Catch assessment of indigenous and exotic carp species of Nasti baor

An investigation on length-weight relationship, length-frequency distribution, catch per unit of effort (CPUE) and stocking and harvesting status of three Indian major carps: rohu Labeo rohita, catla Catla catla and mrigal Cirrhinus mrigala and three exotic carps: silver carp Hypophthalmichthys molitrix, grass carp Ctenopharyngodon idella) and common carp Cyprinus carpio was carried out in Nasti baor (oxbow lake) for the harvesting season from August to December 1995. The length-weight relationship for six carp species was established for the harvesting months of November and December 1995. The b values for different species respectively for the months of November and December were 2.95 and 2.58 for rohu, 3.06 and 2.98 for catla, 2,84 and 2.90 for mrigal, 2.75 and 2.60 for silver carp, 2.51 and 1.97 for grass carp and 2.38 and 2.50 for common carp. In CPUE study, the CPUE was 0.58 kg/ha/hr while the catch per gear was 0.08 kg/ha/hr/purse-seine. The recovery percentage of mrigal was highest (63.57%) and it was lowest (16.81%) in case of silver carp. The density of submerged macrophytes (Hydrilla, Utricularia, Ceratophyllum and Vallisneria) was highest (4.39 kg/sqm) in November and was lowest (0.76 kg/sqm) in September.

Endothall species selectivity evaluation: northern latitude aquatic plant community

Species selectivity of the aquatic herbicide dipotassium salt of endothall (Aquathol® K) was evaluated on plant species typically found in northern latitude aquatic plant communities. Submersed species included Eurasian watermilfoil (Myriophyllum spicatum L.), curlyleaf pondweed (Potamogeton crispus L.), Illinois pondweed (Potamogeton illinoensis Morong.), sago pondweed (Potamogeton pectinatus L.), coontail (Ceratophyllum demersum L.), elodea (Elodea canadensis Michx.) and wildcelery (Vallisneria americana L.). Emergent and floating-leaf plant species evaluated were cattail (Typha latifolia L.), smartweed (Polygonum hydropiperoides Michx.), pickerelweed (Pontederia cordata L.) and spatterdock (Nuphar advena Aiton). The submersed species evaluations were conducted in 7000 L mesocosm tanks, and treatment rates included 0, 0.5 1.0, 2.0, and 4.0 mg/L active ingredient (ai) endothall (dipotassium salt of endothall). The exposure period consisted of a 24-h flow through half-life for 7 d. The cattail and smartweed evaluation was conducted in 860 L mesocosm tanks, and the spatterdock and pickerelweed evaluations were conducted in 1600 L mesocosm tanks. Treatment rates for the emergent and floating-leafed plant evaluations included 0, 0.5, 2.0 and 4.0 mg/L ai endothall, and the exposure period consisted of removing and replacing half the water from each tank, after each 24 h period for a duration of 120 h. Biomass samples were collected at 3 and 8 weeks after treatment (WAT). Endothall effectively controlled Eurasian watermilfoil and curlyleaf pondweed at all of the application rates, and no significant regrowth was observed at 8 WAT. Sago pondweed, wildcelery, and Illinois pondweed biomass were also significantly reduced following the endothall application, but regrowth was observed at 8 WAT. Coontail and elodea showed no effects from endothall application at the 0.5, 1.0, and 2.0 mg/L application rates, but coontail was controlled at 4.0 mg/L rate. Spatterdock, pickerelweed, cattail, and smartweed were not injured at any of the endothall application rates.

Light Reflectance Characteristics and Remote Sensing of Waterlettuce

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.)

