We think of the Delaware and its tributaries as the locale of some of the very best trout fishing in the east, but the area and its angling would be unrecognizable to its earliest anglers. Even though the region remains relatively unpopulated, the river has been transformed by a series of man-made events. And although the angling is now perhaps better than it has been in many years (the 2012 trout season, because of an unusually mild and dry winter, will be remembered as legendary), it is far different from what it had been before settlement by Europeans.

Historically, the only trout in the Delaware and its tributaries were brook trout (which is actually a char, and not a true trout). Brook trout require cold, clean water. The scientific name for the brook trout is Salvelinus fontinalis, or “char of the springs,” and they lived in the smaller headwater streams where temperatures were suitable.

Settlement brought with it industry, transforming the landscape and habitat for the native trout. Perhaps the most destructive industry was tanning, which required bark from native hemlocks as a raw material for tanning hides brought mainly from South America. Enormous tracts of large hemlock were killed for their bark, and the disappearance of these trees led to greater erosion and less shade for the rivers, and consequently higher water temperatures unfavorable for the native brook trout. In addition, waste from the tanneries created pollution that further damaged brook trout habitat, driving them farther into the headwaters.

After the tanning industry went into decline in the second half of the nineteenth century, other assaults on the rivers continued. Precursors to the modern chemical industry, acid factories appeared on the rivers, along with charcoal kilns, both requiring large quantities of wood and producing pollution, so that deforestation continued. (One well-known pool on the Beaverkill is called “Acid Factory.”) By the late nineteenth century, much of the original forest of the Delaware River basin was gone, and its rivers were warmer and their waters less pure. Historical photos show a landscape devoid of trees that would be unrecognizable to either 17th- or 21st-century visitors. (The impacts of industry on the Delaware tributaries are well documented in Ed Van Put’s two books, “Trout Fishing in the Catskills” and “The Beaverkill.”)

However, the area’s fishing had been discovered before industry had seriously degraded brook trout habitat, and photos show enormous catches of trout. Stories abound about anglers who came from the cities and killed hundreds of trout in aweek (or even just a day) of fishing. As fishing declined, as a result of both decreased habitat and over-fishing, many private fishing clubs were formed in an effort to preserve the quality of fishing for those who had the means to join them. Nevertheless, redu-cing angling pressure could not counteract the losses of brook trout habitat.

Two other events began the transformation of the area from a pure brook trout fishery to what it is today. These were the advent of trout hatcheries and the introduction of rainbow trout (native to the American west) and brown trout (native to Europe) in the late 19th century. These fish not only out competed brook trout in the waters that were suitable to both, but prospered in waters that were too warm for brook trout. The brown trout, especially, were also less susceptible to angling pressure, so, despite initial prejudice in favor of the native fish, they kept alive trout fishing in waters that were no longer suitable for brook trout.

Finally, dam building further extended habitat for the introduced rainbow and brown trout. On the New York side of the watershed, New York City constructed reservoirs on the upper East and West Branches of the Delaware and on the Neversink River in the mid-20th century. Each of the three reservoirs have cold-water bottom releases that extends trout habitat far downstream from the dams. From the angler’s point of view, the reservoirs are a mixed blessing, because while the dams create and extend trout habitat, managing them for the city’s water supply trumps maintaining them for ecological reasons, and many external factors influence the city’s operation of the dams. There are continual negotiations between the city and various organizations over the management of flows from the reservoirs.

The Delaware and its tributaries have been transformed from pristine rivers dominated by native brook trout, where anglers could count on catching hundreds of trout in a week’s fishing, to heavily managed streams providing an opportunity to catch a few large, challenging non-native trout. Depending on whether you’re primarily a preservationist or an angler, that’s either a shame or a blessing, but whatever your view, the fishing is completely different from what it was in early times.

[Greg Belcamino is an avid trout fisherman and president of the Delaware Highlands Conservancy, a land trust working in partnership with landowners and communities to conserve the natural heritage and quality of life in the Upper Delaware River region.]