Physiological and Biochemical Changes in Condition and Scope for Growth in Response to Changes in Food Availability in Selectively Bred Families of Flat Oyster (Ostrea chilensis)

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dc.contributor.advisor Hilton, Z en
dc.contributor.advisor Dunphy, BJ en Crossan, Celia en 2016-09-06T22:28:22Z en 2016 en
dc.identifier.uri en
dc.description Full text is available to authenticated members of The University of Auckland only. en
dc.description.abstract Ostrea chilensis is a flat oyster species native to both the Pacific Coast of South America and New Zealand. This species has been commercially fished in the Foveaux Strait and Nelson/Marlborough area from the 1850’s, currently generating more than $23 million per year. However, overfishing and parasite outbreaks have greatly reduced wild production. Thus, aquaculture of O. chilensis represents a prime economic opportunity, and production of this species is currently carried out in Stewart Island and in the Marlborough Sounds. However, within the Marlborough Sounds, mortality levels of cultured O. chilensis are consistently highest in late summer following a spawning peak. Causative agents of this mortality are unclear. A warmer water temperature increases physiological rates which in turn increases energy demand. Primary production can be dependent on nutrient input from freshwater run-off, which in late summer is reduced, and unable to meet this demand. Thus, the aim of this thesis was to investigate the effect of food quantity on the condition of O. chilensis exposed to a putatively stressful summer water temperature in order to establish whether food limitation may be causing physiological stress and contributing to post-spawning mortality. Comparisons were also made among various selectively bred families in order to potentially identify families that are better able to withstand nutrient and temperature stress. Clearance rate, absorption efficiency and metabolic rates were measured in order to calculate the scope for growth in oysters exposed to a water temperature of 20 °C in combination with various algae cell concentrations. Simple gravimetric and visual (subjective) condition measures, as well as biochemical (protein, lipid and carbohydrate) assessment were also used to assess these same oysters, and to compare condition with oysters freshly obtained from the farm site. Results revealed a decline in scope for growth at the highest cell concentration. In general, the other condition measures used showed an improvement in condition as algal cell concentration increased. Examination of the separate components of the scope for growth equation indicated that the absorption rate was low at high food concentrations. This may be explained by saturation of the digestive tract, resulting in a lower absorption rate while in fact condition was positive. This highlights the importance of using multiple condition measures concurrently to gain a thorough understanding of response to different environmental conditions. Large inter-individual variation resulted in no significant differences between families in any of the condition measures. Further investigations using larger sample sizes or longer term trials may be required for any significant differences to become apparent. Scope for growth was more positive under low food environments, suggesting that nutritive stress is not a significant factor in post-spawning mortality. Future research should focus on other potential contributors to late summer mortality, for example warmer water temperature, or infection from parasites such as Bonamia ostreae which has recently been detected in New Zealand populations for the first time. en
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof Masters Thesis - University of Auckland en
dc.relation.isreferencedby UoA99264870293102091 en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. Previously published items are made available in accordance with the copyright policy of the publisher. en
dc.rights Restricted Item. Available to authenticated members of The University of Auckland. en
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dc.title Physiological and Biochemical Changes in Condition and Scope for Growth in Response to Changes in Food Availability in Selectively Bred Families of Flat Oyster (Ostrea chilensis) en
dc.type Thesis en Biological Sciences en The University of Auckland en Masters en
dc.rights.holder Copyright: The author en
pubs.elements-id 540828 en
pubs.record-created-at-source-date 2016-09-07 en

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