The Impact of Endothall on the Aquatic Plant Community of Kress Lake, Washington

CA dense mat-forming population of Eurasian watermilfoil ( Myriophyllum spicatum L . ) was interfering with fishing and recreation in a small western Washington lake. A low concentration (1.5 mg/L active ingredient) of the herbicide endothall formulated as Aquathol® K was used in 2000 to attempt to selectively control the Eurasian watermilfoil. Aquatic plant biomass and frequency data were collected before treatment, ten weeks after treatment and during the growing season for 3 additional years. Macrophyte data were analyzed to assess the herbicide’s impacts on Eurasian watermilfoil as well as the rest of the aquatic plant community. Results showed a significant decrease in Eurasian watermilfoil biomass and frequency 10 weeks after treatment. The Eurasian watermilfoil continued to be present, but at a significantly reduced level through the remainder of the study (3 years after treatment). Of the native plant species, large-leaf pondweed ( Potamogeton amplifolius Tucker . ) frequency and biomass was significantly reduced after treatment. Common elodea ( Elodea canadensis Rich.), muskgrass ( Chara sp. Vallaint.) and bladderwort ( Utricularia sp. L.) all increased significantly after treatment. (PDF has 6 pages.)

Influence of water temperature on the efficacy of diquat and endothall versus curlyleaf pondweed

determine the impact of water temperature on the efficacy of the contact herbicides diquat (6,7-dihydrodipyrido [1,2- α:2’,1’-c] pyrazinediium ion) and endothall (7-oxabicyclo [2.2.1] heptane-2,3-dicarboxylic acid) for control of the exotic nuisance species curlyleaf pondweed (Potamogeton crispus L.) across a range of water temperatures.

Comparison of Experimental Strategies to Control Torpedograss

Studies were conducted to evaluate whether the herbicide imazapyr or a combination of imazapyr and fluridone could be used effectively to control torpedograss ( Panicum repens L.), an exotic perennial plant that has replaced more than 6,000 ha of native vegetation and degraded quality wildlife habitat in Lake Okeechobee, Florida. Torpedograss was controlled for more than one year in some areas following a single aerial treatment using 0.56, 0.84, or 1.12 kg acid equivalents (ae) imazapyr/ha. Combining imazapyr and fluridone did not increase the level of torpedograss control. In areas where plant biomass was reduced by fire prior to being treated with 0.84 or 1.12 kg ae imazapyr/ha, torpedograss was controlled for more than two years and native plant species, including duck potato ( Sagittaria lancifolia L.) and pickerelweed ( Pontederia cordata L.) became the dominant vegetation in less than one year. Although torpedograss was controlled in some areas, little or no long-term control was observed at 16 of the 26 treatment locations. To reduce the uncertainty associated with predicting long-term treatment affects, additional studies are needed to determine whether environmental factors such as periphyton mats, plant thatch, hydroperiod and water depth affect treatment efficacy. , he

Herbicide evaluation for the control of wild taro

Wild taro (Colocasia esculenta (L.) Schott), is an exotic, emergent perennial that has established in many shallow-water wetlands throughout the southern United States. Although wild taro is a cultivated crop in many tropical and subtropical areas of the world, its invasion in riverine and lacustrine wetlands in the U.S. has resulted in the loss of habitat for native plant species. Once established, wild taro forms dense, monotypic stands that reduce the diversity of native vegetation, as has occurred in Louisiana, Florida, and Texas (Akridge and Fonteyn 1981, Simberloff et al. 1997). Akridge and Fonteyn (1981) reported that although wild taro is considered naturalized in south-central Texas, its present dominance along the San Marcos River has altered the native vegetational structure and dynamics of this river system. The objective of this study was to evaluate the efficacy of four aquatic herbicides for control of wild taro.

Factors to consider when using native biological control organisms to manage exotic plants

Biological control of exotic plant populations with native organisms appears to be increasing, even though its success to date has been limited. Although many researchers and managers feel that native organisms are easier to use and present less risk to the environment this may not be true. Developing a successful management program with a native insect is dependent on a number of critical factors that need to be considered. Information is needed on the feeding preference of the agent, agent effectiveness, environmental regulation of the agent, unique requirements of the agent, population maintenance of the agent, and time to desired impact. By understanding these factors, researchers and managers can develop a detailed protocol for using the native biological control agent for a specific target plant. . We found E. lecontei in 14 waterbodies, most of which were in eastern Washington. Only one lake with weevils was located in western Washington. Weevils were associated with both Eurasian ( Myriophyllum spicatum L.) and northern watermilfoil ( M. sibiricum K.). Waterbodies with E. lecontei had significantly higher ( P < 0.05) pH (8.7 ± 0.2) (mean ± 2SE), specific conductance (0.3 ± 0.08 mS cm -1 ) and total alkalinity (132.4 ± 30.8 mg CaCO 3 L -1 ). We also found that weevil presence was related to surface water temperature and waterbody location ( = 24.3, P ≤ 0.001) and of all the models tested, this model provided the best fit (Hosmer- Lemeshow goodness-of-fit = 4.0, P = 0.9). Our results suggest that in Washington State E. lecontei occurs primarily in eastern Washington in waterbodies with pH ≥ 8.2 and specific conductance ≥ 0.2 mS cm -1 . Furthermore, weevil distribution appears to be correlated with waterbody location (eastern versus western Washington) and surface water temperature.

