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Common Carp, (Cyprinus carpio), have long been associated with the degradation of wetlands worldwide. Through their feeding activities they resuspend sediments leading to reductions in the abundance and diversity of submerged macrophytes, and the alteration of water chemistry which can lead to the phytoplankton-dominated state. This study took in Delta Marsh, a freshwater coastal wetland of Lake Manitoba, in Manitoba, Canada. It was the second part of a four-year study in which baseline data were collected in 2001 from ten ponds (1-13 ha) with varying degrees of connectivity to the main marsh and carp-accessibility. I continued to monitor a subset of the control and altered ponds two and three years following their alteration (2003 and 2004); I included new ponds, including one large open bay (20.3 ha). The overall four-year study has shown that the presence of carp is at least partially responsible for the turbid, phytoplankton-dominated state that exists in Delta Marsh, and that carp abundance is an important factor. Ponds previously isolated then exposed to carp activity, particularly in the spring when they were gathered at high densities, shifted to the turbid, phytoplankton-dominated state with few macrophytes, and the removal of carp from ponds led to the clear-water state, though not necessarily an abundance of macrophytes. Due to the complexity of natural ecosystems, the effects of carp were not as predictable as smaller-scale studies would suggest. In my study, water quality, submerged vegetation biomass and algal growth varied both temporally and spatially in carp-accessible and carp-free ponds. Nutrient deficiency among periphyton assemblages was hypothesized to be alleviated by the presence of carp. Using nutrient diffusing substrata, I found that nutrient deficiencies varied from year to year among carp-free and carp-accessible ponds. In 2003 the hypothesis was supported, however, in 2004 two of the carp-free ponds exhibited no-nutrient limitations to periphyton assemblages while N and P co-limitation became prevalent in one carp-accessible pond. Parameters over which there was no control, such as the spatial and temporal distribution of carp, their density within a pond, water depth and unquantified top-down effects, including zooplankton grazing, may have contributed to the variability of the results.

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Invasive Silver Carp (Hypophthalmichthys molitrix) have spread throughout the Mississippi River basin and threaten native species. The Lower Mississippi Alluvial Valley has numerous water-control structures. These structures could potentially be operated to limit expansions of invasive fishes. My goal was to examine the effects of two water-control structures on movements of Silver Carp within a floodplain network of waterbodies, including an oxbow lake (Eagle Lake; LA, MS). I monitored Silver Carp movements with an acoustic array and bi-monthly active tracking. No movements occurred through the structure managed to deter carp while nine carp passed through the structure that is not managed to limit carp movements. The passages happened when i) the structure was opened, ii) hydraulic head was near zero, and iii) when Silver Carp are reportedly staging and spawning. Ultimately, my findings could help managers tailor operations of similar water infrastructure to slow the spread of invasive species.

This study reports on investigation of ways of improving the breeding programme for growth-related traits in common carp in Vietnam. The base population was synthesized following a single pair mating scheme from six carp stocks: (1) 2nd generation of family selection; (2) Hungarian 6th generation of mass selection; (3) Hungarian scaled carp; (4) Indonesian yellow 6th generation of mass selection; (5) Indonesian yellow carp; and (6) Vietnamese 6th generation of mass selection. The next two selected generations were produced using a partial factorial mating scheme, with each family being split and reared using communal early rearing (CER) or separate early rearing (SER) methods. The second generation (G2) was produced from selected fish from the CER G1 group. The total number of selection, control and reference families was 135 in the G1 and 101 in the G2 respectively. The control and reference (Hungarian P33 line) families were produced by single pair mating (reference families with the G2 only). Seven microsatellite loci were used for parentage assignment in the CER groups: 96.8% of the offspring (1284 individuals) and 96.2% offspring (1341 individuals) were unambiguously assigned to 113 families (selection, control) in the G1 and 99 families (selection, control and reference) in the G2 generations, respectively. Restricted maximum likelihood in the individual model was used to estimate phenotypic and genetic parameters. In CER, the estimated heritability values of common carp were from 0.20 ± 0.04 to 0.29 ± 0.05 for both weight and length at final harvest, indicating substantial additive genetic variation for selection on growth-related traits. The overall obtained maternal and common environmental effects were consistently close to zero. The average of direct response to selection for body weight was 15.0% per generation. In SER, the number of families in the G1 and G2 were 135 (selection and control) and 101 (selection, control and reference), respectively. The heritability estimates were from 0.20 ± 0.07 to 0.31 ± 0.08 at final measurement. Common environmental (full-sib family) effect were all lower at tagging and slightly higher at last measurement, ranging from 0.05 to 0.22. The response in each generation of selection as the difference between the selection and control lines was 8.1% on average for weight at final harvest, lower than under CER. The high genetic correlations of growth-related traits between the third (one year old, mature) and second (7 months old) measurements could allow selection to be based on the earlier assessment, reducing handling stress close to spawning. The benefits of using microsatellite markers to ascertain parentage, achieve greater growth rate (close to farming systems), shorten time to maturity and selection, and the overall relative merits of using CER v’s SER in this genetic improvement programme are discussed.

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published_or_final_version / Zoology / Master / Master of Science

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No description available.