カワマス
"Brook trout are Maryland’s only native freshwater trout species. Brook trout in Maryland are valuable for aesthetic, recreational, economic, and biological reasons. Because of their habitat and life history requirements, brook trout are typically found in the pristine, aesthetically pleasant areas of Maryland. While there is no commercial fishery for brook trout, recreational angling has been occurring for centuries, and there is increasing local and national recognition of the uniqueness and quality of fishing for native brook trout. Anthropogenic alterations to Maryland’s environment over the last several centuries, including clear cutting of forests, establishment of large agricultural areas, and urbanization have resulted in the extirpation of brook trout from 62% of their historic habitat in Maryland. Of the remaining 151 populations, more than half are found in Garrett County, the westernmost, mountainous, and least developed area of Maryland. The vast majority (82%) of the remaining populations are classified as 'greatly reduced,' meaning that within the sub-watersheds where they occur they occupy only 1% to 10% of the area that was historically inhabited. A major difficulty in managing the brook trout resource is that only 11% of all brook trout streams and stream miles are fully within state lands, the vast majority of habitat is on private land and a mix of private/public lands. Of the immediate threats to brook trout populations in Maryland, urbanization is the most serious. In watersheds where human land use exceeds 18%, brook trout populations cannot survive and if impervious su rface area is greater than 0.5% in a watershed, brook trout will typically be extirpated. There are also long-term threats, of which global warming is the most serious. Current predictions indicate that warming water temperatures over the next 100 years could eliminate brook trout populations statewide except for western Maryland (Garrett County) by the year 2100."