Fish species diversity in the Victoria and Kyoga lake basins: their conservation and sustainable use

Introduction of exotic fish species especially the Nile perch Lates niloticus, is believed to be responsible for the decline of fish species diversity in lakes Victoria, Kyoga and Nabugabo.About 60% of the haplochromine cichlids are thought to have become extinct from L. Victoria due to predation by the Nile perch. However there are many lakes satelite to the lakes Victoria and Kyoga basins which still have fish fauna similar to that of the main lakes. many of the satellite lakes are separated from the main lakes in, which Nile perch was introduced by extensive swamps that provide a barrier to Nile perch .A survey was carried out in a number of these satelite lakes and an inventory made of existing fish species. Their distribution and relative abundances were also determined. The lakes studied included Nawampasa, Nakuwa,Kawi Lamwa Gigate, Nyaguo, Agu, Nabugabo. Kayanja, Kaytigi, Mburo, Kachera and Wamala.Some habitats within the main lakes Victoria and Kyoga, especially those with rocky outcrops· and macrophyte cover that provide refugia for endangered species from Nile perch,were also surveyed) Various stations along the River Nile were also sampled to quantify the fish species that are still resent. Kyoga minor lakes were found to have the highest number of fish species especially of haplochromine cichlids. Many haplochromine trophic groups that were thought to be extinct from 1. Victoria still occur in these lakes.!Some of the satellite lakes, especially lakes Kayugi, Mburo and Kachera still contain .healili populations of oreochromis. I esculentus that could be used as brood stock in fish farming. Many of these lakes should .I ( I therefore be protected for conservation offish species diversity

Using Remote Sensing and Spatial Information Technologies to Detect and Map Two Aquatic Macrophytes

This paper describes the light reflectance characteristics ofwaterhyacinth [Eichhornia crassipes (Mort.) Solms] and hydrilla [Hydrilla verticillata (L.F.) Royle] and the application of airborned videography with global positioning system (GPS) and geographic information system (GIS) technologies for distinguishing and mapping the distribution of these two aquatic weeds in waterways of southern Texas. Field reflectance measurements made at several locations showed that waterhyacinth generally had higher near-infrared (NIR) reflectance than associated plant species and water. Hydrilla had lower NIR reflectance than associated plant species and higher NIR reflectance than water. Reflectance measurements made on hydrilla plants submerged below the water surface had similar spectral characteristics to water. Waterhyacinth and hydrilla could be distinguished in color-infrared (CIR) video imagery where they had bright orange-red and reddish-brown image responses, respectively. Computer analysis of the imagery showed that waterhyacinth and hydrilla infestaions could be quantified. An accuracy assessment performed on the classified image showed an overall accuracy of 87.7%. Integration of the GPS with the video imagery permitted latitude/longitude coordinates of waterhyacinth and hydrilla infestation to be recorded on each image. A portion of the Rio Grande River in extreme southern Texas was flown with the video system to detect waterhyacinth and hydrilla infestaions. The GPS coordinates on the CIR video scenes depicting waterhyacinth and hydrilla infestations were entered into a GIS to map the distribution of these two noxious weeds in the Rio Grande River.

