title: Sustainable shellfish growth: Investigating microalgae production techniques and species selection for Perna canaliculus larvae in a commercial hatchery

authors: Norgate, Summer

subjects: perna canaliculus

abstract: In order to fulfil the Aquaculture Strategy employed by the New Zealand Government and achieve the goal of increasing industry revenue to $3billion by 2035, more mussel spat hatcheries must be developed to deliver reliable spat supplies. Hatcheries are expensive to operate, especially to produce microalgae for larval feed; therefore, finding the most efficient procedures for spat deliverance and algae production is of utmost importance. 
Diets high in Chaetoceros calcitrans supplemented with Tisochrysis lutea are conventionally fed to Perna canaliculus larvae and current production methods are not feasible in a commercial scale hatchery due to the high cost and labour of operating the systems. Therefore, the effect of microalgal diet on larval performance was investigated for two diets significantly reducing the C. calcitrans proportion compared to the conventional diet (control). Furthermore, batch crashes of microalgae are common and disrupt daily operations due to the sensitivity of larvae to changes in food availability or species compositions, which could result in significant setbacks for a hatchery. Therefore, it is necessary to investigate alternative production methods or substitute proportions of the species with an alternative microalgae species. A fourth diet completely substituting T. lutea with Diacronema lutheri was investigated to determine if the species could be interchanged in the case of a batch failure.
Fatty acid analysis alongside indicators such as larval growth, umbo yield, pediveliger yield, spat yield, settlement success, ingestion rates and capture efficiency were investigated to determine larval performance.  In contrast to previous studies suggesting that high levels of DHA and EPA are essential for larval growth and survival, there was no clear pattern as to how high DHA and EPA levels benefit larval performance in P. canaliculus. It was found that P. canaliculus larvae fed the lowest proportion of C. calcitrans supplemented with C. muelleri had the lowest EPA content across the larval period but performed the best, in contrast to larvae fed the most EPA rich- diet consisting of C. calcitrans and D. lutheri which performed the worst. Findings from this study imply that it is more beneficial to investigate precursor fatty acids or the sum of n-3 and n-6 fatty acids, opening opportunity for further research to better identify nutritional requirements of P. canaliculus larvae. 
In conclusion, a reduction in C. calcitrans did not adversely affect the growth or yield of larvae. In fact, the yields and settlement success were similar to that of the conventional microalgal diet. Therefore, diets with low C. calcitrans replaced by C. muelleri may be better suited for application to a commercial scale hatchery to reduce the strain placed on labour and logistics associated with C. calcitrans batch production. Furthermore, it was found that the use of D. lutheri as a complete replacement of T. lutea is not recommended due to the low larval performance associated with the diet. These findings enable resources and energy to be focussed elsewhere allowing the production of more mussels with lower resource inputs, reducing the environmental footprint of aquaculture operations.

text: Sustainable shellfish growth: Investigating microalgae production techniques and species selection for Perna canaliculus larvae in a commercial hatchery In order to fulfil the Aquaculture Strategy employed by the New Zealand Government and achieve the goal of increasing industry revenue to $3billion by 2035, more mussel spat hatcheries must be developed to deliver reliable spat supplies. Hatcheries are expensive to operate, especially to produce microalgae for larval feed; therefore, finding the most efficient procedures for spat deliverance and algae production is of utmost importance. 
Diets high in Chaetoceros calcitrans supplemented with Tisochrysis lutea are conventionally fed to Perna canaliculus larvae and current production methods are not feasible in a commercial scale hatchery due to the high cost and labour of operating the systems. Therefore, the effect of microalgal diet on larval performance was investigated for two diets significantly reducing the C. calcitrans proportion compared to the conventional diet (control). Furthermore, batch crashes of microalgae are common and disrupt daily operations due to the sensitivity of larvae to changes in food availability or species compositions, which could result in significant setbacks for a hatchery. Therefore, it is necessary to investigate alternative production methods or substitute proportions of the species with an alternative microalgae species. A fourth diet completely substituting T. lutea with Diacronema lutheri was investigated to determine if the species could be interchanged in the case of a batch failure.
Fatty acid analysis alongside indicators such as larval growth, umbo yield, pediveliger yield, spat yield, settlement success, ingestion rates and capture efficiency were investigated to determine larval performance.  In contrast to previous studies suggesting that high levels of DHA and EPA are essential for larval growth and survival, there was no clear pattern as to how high DHA and EPA levels benefit larval performance in P. canaliculus. It was found that P. canaliculus larvae fed the lowest proportion of C. calcitrans supplemented with C. muelleri had the lowest EPA content across the larval period but performed the best, in contrast to larvae fed the most EPA rich- diet consisting of C. calcitrans and D. lutheri which performed the worst. Findings from this study imply that it is more beneficial to investigate precursor fatty acids or the sum of n-3 and n-6 fatty acids, opening opportunity for further research to better identify nutritional requirements of P. canaliculus larvae. 
In conclusion, a reduction in C. calcitrans did not adversely affect the growth or yield of larvae. In fact, the yields and settlement success were similar to that of the conventional microalgal diet. Therefore, diets with low C. calcitrans replaced by C. muelleri may be better suited for application to a commercial scale hatchery to reduce the strain placed on labour and logistics associated with C. calcitrans batch production. Furthermore, it was found that the use of D. lutheri as a complete replacement of T. lutea is not recommended due to the low larval performance associated with the diet. These findings enable resources and energy to be focussed elsewhere allowing the production of more mussels with lower resource inputs, reducing the environmental footprint of aquaculture operations.

