The ecosystem of the upper Williamson river is completely different than that of the better known lower Williamson river. Even the fish found in the Upper Williamson are completely unrelated to those found below the Klamath Marsh.
At present the Williamson river burbles up out of the ground born as a river in its entirety. Then, contrary to what seems natural, the river flows due north for about 30 miles. It then comes to a ridge which turns the river west and shortly thereafter it spreads out and becomes the Klamath Marsh. However, it has been determined through careful, scientific sleuthing that thousands of years ago, during the pleistocene era, the river turned east when it hit the ridge passing through a now non-existent drainage cut between Yamsi mountain and little Yamsi butte. And just east of Yamsi mountain lie the ancient beginnings of the Great Basin. During the pleistocene period the great basin was a huge lake with the rocky mountains forming its eastern shore. Therefore, it has been theorized, the fish in the Upper Williamson river originally invaded from the east and are most closely related to trout from the rocky mountain region. Upon further studying it was discovered that these fish are very similar to the trout found in Paradise creek which flows east out of the nearby Sycan marsh.
Of course the Klamath Marsh and an ancient series of waterfalls located above the Kirk springs on the lower Williamson have prevented the Upper Williamson River fish from mingling with those of the lower Williamson, maintaining a native population of trout now identified as the upper Williamson river Redband. They are indigenous only to this river.
In 1996, while conducting studies on the Williamson river fisheries, it was confirmed that these fish are anadromous and had been migrating from the ocean for centuries. The fish you now catch in the Williamson river or Klamath Lake evolved from steelhead and spring chinook migrating from the ocean to spawn in the Kirk springs area. It has been determined that all these related fish over time have evolved to resist a disease called ceratomyxia shasta. All fish found downstream from Kirk springs are resistant to this disease. The upper Williamson River Redbands have no resistance nor do other great basin related species. This further proved that the Upper Williamson River Redbands migrated and evolved from waters of the Rocky mountains and that when you fish the upper Williamson river you will be catching an old and native trout found only in the Yamsi valley.
The trout at Aspen Ridge Ranch range from 10 to 30 inches and can weigh up to five pounds. Due to the drought conditions of the early 2000's, the average size dropped down to 12 - 16 by 2004. With the return of the massive black drake hatches starting in 2005, the fish have gorging themselves and average size has been increasing. By 2006, 20 inchers were the rule with many over 24 inches being caught. The winter of 2007-2008 is gearing up to be a wet, cold one, which should result in another healthy hatch and another bump in the size of the fish. Even with their over-stuffed bellies full of flies, these fish are very athletic and are great fighters, often jumping out of the water numerous times before tiring.