Population Characteristics of Largemouth Bass Associated with Changes in Abundance of Submersed Aquatic Vegetation in Lake Seminole, Georgia

Population characteristics of largemouth bass ( Micropterus salmoides L.) including growth, body condition (relative weight), survival, and egg production were examined in relation to abundance of submersed aquatic vegetation (SAV) coverage (primarily hydrilla [ Hydrilla verticillata L.f. Royle]) in three embayments of Lake Seminole, GA, and compared to a previous study conducted in 1998. (PDF has 8 pages.)

Aquatic Vegetation, Largemouth Bass and Water Quality Responses to Low-Dose Fluridone Two Years Post Treatment

Whole-lake techniques are increasingly being used to selectively remove exotic plants, including Eurasian watermilfoil ( Myriophyllum spicatum L.). Fluridone (1-methyl-3-phenyl- 5-[3-(trifluoromethyl)phenyl]-4(1 H )-pyridinone), a systemic whole-lake herbicide, is selective for Eurasian watermilfoil within a narrow low concentration range. Because fluridone applications have the potential for large effects on plant assemblages and lake food webs, they should be evaluated at the whole-lake scale. We examined effects of low-dose (5 to 8 ppb) fluridone applications by comparing submersed plant assemblages, water quality and largemouth bass ( Micropterus salmoides ) growth rates and diets between three reference lakes and three treatment lakes one- and two-years post treatment. In the treatment lakes, fluridone reduced Eurasian watermilfoil cover without reducing native plant cover, although the duration of Eurasian watermilfoil reduction varied among treatment lakes. (PDF has 11 pages.)

Natural Suppression of the Aquatic Weed Salvinia molesta D.S. Mitchell, by Two Previously Unreported Fungal Pathogens

Salvinia molesta D. S. Mitchell (Salviniaceae), variously called giant salvinia, water fern or African payal, is a vegetatively reproducing, perennial, free-floating, aquatic weed, native to southeastern Brazil (Waterhouse and Norris 1987). It (hereafter called salvinia) is a very serious weed in most regions outside its native range (Harley and Mitchell 1981) including India. The purpose of this paper is to report on two fungal pathogens that were found to be the cause of a sudden decline in salvinia in Bangalore.(PDF has 4 pages.)

Physical Constraints to Aquatic Plant Growth in New Zealand Lakes

The nature of aquatic plant communities often defines benthic habitat within oligotrophic and mesotrophic lakes and lake management increasingly recognizes the importance of maintaining plant diversity in order to sustain biological diversity and capacity within lakes. We have developed simple statistical relationships between key physical and vegetation variables that define the habitat requirements, or “habitat-templates”, of key vegetation types to facilitate management of plant communities in New Zealand lakes. Statistical relationships were derived from two datasets. The first was a multi-lake dataset to determine the effects of water level fluctuation and water clarity. The second dataset was from a comprehensive shoreline survey of Lake Wanaka, which allowed us to examine within-lake variables such as beach slope and wave action. Sufficient statistical relationships were established to develop a habitat template for each of the major species or assemblages. The relationships suggested that the extent and diversity of shallow-growing species was related to a combination of the extent of water level fluctuation and wave exposure. (PDF contains 9 pages.)

Economic Impacts of Aquatic Vegetation to Angling in Two South Carolina Reservoirs

Angler creel surveys and economic impact models were used to evaluate potential expansion of aquatic vegetation in Lakes Murray and Moultrie, South Carolina. (PDF contains 4 pages.)

The Use of Herbicides to Control Hydrilla and the Effects on Young Largemouth Bass Population Characteristics and Aquatic Vegetation in Lake Seminole, Georgia

From 1997 to 2003, we examined the impacts of two aquatic herbicides, fluridone (Sonar; 1-methyl-3-phenyl-5-[3-(trifluromethl) phenyl]-4(1H)-pyridinone), and dipotassium salt of endothall (Aquathol K; 7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid), used to control dense hydrilla (Hydrilla verticillata L. f. Royle), on population characteristics of juvenile largemouth bass (Micropterus salmoides Lacepede) in small coves (<10 ha) in Lake Seminole, Georgia. In addition, we estimated areal coverage and species composition of submersed aquatic vegetation (SAV) communities in each cove. Fish and plants were sampled in both control (hydrilla infested)and herbicide treated coves in November and March- April each year. Electrofishing catch-per-effort for both number and weight of age-0 and age-1 fish for the 1997 to 2002 year classes was either the same or higher (p < 0.05) in herbicide treated than in control coves. Age-0 fish were larger (p <0.05) in treated, than in control coves in November, but at age-1 in the following spring, fish were slightly longer (p <0.05) in the control coves. Higher age-0 catches were associated with greater percent reductions in numeric catch between age-0 and age-1 and reduced lengths of fish in November indicating density-dependent effects. Age-0 fish lengths were also negatively correlated to percent cover of both total and native SAV. Total or native SAV coverages were not associated with catch-per-unit effort for number and weight, but nearly all control and herbicide treated coves had total SAV coverage greater than 40%. Applications of both Sonar and Aquathol K reduced total SAV coverage and hydrilla, permitted the establishment of native SAVs, and had either neutral or positive impacts on young largemouth bass in small coves in Lake Seminole. (PDF contains 7 pages.)

