Monday, June 18, 2012

Who's Who: Justin Walker

Justin Walker is a second-year masters student in Geology at the University of Delaware. He is currently at work processing data from his masters thesis project, an investigation into scallop distribution and size in the Mid-Atlantic Bight. The purposes of his project are to determine scallop distribution in this region and develop a new method of assessing this economically important marine organism. This small-scale stock assessment utilized an AUV to capture almost 254,000 images of the Atlantic seafloor. This collection technique replaced more common methods such as dredging, which are significantly detrimental to the ocean floor and its inhabitants. The images taken by the AUV were later analyzed and Justin is now working to process and visualize the scallop data.


Over 27 three hour missions on the F/V Christian and Alexa last summer, Justin and his research team took roughly 14,000 scallop-containing photographs with the AUV, amounting to approximately 18,000 scallops. Each image was 1.7m x 1.3m in span and was taken about two meters above the seafloor. Naturally, analyzing the images could not be efficiently completed by hand. Justin therefore used a custom computer program to count and size the scallops in each of the photos taken. The size of the scallops also amounts to its age. The shells of scallops, like trees, accumulate one ring each year of existence. A team of four, including Justin and three interns, completed the scallop counting.


Much of the statistical analysis that Justin is performing now is to observe the distribution of the scallops. Do scallop populations patch, or are they evenly distributed? Are more scallops likely to be found where other scallops reside? Justin hopes to answer these and other inquiries in the conclusions of his thesis. He notes that the scallops seem to follow a random distribution pattern based on the preliminary results. Using software like ArcMap and MatLab, the data was visualized in the form of various charts and images.


Additionally, Justin's project was extended to make comparisons between his scallop data and the data collected by the National Marine Fisheries Service (NMFS). As previously mentioned, dredging is the primary method for making annual stock assessments of scallop populations. In the areas of the Bight where NMFS had previously dredged, Justin deployed the AUV in the same transects. This was possible due to the dredge scars that are visible on the seafloor for sometimes several weeks after the initial data collection. By comparing amount of scallops photographed by the AUV by the scallops collected by the dredge, the efficiency of the dredge could be calculated. As one might assume, dredges are not completely efficient, as scallops can escape detainment. The AUV is assumed to be almost completely efficient unless the water is particularly cloudy or the camera lens is inhibited in some way. As expected, the dredge collections were about 55-60% less efficient than the photographic collections.


Justin is hard at work on his master's thesis, and we are all excited to see how his project culminates!

No comments: