928 resultados para aquatic mesocosms


Relevância:

10.00% 10.00%

Publicador:

Resumo:

About 1,200 ha of hydrilla ( Hydrilla verticillata L.f. Royle) was eliminated in the Spring Creek embayment of Lake Seminole, Georgia, using a drip-delivery application of fluridone (1- methyl-3-phenyl-5-[3-(trifluoromethl) phenyl]-4(1H)-pyridinone) in 2000 and 2001. Two groups of 15 and 20 largemouth bass (Micropterus salmoides Lacepede) were implanted with 400-day radio tags in February 2000 and 2001 to determine changes in movement and behavior before and after hydrilla reduction.(PDF contains 8 pages.)

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Waterlettuce ( Pistia stratiotes L.) is a free-floating exotic aquatic weed that often invades and clogs waterways in the southeastern United States. A study was conducted to evaluate the potential of using remote sensing technology to distinguish infestations of waterlettuce in Texas waterways. Field reflectance measurements showed that waterlettuce had higher visible green reflectance than associated plant species. Waterlettuce could be detected in both aerial color- infrared (CIR) photography and videography where it had light pink to pinkish-white image tonal responses. Computer analysis of CIR photographic and videographic images had overall accuracy assessments of 86% and 84%, respectively. (PDF contains 6 pages.)

Relevância:

10.00% 10.00%

Publicador:

Resumo:

There is strong evidence to suggest that ground-water nitrate concentrations have increased in recent years and further increases are expected along portions of the central Gulf coast of Florida. Much of the nitrate enriched groundwater is discharged into surface waters through numerous freshwater springs that are characteristic of the area and the potential for eutrophication of their receiving waters is a legitimate concern. To test the potential effects of elevated nutrient concentrations on the periphyton community an in situ nutrient addition experiment was conducted in the spring-fed Chassahowitzka River, FL, USA, during the summer of 1999. Plastic tubes housing arrays of glass microscope slides were suspended in the stream. Periphyton colonizing the microscope slides was subjected to artificial increases in nitrogen, phosphorus or a combination of both. Slides from each tube were collected at 3- to 4- day intervals and the periphyton communities were measured for chlorophyll concentration. The addition of approximately 10 μg/L of phosphate above ambient concentrations significantly increased the amount of periphyton on artificial substrates relative to controls; the addition of approximately 100 μg/L of nitrate above ambient concentrations did not. The findings from this experiment implicated phosphorus, rather than nitrogen, as the nutrient that potentially limits periphyton growth in this system.(PDF contains 4 pages.)

Relevância:

10.00% 10.00%

Publicador:

Resumo:

CONTENTS: Livelihoods and languages: a SPARK-STREAM learning and communications process, by Kath Copley and William Savage. Towards broader contextual understandings of livelihoods, by Elizabeth M. Gonzales, Nguyen Song Ha, Rubu Mukherjee, Nilkanth Pokhrel and Sem Viryak. Using tools to build shared understandings, using a sustainable livelihoods framework to learn, by Nuchjaree Langkulsane. Learning about rattan as a livelihood, by Mariel de Jesus and Christine Bantug. Meanings of “community-managed area,” by Arif Aliadi. Lessons learnt about processes for learning and communicating, by Graham Haylor and Ronet Santos.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

CONTENTS: Livelihood Improvements through fisheries in the Pode community in Pokhara, Nepal, by Tek Bahadur Gurung and Jay Dev Bista. Women’s participation in coastal resources management and livelihoods in Khanh Hoa Province, Vietnam, by Nguyen Thu Hue, Than Thi Hien, Pham Thi Phuong Hoa, Nguyen Viet Vinh and Dao Viet Long. Supporting people’s efforts and interactions in coastal resources management in Indonesia, by Tabitha Yulita. Planning for a community fisheries M&E system, by Heather Airlie and Haiko Meelis. Identifying needs and recommendations for efficient stakeholder communications through an information access survey, by Elizabeth M. Gonzales, Malene Felsing and Erwin L Pador. IEC seminar-workshop in support of fisheries ordinance implementation in Roxas City, Philippines, by Belinda M. Garrido and Elizabeth M. Gonzales.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Four methods to control the smooth cordgrass Spartina (Spartina alterniflora) and the footwear worn by treatment personnelat several sites in Willapa Bay, Washington were evaluatedto determine the non-target impacts to eelgrass (Zostera japonica). Clone-sized infestations of Spartina were treated bymowing or a single hand-spray application of Rodeo® formulatedat 480 g L-1acid equivalence (ae) of the isopropylaminesalt of glyphosate (Monsanto Agricultural Co., St. Louis, MO;currently Dow AgroSciences, Indianapolis, IN) with the nonionic surfactant LI 700® (2% v/v) or a combination of mowing and hand spraying. An aerial application of Rodeo® with X-77 Spreader® (0.13% v/v) to a 2-ha meadow was also investigated. Monitoring consisted of measuring eelgrass shoot densities and percent cover pre-treatment and 1-yr post-treatment. Impacts to eelgrass adjacent to treated clones were determined 1 m from the clones and compared to a control 5-m away. Impacts from footwear were assessed at 5 equidistant intervals along a 10-m transect on mudflat and an untreated control transect at each of the three clone treatment sites. Impacts from the aerial application were determined by comparing shoot densities and percent cover 1, 3 and 10 m from the edge of the treated Spartina meadow to that at comparable distances from an untreated meadow. Methods utilized to control Spartina clones did not impact surrounding eelgrass at two of three sites. Decreases in shoot densities observed at the third site were consistent across treatments. Most impacts to eelgrass from the footwear worn by treatment personnel were negligible and those that were significant were limited to soft mud substrate. The aerial application of the herbicide was associated with reductions in eelgrass (shoot density and percent cover) at two of the three sampling distances, but reductions on the control plot were greater. We conclude that the unchecked spread of Spartina is a far greater threat to the survival and health of eelgrass than that from any of the control measures we studied. The basis for evaluating control measures for Spartina should be efficacy and logistical constraints and not impacts to eelgrass. PDF is 7 pages.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

