Acoustic surveys of New Zealand deep-water seamounts often show fish aggregations up to 150 m high on the summit. Although bottom trawls on the seamount slopes catch predominantly orange roughy (Hoplostethus atlanticus), species composition in the midwater plumes is extremely uncertain. In June 2010, moored underwater video cameras were deployed on the summit of the Morgue seamount (summit depth 890 m), a feature that has been closed to fishing since 2001. Cameras and lights were timed to come on for 2 min every 2 h. Fish response to the mooring was monitored using vessel-mounted echosounders. Moored cameras confirmed that orange roughy were present up to 70 m above the seamount summit. Orange roughy made up 97% of the fish identified from the video. Other species observed included smooth oreo (Pseudocyttus maculatus), spiky oreo (Neocyttus rhomboidalis), deep-water dogfish, cardinalfish (Epigonus spp.), and squid. Total along-track backscatter from the plume varied by a factor of 25 over a period of hours. Peak acoustic densities in the plume (equivalent to 20 orange roughy m−3) were an order of magnitude higher than peak visual estimates (0.64 orange roughy m−3), but relative densities between paired video and acoustic observations were generally consistent.

doi:  http://dx.doi.org/10.1093/icesjms/fss010

Related posts:

1. Seamounts may serve as refuges for deep-sea animals that struggle to survive elsewhere
2. Can acoustic shadows identify fish species? A novel application of imaging sonar data

Nitrate is naturally found within the environment as part of the nitrogen cycle. However, anthropogenic inputs have greatly increased nitrate loads within ground and surface waters. This has had a severe impact on aquatic ecosystems and has given rise to health considerations in humans and livestock. Therefore, the identification of nitrate sources is important in preserving water quality and achieving sustainability of our water resources. Nitrate sources can be determined based on the nitrate nitrogen (N) and oxygen (O) isotopic compositions (δ15N, δ18O). However, sewage and manure have overlapping δ15N and δ18O values making their differentiation on this basis problematic. The specific differentiation between sources of faecal contamination is of particular importance, because the risk to humans is usually considered higher from human faecal contamination (sewage) than from animal faecal contamination. This review summarises the current state of knowledge in using isotope tracers to differentiate various nitrate sources and identifies potential chemical tracers for differentiating sewage and manure. In particular, an in depth review of the current state of knowledge regarding the necessary considerations in using chemical markers, such as pharmaceuticals and food additives, to differentiate sewage and manure sources of nitrate contamination will be given, through an understanding of their use, occurrence and fate, in order to identify the most suitable potential chemical markers.

http://dx.doi.org/10.1016/j.watres.2012.01.044

No related posts.

This study addresses a fish species discrimination method based on normalised elliptic Fourier descriptors applied to acoustic shadows derived by Dual-frequency Identification Sonar (DIDSON). Acoustic shadows of templates (20, 30, 40 and 50 cm) and live fish of four species [bream, Abramis brama (L.); barbel, Barbus barbus (L.); chub, Leuciscus cephalus (L.); and trout, Salmo trutta (L.)] were projected on a plate in an experimental set-up and tested on suitability for species discrimination. Twenty-centimetre templates were correctly classified in 97.5% of the cases, indicating a size threshold. The larger templates reached values of 100% correct classification based on cross-validated discriminant function analysis. It was also possible to classify moving fish based on screenshots of their acoustic shadows with a certainty of 83.9%. Extended field tests are required to evaluate the method for use in practical monitoring applications in multispecies river environments.

DOI: http://dx.doi.org/10.1111/j.1365-2400.2011.00843.x

Related posts:

1. Species identification in seamount fish aggregations using moored underwater video
2. Application of DNA-Based Methods to Identify Fish and Seafood Substitution on the Commercial Market

DOI:  http://dx.doi.org/10.1016/j.rse.2011.09.015

No related posts.

Measles epidemics in West Africa cause a significant proportion of vaccine-preventable childhood mortality. Epidemics are strongly seasonal, but the drivers of these fluctuations are poorly understood, which limits the predictability of outbreaks and the dynamic response to immunization. We show that measles seasonality can be explained by spatiotemporal changes in population density, which we measure by quantifying anthropogenic light from satellite imagery. We find that measles transmission and population density are highly correlated for three cities in Niger. With dynamic epidemic models, we demonstrate that measures of population density are essential for predicting epidemic progression at the city level and improving intervention strategies. In addition to epidemiological applications, the ability to measure fine-scale changes in population density has implications for public health, crisis management, and economic development.

DOI: http://dx.doi.org/10.1126/science.1210554

No related posts.

In situ data are widely used to provide a ground truth for the calibration and validation of satellite sea-surface temperature (SST) retrievals. They are also used to monitor long-term changes in the climate. For these applications, and others, it is necessary to understand the uncertainties in the data. Near-coincident SST observations from the Advanced Along-Track Scanning Radiometer (AATSR) and in situ platforms were used to understand the characteristics of errors in the measurements. The mean random error on the AATSR retrievals was found to be 0.14 K. The in situ errors were modelled as a constant offset plus a random error. For ships, the standard deviation of the constant offset was estimated to be 0.71 K and the mean random error was 0.74 K. For drifting buoys, the standard deviation of the constant offset was estimated to be 0.29 K and the mean random error was 0.26 K. These results suggest that there is a need to revisit current assessments of the adequacy of in situ observing systems. The trend in global-average SST between 1991 and 2007 calculated from in situ data was compared to its counterpart calculated from the ATSR instruments. The in situ record warms more slowly than the ATSR record, probably due to a decrease in the fraction of relatively warm-biassed ship observations contributing to the global-average SST over the period and a corresponding increase in the fraction of relatively unbiassed drifting buoy observations.

doi:10.1016/j.rse.2010.11.021

Related posts:

1. Climate Change’s Impact on Global Crop Prduction: Trends Since 1980
2. Perspectives on empirical approaches for ocean color remote sensing of chlorophyll in a changing climate