Photo below, Willamette River at Portland, Oregon, in summer, near the entry into the Columbia River, and about 20 miles downstream from Willamette Falls.
-Willamette River, Portland, Oregon, same location
The Willamette River (above) enters the Columbia River at Portland, Oregon, about 100 miles upstream from the ocean at Astoria. Tides affect both rivers up to and beyond Portland. Willamette Falls, about 26 miles upstream on the Willamette, has a drop of about 42 feet, and a flow of about 5000 cubuc feet per second.
The Lower Willamette would thus seem to be quite separated ecologically from the river above the falls. Ocean tides raise and lower water levels about 3 feet at the falls.
The report on the link below gives details of the ecology of the lower Willamette.
Samples taken in winter , January 2010, at Albany, Oregon (see above for photos of the same area in summer) yielded large numbers of specimens, dominated by two or more species of Ephemerella and a species o Heptageniidae, but also present was a Baetid species, plus a species of Ameletus, which was quite abundant. Trichoptera, Plecoptera, Hemiptera/Corixidae, annelids, and Gammarids were also present. Details to follow.
About 20 species of Ameletusare found in Oregon. A. exquisitus has previously been reported from the Willamette River. The as yet unidentified species below was abundant at Albany in winter. The specimen below is freshly preserved in alcohol, and has the most of the original coloration, - colors fade in preserved specimens.
SeeHome for a photo of the living individual. below.
New collections and photos (below) from 14 February 2010:
This Ameletus species was collected in January 2010. Note the mid-tail black band and the black tip of the tails, the lack of pigment in the gills, and the distinct dorsal color pattern of the abdomen. Compare with the individual pictred below, collected Feg. 14, 2010.
This is a second species of Ameletus collected at the same site as above (Albany). Collection date, 14 Feb. 2010. Note the black mid- band on the antennae, the dark pigment on the tips of all the gills, the broad middle band on the tails, and the color pattern on the dorsal abdomen- clearly a different species compare to the above.
Middle above- ventral color pattern, directly above- the two species side by side, both collected 14 February 2010
March 2010, Willamette River, Albany, Oregon: grass is green and growing, trees are showing may new leaves.
Photos above and below, 25 March 2010.
Previously uncollected Baetid from the Willamette River, Albany, Oregon
In the older keys, this individual would be identified as a "Centroptilum" species. The new classification of Baetidae is completely different, and the identity of this individual is unknown at present. It is not one of the four species of Baetidae listed in Meyer and McCafferty 2007 above.
In this specimen (photographed alive) there are 7 pairs of gills, the first pair being very small, and there are no denticles on the claws, which are short.
Above "Centroptilum" collected on 25 March 2010 at Albany Oregon. Willamette River.
The next day, I attempted to collect more specimens at the same site, but because of rains the water level had risen about two feet, and almost nothing was collected, including no more of the above species. A week later, water had risen about 10-12 feet, flooding the rocky shore and all of the grassy area (see below) the water reaching the trees at left in the photo above.
The previous sampling areas are under more than 10 feet of water because of rains.