Biology Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2749
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Item TOOL DEVELOPMENT TO CONSTRAIN AND OPTIMIZE SHELLFISH AQUACULTURE GEAR PERFORMANCE(2022) Campbell, Brendan; Gray, Matthew W; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)To produce virginica cultured Crassostrea more efficiently, current grow out techniques require better understanding to allow for more consistent growth and quality. While the basic physical conditions that influence shellfish growth have been well researched, there are limited studies that consider how physical conditions (i.e. water flow and wave motion) influence shellfish growth within the context of an off-bottom aquaculture farm. Since oysters are suspension feeders, they require food to be delivered to their siphons through ambient processes. Changes in water flow can influence the overall survival, growth rate, and quality of oysters. Additionally, the motion, or jostling, of cages are thought to cause chipping on the outer portion of oyster shells, influencing the overall shape and growth of oysters. There are many techniques and equipment that have the potential to influence the water delivery and movement of oysters in containerized culture; however, little research has addressed how culture practices influence physical forcing surrounding cultured oysters and what impact those changes have on oyster performance. The biophysical relationship occurring in shellfish aquaculture is not being properly characterized partially due to a lack of affordable tools capable of monitoring physical forces in constrained spaces. This dissertation summarizes the current understanding of how culture practices influence oyster aquaculture production and demonstrates the novel use of affordable and commonly available tools that can be utilized in shellfish aquaculture research across multiple operational scales. The development of a novel clod card method and predictive model was attempted for use in characterizing mass transfer rate of water. The clod card, along with accelerometer loggers were utilized to understand the effects of physical forcing on the production of off-bottom cultured oysters when exposed to a range of biofouling mitigation treatments, grown using different culture methods, and spatially across an active shellfish aquaculture lease. These experiments validated the value in characterizing physical forcing in shellfish aquaculture and identified trade-offs between oyster shell growth and market quality that are linked to changes in the physical environment, which were produced by changing culture practices. Additionally, these validation experiments determined that variability in oyster growth and performance can change over small spatial scales, smaller than the typical grow-out shellfish aquaculture lease, which can influence water movement inside cages, water quality, and the efficiency of a commercial shellfish operation. By considering the local physical environment, growers can strategically employ culture practices that optimize the water flow through and movement of oysters to enhance farm profitability.Item Optimizing desiccation as a biofouling control strategy for water-column cultured oysters, Crassostrea virginica, in the Chesapeake Bay(2022) Hood, Shannon Marie; Plough, Louis V; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Oyster aquaculture is flourishing in the US and internationally, delivering wide-ranging benefits to coastal communities, economies, and ecosystems. While the oyster aquaculture industry has grown substantially, a number of ongoing challenges limit industry growth. The issue of biofouling is paramount among these impediments to industry growth and farmers employ a range of techniques for biofouling control, including chemical immersion, physical methods, paints or coatings, and biological control methods. Desiccation, or the periodic aerial exposure of oysters and cages, is a popular biofouling control strategy and previous research has demonstrated the effectiveness of 24 consecutive hours of desiccation at a weekly frequency (compared to 24 hours bi-weekly, monthly, or seasonally), but this treatment has yielded a growth penalty in addition to biofouling control. The optimal interval (duration) of desiccation has not been thoroughly investigated and shorter intervals applied at a weekly frequency may yield different results. Therefore, this dissertation set out to investigate the effects of multiple weekly desiccation intervals (0-, 4-, 8-, and 24-hours) on eastern oyster (Crassostrea virginica) production and biofouling control. In Chapter 2, I examined responses of the biofouling community and oysters to three weekly desiccation intervals (0-, 8-, and 24-hours) at three commercial oyster farms in the Chesapeake Bay over 4 months. In Chapter 3, I