessels and provide insight on environmental factors associated with variation in krill abundance at South Georgia. Mooring data may aid ecosystem-based management.last_img read more

Poll shows gap between parent views and expert assessments of quality of U.S. child care

first_imgA new NPR/Robert Wood Johnson Foundation/Harvard T.H. Chan School of Public Health poll suggests a major gap between parents’ views and research experts’ assessments of the quality of child care in the U.S. Most parents (59 percent) believe their child receives “excellent” quality child care. By contrast, the most recent major study on the state of U.S. child care suggests a majority of child care is not high quality.NPR, RWJF, and the Harvard Chan School polled 1,120 parents or guardians of children 5 years old or younger who were not yet in kindergarten and received regularly scheduled care at least once a week from someone other than a parent, and found that about three in five parents (59 percent) rate the quality of care their child receives as “excellent.” However, findings from the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development published in 2006 indicated that a majority of child care in the U.S. is of “fair” quality.“This poll gives voice to the challenges that many parents face in finding high quality and affordable care for their children,” says Gillian SteelFisher, deputy director of the Harvard Opinion Research Program at Harvard Chan School, who directed the poll.View the complete poll findings. To read the full release, visit the Harvard Chan School website.Tune in to The Forum at Harvard T.H. Chan School of Public Health on from 12:30 to 1:30 p.m. today  for expert perspectives on the topic. Visit this link to learn more about the event, watch the live broadcast, and access the on-demand recording once it becomes available.last_img read more