title: Gut structure and diet adaptability of yellowbelly flounder: A step towards integrating Rhombosolea leporina into New Zealand aquaculture

authors: Thomson, Caitlin

subjects: gut structure

abstract: Aquaculture is a rapidly expanding industry as wild fish stocks decline due to overfishing, climate change, and increased seafood consumption. Flatfish, being highly prized, have faced significant declines in the wild, but several species are now being cultivated in land-based recirculating aquaculture systems to meet market demand. Flatfish are low-trophic feeders and thrive in relatively simple farming setups, making them viable candidates for sustainable aquaculture.
In New Zealand, the yellowbelly flounder (Rhombosolea leporina), or pātiki, is a sought-after species in commercial and recreational fisheries. Introducing this species into aquaculture could support the local seafood market and aid in replenishing wild stocks. However, limited research exists on yellowbelly flounder compared to other flatfish, particularly regarding its digestive system and dietary needs. Feed costs are a significant challenge in aquaculture, especially when striving to reduce reliance on unsustainable ingredients like fishmeal and oil while maintaining low feed conversion ratios. Understanding the digestive tract structure and function of the yellowbelly flounder is critical for developing sustainable, species-specific diets.
This study examined the gut structure and function of wild-caught adult and juvenile yellowbelly flounder, as well as juveniles fed a mussel-based diet, a fishmeal-based pellet diet, or subjected to starvation. The histological analysis examined the muscularis externa, mucosal folds, and goblet cell distribution throughout the alimentary canal, while qPCR assessed the expression of the cholecystokinin hormone paralogs (ccka and cckb).
Unexpectedly, findings suggested that yellowbelly flounder may be agastric, differing from other flatfish. Consistent gut tissue patterns, goblet cell presence, and ccka and cckb expression throughout the canal supported this conclusion. The pellet diet did cause higher ccka expression compared to the mussel diet, but overall, the results suggested the yellowbelly flounder is adaptable to varying feeds. While limited by a small-scale study, these results provided a basis for further exploration of yellowbelly flounder digestive capabilities in hopes of facilitating this species into the New Zealand aquaculture industry.

text: Gut structure and diet adaptability of yellowbelly flounder: A step towards integrating Rhombosolea leporina into New Zealand aquaculture Aquaculture is a rapidly expanding industry as wild fish stocks decline due to overfishing, climate change, and increased seafood consumption. Flatfish, being highly prized, have faced significant declines in the wild, but several species are now being cultivated in land-based recirculating aquaculture systems to meet market demand. Flatfish are low-trophic feeders and thrive in relatively simple farming setups, making them viable candidates for sustainable aquaculture.
In New Zealand, the yellowbelly flounder (Rhombosolea leporina), or pātiki, is a sought-after species in commercial and recreational fisheries. Introducing this species into aquaculture could support the local seafood market and aid in replenishing wild stocks. However, limited research exists on yellowbelly flounder compared to other flatfish, particularly regarding its digestive system and dietary needs. Feed costs are a significant challenge in aquaculture, especially when striving to reduce reliance on unsustainable ingredients like fishmeal and oil while maintaining low feed conversion ratios. Understanding the digestive tract structure and function of the yellowbelly flounder is critical for developing sustainable, species-specific diets.
This study examined the gut structure and function of wild-caught adult and juvenile yellowbelly flounder, as well as juveniles fed a mussel-based diet, a fishmeal-based pellet diet, or subjected to starvation. The histological analysis examined the muscularis externa, mucosal folds, and goblet cell distribution throughout the alimentary canal, while qPCR assessed the expression of the cholecystokinin hormone paralogs (ccka and cckb).
Unexpectedly, findings suggested that yellowbelly flounder may be agastric, differing from other flatfish. Consistent gut tissue patterns, goblet cell presence, and ccka and cckb expression throughout the canal supported this conclusion. The pellet diet did cause higher ccka expression compared to the mussel diet, but overall, the results suggested the yellowbelly flounder is adaptable to varying feeds. While limited by a small-scale study, these results provided a basis for further exploration of yellowbelly flounder digestive capabilities in hopes of facilitating this species into the New Zealand aquaculture industry.

