An inexpensive and rapid technique for mapping instream habitat of navigable rivers is needed by natural resource professionals. Unlike more expensive side scan sonar devices, the Humminbird® Side Imaging system employs a boat‐mounted transducer enabling the survey of shallow, rocky streams. This device can be used to obtain high resolution, georeferenced images of underwater habitat. We developed a technique employing geographic information systems (GIS) to transform raw sonar images to fit the configuration of a stream channel. The end product is a GIS layer that can be interpreted to map instream habitat. We demonstrated this approach by mapping substrate and large woody debris in a southwest Georgia stream, and evaluated the technique through a comprehensive accuracy assessment. An overall classification accuracy of 77% was observed for substrate mapping and sonar estimates of large woody debris were correlated (r2 = 0.79) with actual wood abundance. Sonar mapping generated estimates of reach and substrate area comparable to a traditional field approach, and reduced the time investment by 90%. Applications for high resolution habitat maps are widespread and numerous; the ability to produce these maps at low cost is now within the grasp of researchers and managers alike.

An efficient, low-cost approach for mapping habitat features in navigable streams is needed to support the research and management of aquatic ecosystems at the landscape level. We developed a method that uses high-resolution (455 kHz) side-scan sonar imagery obtained with the inexpensive (~$2000) Humminbird W Side Imaging system and ArcGIS to produce sonar image maps (SIMs) used to interpret and map habitat features such as substrates and large woody debris, in addition to continuously recording depth along the survey route. This method was recently demonstrated and evaluated in several small streams in southwestern Georgia (30-50 m width, 40 km mapped). To evaluate the feasibility of this method for mapping substrate and depth in larger rivers and over greater spatial extents, we conducted a sonar survey and generated SIMs for 124 km of the lower Flint River (85-140 m width). We interpreted the SIMs to digitize and classify substrate and bank boundaries. To assess classification accuracy, we visually inspected substrate at randomly assigned reference locations. A comparison of reference and map data revealed an overall classification accuracy of 84%. These results were consistent with previous findings and indicate that low-cost side-scan sonar is also an effective mapping tool for larger rivers. The sonar survey did, however, result in more missing and unsure substrate data and a lower map accuracy for fine-textured substrates than previously achieved when mapping smaller streams. We found a strong, positive relationship (r 2 = 0.89) between the sonar range and the proportion of unsure substrate in the map, suggesting that a multi-pass, parallel-transect sonar survey could be used to maintain high-image resolution when stream widths exceed 100 m and/or obstructions, such as islands, are encountered. Applications for sonar-based habitat maps are widespread and numerous. The ability to produce these maps efficiently at low-cost is within the grasp of researchers and managers alike.

The spin polarizabilities of the nucleon describe how the spin of the nucleon responds to an incident polarized photon. The most model-independent way to extract the nucleon spin polarizabilities is through polarized Compton scattering. Double-polarized Compton scattering asymmetries on the proton were measured in the Δð1232Þ region using circularly polarized incident photons and a transversely polarized proton target at the Mainz Microtron. Fits to asymmetry data were performed using a dispersion model calculation and a baryon chiral perturbation theory calculation, and a separation of all four proton spin polarizabilities in the multipole basis was achieved. The analysis based on a dispersion model calculation yields γ E1E1 ¼ −3.5 AE 1.2, γ M1M1 ¼ 3.16 AE 0.85, γ E1M2 ¼ −0.7 AE 1.2, and γ M1E2 ¼ 1.99 AE 0.29, in units of 10 −4 fm 4 . DOI: 10.1103/PhysRevLett.114.112501 PACS numbers: 25.20.Lj, 13.40.-f, 13.60.Fz, 13.88.+e Electromagnetic polarizabilities are fundamental properties of composite systems such as molecules, atoms, nuclei, and hadrons [1]. Whereas magnetic moments provide information about the ground-state properties of a system, polarizabilities provide information about the excited states of the system. For atomic systems, polarizabilities are of the order of the atomic volume. For hadrons, polarizabilities are much smaller than the volume, typically of order PRL 114,

The Shoal Bass Micropterus cataractae is a fluvial specialist endemic to the Apalachicola River drainage in Alabama, Florida, and Georgia that has experienced declines throughout much of its range. The Flint River, Georgia, represents the largest remaining intact ecosystem for Shoal Bass in their native range. Spotted Bass M. punctulatus have recently been introduced into this system, causing concern about the potential negative impacts the species may have on the native populations of Shoal Bass and Largemouth Bass M. salmoides. To assess the symmetry and strength of competition and gain the greatest perspective on the interrelationships among these sympatric, congeneric species, we compared the movement patterns and habitat use of all three species of black bass present in this system. Fifteen Shoal Bass, 10 Largemouth Bass, and 6 Spotted Bass were implanted with radio transmitters in the Flint River and tracked for a period of 1 year (2008). Daily and hourly movements did not vary among species or season, though individuals of each species were observed moving >5 km to shoal complexes during spring. Habitat overlap varied between species during the study; overlap was highest between Spotted Bass and Largemouth Bass, intermediate between Spotted Bass and Shoal Bass, and lowest between Shoal Bass and Largemouth Bass. Shoal Bass tended to select coarse rocky habitat, while Largemouth Bass tended to select depositional habitat. Spotted Bass exhibited the widest niche breadth and generally used habitat in proportion to its availability. Use of similar habitats by these three species during the spring spawning period highlights the potential risk of genetic introgression of the two native species by introduced Spotted Bass. Physical barriers that restrict access to habitat during long‐distance seasonal movements, as observed for several Shoal Bass in this study, may negatively impact populations of this species. Received March 31, 2012; accepted October 12, 2012

No abstract