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At least 397 records · Page 22Linked to original sources
USGS2006

Measurements of bed load transport on Pacific Creek, Buffalo Fork and The Snake River in Grand Teton National Park, Wyoming

Dams disrupt the flow of both of water and sediment through a watershed. Channel morphology is a function of discharge and sediment load, and perturbations caused by dams often alter channel form, causing significant geomorphic and, potentially, ecological changes (e.g. Petts and Gurnell, 2005). At the first order, dams often produce a flow regime that is profoundly altered in the timing, magnitude, and frequency of flows (Magilligan and Nislow, 2005). Yet, the nature of channel adjustments will be specific to both the physical setting, size of the river, dam characteristics, and nature and severity of the flow regulation (Church 1995; Knighton, 1998).

Wyoming↗
USGS1989

Sensitivity of endemic Snake River cutthroat trout to acidity and elevated aluminum

Acidic episodes in waters of the western USA, do not last as long and are not as intense as those in the eastern USA, but we found that the native western cutthroat trout Oncorhynchus clarki is sensitive to even brief reductions in pH. In laboratory studies, fish were exposed to acidity (pH 4.5–6.5) alone or in the presence of aluminum during the first 7 d of the freshly fertilized egg, eyed embryo, alevin, or swim-up larva stages of development. Following exposure to acidity and aluminum, eggs and fish were held under control water quality conditions to 40 d posthatch to assess effects of the exposure on subsequent development. Reductions in pH from 6.5 to 6.0 in low-calcium water (1.4 mg/L) did not affect survival, but reduced growth offish in the early life stages. The presence of as little as 50 μg A1/L at low pH further decreased growth and reduced survival. The most sensitive indicators of stress were loss of ions (determined from whole-body sampling) and reduced swimming in alevins, reduction in the ratio of RNA:DNA, feeding inhibition, and pathology of gill tissue in swim-up larvae. A pH of 6.0 and 50 μg Al/L reduced whole-body sodium by 72% and potassium by 50% in alevins. Reductions in the RNA: DNA ratio, correlated with lower growth rates, were observed in swim-up larvae exposed to pH 5.5 and 50 μg Al/L. Exposure to 50 μg Al/L at pH 6.0 reduced swimming activity of alevins by 68% and feeding rates of swim-up larvae by 67%. In the presence of 50 μg A1/L, pathological changes in gill tissue were observed in swim-up larvae exposed to pH 6.0 or less. Although acidification is not widespread in the western USA, cutthroat trout have a narrow margin of safety between conditions that currently exist and those at which pH and aluminum reduce survival and growth.

Transactions of the American Fisheries Society↗
USGS1992

Rediscovery of the Central American Colubrid snake, Sibon argus, with comments on related species from the region

Sibon argus Cope, 1875, long known only from the holotype, is redescribed based on material from Costa Rica and Panama. It differs from the only other member of the genus having an ocellate dorsal pattern (S. longifrenis) in its attenuate habitus, enlarged blunt head, protuberant eyes, and high segmental counts (ventrals 181-201, subcaudals 112-121, total segmental counts 294-312). Sibon longifrenis of Atlantic slope Costa Rica and western Panama (ventrals 151-173, subcaudals 82-103, total segmental counts 231-275) is also redescribed. These species differ from all other Sibon in having an ocellate pattern and an enlarged penultimate supralabial bordering the orbit. The allied species, S. annulatus (Costa Rica and Panama) and S. dimidiatus (Mexico to southwestern Costa Rica), are shown to be distinct from S. argus and S. longifenis in scalation and coloration. Although allopatric, S. annulatus and S. dimidiatus differ from one another most strikingly in adult coloration, postmental character states, and ventral counts (x = 175.8 in annulatus and 193.6 in dimidiatus), and are regarded as valid species. Sibon annulatus occurs sympatrically with S. argus in Panama and with S. longifrenis in Costa Rica. Although S. argus and S. longifrenis occur in the same general area on the Atlantic slope of Costa Rica, they have not yet been taken at the same locality.

Copeia↗
USGS2023

On the origin and current distribution of the Oceania Snake-Eyed Skink (Cryptoblepharus poecilopleurus) in the Hawaiian archipelago

Because of its extreme isolation and lack of historical connection to a mainland, the Hawaiian Archipelago is thought to have no native nonvolant terrestrial reptiles. Several squamate species have been introduced to the archipelago, likely starting with early Polynesian contact, and increasing as human traffic in the Pacific has amplified. Of the earlier introductions, one species of skink, Cryptoblepharus poecilopleurus , belongs to a genus known for its ability to naturally disperse long distances, even across oceans. The earliest herpetofaunal surveys from Hawai‘i describe the skink as widespread and abundant across the archipelago. A recent phylogenetic analysis reveals substantial haplotype divergence between Hawaiian individuals and other known populations in the Pacific, raising the possibility that this species was an early and natural arrival to the archipelago before human contact. Recent surveys suggest that the species has undergone a dramatic reduction in range across the archipelago, possibly due to the invasion of highly competitive species. Given this information, we aim to further assess the origin of C. poecilopleurus in Hawai‘i, determine its current range, and suggest specific needs for future work. Here, we review the earliest European voyages in the Pacific that are known to have sampled C. poecilopleurus , review literature and museum specimens to develop an understanding of this species’ history in the islands, survey the island of O‘ahu to characterize its current range, and provide preliminary genetic analyses to show the relationship of the Hawai’i populations to the rest of the Pacific.

Hawaii↗