Production rates of seven species of fish, along with food-web interactions, were determined for one year in a pond. Production of fish in the pond amounted to 208.9 q/m2/yr. Over 95% of the production occurred in the summer, with Y of Y fish contributing 83.8%. There were two food-web interactions observed in Y of Y fishes: crappie vs. bass and bullhead vs. sunfish. When Y of Y fish shifted to benthic diets in the spring, the small biomass of benthos available could not sustain the larger biomass of fish. Competition for the available food resulted in decreased production rates for the fish community.

Thesis (Ph. D.)--Deakin University, 2001. / Title from PDF title page (viewed on May 16, 2005). Includes bibliographical references (p. 203-224).

Pond harvesting is an integral part of fish farming procedures in pond culture and overall fish production. This study was aimed at the evaluation of environmental conditions during pond harvesting, based on the comparison of values monitored in the trawl-net with fish located in a harvesting pit and outside it. The monitored parametres comprised the oxygen content and saturation, temperature, pH, conductivity and turbidity. The monitoring was performed on three autumn harvests (Potěšil, Rod, Jaroslavický dolní) and two spring harvests (Vrbenský přední and Vrbenský nový), always during the fish removal from the net (seine). The monitored determinants were recorded in 30-min intervals inside the net with fish and outside it in 15m distance. During the statistical comparision of the oxygen content and saturation in the net and outside it with the count on fish biomass was statistically signifiant differences in the four of twelve raids evaluated, which means keeping fishes in the net during the yielding was adequately treated by installation of fresh water jet.When the fresh water jet had been stopped worsen of the conditions in the fish net and even in the harvesting pit appeared.

The aim of the thesis is to assess the possibility of establishing a water reservoir in s selected location witch regard to its possible water management activities including geological conditions. The thesis also defines basic terms related to water reservoir and their parts. This work was elaborated with the help of available literature and valid laws of the Czech Republic concerning the given issue. At the end of the work will be valued land meeting the conditions for the construction of a small water tank. The award will take place in two ways according to the decree and direct comparison.

Seven species of planktonic microcrustacea were identified from the North Texas State University Golf Course Pond. Total adult microcrustacean community density, biomass and biocontent, and seasonal cycles of each species were compared with northern populations. Species diversity and evenness indices were highest in summer and lowest in spring. Variations in microcrustacean density showed a positive correlation with density of phytoplankton. Temperature had a direct effect on metabolic rates of two species of copepods. Metabolic rates of pond species were lower at common temperatures than those of northern populations. An estimate of annual energy flow through the pond ecosystem showed cladocerans contributed the greater percentage of total energy to the next trophic level.

This dissertation addresses the question of how leaf litter from trees affects animals that live in aquatic environments, with an emphasis on the effect of Chinese tallow (Triadica sebifera) leaf litter on anuran larvae (i.e., frog tadpoles). This question is important to our understanding of how allochthonous inputs to aquatic habitats drive biodiversity in wetlands. It also addresses a timely conservation concern in southeastern Louisiana where invasion by Chinese tallow trees (Triadica sebifera) is displacing native trees. The invasion process is homogenizing forest composition and changing the quantity and quality of litter inputs to ponds from those produced by a mixture of native species to that of a single invasive species. This change in litter quality may have important effects on aquatic animals because leaf litter that falls into ponds is an important source of nutrients and energy in wetland foodwebs. Leaf litter also affects water quality via effects on dissolved oxygen and leaching of defensive compounds, which may subsequently affect the diversity and performance of aquatic animals. Herein I address these issues by presenting a series of studies in which tadpole and aquatic invertebrate responses were tested using leaf litter from Chinese tallow leaves and three native tree species. The major findings of this research are: (1) Leaf litter has a direct effect on water quality (2) Chinese tallow can cause differential survival and performance of tadpoles (3) Differences in water quality due to leaf litter can cause changes in tadpole behavior (4) Chinese tallow leaf litter breaks down much faster than litter from native trees (5) Difference in litter breakdown rates influence aquatic community composition.