year: 2025

title: The Fate and Effects of Contaminants in Estuarine Environments

authors: Huteau, Julien

subjects: estuary

abstract: Estuaries are sensitive environments regarding their response to anthropogenic events. The accumulation of toxic trace elements, such as Cd and Pb, has detrimental consequences on benthic community composition and function that can lead to human health issues when seafood is consumed. Eutrophic water can generate blooms of macroalgae and can induce adverse changes in the structure of an entire food web. 
Environmental research is of fundamental importance to understand the sources, fates and effects of contaminants. It will permit the development of remediation strategies to improve sustainable practices. The approach taken in the research presented is focused on the measurement of trace elements in sediment, water and biota, and the application of stable isotopes in the detection of sources of contaminants. A novel set of data on New Zealand estuarine species, not usually screened for pollutants, has been assembled in the context of a number of estuarine systems that have been influenced by a range of anthropogenically generated contamination events. The combined use of diffuse gradient ‘in thin films’ (DGT) and the analysis of δ15N-NO3 and δ18O-NO3 in water, are new for New Zealand estuarine systems; the correlations generated will enhance baseline datasets for future environmental studies. This research additionally led to the development of a novel environmental indicator, “Ecohardness”, reflecting the estuarine chemical budget by the analysis of the material strength of cockle shell. 
From this research, lead, cadmium and zinc were found to be the most concerning polluting elements in the study location, with levels above sedimentary ANZECC safety guidelines. Phosphorus was found in high concentration in urban and rural estuaries heavily impacted by agricultural practices. Isotopic analysis confirmed sources of pollution with higher values of δ13C and δ15N near treated wastewater ponds. The accumulation of contaminants was also associated with river and stormwater inputs and the intensive use of fertilisers. The accumulation of trace elements was specifically associated with metal pathways rather than sedimentary composition. However, metal speciation is of fundamental importance in ecotoxicology and is regarded as more significant than bulk concentrations in water and sediment in the understanding of biological response of organisms to trace elements. Accumulation of trace elements in biota was found to be strongly associated to those that were captured in DGT devices deployed in the water (‘DGT-labile’ elements). DGT-labile elements can be defined as the “bioavailable” fraction, as this technique uses a hydrogel layer to control the diffuse transport of trace elements in solution, to a binding resin. All labile elements were found in higher concentration in the stream/estuarine environment than the ocean, demonstrating the characteristic of estuaries as a sink for trace elements. Further insight into the speciation of the various elements was permitted by calculating the rate of accumulation in different hydrogel thicknesses. Each element could be classified according to their behaviour ranking from putatively free simple inorganic cations with no resupply from complex ligands (e.g. Cd at Bureta), to fully sustained conditions with a constant degree of resupply of free ions and labile complexes (e.g. Ni, Fe and Cu at Bureta). 
The development of a novel environmental parameter “EcoHardness”, has application to examining pollutant response in estuarine bivalves. While microhardness has been measured previously in bivalves (cockle shell) and correlated to microstructure, this is the first time that microhardness for the same species was analysed in different estuaries that have different anthropogenic pollution attributes. The method demonstrated an increase of microhardness in response to a decrease of Ca content, that appeared to be inversely correlated to an increase of trace elements that were associated with the general chemical state of estuaries. Hence, harder shells were associated with more polluted estuarine areas. This parameter could be a valuable tool in the assessment of environmental changes linked to the increase of trace metal pollutants as observed around the world in the last few decades. 
This work has extended research into the environmental health of estuaries by combining a number of known analytical methodologies in a novel manner and through the development of a new technology. In addition, the work has examined a relevant trophic cascade of species further providing an insight into ecosystem functioning against a backdrop of human presence.

