Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 89-92). Also available via the Internet.

The research demonstrated that an easily cultivated fungus was screened from filter materials of fresh water recycle aquaculture system. A fungus, characterized as being able to remediate multiple nitrogenous wastes, was identified as Aspergillus niger NBG5. A. niger NBG5 was developed as superior fungus through bioreactor so as to establish a nitrogenous removal system of single tank stirred tank reactor (SSTR). A. niger NBG5¡¦s remediative responses were tested under various temperatures. The experiment showed that specific nitrogen consumption rate was 0.047 g-N g-cell-1 day-1 at 30¢J which were better than nitrite nitrogen and protein nitrogen consumption. When the artificial wastes¡¦ ammonium concentration was set as 50 mg L-1, its ammonium consumption rate was 4.8 mg m-2 day-1. The ammonium consumption rate reached 0.32 mg m-2 day-1 with aquaculture wastes. The result revealed that SSTR removed nitrogen from aquaculture wastes by A. niger NBG5 and achieved a purpose of decreasing ammonium within aquaculture wastes. The research simulated ammonium variable numerals between SSTR and BSTR (the system of bi-tank stirred tank reactor). Through BSTR, regression formula with water flow rate and ammonium removal efficiency rate was y = 5.7219x-0.9616 when the ammonium concentration was set as 50 mg L-1. SSTR simulated a phenomenon¡Xthe more ammonium concentration aquaculture wastes reached, the much waste water volume of aquaculture tank it had. Based on the same requirements, a better water flow rate would be concluded through various water flow rate simulation tests. SSTR numerical simulation system could simulate ammonium production rate of fish tank to get consumption trends of ammonium concentration in fish tank and reactor. The simulation results would be able to decide later system design, water flow rate, feed timing and similar research references.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 134-143). Also available via the Internet.

Thesis (Ph.D.)--University of Washington, 1994. / Vita. Includes bibliographical references (leaves [62]-65).

Mémoire (M. Sc.)-- Université du Québec à Chicoutimi, 1985. / Bibliogr.: f. 99-102. Document électronique également accessible en format PDF. CaQCU

Mémoire (M.P.aquat.)-- Université du Québec à Chicoutimi, 1992. / Bibliogr.: f. 97-101. Document électronique également accessible en format PDF. CaQCU

Long-lining is a frequently used method in marine fisheries. Similarly to trawling and nets, also long-lining is associated with bycatch which may have negative impacts on the ecosystems. However, different methods of long-lining may vary in the amount and ratio of bycatch but methods have rarely been compared directly. This study investigates whether the fishing method of floated demersal longlining baited with live Pacific Anchoveta (Cetengraulis mysticetus) has a lower bycatch ratio or bycatch amount than using demersal long lines baited with filet pieces of dead fish. The study was carried out in collaboration with artisanal small-scale fishermen in the Paquera area of the Gulf of Nicoya in Costa Rica. Six efforts were made in February of 2023, and were then compared to dead bait data from the same area from 2015 and 2016 collected by Universidad Nacional de Costa Rica. This comparison showed no significant difference between the two methods in bycatch ratio but showed that live bait longlining captures significantly more total fish and bycatch per catch per unit effort (CPUE). There are also ethical issues and issues with bait fish acquirement that points against live bait fishing. However, there are certain arguments in support of the method, such as broadening the exploitation strain across more species and not hindering financially struggling artisanal fishermen further.

