Thesis (M.S.)--University of Kerala. / "Issued as a special number of the Bulletin of the Department [of Marine Biology and Oceanography of the University of Kerala]" Bibliography: p. 53-68.

No description available.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1956. / Typescript. Abstracted in Dissertation abstracts, v. 16 (1956) no. 5, p. 1022. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 188-193).

Thesis (Ph. D.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 119-131). Also available on the World Wide Web.

No description available.

Suspension-feeding bivalves produce biodeposits (faeces and pseudofaeces) that have much higher sinking velocities than their constituent particles. Consequently they cause sedimentation of material that might otherwise not be deposited. The benthic remineralisation of biodeposits increases sediment oxygen demand and nutrient regeneration, thus enhancing the benthic-pelagic coupling of nearshore ecosystems. In New Zealand the mussel Perna canaliculus has a high natural abundance and is also intensively cultured. This thesis examines the dispersal and remineralisation characteristics of mussel P. canaliculus biodeposits and the impacts of sedimentation from a mussel farm in the Firth of Thames on sediment biogeochemistry by combining laboratory, field and modelling studies. Dispersal characteristics were examined in the laboratory by measuring sinking velocities and erosion thresholds of biodeposits produced by mussels of a wide size range fed three experimental diets. The results show that biodeposit dispersal is a function of mussel diet and size and thus could differ significantly between locations and seasons. Estimates of dispersal distances based on these results demonstrated that the initial dispersal of biodeposits produced by cultured mussels is not far. Depending on the hydrodynamic conditions, secondary dispersal via resuspension potentially plays a more important role in the dispersal of biodeposits from mussel farms than initial dispersal and almost certainly serves as the major means of transport of biodeposits from natural mussel beds. Biodeposit mineralisation was studied by incubating coastal sediments with added biodeposits and measuring oxygen and nutrient fluxes as well as sediment characteristics over an 11 d period. Sediment oxygen consumption and ammonium release increased immediately after biodeposit addition and remained elevated compared to control cores without additions for the incubation period. A biodeposit decay rate (0.16 d-1) was calculated by fitting a first-order G model to the observed increase in oxygen consumption. This rate is 1 - 2 orders of magnitude higher than published decay rates of coastal sediments without organic enrichment or plant material. Nutrient fluxes during the incubation period illustrated that biodeposit remineralisation alters the stoichiometry of the nutrients released from the sediments which may potentially be more significant than the changes of the individual fluxes. To determine the impact of a mussel farm in the Firth of Thames I measured sediment oxygen and nutrient fluxes by deploying benthic chambers, sediment characteristics by collecting sediment cores and sedimentation rates by deploying sediment traps in four seasons. Oxygen consumption and sediment nutrient release rates were generally higher under the farm compared to a reference site, demonstrating the typical response to increased organic input. Unusually low nitrogen release rates measured in summer may indicate enhanced denitrification under the farm. A simple budget demonstrated the importance of benthic nutrient regeneration in maintaining primary production in this region and that mussel culture can lead to a redistribution of nutrients. This study showed that site-specific hydrodynamic and biogeochemical conditions have to be taken into account when planning new mussel farms to prevent excessive modifications of nutrient dynamics. Results of the laboratory and field studies conducted in this thesis were used to parameterise, calibrate and validate models of mussel biodeposit dispersal and remineralisation. A particle tracking model showed that the maximum initial dispersal of faecal pellets from the mussel farm is approximately 300 m and that pellets can be transported several times this distance via resuspension. The remineralisation model was able to simulate the increased nitrogen fluxes from the sediments well and highlighted the need for thorough calibration and parameterisation of the model. This thesis contributed to the current understanding of the ecosystem impacts of mussel culture and provided numerical models and model parameters that will assist in the assessment of mussel culture sustainability and the contribution of mussels to the nutrient cycling in nearshore ecosystems.

Live juvenile cobia (Rachycentron canadum) transport methods were examined to determine opportunities for increasing packing density in closed containers for temporal durations up to 24 hours. Juvenile cobia (27 to 46 days-post-hatch (dph)) were tested for salinity tolerance following abrupt transfer from 35 ppt salinity water to salinities ranging from 0 ppt to 55 ppt. Results indicate a wide range of tolerance, with 100% survival at 24 hours post-transfer in salinities between 11 ppt and 45 ppt. Salinity preference was also tested to determine a possible correlation between acclimation salinity and salinity preference using an experimental horizontal salinity gradient with juvenile cobia (87 dph) over a period of 24 hours. Results of the salinity preference trials showed that salinity preference was directly related to acclimation salinity. Using two different salinities within the range tested in the tolerance trials (12 ppt and 32 ppt), a 24 hour simulated shipping trial was conducted comparing final survival between the two salinities at each of four packing densities (5 kg/m3, 10 kg/m3, 15 kg/m3, and 20 kg/m3). Results indicated a significant relationship between salinity and stocking density on survival of juvenile cobia following a 24 hour simulated shipment. At packing densities above 10 kg/m3, survival was significantly higher in the low salinity (12 ppt) treatments as compared to survival rates in the higher salinity (32 ppt) treatments. To help aquaculture professionals make accurate and economical decisions regarding the shipment of live juvenile cobia in closed containers, a bioeconomic model was constructed using survival data at different packing densities (1 kg/m3 to 20 kg/m3) and salinities (12 ppt and 32 ppt) obtained in the experimental trials combined with shipping cost and fingerling price data. The resulting model enables cobia fingerling producers to optimize their shipping methods and protocols, allowing for reductions in labor and material costs.

No description available.

Knowledge of mercury concentrations in fish is essential for human health protection. Mercury is a naturally occurring element that acts as a neurotoxin to humans and other species. The biologically available mercury form, methylmercury (MeHg), bio accumulates from small benthic invertebrates to large pelagic fish, and therefore high end consumers and terminal predators have elevated Hg concentrations. The main pathway of MeHg exposure in humans is by consumption of contaminated fish. In this study total Hg concentrations were measured in 10 Gulf of Mexico pelagic fish species using a DMA 80 analyzer. Total Hg concentrations ranged from 0.004 to 3.55 ppm (wet wt). The highest mean concentration (1.04 ppm, wet wt) recorded in king mackerel (Scomberomorus cavalla) exceeded FDA recommended criteria of 1ppm. Dolphinfish (Coryphaena hippurus) and vermilion snapper (Rhomboplites aurorubens) had lowest mean Hg concentrations (<0.3 ppm). The rest of the species were above the EPA advisory level of 0.3 ppm. Wahoo (Acanthocybium solandri), greater amberjack (Seriola dumerili) and gag grouper (Mysteroperca microlepsis) had high Hg concentrations of approximately 0.7 ppm wet wt. Blackfin tuna (Thunnus atlanticus) and yellowfin tuna (Thunnus albacores) had moderate Hg concentrations (0.39 and 0.36 ppm wet wt respectively). Little tunny (Euthynnus alletteratus) and blacktip shark (Carcharhinus limbatus) had mean concentrations of 0.69 and 0.51 ppm respectively. The relationship between fish length and Hg concentrations was significant for four species.

Magister Scientiae (Biodiversity and Conservation Biology) / 2022-01-31