title: Characterising the Physiological Responses of Chinook Salmon (Oncorhynchus tshawytscha) Subjected to Heat and Oxygen Stress.

authors: Marcoli, Roberta

subjects: Chinook salmon

abstract: In New Zealand, during the hottest periods of the year, some salmon farms in the Marlborough Sounds reach water temperatures above the optimal range for Chinook salmon. High levels of mortality are recorded during these periods, emphasising the importance of understanding thermal stress in this species. In this study, the responses of Chinook salmon (Oncorhynchus tshawytscha) to chronic, long-term changes in temperature and dissolved oxygen were investigated. This is a unique investigation due to the duration of the stress events the fish were exposed to. Health and haematological parameters were analysed alongside gene expression results to determine the effects of thermal stress on Chinook salmon. Six copies of heat shock protein 90 (HSP90) were discovered and characterised: HSP90AA1.1a, HSP90AA1.2a, HSP90AA1.1b, HSP90AA1.2b, HSP90AB1a and HSP90AB1b, as well as two copies of SOD1, named SOD1a and SOD1b. The amino acid sequences contained features similar to those found in other vertebrate HSP90 and SOD1 sequences, and the phylogenetic tree and synteny analysis provided conclusive evidence of their relationship to other vertebrate HSP90 and SOD1 genes. Primers were designed for qPCR to enable the expression of all copies of HSP90 and SOD1 to be analysed. The expression studies showed that HSP90 and SOD1 were downregulated in the liver and spleen in response to longer term exposure to high temperatures and lower dissolved oxygen. HSP90 was also downregulated in the gill; however, the results for SOD1 expression in the gill were not conclusive. This study provides important insights into the physiological and genetic responses of Chinook salmon to temperature and oxygen stress, which are critical for developing sustainable fish aquaculture in an era of changing global climates.

text: Characterising the Physiological Responses of Chinook Salmon (Oncorhynchus tshawytscha) Subjected to Heat and Oxygen Stress. In New Zealand, during the hottest periods of the year, some salmon farms in the Marlborough Sounds reach water temperatures above the optimal range for Chinook salmon. High levels of mortality are recorded during these periods, emphasising the importance of understanding thermal stress in this species. In this study, the responses of Chinook salmon (Oncorhynchus tshawytscha) to chronic, long-term changes in temperature and dissolved oxygen were investigated. This is a unique investigation due to the duration of the stress events the fish were exposed to. Health and haematological parameters were analysed alongside gene expression results to determine the effects of thermal stress on Chinook salmon. Six copies of heat shock protein 90 (HSP90) were discovered and characterised: HSP90AA1.1a, HSP90AA1.2a, HSP90AA1.1b, HSP90AA1.2b, HSP90AB1a and HSP90AB1b, as well as two copies of SOD1, named SOD1a and SOD1b. The amino acid sequences contained features similar to those found in other vertebrate HSP90 and SOD1 sequences, and the phylogenetic tree and synteny analysis provided conclusive evidence of their relationship to other vertebrate HSP90 and SOD1 genes. Primers were designed for qPCR to enable the expression of all copies of HSP90 and SOD1 to be analysed. The expression studies showed that HSP90 and SOD1 were downregulated in the liver and spleen in response to longer term exposure to high temperatures and lower dissolved oxygen. HSP90 was also downregulated in the gill; however, the results for SOD1 expression in the gill were not conclusive. This study provides important insights into the physiological and genetic responses of Chinook salmon to temperature and oxygen stress, which are critical for developing sustainable fish aquaculture in an era of changing global climates.

year: 2023-10-17

title: Magnetic reconnection in incompressible fluids

authors: DeLuca, Edward E.

abstract: We investigate the dynamical relaxation of a disturbed X-type magnetic neutral point in a periodic geometry, with an ignorable coordinate, for an incompressible fluid. We find that the properties of the current sheet cannot be understood in terms of steady state reconnection theory or more recent linear dynamical solutions. Accordingly we present a new scaling law for magnetic reconnection consistent with fast energy dissipation, i.e., the dissipation rate at current maximum is approximately independent of magnetic diffusivity (η). The flux annihilation rate, however, scales as η1/4, faster than the Sweet-Parker rate of η1/2 but asymptotically much slower than the dissipation rate. These results suggest a flux pile-up regime in which the bulk of the free magnetic energy is released as heat rather than as kinetic energy of mass motion. The implications of our results for reconnection in the solar atmosphere and interior are discussed.

text: Magnetic reconnection in incompressible fluids We investigate the dynamical relaxation of a disturbed X-type magnetic neutral point in a periodic geometry, with an ignorable coordinate, for an incompressible fluid. We find that the properties of the current sheet cannot be understood in terms of steady state reconnection theory or more recent linear dynamical solutions. Accordingly we present a new scaling law for magnetic reconnection consistent with fast energy dissipation, i.e., the dissipation rate at current maximum is approximately independent of magnetic diffusivity (η). The flux annihilation rate, however, scales as η1/4, faster than the Sweet-Parker rate of η1/2 but asymptotically much slower than the dissipation rate. These results suggest a flux pile-up regime in which the bulk of the free magnetic energy is released as heat rather than as kinetic energy of mass motion. The implications of our results for reconnection in the solar atmosphere and interior are discussed.

year: 1992

title: Social consequences of Tūhoe migration: Voices from home in Te Urewera

authors: Nikora, Linda Waimarie

subjects: age effects

abstract: A previous study by Nikora, Guerin, Rua & Te Awekotuku (2004) of the social consequences of Tūhoe moving to the Waikato region found employment and a tertiary education to be the primary motivators. Tūhoe ‘movers’ remained in contact with those who remain in Te Urewera and retained a wish to return to their tribal homelands if presented with work opportunities or upon retirement. Through 29 intensive conversational interviews conducted by Tūhoe community researchers with Tūhoe people we explored the social consequences of migration upon those who had remained ‘at home’. Most participants recognised and strongly supported ‘movers’ to better themselves and find successful futures but hoped that they would one day return. An emerging theme was an apparent age-distribution gap of people between about 20 and 50 years of age in the Tuhoe homelands. This is concerning for a number of reasons.  The ‘age gap’ may potentially bring about a) a lack of good role-models for younger children; b) a lack of people to help out with heavy work; c) a gap in people to sustain traditional teaching models for children, and d) a lack of qualified people in trades and professions. The age gap also means that a whole middle-aged group that in other communities might be contributing funds for capital expenditures are not present in the community.

text: Social consequences of Tūhoe migration: Voices from home in Te Urewera A previous study by Nikora, Guerin, Rua & Te Awekotuku (2004) of the social consequences of Tūhoe moving to the Waikato region found employment and a tertiary education to be the primary motivators. Tūhoe ‘movers’ remained in contact with those who remain in Te Urewera and retained a wish to return to their tribal homelands if presented with work opportunities or upon retirement. Through 29 intensive conversational interviews conducted by Tūhoe community researchers with Tūhoe people we explored the social consequences of migration upon those who had remained ‘at home’. Most participants recognised and strongly supported ‘movers’ to better themselves and find successful futures but hoped that they would one day return. An emerging theme was an apparent age-distribution gap of people between about 20 and 50 years of age in the Tuhoe homelands. This is concerning for a number of reasons.  The ‘age gap’ may potentially bring about a) a lack of good role-models for younger children; b) a lack of people to help out with heavy work; c) a gap in people to sustain traditional teaching models for children, and d) a lack of qualified people in trades and professions. The age gap also means that a whole middle-aged group that in other communities might be contributing funds for capital expenditures are not present in the community.

year: 2008