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.

Presidential Address: The Aquatic Plant Management Society and Our Future Sphere of Influence

Presidential address of Alison M. Fox

The influence of disparate levels of submersed aquatic vegetation on largemouth bass population characteristics in a Georgia reservoir

Population characteristics of largemouth bass (Micropterous salmoides L.) including growth, body condition (relative weight), size structure, survival, and fecundity were examined in relation to abundance of submersed aquatic vegetation (SAV) coverage (primarily hydrilla Hydrilla verticillata L.f. Royle) in three major embayments of Lake Seminole, Georgia. Relative weight, fecundity, and growth of large-mouth bass in the Spring Creek embayment (76% areal SAV coverage) was considerably less than measured in the Chattahoochee and Flint river arms that contained lower SAV coverages (26% and 32%). It took fish 1.8 years longer to reach 406 mm in Spring Creek compared to the Chattahoochee-Flint arms. Consequently, fish were smaller in Spring Creek than in the Chattahoochee-Flint arms. In addition, due to slower growth rates and lower fecundity-to-body weight relation, we predicted a 47% reduction in total potential ova production in Spring Creek compared to the other two reservoir embayments. The annual survival rate of 3 to 10 year old largemouth bass was higher in Spring Creek (84%) than in the Chattahoochee-Flint arms (72%) and suggested either lower harvest and/or lower accessibility of particularly larger fish to angling in dense vegetation. Contrary to our expectaions, the fit between number-at-age and age in a catch-curve regression was weaker for fish collected in Spring Creek and suggested greater recruitment variability has occurred over time in this highly vegetated embayment. In Lake Seminole, spatial differences in largemouth bass population characterstics were associated with disparate levels of SAV. Our data suggest that a reduction in hydrilla, but maintenance of an intermediate level of SAV in Spring Creek, should improve largermouth bass population in this arm of the reservoir.

Water quality impacts of mechanical shredding of aquatic macrophytes

We examined the impacts of mechanical shredding (i.e.. shredding plants and leaving biomass in the system) of the water chestnut (Trapa natans) on water quality and nutrient mobilization in a control and experimental site in Lake Champlain (Vermont-New York). A 1-ha plot was mechanically shredded within 1 h on 26 July, 1999. Broken plant material was initially concentrated on the lake surface of the experimental station after shredding, and was noticeable on the lake surface for 19 d. Over a two week period after shredding. concentrations of total nitrogen (N) and phosphorus (P), and soluble reactive P increased in the lower water column of the experimental station, coinciding with decomposition of water chestnut. Sediments in the control and experimental stations exhibited vet-v low rates of N and P release and could not account for increases in nutrient concentrations in the water column after mechanical shredding. Shredded plant material deployed in mesh bags at the experimental station lost similar to 70% of their total mass, and 42%, N and 70% P within 14 d. indicating Substantial nutrient mobilization via autolysis and decomposition. Chlorophyll a concentrations increased to 35 g/L at the experimental station on day 7 after shredding, compared to a concentration of 4 g/L at the control station. suggesting uptake of mobilized nutrients by phytoplankton. Disruption Of the Surface canopy of water chestnut by shredding was associated with marked increases in turbidity and dissolved oxygen, suggesting increased mixing at the experimental site.

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.

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.)

A Review of the Aquatic Environmental Fate of Triclopyr and its Major Metabolites

The purpose of this paper is to provide an overview of the aquatic environmental fate of triclopyr and its major metabolites, TCP and TMP. This review is primarily based on results of laboratory and field studies conducted by various Federal Agencies and the registrant to support the US aquatic registration for triclopyr TEA.

Monitoring hydrilla using two RAPD procedures and the Nonindigenous Aquatic Species database

Hydrilla ( Hydrilla verticillata (L.f.) Royle), an invasive aquatic weed, continues to spread to new regions in the United States. Two biotypes, one a female dioecious and the other monoecious have been identified. Management of the spread of hydrilla requires understanding the mechanisms of introduction and transport, an ability to map and make available information on distribution, and tools to distinguish the known U.S. biotypes as well as potential new introductions. Review of the literature and discussions with aquatic scientists and resource managers point to the aquarium and water garden plant trades as the primary past mechanism for the regional dispersal of hydrilla while local dispersal is primarily carried out by other mechanisms such as boat traffic, intentional introductions, and waterfowl. The Nonindigenous Aquatic Species (NAS) database is presented as a tool for assembling, geo-referencing, and making available information on the distribution of hydrilla. A map of the current range of dioecious and monoecious hydrilla by drainage is presented. Four hydrilla samples, taken from three discrete, non-contiguous regions (Pennsylvania, Connecticut, and Washington State) were examined using two RAPD assays. The first, generated using primer Operon G17, and capable of distinguishing the dioecious and monoecious U.S. biotypes, indicated all four samples were of the monoecious biotype. Results of the second assay using the Stoffel fragment and 5 primers, produced 111 markers, indicated that these samples do not represent new foreign introductions. The differences in the monoecious and dioecious growth habits and management are discussed.