How to Map Essential Fish Habitats in Oregon
- 1). Define "essential fish habitat," which could vary depending on your perception of the terms. The State of Oregon, for example, considers "essential salmonid habitat" to refer to "the habitat necessary to prevent the depletion of native salmon species ... during their life history stages of spawning and rearing." Your definition may be similar, centered around what habitat characteristics maintain a viable fish population in a given area.
- 2). Establish what you consider to be the characteristics of essential fish habitat. This will depend largely on the type of fish you are concerned about and will likely be based upon both empirical research specific to the region and extrapolation springing from other studies. For example, in Oregon, you might be considering for salmon or steelhead the percentage of a stream surface shaded by riparian tree canopy; the substrate of the stream bottom, whether silt, gravel, mud or other matter; and the proximity and extent of any human-induced modifications to the channel, like dams or diversions. You will likely also have to gather data on other human effects like measured pollutants from urban, industrial, agricultural and other land-use areas, not to mention the present known distribution of any exotic, non-native species that might adversely impact your target fish. Beyond these observable variables, you will be cross-referencing with established knowledge about fish biology: preferred spawning habitat, dispersal rates and range, desired habitat and food sources and the like.
- 3). Map your various factors using modern means like Geographic Information Systems software. This translates to collating all those multifarious bits of information: layering together human land-use patterns, ecological characteristics like shade cover and stream gradient and the specific biological needs of a sturgeon, halibut or any other kind of fish you are studying. In its most generalized and basic form, your map of "essential fish habitat" will spring from the intersection of various parameters you have set: where there is a certain minimum level of human pollution, stream-channel modification and exotic-species habitat, for example, overlapping with desirable hydrological aspects like gravel beds, logjams and water temperature.
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