Characterization of a midwestern fishery with limited exploitation

Ada Hayden Heritage Park, Ames, Iowa, a mesotrophic quarry-pit fishery, was opened for new public exploitation on July 1, 2004 after many decades of private ownership and limited exploitation. A monthly, electro-fishing, population survey was conducted to both characterize the fishery and document any significant angler impacts from June 2003 to October 2004; an expandable creel survey was conducted from July 2004 to October 2004 to estimate angler use and analyze harvest change. The fishery is characterized by little to no structural habitat, high water quality, high diversity of 32 fish taxa including gizzard shad, low sport fish biomass, and an unbalanced bluegill population. Angler use peaked in July 2004 with 220 angler hrs/ha and fell rapidly to low levels. Creeled crappie, channel catfish, and yellow perch saw significant declines in average weight over time. Creel catch per unit effort (CPUE) did not significantly change as angling progressed for any species. Approximately 80% of the total fish biomass harvested since July 2004 was crappie species. Bluegill, channel catfish, yellow perch, freshwater drum, and green sunfish comprised the remaining 20%. Angler exploitation rate of bluegill [greater than or equal to] 100 mm during the creel period was 13%. No significant changes in CPUE, proportional stock densities, and relative weights were detected after this fishery was opened to public fishing. However, largemouth bass stomach analyses indicated increased gizzard shad use after exploitation began. Due to the limited scope of the post-exploitation study period, future changes due to exploitation may be possible

Beyond the Chart: The use of Satellite Remote Sensing for Assessing the Adequacy and Completeness Information

Chart adequacy and completeness information consists of the symbols, abbreviations and warnings used to inform mariners of the level of confidence that should be given to data on a nautical chart. This information is derived both from the nautical chart and sailing directions. However, analysis based solely on these datasets is limited without access to the sources (e.g., smooth sheets). Publically-available, multi-spectral satellite imagery and published algorithms can be used to derive estimates of the relative bathymetry in shallow, clear waters. In this study, we evaluate the potential of these methods for supplementing the procedure to assess the adequacy of hydrographic surveying and nautical charting coverage. Optically-derived bathymetry provides information in areas that have not been surveyed and monitor any seafloor changes that may have occurred since the last survey of the area. Preliminary results show that multi-spectral satellite remote sensing is also potentially beneficial as a reconnaissance tool prior to a hydrographic acoustic survey

Development of a Geo-spatial Analysis Methodology for Assessing the Adequacy of Hydrographic Surveying and Nautical Charts

IHO Publication C-55 (Status of Hydrographic Surveying and Nautical Charting Worldwide) contains information about the progress of hydrographic surveying and nautical charting for a country with navigable waters under its jurisdiction. Listed primarily as percent coverage, it is difficult to use this information to determine: 1) if the current level of surveying or charting is adequate or in need of action, or 2) can be used to compare different locations. An analysis and assessment methodology has been developed to assess the adequacy hydrographic surveying and nautical charting coverage. Indications of chart adequacy and completeness as depicted on current charts or sailing directions are spatially correlated with significant maritime sites/areas associated with social, environmental and economic factors. The procedure was developed in a GIS environment for Belize and Nigeria. Areas within the charts were prioritized based on zone of confidence, source diagrams, chart quality symbols/indicators, doubtful danger markings, survey completeness, navigationally-significant depths, and areas of significant maritime importance

Learning Synergies between Pushing and Grasping with Self-supervised Deep Reinforcement Learning

Skilled robotic manipulation benefits from complex synergies between non-prehensile (e.g. pushing) and prehensile (e.g. grasping) actions: pushing can help rearrange cluttered objects to make space for arms and fingers; likewise, grasping can help displace objects to make pushing movements more precise and collision-free. In this work, we demonstrate that it is possible to discover and learn these synergies from scratch through model-free deep reinforcement learning. Our method involves training two fully convolutional networks that map from visual observations to actions: one infers the utility of pushes for a dense pixel-wise sampling of end effector orientations and locations, while the other does the same for grasping. Both networks are trained jointly in a Q-learning framework and are entirely self-supervised by trial and error, where rewards are provided from successful grasps. In this way, our policy learns pushing motions that enable future grasps, while learning grasps that can leverage past pushes. During picking experiments in both simulation and real-world scenarios, we find that our system quickly learns complex behaviors amid challenging cases of clutter, and achieves better grasping success rates and picking efficiencies than baseline alternatives after only a few hours of training. We further demonstrate that our method is capable of generalizing to novel objects. Qualitative results (videos), code, pre-trained models, and simulation environments are available at http://vpg.cs.princeton.eduComment: To appear at the International Conference On Intelligent Robots and Systems (IROS) 2018. Project webpage: http://vpg.cs.princeton.edu Summary video: https://youtu.be/-OkyX7Zlhi