CONTENTS: An experience with group formation in Jabarrah, West Bengal, by Amar Prasad, Virendra Singh, Binay Sahay and Gautum Dutta. Aquaculture self-help groups in rural West Bengal, by Satyendra Tripathi, Graham Haylor and William Savage in consultation with Jagdish Gangwar, Virendra Singh, Gautam Dutta and Prabhat Pathak. Lessons learned for Fulwar Toli from an exposure visit to Jabarrah Bhim Nayak and Rubu Mukherjee. Livelihood intervention by Fish Farmers Development Agency: a success story from Mayurbhanj, Orissa, by G.B. Parida. Understanding of assets-based livelihoods through participatory rural appraisal to eliminate hunger, by Binay Sahay. Poverty ranking tools in PRA: experiences of EIRFP in addressing vulnerability, by Binay Sahay.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

CONTENTS: Creating understanding and ownership of collaborative research results through ‘learning by doing,’ by Robert Arthur and Caroline Garaway. Fish culture, farming, markets and promotion: an integrated, sustainable approach to aquaculture and rural development, by Pen Rotha and Brendan Boucher. Fisheries policy reform impact assessment in Cambodia: understanding policy and poor people, by Philip Townsley and Sem Viryak. “Shrimp Hero” Phan The Phuong, by Ngo Minh Khoi. Coral farming in Vietnam, by Nguyen Viet Vinh. The global fisheries market: can rural poor people benefit? Issues raised by STREAM Media Monitoring Reports, by Paul Bulcock.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

CONTENTS: BFAR moves on in Region 6, by Janice N. Tronco. Livelihoods initiatives in Sapian Bay, by Tee-Jay A. San Diego. Improving access to information through Barangay Learning Resource Centers, by Elizabeth M. Gonzales. The Philippines Fisheries Information System, by Agnes C. Solis. The contributions of planning activities in the participatory process, by Rommel P. Guarin. Inter-LGU alliance building: a key to sustaining the Integrated Fisheries and Aquatic Resource Management Council (IFARMC), by Josephine P. Savaris.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Water chestnut (Trapa natans L.,sensu lato) is an annual, floating-leaved aquatic plant of temperate and tropical freshwater wetlands, rivers, lakes, ponds, and estuaries. Native to Eurasia and Africa, water chestnut has been widely gathered for its large nutritious seed since the Neolithic and is cultivated for food in Asia. Water chestnut is now a species of conservation concern in Europe and Russia. Introduced to the northeastern United States in the mid-1800s, the spread of water chestnut as a nuisance weed was apparently favored by cultural eutrophication. Water chestnut is considered a pest in the U.S. because it forms extensive, dense beds in lakes, rivers, and freshwater-tidal habitats.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

(4pp.)

Relevância:

10.00% 10.00%

Publicador:

Resumo:

(4pp.)

Relevância:

10.00% 10.00%

Publicador:

Resumo:

(4pp.)

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Two biotypes of hydrilla [Hydrilla verticillata(L.f.) Royle] occur in the United States, a dioecious type centered in the southeast and a monoecious type in the central Atlantic and northeastern states. Ecosystem managers need tools to distinguish the types as the ranges of each type expand and begin to overlap. A molecular tool using the randomly amplified polymorphic DNA (RAPD) procedure is available but its use is limited by a need for reference samples. We describe an alternative molecular tool which uses “universal primers” to sequence the trnL intron and trnL-F intergenic spacer of the chloroplast genome. This sequence yields three differences between the biotypes (two gaps and one single nucleotide polymorphism). A primer has been designed which ends in a gap that shows up only in the dioecious plant. A polymerase chain reaction (PCR) using this primer produces a product for the monoecious but not the dioecious plant.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Dense, monospecific cattail (Typha spp.) stands are a problem in many prairie wetlands because they alter habitat structure and function, resulting in a decrease in use by wildlife species. Cheyenne Bottoms Wildlife Area, a Wetland of International Importance in central Kansas, has experienced a large increase in cattails and a subsequent decrease in migratory wetland bird use. As a consequence, intensive cattail management is practiced. We assessed the effectiveness of prescribed burning, discing following prescribed burning, and cattle grazing following prescribed burning at two stocking rates of 5 and 20 head per 11 ha in suppressing cattail, as well as the effects of these treatments on non-cattail vegetation.