year: 2024

title: Toward-1mm depth precision with a solid state full-field range imaging system

authors: Dorrington, Adrian A.

subjects: solid-state

abstract: Previously, we demonstrated a novel heterodyne based solid-state full-field range-finding imaging system. This system is comprised of modulated LED illumination, a modulated image intensifier, and a digital video camera. A 10 MHz drive is provided with 1 Hz difference between the LEDs and image intensifier. A sequence of images of the resulting beating intensifier output are captured and processed to determine phase and hence distance to the object for each pixel. In a previous publication, we detailed results showing a one-sigma precision of 15 mm to 30 mm (depending on signal strength). Furthermore, we identified the limitations of the system and potential improvements that were expected to result in a range precision in the order of 1 mm. These primarily include increasing the operating frequency and improving optical coupling and sensitivity. In this paper, we report on the implementation of these improvements and the new system characteristics. We also comment on the factors that are important for high precision image ranging and present configuration strategies for best performance. Ranging with sub-millimeter precision is demonstrated by imaging a planar surface and calculating the deviations from a planar fit. The results are also illustrated graphically by imaging a garden gnome.

text: Toward-1mm depth precision with a solid state full-field range imaging system Previously, we demonstrated a novel heterodyne based solid-state full-field range-finding imaging system. This system is comprised of modulated LED illumination, a modulated image intensifier, and a digital video camera. A 10 MHz drive is provided with 1 Hz difference between the LEDs and image intensifier. A sequence of images of the resulting beating intensifier output are captured and processed to determine phase and hence distance to the object for each pixel. In a previous publication, we detailed results showing a one-sigma precision of 15 mm to 30 mm (depending on signal strength). Furthermore, we identified the limitations of the system and potential improvements that were expected to result in a range precision in the order of 1 mm. These primarily include increasing the operating frequency and improving optical coupling and sensitivity. In this paper, we report on the implementation of these improvements and the new system characteristics. We also comment on the factors that are important for high precision image ranging and present configuration strategies for best performance. Ranging with sub-millimeter precision is demonstrated by imaging a planar surface and calculating the deviations from a planar fit. The results are also illustrated graphically by imaging a garden gnome.

year: 2006

title: Kaupapa Māori Science

authors: Stewart, Georgina Marjorie

subjects: Kaupapa Maori

abstract: This thesis investigates how Māori knowledge and language articulate with current discourses of Pūtaiao education, and possible alternative articulations. A Kaupapa Māori version of critical discourse analysis methodology is developed and applied to discourses relevant to Pūtaiao, or Māori-medium science education. This topic represents an intersection between language, science, education, and culture - fields which are all highly politically charged. Therefore, it is essential that a politically robust Kaupapa Māori position be taken in relation to the research topic. Not only the issues being investigated but the underlying research paradigm must be interrogated using Kaupapa Māori theory at each stage of the project.

The goal is to study the range of possible meanings for the notions of 'Pūtaiao' and 'Māori science' by exploring the relevant dialectical issues, critiquing the assumptions and positions taken on language, knowledge, identity and ethos, in order to inform further Pūtaiao curriculum development. The research project is a narration of the larger story of Pūtaiao education: what is the current situation, how did it come about, what theoretical issues have been influential in this process, and what possibilities are there for further development of Pūtaiao curriculum and pedagogy? 

The thesis research consists of a series of discourse analyses of varying levels of focus and intersection with Pūtaiao:
Wāhanga 1: Translated NCEA L1 science and mathematics examinations, and a traditional Taitokerau oral text;
Wāhanga 2: Māori science curriculum policy;
Wāhanga 3: Multicultural science education research;
Wāhanga 4: Curriculum politics, preventive linguistics, language of science;
Wāhanga 5: Mātauranga, rationality, philosophy of science.

