The effects of vessel noise on the antipredator behaviour of juvenile reef fishes

Laura investigated the effects of vessel noise on reef fishes. She found that the noise produced by ships and small boats affected the antipredator behaviour of juvenile fishes, moreover boat noise had long-term effects on growth. These results suggest that vessel noise has the potential of compromising the survival of juvenile fishes

Nonprehensile Manipulation of an Underactuated Mechanical System With Second-Order Nonholonomic Constraints: The Robotic Hula-Hoop

A mechanical system consisting of a hoop and a pole is considered, for which the corresponding dynamic model represents an underactuated system subject to second-order nonholonomic constraints. The pursued goal is to simultaneously track a trajectory in the unactuated coordinates and to stabilize the actuated ones. For the model under consideration, the well-known noncollocated partial feedback linearization algorithm fails since the corresponding zero dynamics is unstable. In this work, we show that the actuated coordinates, i.e., the pole can be stabilized by exploiting the null space of the coupling inertia matrix without affecting the performance in the underactuated coordinates tracking. We present a formal mathematical analysis, which guarantees ultimate boundedness of all coordinates. Performed simulations bolster the proposed approach

Seasonal Movements, Migratory Behavior, and Site Fidelity of West Indian Manatees along the Atlantic Coast of the United States as Determined by Radio-telemetry

The study area encompassed the eastern coasts of Florida, Georgia, and South Carolina, including inland waterways such as the St. Johns River (Fig. 1). Manatees inhabited the relatively narrow band of water that lies between the barrier beaches and the mainland, occasionally venturing into the ocean close to shore. Between Miami and Fernandina Beach, Florida, 19 inlets provided manatees with corridors between the intracoastal waters and the Atlantic Ocean; the distance between adjacent inlets averaged 32 km(SD = 24 km) and varied from 3 to 88 km. Habitats used by manatees along this 900-km stretch ofcoastline varied widely and included estuaries, lagoons, rivers and creeks, shallow bays and sounds, and ocean inlets. Salinities in most areas were brackish, but ranged from completely fresh to completely marine. The predominant communities of aquatic vegetation also varied geographically and with salinity: seagrass meadows and mangrove swamps in brackish and marine waters along the southern half of peninsular Florida; salt marshes in northeastern Florida and Georgia; benthic macroalgae in estuarine and marine habitats; and a variety of submerged, floating, and emergent vegetation in freshwater rivers, canals, and streams throughout the region. Radio-telemetry has been used successfully to track manatees in other regions ofFlorida (Bengtson 1981, Powell and Rathbun 1984, Lefebvre and Frohlich 1986, Rathbun et al. 1990) and Georgia (Zoodsma 1991), but these early studies relied primarily on conventional VHF (very high frequency) transmitters and were limited in their spatial and temporal scope (see O'Shea and Kochman 1990 for overview). Typically, manatees were tagged at a thermal refuge in the winter and then tracked until the tag detached, usually sometime between the spring and fall of the same year. Our study differs from previous research on manatee movements in several important respects. First, we relied heavily on data from satellite-monitored transmitters using the Argos system, which yielded a substantially greater number of locations and more systematic collection of data compared to previous VHF tracking studies (Deutsch et al. 1998). Second, our tagging and tracking efforts encompassed the entire range of manatees along the Atlantic coast, from the Florida Keys to South Carolina, so inferences were not limited to a small geographic area. Third, we often used freshwater to lure manatees to capture sites, which allowed tagging in all months of the year; this provided more information about summer movement patterns than had previous studies which emphasized capture and tracking at winter aggregations. Finally, the study spanned a decade, and success in retagging animals and in replacing transmitters allowed long-term tracking ofmany individuals. This provided the opportunity to investigate variation in seasonal movements, migratory behavior, and site fidelity across years for individual manatees. (254 page document.

New working watercraft : a return to former capabilities

Based on reports of boat design and construction consultancies originally prepared for clients in the Third World beginning in October, 1981 Special report from the National Conference on Applications of Sail-Assisted Power Technology, Norfolk, Virginia, 1982 Printed in cooperation with Virginia Sea Grant Program, Virginia Institute of Marine Science, College of William and Mar

Comparison of Satellite-Derived Bathymetry Algorithm Accuracy Using Sentinel-2 Multispectral Satellite Image

The utilization of satellite image data and image data processing techniques has become an efficient alternative to obtain bathymetric data in a broad and complicated area. This study aimed to determine the algorithm's performance in the waters of Lambasina Island. Atmospheric and radiometric correction using the Dark Object Subtraction (DOS) method for initial processing of Sentinel-2 images. The multispectral channel used, namely the blue, green, and red bands, was tested by regression using field observation data. The algorithms used to estimate bathymetry include Lyzenga, Stumpf, and Support Vector Machine (SVM). The test results of the three algorithms showed that the support vector machine algorithm was the best algorithm for estimating bathymetry after the Stumpf and Lyzenga algorithms. The correlation results of the SVM algorithm in the waters of the small Lambasina island got a correlation coefficient of determination R2 = 0.81 and the large Lambasina waters area R2 = 0.82. The second-best algorithm was Stumpf, with a correlation coefficient of determination of R2 = 0.79 in the waters of the small Lambasina island and R2 = 0.80 in the waters of the large Lambasina island. Lyzenga's algorithm got the correlation coefficient of determination R2 = 0.78 on small Lambasina Islands and large Lambasina Islands with a determination correlation coefficient value of R2 = 0.79