conducted longer term (7 month) monitoring of the response of the biofouling community and oysters to four weekly desiccation intervals (0-, 4-, 8-, and 24-hours) at a single site in the Choptank River. In Chapter 4, I examined molecular (heat shock protein expression) and physiological (filtering rate, gametogenic stage, glycogen content) responses of oysters to four weekly desiccation intervals (0-, 4-, 8-, and 24-hours) in the Choptank River over 3 months. Results indicate broad-scale effectiveness of all desiccation treatments in reducing total biofouling coverage, although species- and site-specific responses were observed. Oyster growth was inconsistently affected by desiccation treatment, but reduced growth was observed in the 8- and 24-hour treatments in two of the three years of field investigations, perhaps influenced by reduced time spent in the water feeding and a delay in the onset of filtering post-desiccation. However, the timing of the greatest reduction in growth rates with desiccation suggests that concomitant stress of desiccation plus gametogenesis may have elevated the oysters’ stress response (reduced growth). Indeed, gametogenic stage and glycogen content were influenced by desiccation interval and oysters in the 24-hour treatment were the most likely to spawn. A high-level stress response via the upregulation of heat shock proteins (HSPs) was absent in oysters from the 8- and 24-hour treatments, indicating depressed HSP expression (and cellular protection) among the most stressed oysters. Future research into the importance of environmental factors during desiccation (air temperature, wind, humidity, etc.) could yield useful information to allow oyster farmers to target desiccation during optimal conditions, potentially limiting oyster exposure time in order to minimize oyster stress. Fouling reduction was significant in all treatments (4-, 8-, and 24-hour) and most consistent in the longer (8- and 24-hour) treatments. Therefore, a tradeoff is present between biofouling control and yield. Farmers prioritizing minimal biofouling may opt to desiccate for 8 or 24 hours weekly, while farmers seeking to maximize growth rates and minimize oyster stress may opt to desiccate for 4 hours weekly. Individual farmers must consider their own preferences regarding suitability of this husbandry technique, but results suggest that desiccation is an effective approach to biofouling control and can be applied with minimal stress to the oysters.Item MORTALITY AND REOVIRUS INFECTION IN SOFT-SHELL BLUE CRAB (CALLINECTES SAPIDUS) AQUACULTURE(2019) Spitznagel, Matthew Isaac; Schott, Eric J; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Soft-shell blue crab production the United States is an undervalued aquaculture practice experiencing high crab mortality rates from a series of stressors, including disease. The impact of one disease, the reovirus CsRV1, remains unquantified in major soft-shell crab production regions, despite the virus’ known ubiquity and lethality. My research examined the mortality and CsRV1 infection rates of pre- and post-production crabs in Maryland, Virginia, and Louisiana soft-shell crab production facilities in 2016-2017, attempting to link these rates to water quality and aquaculture practice variables. I found that recirculating aquaculture systems lost half the proportion of crabs (16%) that flow-through systems did (33%). CsRV1 infection was the primary predictor of crab death in Chesapeake aquaculture, presenting in 75% of dead crabs compared to 22% of dead crabs in Louisiana aquaculture. Multi-state data suggests crab losses worth over $2 million are attributable to CsRV1, indicating a need for aquaculture effluent and discard control.Item The effect of aquaculture gear and tidal zone on the growth and shape of the oyster Crassostrea virginica during a “finishing period” in Chesapeake Bay.(2016) Thomas, Laura Landis; Plough, Louis V; Cornwell, Jeffrey C; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This study investigated how aquaculture gear type and increased wave action influenced growth and shape of eastern oysters Crassostrea virginica during a “finishing” period in Chesapeake Bay. Oysters were deployed in three different gear treatments in the intertidal or upper water column: bottom cages, OysterGro™ floats, and rack and bag, and a bottom cage was also deployed in the subtidal zone as an industry control. Shell length(L), width(W), height(H), total weight and wet meat weight were measured each month from August to December 2015 and an index of shell shape (deviation of L-W-H from idealized 3-2-1 ratio) calculated. OysterGro™ floats produced the greatest increase in wet and total weight and the most ideal shaped oysters (lowest 3-2-1 ratio deviation). Overall, these results demonstrate the benefit of deploying oysters in higher wave action gear types such as the OysterGro™ and will increase the available data on gear performance in Chesapeake Bay.Item Taurine: An Indispensable Ingredient in the Development of Sustainable Aquafeeds(2013) Watson, Aaron Mackenzie; Place, Allen R.