Panel Discussion - Management of Eurasian watermilfoil in the United States using native insects: State regulatory and management issues

While researchers have evaluated the potential of native insect herbivores to manage nonindigenous aquatic plant species such as Eurasian watermilfoil ( Myriophyllum spicatum L.), the practical matters of regulatory compliance and implementation have been neglected. A panel of aquatic nuisance species program managers from three state natural resource management agencies (Minnesota, Vermont and Washington) discussed their regulatory and policy concerns. In addition, one ecological consultant attempting to market one of the native insects to manage Eurasian watermilfoil added his perspective on the special challenges of distributing a native biological control agent for management of Eurasian watermilfoil.

Studies of the effects from extracts from two local plants (Tephrosia vogelii and Parkia clappertoniana) on Clarias gariepinus (Tengels)

Studies were carried out using 96hr static toxicity bioassay to determine the effect of lethal concentrations of extracts from two local plants Tephrosia vogelii and Parkia clappertoniana which are known fish poison, on a species of mud fish. Clarias gariepinus Phytochemical analysis of the plant extracts was done and the extract from T. vogelii was found to contain alkaloids, tannins and flavonoids, while the extract from P. clappertoniana was formed to contain alkaloids tannins and saponins. Experimental fish were exposed to test water separately polluted by varying concentrations of extraction of both plant species ranging from 0.50mgl super(-1), 1.50mgl super(-1), 2.50mgl super(-1), 3.0mgl super(-1), 5.00mgl super(-1), 10.00mgl super(-1) in the case of T. vogelii and 5.00mgl super(-1), 7.50mgl super(-1), 10.00mgl super(-1), 15.00mgl super(-1), 20.00mgl super(-1) and 30.00mgl super(-1) in the case of P. clappertaniana. Behavioural hispathological and heamatological examinations were made. Both plant extracts were found to have lethal effects at the higher concentrations, affecting the gills and the central nervous system as well as having a depressive effect on the total count and increasing platelet and white blood cell count. Symptoms of toxicosis observed include, initial inactivation agitated swimming, tumbling movement air gulping, increased opercular beat and period of quiescence/knockdown before death. Marked differences were also observed in the hematological and histopathological analysis of poisoned fish. Lower concentrations of the extracts had sub lethal effects on the fish, which manifested as zigzag movement air gulping increased opercular movement etc. None of these effects were observed in the control experiment

The ecology of Atlantic white cedar wetlands: a community profile

This monograph on the ecology of Atlantic white cedar wetlands is one of a series of U.S. Fish and Wildlife Service profiles of important freshwater wetland ecosystems of the United States. The purpose of the profile is to describe the extent, components, functioning, history, and treatment of these wetlands. It is intended to provide a useful reference to relevant scientific information and a synthesis of the available literature. The world range of Atlantic white cedar (Chamaecyparis thyoides) is limited to a ribbon of freshwater wetlands within 200 km of the Atlantic and Gulf coasts of the United States, extending from mid-Maine to mid-Florida and Mississippi. Often in inaccessible sites and difficult to traverse, cedar wetlands contain distinctive suites of plant species. Highly valued as commercial timber since the early days of European colonization of the continent, the cedar and its habitat are rapidly disappearing. This profile describes the Atlantic white cedar and the bogs and swamps it dominates or codominates throughout its range, discussing interrelationships with other habitats, putative origins and migration patterns, substrate biogeochemistry, associated plant and animal species (with attention to those that are rare, endangered, or threatened regionally or nationally), and impacts of both natural and anthropogenic disturbance. Research needs for each area are outlined. Chapters are devoted to the practices and problems of harvest and management, and to an examination of a large preserve recently acquired by the USFWS, the Alligator River National Wildlife Refuge in North Carolina.

Broodstock management status and some suggestions to control negative selection and inbreeding in hatchery stocks in Bangladesh

The freshwater river systems and floodplains of Bangladesh are the breeding grounds for 13 endemic species of carps and barbs and a large number of other fish species, including a number of exotic carps and other species that have been introduced for aquaculture. Since 1967, breeding of endemic and exotic aquaculture species for seed producton through hypophysation techniques has become a common practice. The paper describes the present status of broodstock management, identifies problems, and suggests some guidelines to control negative selection and inbreeding in hatchery stocks in Bangladesh.