Eight identical and independent pilot scale recirculating aquaculture production systems were populated with fingerling hybrid striped bass <i>(Morone chrysops</i> female x <i>Morone saxatilis male</i>). Three population densities were established with two replicates at 132 fishlm3 and three replicates each at 66 and 33 fishlm3. Water chemistry and water quality characteristics were monitored throughout the 228 day growth trial for all eight systems. A system component performance analysis was done for both the multi-tube solids clarifier and rotating biological contactor (RBC). Water chemistry and water quality analysis included dissolved oxygen (DO), alkalinity, ions, carbonaceous biochemical oxygen demand (CBODS), chemical oxygen demand (COD), dissolved organic carbon (DOC), total suspended solids (TSS), volatile suspended solids (VSS), total ammonia nitrogen (TAN) , nitrite and nitrate. The major ions present were chloride, nitrate, sulfate, phosphate, sodium, calcium, magnesium and potassium. Trace levels of TAN, nitrite, iron and copper were also observed. Sodium, calcium and chloride levels were controlled based on a preplaned water exchange and chemical management method. TAN, nitrite and nitrate levels increased over time with increasing feed rates but never reached levels toxic to the fish population. CBODS,COD, DOC, TSS and VSS increased over time increasing as a function of increasing feed rates. No correlation was observed between fish mortality or fish growth rates for the range of organic and solids parameters observed during this study. On average 67% of the TSS present was between 1.5 and 30 microns in size. Diurnal cycles were observed for DO, TAN and alkalinity. The magnitude of these cycles were population dependent. Multi-tube clarifiers removed an average 56% of all suspended solids in a single pass with 81 % removal efficiency for particles above 70 microns in size. Analysis of the system effluent generated by the clarifier indicates a high degree of similarity between the aquaculture effluent and standard municipal waste on a nutrient basis but with much higher levels of nitrogen and phosphate species. RBC nitrification performance was fitted to an empirical equation. A nearly constant TAN removal rate was observed over the range of mass loading experienced in this growth trial. This implies that within a reasonable range higher flow rates resulting in higher mass loading will yield higher TAN removal rates for a given RBC. / Master of Science

Aquaculture is of growing importance in the global seafood production. The environmental impact of aquaculture will largely depend on the type of environment in which the aquaculture system is placed. Sometimes, due to the abiotic or biotic conditions of the seascape, certain aquaculture systems tend to be placed within or near specific ecosystems, a phenomenon that in this thesis is referred to as aquaculture system - ecosystem links. The exposed ecosystems can be more or less sensitive to the system specific impacts. Some links are known to be widespread and especially hazardous for the subjected ecosystem such as the one between the shrimp aquaculture and the mangrove forest ecosystem. The aim of this thesis was to identify and investigate causes and consequences of other spatial links between aquaculture and ecosystems in the tropical seascape. Two different aquaculture system - ecosystem links were identified by using high resolution satellite maps and coastal habitat maps; the link between sea cage aquaculture and coral reefs, and the one between seaweed farms and seagrass beds. This was followed by interviews with the sea cage- and seaweed farmers to find the drivers behind the farm site selection. Many seaweed farmers actively choose to establish their farms on sea grass beds but sea cage farmers did not consider coral reefs when choosing location for their farms. The investigated environmental consequences of the spatial link between sea cage aquaculture and coral reefs were considerable both on the local coral reef structure, and coral associated bacterial community. Furthermore, coral reef associated fish are used as seedlings and feed on the farms, which likely alter the coral food web and lower the ecosystem resilience. Unregulated use of last resort antibiotics in both fish- and lobster farms were also found to be a wide spread practice within the sea cage aquaculture system, suggesting a high risk for development of antibiotic resistant bacteria. The effects of seaweed farms on seagrass beds were not studied in this thesis but have earlier been shown to be rather substantial within the borders of the farm but less so outside the farm. Further, a nomenclature is presented to facilitate the discussion about production system - ecosystem links, which may also be used to be able to incorporate the landscape level within eco-certifying schemes or environmental risk assessments. Finally - increased awareness of the mechanisms that link specific aquaculture to specific habitats, would improve management practices and increase sustainability of an important and still growing food producing sector - the marine aquaculture. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.</p>

Thesis (M. A. (Aquaculture )) -- University of Limpopo, 2006 / Refer to document / NRF (National Research Foundation) and Canon Collins Educational Trust for Southern Africa (CCETSA)