This report was funded by the Bonneville Power Administration (BPA), U.S. Department of Energy, as part of BPA's program to protect, mitigate, and enhance fish and wildlife affected by the development and operation of hydroelectric facilities on the Columbia River and its tributaries. The views in this report are the author's and do not necessarily represent the views of BPA.
An understanding of the distribution and structure of discontinuous nearshore habitats is critical to effectively manage estuarine resources, especially migratory and mobile nekton that may depend on the integrity of shallow-water environments. We used 19-band compact airborne spectrographic imager (CASI) imagery, collected at 1.5 m spatial resolution, to map two cover classes of eelgrass (Zostera marina) and six other estuarine habitat classes along 64 km of the intertidal shoreline of Hood Canal in the Pacific Northwest, United States. We used control points derived from digital orthoquads (DOQ) and a differential global positioning system (GPS) to geometrically correct CASI flight lines to within 4.3-23.5 m root mean square error (RMSE). After unsupervised and supervised classification, we found good correspondence between classified eelgrass polygons and field training and ground-truthing data. Although this was not the focus of our habitat mapping, the same was true for most of the other habitat classes, except for oyster beds, which were difficult to separate from the wet sand-gravel-cobble class. We are encouraged by the ability of CASI to produce spatially accurate, high-resolution descriptions of intertidal habitat structure. Results from this study will become the foundation of a broader study to develop a quantitative index of essential habitat quality for migrating juvenile summer chum salmon (Oncorhynchus keta) in Hood Canal. When CASI image processing is complete, fisheries scientists-managers will be able to effectively evaluate estuarine landscape patterns at a spatial scale appropriate for migrating juvenile summer chum salmon.Résumé. Une connaissance de la distribution et de la structure des habitats côtiers discontinus est essentielle pour gérer efficacement les ressources estuariennes, spécialement les nectons migratoires et mobiles qui peuvent dépendre de l'intégrité des environnements en eau peu profonde. Nous avons utilisé des images à 19 bandes du capteur « compact airborne spectrographic imager » (CASI) acquises à une résolution spatiale de 1,5 m pour cartographier deux classes de couvert de zostères marines (Zostera marina) et six autres classes d'habitats estuariens sur une distance de 64 km le long de la zone intertidale du Canal Hood, dans le Pacific Northwest, aux États-Unis. Nous avons utilisé des points de contrôle dérivés des « digital orthoquads » (DOQ) et des données de système de positionnement global différentiel (GPS) pour corriger géométriquement les lignes de vol CASI en fonction d'une erreur quadratique moyenne (RMSE) réduite variant de 4,3-23,5 m. Après l'application d'une classification non dirigée et dirigée, nous avons trouvé une bonne correspondance entre les polygones classifiés de zostères marines et les données d'échantillonnage et de réalité de terrain acquises au sol. Même si cela ne constituait pas l'objet de notre cartographie des habitats, cette même observation s'appliquait également à la majorité des autres classes d'habitats, à l'exception des bancs d'huîtr...
Previous studies have concluded that biological control of Lythrum salicaria may not be possible in tidal environments because the biological control agents are easily removed from their host plants by tidal action. In this study, we examined the spatial relationships between L. salicaria, its biocontrol agents, and the agents' feeding damage in relation to elevation using Spatial Analysis by Distance IndicEs (SADIE) at three sites within the Columbia River Estuary (CRE), USA. We then compared the abundances of overwintering Galerucella pusilla adults recovered along an elevational gradient at two sites within the CRE. Galerucella pusilla aggregated most frequently at elevations above mean high water; however, clusters of feeding damage tended to be evenly spread across all elevations. We found significantly more overwintering beetles at high elevations than low elevations, despite similarities in the availability of overwintering habitat (number of dead stems). Our results indicate that although biological control of L. salicaria may be possible at higher elevations in tidal estuaries such as the CRE, it will not likely be an effective means of controlling infestations at low elevation areas. An approach that integrates multiple management strategies to control L. salicaria is therefore recommended for tidal ecosystems.
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