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: Impacts of deforestation and burning, and the role of bracken fern, on the properties of surficial or buried soil A-horizons

authors: Lowe, David J.

subjects: bracken fern

abstract: Bracken fern (Pteridium spp.) is an aggressive plant that commonly invades disturbed sites. Its success as an invader is attributable, in part, to its ability to produce abundant growth, both below ground in the form of rhizomes and fine roots and above ground as fronds and stems. This biomass production has been shown to affect numerous soil properties. In describing soils of the „Pumice Lands‟ (Pumice Soils or Vitrands mainly) in New Zealand, Molloy and Christie (1998) attributed black A horizons „to bracken fern, which replaced much of the forest‟. Analyses of humus and phytoliths in the A horizons of soils developed especially on Kaharoa and Taupo tephras in central North Island (buried beneath 1886 Tarawera eruptives in the Rerewhakaaitu area) showed that type-A humic acids predominated and that fernland and grassland had replaced the pre-existing forests (Birrell et al., 1971; Sase et al., 1988; Hosono et al., 1991; Sase and Hosono, 1996). Pollen, phytolith and associated studies, together with tephrochronology, have shown that human-induced deforestation by burning began in New Zealand soon after Polynesian settlers arrived (e.g. McGlone, 1989; Clarkson et al., 1992; Kondo et al., 1994; McGlone et al., 1994; Newnham et al., 1998; McGlone and Wilmshurst, 1999; Watanabe and Sakagami, 1999; see also article on Polynesian settlement by Lowe, this volume). The repeated burning resulted in the formation of extensive fernlands (McGlone et al., 2005).

text: Impacts of deforestation and burning, and the role of bracken fern, on the properties of surficial or buried soil A-horizons Bracken fern (Pteridium spp.) is an aggressive plant that commonly invades disturbed sites. Its success as an invader is attributable, in part, to its ability to produce abundant growth, both below ground in the form of rhizomes and fine roots and above ground as fronds and stems. This biomass production has been shown to affect numerous soil properties. In describing soils of the „Pumice Lands‟ (Pumice Soils or Vitrands mainly) in New Zealand, Molloy and Christie (1998) attributed black A horizons „to bracken fern, which replaced much of the forest‟. Analyses of humus and phytoliths in the A horizons of soils developed especially on Kaharoa and Taupo tephras in central North Island (buried beneath 1886 Tarawera eruptives in the Rerewhakaaitu area) showed that type-A humic acids predominated and that fernland and grassland had replaced the pre-existing forests (Birrell et al., 1971; Sase et al., 1988; Hosono et al., 1991; Sase and Hosono, 1996). Pollen, phytolith and associated studies, together with tephrochronology, have shown that human-induced deforestation by burning began in New Zealand soon after Polynesian settlers arrived (e.g. McGlone, 1989; Clarkson et al., 1992; Kondo et al., 1994; McGlone et al., 1994; Newnham et al., 1998; McGlone and Wilmshurst, 1999; Watanabe and Sakagami, 1999; see also article on Polynesian settlement by Lowe, this volume). The repeated burning resulted in the formation of extensive fernlands (McGlone et al., 2005).

year: 2008

title: Adolescent Māori mothers experiences with social support during pregnancy, birth and motherhood and their participation in education

authors: Rawiri, Casey

subjects: social support

abstract: The purpose of this research was to investigate the role of social support in helping
adolescent Māori mothers cope with pregnancy, birth and motherhood, with a
particular emphasis on its role in enabling them to continue at school. The aim of this
research is to understand and make sense of these experiences and to perhaps identify
gaps within an individual's social network. The analysis and methodology of the
research was underpinned by a community psychology framework.
Nine interviews were conducted with young Māori women who had become pregnant
and continued with their pregnancy, all before the age of 20. The in depth interviews
included questions focusing on the young women learning of pregnancy, the
pregnancy, birth, caring for their child and their experiences with education and future
plans.
Negative experiences were usually those which involved unsupportive people.
Positive interactions were those where support, of all types, was offered and useful to
my participants and their children. Education was highlighted as the most effective
way of providing a better life for adolescent mothers and their children.
The research highlights the importance of social support and the continuation of
education. Combining the efforts of positive social networks and social support
services can improve the lives of adolescent Māori mothers and their children.

text: Adolescent Māori mothers experiences with social support during pregnancy, birth and motherhood and their participation in education The purpose of this research was to investigate the role of social support in helping
adolescent Māori mothers cope with pregnancy, birth and motherhood, with a
particular emphasis on its role in enabling them to continue at school. The aim of this
research is to understand and make sense of these experiences and to perhaps identify
gaps within an individual's social network. The analysis and methodology of the
research was underpinned by a community psychology framework.
Nine interviews were conducted with young Māori women who had become pregnant
and continued with their pregnancy, all before the age of 20. The in depth interviews
included questions focusing on the young women learning of pregnancy, the
pregnancy, birth, caring for their child and their experiences with education and future
plans.
Negative experiences were usually those which involved unsupportive people.
Positive interactions were those where support, of all types, was offered and useful to
my participants and their children. Education was highlighted as the most effective
way of providing a better life for adolescent mothers and their children.
The research highlights the importance of social support and the continuation of
education. Combining the efforts of positive social networks and social support
services can improve the lives of adolescent Māori mothers and their children.

year: 2007