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Aquaculture as a global industry is at a crossroad; increased production cannot rely on the unsustainable harvest of forage fish for feed production. The use of fishmeal and fish oil as components in feeds for aquaculture, most notably for high value marine carnivores must be reduced or eliminated. The most promising and sustainable sources of replacement feed must be plant derived, such as soybean meal, wheat flour, and corn gluten along with dozens of other plant derived sources. Likewise for fish oil the most promising sources are plant oils such as soybean and canola oil supplemented with necessary omega-3 fatty acids. This work was undertaken to examine the effects of switching marine carnivores from fishmeal-based feeds to fishmeal-free, plant-based diets. The majority of this research has been conducted with cobia, Rachycentron canadum, a promising species for intensive aquaculture due to its rapid growth rates, high disease resistance, and lack of a major commercial fishery as competition. A variety of plant proteins, plant protein blends and alternative lipid sources were examined for digestibility and efficacy as fishmeal replacement sources in regards to their effects on growth rates, feed conversion, and a range of physiological characteristics. This work has explored the hypothesis that marine carnivores have lost the ability to synthesize taurine, a non-protein amino acid, in sufficient quantities and must therefore be supplied through the diet, and should be considered essential for all marine carnivores. By measurement of gene expression of the genes in taurine biosynthesis, this work shows that cobia do not possess the ability to regulate taurine biosynthesis confirming taurine must be supplied through the diet. Overall, this work has developed multiple plant protein-based feeds that perform equivalently or better than commercial and commercial-like diets. Taurine has been shown to be an essential ingredient when seeking to reduce or preferably, eliminate fishmeal and thereby making aquaculture sustainable in providing protein to meet the world's growing population.Item Hepatic Phase I and II Biotransformation Kinetics in Fishes: A Comparative Study(2006-12-04) Gonzalez, Jaime Fernando; Kane, Andrew S; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Eight finfish species were selected to test the similarities and dissimilarities on their phase I and II biotransformation capabilities using microsomal and cytosolic fractions of the liver. This research had three main objectives: 1) a comparison among the kinetics of the 8 species using model substrates, 2) farm-raised and laboratory-acclimated specimens of channel catfish, rainbow trout and tilapia were compared to determine similarities and differences in the biotransformation reactions, and 3) the same latter three species were tested to compare in vitro hepatic metabolism of albendazole, a drug that undergoes metabolic biotransformation mainly through hepatic phase I reactions. The comparison among the 8 finfish species showed that some of them had higher biotransformation capabilities than others. For most of the seven phase I- II reactions that were tested; rainbow trout, tilapia, channel catfish and Atlantic salmon had higher enzymatic efficiencies than those showed by of striped bass, hybrid striped bass and bluegill. Largemouth bass shared some enzymatic capabilities with one group or the other. The comparison between lab-acclimated and farm-raised specimens of tilapia, channel catfish and rainbow trout did not show biologically significant differences among the two groups of fish for the 3 species. All the values found for the kinetics of the reactions were within the ranges of the constitutive expression that has been reported for them and far below those found in other works when inducers (e.g. pollutants) of enzymatic reactions have been used. The phase I-mediated hepatic sulfoxidation of albendazole in tilapia, channel catfish and rainbow trout showed significant differences in Vmax and Km values among the three species. However, the catalytic efficacies of the reaction (Vmax/Km) in the 3 species transforming the parent compound were similar. In addition, albendazole induced EROD activity (2.6 fold) in in vivo dosed channel catfish. The results found in the present study showed that the catalytic efficiency of hepatic phase I-II enzymatic reactions varied among finfish species. Some of them may be categorized as "more efficient metabolizers" than others. This may have important implications in drug metabolism and residue depletion patterns.