Geology topics

James L. Shelton

Publications and source records attributed to James L. Shelton.

4 recordsLinked to original sources

USGS2013

Pathologic and physiologic effects associated with long-term intracoelomic transmitters in captive Siberian sturgeon

Intracoelomic transmitters are commonly used to evaluate migratory patterns, distribution, and habitat use of many species of fish. Currently, transmitter implantation relies mostly on the assumption that transmitters do not cause any adverse physiological or pathological effects on the animal. To investigate these effects, we surgically implanted 60 Siberian Sturgeon Acipenser baeri with transmitters that weighed less than 2% of their body weight. Postoperative assessments were conducted at 1, 2, 8, 12, 26, and 55 weeks to evaluate surgical healing and transmitter retention. Blood samples were collected before and after the 55-week study for serum cortisol analysis. Overall transmitter loss was 32%. Minor to moderate adhesions were noted at necropsy but did not appear to affect organ function. One fish was noted to have an intraintestinal transmitter at necropsy, but the fish was in overall good health. Long-term transmitter presence does not appear to increase serum cortisol levels or affect overall growth more than nontransmitter fish. Although long-term telemetry studies can be undertaken with minimal concern for negative physiological or pathological effects from transmitters, researchers should be aware that transmitter loss rates may be higher than previously thought. Mechanisms for transmitter loss may include expulsion through the surgical incision, expulsion through the mucocutaneous junction between the large intestine and the vent, or intraintestinal capture and expulsion through the vent. Received February 10, 2013; accepted June 10, 2013

North American Journal of Fisheries Management↗

USGS2013

Evaluation of four suture materials for surgical incision closure in Siberian sturgeon

The visual and microscopic tissue reactions to the absorbable monofilament Monocryl, absorbable monofilament triclosan-coated Monocryl-Plus, absorbable multifilament Vicryl, and nonabsorbable monofilament Prolene were evaluated for their use of surgical closure in Siberian Sturgeon Acipenser baerii . Postoperative assessments were conducted at 1, 2, 8, 12, and 26 and 55 weeks to visually evaluate the surgical incision for suture retention, incision healing, erythema, and swelling. Incisions were also assessed microscopically at 1, 2, and 8 weeks for necrosis, inflammation, hemorrhage, and fibroplasia. The results indicated that incisions closed with either Vicryl or Prolene suture materials were more likely to exhibit more erythema or incomplete healing compared with those closed with Monocryl or Monocryl-Plus. The surgical implantation of a transmitter in the coelomic cavity did not significantly affect the response variables among the four suture materials. Monocryl or Monocryl-Plus were equally effective and superior to other suture materials used for closing surgical incisions in Siberian Sturgeon or closely related species of sturgeon. Furthermore, Monocryl or Monocryl-Plus may decrease the risk of transmitter expulsion through the incision, as surgical wounds appear to heal faster and exhibit less erythema compared with those closed with Vicryl.

Transactions of the American Fisheries Society↗

USGS2008

Regional nitrate and pesticide trends in ground water in the eastern San Joaquin Valley, California

Protection of ground water for present and future use requires monitoring and understanding of the mechanisms controlling long-term quality of ground water. In this study, spatial and temporal trends in concentrations of nitrate and pesticides in ground water in the eastern San Joaquin Valley, California, were evaluated to determine the long-term effects of agricultural and urban development on regional ground-water quality. Trends in concentrations of nitrate, the nematocide 1,2-dibromo-3-chloropropane, and the herbicide simazine during the last two decades are generally consistent with known nitrogen fertilizer and pesticide use and with the position of the well networks in the regional ground-water flow system. Concentrations of nitrate and pesticides are higher in the shallow part of the aquifer system where domestic wells are typically screened, whereas concentrations are lower in the deep part of the aquifer system where public-supply wells are typically screened. Attenuation processes do not seem to significantly affect concentrations. Historical data indicate that concentrations of nitrate have increased since the 1950s in the shallow and deep parts of the aquifer system. Concentrations of nitrate and detection of pesticides in the deep part of the aquifer system will likely increase as the proportion of highly affected water contributed to these wells increases with time. Because of the time of travel between the water table and the deep part of the aquifer system, current concentrations in public-supply wells likely reflect the effects of 40- to 50-yr-old management practices. Copyright ?? 2008 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.

Conference Paper↗

USGS2007

Temporal trends in concentrations of DBCP and nitrate in groundwater in the eastern San Joaquin Valley, California, USA

Temporal monitoring of the pesticide 1,2-dibromo-3-chloropropane (DBCP) and nitrate and indicators of mean groundwater age were used to evaluate the transport and fate of agricultural chemicals in groundwater and to predict the long-term effects in the regional aquifer system in the eastern San Joaquin Valley, California. Twenty monitoring wells were installed on a transect along an approximate groundwater flow path. Concentrations of DBCP and nitrate in the wells were compared to concentrations in regional areal monitoring networks. DBCP persists at concentrations above the US Environmental Protection Agency's maximum contaminant level (MCL) at depths of nearly 40 m below the water table, more than 25 years after it was banned. Nitrate concentrations above the MCL reached depths of more than 20 m below the water table. Because of the intensive pumping and irrigation recharge, vertical flow paths are dominant. High concentrations (above MCLs) in the shallow part of the regional aquifer system will likely move deeper in the system, affecting both domestic and public-supply wells. The large fraction of old water (unaffected by agricultural chemicals) in deep monitoring wells suggests that it could take decades for concentrations to reach MCLs in deep, long-screened public-supply wells, however. ?? Springer-Verlag 2007.

Hydrogeology Journal↗