A computer-aided framework for subsurface identification of white shark pigment patterns

Subsurface video footage can be used as a successful identification tool for various marine organisms; however, processing of such information has proven challenging. This study tests the use of automated software to assist with photo-identification of the great white shark Carcharodon carcharias in the region of Gansbaai, on the south coast of South Africa. A subsurface photo catalogue was created from underwater video footage. Single individuals were identified by using pigmentation patterns. From this catalogue, two images of the head for each individual were inserted into automated contour-recognition software (Interactive Individual Identification System Beta Contour 3.0). One image was used to search the database, the other served as a reference image. Identification was made by means of a contour, assigned using the software to the irregular border of grey and white on the shark's head. In total, 90 different contours were processed. The output provided ranks, where the first match would be a direct identification of the individual. The method proved to be accurate, in particular for high-quality images where 88.24% and 94.12%, respectively, were identified by two independent analysts as first match, and with all individuals identified within the top 10 matches. The inclusion of metadata improved accuracy and precision, allowing identification of even low-quality images.     

On the nature of temperature variations in borehole kun-1 (Kunashir Island)

The study presents the result of continuous temperature monitoring in a 300 m deep borehole located on the Pacific coast of the Kunashir Island. Temperature variations at of 20–240 m depths with periods from a few tens of minutes to a few tens of days and amplitudes in the order of thousandths to tenths of degree are found to result from three main causes: tidal variations of groundwater level in the borehole, natural convection in the borehole, and nonperiodic and spatially heterogeneous changes of the pore pressure resulting in the appearance of an anomalous subsurface fluid regime and generating crossflow between the different aquifers through the annular space. Joint analysis of temperature and seismic data revealed that shallow-focus (up to 30 km) earthquakes with M > 5 occurred southeast of the seismic station created more expressed temperature response at 240 m depth. This response has the form of a 0.05–0.3 K temperature drop, which precedes a seismic event within a period of a few hours to a few days. Tidal analysis of borehole temperature measurements can be used to calculate the strain sensitivity and the method of borehole temperature monitoring can be used to investigate the tectonic regime of the Earth’s crust.     

Investigation of temperature variations in borehole Kun-1 (Kunashir Island)

Doklady Earth Sciences -