The main focus of the thesis is the reconstruction of 3D models and digital elevation models of five abandoned splash dams in Roklanský brook catchment using UAV photogrammetry methods. The aim of this work is to compare accuracy of the models with available conventional data sources and historical sources. Parallel topic is the research of accuracy of the models created through UAV methods and application of retention potential of small water reservoirs, in headwater areas. The images were taken with a drone-mounted camera. Modelling was done by processing images in software Agisoft PhotoScan through a workflow process, dense point cloud classification and subsequent DEM interpolation. Subsequent delineation of reservoirs retention space, altimetry correction and bathymetric analysis was performed in ArcMap over the interpolated DEM. The results and discussion point to the benefits and limitations of UAV methods, especially to altimetric accuracy of the resulting models relative to conventional DMR5G data and bathymetric characteristics derived from the models. Keywords: UAV; DEM; retention; GIS; model; pond

Earthworking activities have the potential to accelerate soil erosion through vegetation clearance and soil compaction processes. The eroded sediment can have many detrimental effects on receiving aquatic environments, and thus its discharge is controlled under the Resource Management Act, 1991. Two chemically dosed sediment retentions ponds at the SH20 extension project in Mount Roskill, Auckland were investigated, and the impact of the discharge of one of these ponds on a receiving waterbody was assessed using the Stream Ecological Valuation (SEV) method. Rainfall and suspended solid data was collected for a nine month period between November 2006 and August 2007, although sampling did not commence at one of the ponds until March 2007. Two SEV samples were undertaken within the receiving waterbody; one in November 2006 and the other in November 2007 to assess environmental changes resulting from the sediment retention pond discharge. The suspended solids results measured within the sediment retention ponds during this study were much lower than those reported by other studies on earthwork sites. This is believed to be due to the effective implementation of sediment and erosion control measures onsite. The Somerset Road pond was very effective at removing suspended solids throughout the sampling period, with the majority of suspended solid removal occurring in the forebay as it typically did not become full enough to overflow into the main pond. When the forebay was full of water, the PAC dosing system resulted in large reductions in suspended solid levels over a short horizontal distance within the forebay. A smaller amount of suspended solid reduction was achieved in the main pond, predominately through dilution, with the major function of the main pond being additional storage capacity for runoff. Discharge from the Somerset Road Pond was not continuous due to low water levels in the main pond. However, when discharge did occur, the suspended solids levels were very low compared with other studies investigating sediment retention pond discharge. The Richardson Road pond was less effective at removing suspended solids due to the flow regime within the forebay. There were two runoff channels entering the forebay, as well as a continual flow of groundwater. Only one of the runoff channels was directly dosed with PAC, and as the water level in the forebay was typically at, or just below, the level spreader at all times, there was a decreased potential for the PAC to become evenly distributed through the forebay and achieve dosing of all runoff. Furthermore, the main pond discharged continuously during the study period, resulting in reduced residence times of runoff within the pond system. Nonetheless, the discharge from the main pond was much lower than other studies, implying suspended solid reduction was being achieved. The SEV method indicated that the receiving environment was already degraded due to modifications to the riparian vegetation, increased dissolved oxygen demand, and moderate bank erosion. This was reflected in the macroinvertebrate population, with only pollution tolerant taxa being collected, thus limiting the use of macroinvertebrates as an assessment tool in this study. However, the SEV method, which assesses a wide range of ecological functions, implied that very little environmental change occurred as a result of the sediment retention pond discharge. A small increase in deposited sediment was observed on the stream bed, however indications are that deposited sediment is rapidly washed away once earthworks are completed. Thus this deposited sediment may not have a permanent impact within the receiving environment.

ABSTRACT The mortalities for aquaculture animals in a newly established pond tend to be high. The phenomenon can be described as the ¡§new pond syndrome¡¨. The main reason for the phenomenon is still unclear. However, it is suspected that the accumulation of ammonia due to insufficient nitrifying bacteria in the system may have been the cause. The purposes of this thesis are to test the theory and to rectify the problem by introducing a nitrifying trickling filtration system using E. amblycephalus as the experimental animal. It was found that the ammonia concentrations did increase to the levels detrimental to the newly hatched fries within 6 days. The LD50 of ammonia to the young fries was determined to be 0.034 ppm in 48 hr. The nitrifying filtration system could reduce the ammonia concentrations substantially and raise the breeding rates for the fries. On two separate trials, one with fish tanks in the laboratory and the other in the ponds of a fish farm, 12.3% and 4.2% of the newly hatched fries were still alive after 34 days, respectively, as compared to 0% and 0.035% for the controls. Meanwhile, a pH value of equal to or greater than 8.6 was detrimental to the fries. Therefore, the low breeding rates for the E. amblycephalus fries may have been caused by the ¡§new pond syndrome¡¨ due to the toxic effects of accumulated ammonia in the early stage of the pond usage. Removal of ammonia with the filtration system could increase the survival rates for the fries.

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Civil and Environmental Engineering." Includes bibliographical references (p. 259-263).