Each analysis takes the form of a narrative history, based on a selected corpus of previously published scholarship (in Wāhanga 1, including numerical data and oral tradition) on the issue under examination, from a Kaupapa Māori perspective. Mainly in the first two chapters, analysis at times also draws on 'personal narrative' accounts of previously unpublished details relating to Pūtaiao.
 
Additionally, an investigation of various qualified notions of 'science' is undertaken, beginning in Wāhanga 2, concluding in Wāhanga 5, in order to explore the nature and boundaries of science as a system of knowledge, and its relationship to other types or systems of knowledge. 

Synopses are included of the following concepts and theoretical issues impacting on the discourses under analysis: 
Wāhanga 1: Ethnicity, 'race', critical theory, Kaupapa Māori theory. 
Wāhanga 2: Science, scientism, science ideology and anti-science.
Wāhanga 4: Identity, linguistic purism, the Sapir-Whorf hypothesis.

Informed by this research, in Wāhanga 5 an original model for the relationship between mātauranga and science is proposed, and the notion of Kaupapa Māori science/epistemology is explored. An analogy between the Sapir-Whorf hypothesis and multicultural science is used to draw together the cultural debates in language and knowledge, which are surmised to intersect at the level of discourse. 

The final chapter presents a re-articulation of Pūtaiao as the notion of Kaupapa Māori science education, and some recommendations for language and content knowledge in further development of Pūtaiao curriculum policy.

text: Kaupapa Māori Science This thesis investigates how Māori knowledge and language articulate with current discourses of Pūtaiao education, and possible alternative articulations. A Kaupapa Māori version of critical discourse analysis methodology is developed and applied to discourses relevant to Pūtaiao, or Māori-medium science education. This topic represents an intersection between language, science, education, and culture - fields which are all highly politically charged. Therefore, it is essential that a politically robust Kaupapa Māori position be taken in relation to the research topic. Not only the issues being investigated but the underlying research paradigm must be interrogated using Kaupapa Māori theory at each stage of the project.

The goal is to study the range of possible meanings for the notions of 'Pūtaiao' and 'Māori science' by exploring the relevant dialectical issues, critiquing the assumptions and positions taken on language, knowledge, identity and ethos, in order to inform further Pūtaiao curriculum development. The research project is a narration of the larger story of Pūtaiao education: what is the current situation, how did it come about, what theoretical issues have been influential in this process, and what possibilities are there for further development of Pūtaiao curriculum and pedagogy? 

The thesis research consists of a series of discourse analyses of varying levels of focus and intersection with Pūtaiao:
Wāhanga 1: Translated NCEA L1 science and mathematics examinations, and a traditional Taitokerau oral text;
Wāhanga 2: Māori science curriculum policy;
Wāhanga 3: Multicultural science education research;
Wāhanga 4: Curriculum politics, preventive linguistics, language of science;
Wāhanga 5: Mātauranga, rationality, philosophy of science.

Each analysis takes the form of a narrative history, based on a selected corpus of previously published scholarship (in Wāhanga 1, including numerical data and oral tradition) on the issue under examination, from a Kaupapa Māori perspective. Mainly in the first two chapters, analysis at times also draws on 'personal narrative' accounts of previously unpublished details relating to Pūtaiao.
 
Additionally, an investigation of various qualified notions of 'science' is undertaken, beginning in Wāhanga 2, concluding in Wāhanga 5, in order to explore the nature and boundaries of science as a system of knowledge, and its relationship to other types or systems of knowledge. 

Synopses are included of the following concepts and theoretical issues impacting on the discourses under analysis: 
Wāhanga 1: Ethnicity, 'race', critical theory, Kaupapa Māori theory. 
Wāhanga 2: Science, scientism, science ideology and anti-science.
Wāhanga 4: Identity, linguistic purism, the Sapir-Whorf hypothesis.

Informed by this research, in Wāhanga 5 an original model for the relationship between mātauranga and science is proposed, and the notion of Kaupapa Māori science/epistemology is explored. An analogy between the Sapir-Whorf hypothesis and multicultural science is used to draw together the cultural debates in language and knowledge, which are surmised to intersect at the level of discourse. 

The final chapter presents a re-articulation of Pūtaiao as the notion of Kaupapa Māori science education, and some recommendations for language and content knowledge in further development of Pūtaiao curriculum policy.

year: 2007