text: The Fate and Effects of Contaminants in Estuarine Environments Estuaries are sensitive environments regarding their response to anthropogenic events. The accumulation of toxic trace elements, such as Cd and Pb, has detrimental consequences on benthic community composition and function that can lead to human health issues when seafood is consumed. Eutrophic water can generate blooms of macroalgae and can induce adverse changes in the structure of an entire food web. 
Environmental research is of fundamental importance to understand the sources, fates and effects of contaminants. It will permit the development of remediation strategies to improve sustainable practices. The approach taken in the research presented is focused on the measurement of trace elements in sediment, water and biota, and the application of stable isotopes in the detection of sources of contaminants. A novel set of data on New Zealand estuarine species, not usually screened for pollutants, has been assembled in the context of a number of estuarine systems that have been influenced by a range of anthropogenically generated contamination events. The combined use of diffuse gradient ‘in thin films’ (DGT) and the analysis of δ15N-NO3 and δ18O-NO3 in water, are new for New Zealand estuarine systems; the correlations generated will enhance baseline datasets for future environmental studies. This research additionally led to the development of a novel environmental indicator, “Ecohardness”, reflecting the estuarine chemical budget by the analysis of the material strength of cockle shell. 
From this research, lead, cadmium and zinc were found to be the most concerning polluting elements in the study location, with levels above sedimentary ANZECC safety guidelines. Phosphorus was found in high concentration in urban and rural estuaries heavily impacted by agricultural practices. Isotopic analysis confirmed sources of pollution with higher values of δ13C and δ15N near treated wastewater ponds. The accumulation of contaminants was also associated with river and stormwater inputs and the intensive use of fertilisers. The accumulation of trace elements was specifically associated with metal pathways rather than sedimentary composition. However, metal speciation is of fundamental importance in ecotoxicology and is regarded as more significant than bulk concentrations in water and sediment in the understanding of biological response of organisms to trace elements. Accumulation of trace elements in biota was found to be strongly associated to those that were captured in DGT devices deployed in the water (‘DGT-labile’ elements). DGT-labile elements can be defined as the “bioavailable” fraction, as this technique uses a hydrogel layer to control the diffuse transport of trace elements in solution, to a binding resin. All labile elements were found in higher concentration in the stream/estuarine environment than the ocean, demonstrating the characteristic of estuaries as a sink for trace elements. Further insight into the speciation of the various elements was permitted by calculating the rate of accumulation in different hydrogel thicknesses. Each element could be classified according to their behaviour ranking from putatively free simple inorganic cations with no resupply from complex ligands (e.g. Cd at Bureta), to fully sustained conditions with a constant degree of resupply of free ions and labile complexes (e.g. Ni, Fe and Cu at Bureta). 
The development of a novel environmental parameter “EcoHardness”, has application to examining pollutant response in estuarine bivalves. While microhardness has been measured previously in bivalves (cockle shell) and correlated to microstructure, this is the first time that microhardness for the same species was analysed in different estuaries that have different anthropogenic pollution attributes. The method demonstrated an increase of microhardness in response to a decrease of Ca content, that appeared to be inversely correlated to an increase of trace elements that were associated with the general chemical state of estuaries. Hence, harder shells were associated with more polluted estuarine areas. This parameter could be a valuable tool in the assessment of environmental changes linked to the increase of trace metal pollutants as observed around the world in the last few decades. 
This work has extended research into the environmental health of estuaries by combining a number of known analytical methodologies in a novel manner and through the development of a new technology. In addition, the work has examined a relevant trophic cascade of species further providing an insight into ecosystem functioning against a backdrop of human presence.

year: 2017

title: The gown and the korowai: Maori doctoral students and the spatial organization of academic knowledge

authors: Middleton, Sue

subjects: culture

abstract: This paper draws on 38 student interviews carried out in the course of the team research project Teaching and Learning in the Supervision of Māori Doctoral Students. Māori doctoral thesis work takes place in the intersections between the Māori (tribal) world of identifications and obligations, the organisational and epistemological configurations of academia, and the bureaucratic requirements of funding or employing bureaucracies. To explore how students accommodate cultural, academic and bureaucratic demands, we develop analytical tools combining three intellectual traditions: Māori educational theory, Bernstein’s sociology of the academy, and Lefebvre’s conceptual trilogy of perceived, conceived, and lived space.

text: The gown and the korowai: Maori doctoral students and the spatial organization of academic knowledge This paper draws on 38 student interviews carried out in the course of the team research project Teaching and Learning in the Supervision of Māori Doctoral Students. Māori doctoral thesis work takes place in the intersections between the Māori (tribal) world of identifications and obligations, the organisational and epistemological configurations of academia, and the bureaucratic requirements of funding or employing bureaucracies. To explore how students accommodate cultural, academic and bureaucratic demands, we develop analytical tools combining three intellectual traditions: Māori educational theory, Bernstein’s sociology of the academy, and Lefebvre’s conceptual trilogy of perceived, conceived, and lived space.

year: 2009