Kelp distribution off California

This data set delineates kelp beds (Nereocystis leutkeana and Macrocystis spp.) along the Pacific Coast of California. Multiple years of kelp mapping data for the state have been compiled into a single coastwide data set. Due to variability in oceanographic and climatic conditions, kelp bed abundance and distribution is extremely variable from year to year. Therefore kelp bed locations and extent in a particular year may not reflect current or past conditions. In addition, the methods for mapping kelp in California have changed over time. Despite these caveats, this multi-year kelp coverage can be used to identify areas that have been known to support kelp growth, and investigate general patterns of kelp distribution on a coastwide scale.California has three coastal kelp surveys. The first survey, 1989, was a coastwide survey using the same contractor and method as Washington State. Kelp canopy data from the second survey, 1999, was created from digital image processing of scanned aerial photographs. The 2002 survey was performed with a Digital Multispectral Video (DMSV) sensor and kelp beds were delineated by digital image processing techniques.

These data were developed for Pacific States Marine Fisheries Commission in cooperation with the National Marine Fisheries Service Northwest Region and the Pacific Fishery Management Council in support of an Environmental Impact Statement (EIS) to consider the designation and conservation of Essential Fish Habitat (EFH) for Pacific Coast Groundfish. These data were consolidated and integrated in a GIS format to support spatially explicit groundfish habitat modelling and impacts assessment on a coastwide scale.

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Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 2; ESRI ArcCatalog 9.0.0.535

Final habitat codes were reviewed for conformance to the list of all potential species codes. The absolute accuracy of species identification is dependent upon the source data and was not validated for this multi-year data compilation.

Horizontal accuracy was not assessed, so the positional accuracy is unknown.

Data are generally comprehensive for the marine nearshore area off the California Coast of the United States. West Coast estuaries (including San Francisco Bay and smaller coastal estuaries) are not included. The 1989 kelp survey in California was comprehensive, but the surveys in 1999 and 2002 did not cover the entire coastline.

Kelp bed distribution and abundance are highly variable between years. Therefore, kelp bed locations and extent in a particular year may not reflect current or past conditions. The use of various techniques means that the delineation of a kelp bed is not necessarily consistent over time. These variations include: the level of generalization of kelp bed boundaries, the inclusion or omission of water polygons entirely contained within a kelp polygon, and the minimum kelp bed detected and delineated (i.e., minimum mapping unit). In addition, surveys were not comprehensive for all years mapped.