title: The aquatic ecology of Lake Rotokare

authors: Smith, Dylan Ross

subjects: Conservation

abstract: The biology of three endemic and one exotic species of fish (banded kokopu, Galaxias fasciatus; shortfin eel, Anguilla australis; longfin eel, Anguilla dieffenbachii; and the European perch, Perca fluviatilis) was investigated in Lake Rotokare. Little is currently known regarding the local ecology of the lake. This study improves the understanding of the biological processes in Lake Rotokare and investigates the characteristics of the lake’s water quality.

Fish sampling occurred in the lake using a combination of boat electrofishing, gill netting, and fyke netting. The tributary was sampled using night time spotlighting. Fish taken from the lake were used to determine length-weight relationships, size frequencies, CPUE, abundance estimations, fish biomass, stable isotope analyses, trophic levels, and perch diet. Water quality sampling was also undertaken to further build upon data from previous studies. 

The majority of fish sampled in Lake Rotokare were perch, with a mixture of size classes, but dominated by a large juvenile size class. Perch density was high (16.55 fish 100 m-2). Longfin eels showed a cohort of large individuals with no evidence of recruitment occurring; while shortfin eels exhibited a distribution of size ranges with evidence of juvenile recruitment occuring. 

Electrofishing showed evidence of banded kokopu inhabiting the lake, even at distance from the tributary outlet, suggesting the possibility of a lake fringe population of kokopu. Spotlight sampling in June and December revealed a stable kokopu and kōura population residing in the lakes’ main tributary. Water quality data showed an overall decrease in total nitrogen and phosphorous loads within the lake since 1979. However, the lake has shown strong thermal stratification over summer over multiple years (1977, 2013, February 2017 and December 2017), and remains in poor condition, with a eutrophic TLI 4 rating of 4.1. Frequent cyanobacterial blooms continue to occur during the summer season, resulting in closure of the lake for contact recreation. 

Both dietary and stable isotope analyses showed indications that chironomid larvae and Daphnia sp. constituted the bulk of the primary production of the food web; juvenile perch were found to be the predominant food source of the three resident fish species. A three-end member mixing model was created to duplicate the theoretical food-web within the lake with chironomid larvae, dragonfly larvae, and juvenile perch at the base. Lipid treatment techniques were examined in this study for eel fin and muscle tissue. The results indicate that lipid treatment is needed for 13C isotope values for both longfin and shortfin muscle, and longfin fin tissue for accurate results. Mathematical equations were constructed to correct untreated fin tissue values into treated muscle values for 13C and 15N; avoiding the necessity for future lethal sampling methods.

text: The aquatic ecology of Lake Rotokare The biology of three endemic and one exotic species of fish (banded kokopu, Galaxias fasciatus; shortfin eel, Anguilla australis; longfin eel, Anguilla dieffenbachii; and the European perch, Perca fluviatilis) was investigated in Lake Rotokare. Little is currently known regarding the local ecology of the lake. This study improves the understanding of the biological processes in Lake Rotokare and investigates the characteristics of the lake’s water quality.

Fish sampling occurred in the lake using a combination of boat electrofishing, gill netting, and fyke netting. The tributary was sampled using night time spotlighting. Fish taken from the lake were used to determine length-weight relationships, size frequencies, CPUE, abundance estimations, fish biomass, stable isotope analyses, trophic levels, and perch diet. Water quality sampling was also undertaken to further build upon data from previous studies. 

The majority of fish sampled in Lake Rotokare were perch, with a mixture of size classes, but dominated by a large juvenile size class. Perch density was high (16.55 fish 100 m-2). Longfin eels showed a cohort of large individuals with no evidence of recruitment occurring; while shortfin eels exhibited a distribution of size ranges with evidence of juvenile recruitment occuring. 

Electrofishing showed evidence of banded kokopu inhabiting the lake, even at distance from the tributary outlet, suggesting the possibility of a lake fringe population of kokopu. Spotlight sampling in June and December revealed a stable kokopu and kōura population residing in the lakes’ main tributary. Water quality data showed an overall decrease in total nitrogen and phosphorous loads within the lake since 1979. However, the lake has shown strong thermal stratification over summer over multiple years (1977, 2013, February 2017 and December 2017), and remains in poor condition, with a eutrophic TLI 4 rating of 4.1. Frequent cyanobacterial blooms continue to occur during the summer season, resulting in closure of the lake for contact recreation. 

Both dietary and stable isotope analyses showed indications that chironomid larvae and Daphnia sp. constituted the bulk of the primary production of the food web; juvenile perch were found to be the predominant food source of the three resident fish species. A three-end member mixing model was created to duplicate the theoretical food-web within the lake with chironomid larvae, dragonfly larvae, and juvenile perch at the base. Lipid treatment techniques were examined in this study for eel fin and muscle tissue. The results indicate that lipid treatment is needed for 13C isotope values for both longfin and shortfin muscle, and longfin fin tissue for accurate results. Mathematical equations were constructed to correct untreated fin tissue values into treated muscle values for 13C and 15N; avoiding the necessity for future lethal sampling methods.

year: 2018

title: Switching toxin production on and off: intermittent microcystin synthesis in a Microcystis bloom

authors: Wood, Susanna A.

subjects: biology

abstract: Toxic cyanobacterial blooms are increasing in prevalence. Microcystins are the most commonly produced cyanotoxin. Despite extensive research the variables regulating microcystin production remain unclear. Using a RT-QPCR assay that allowed the precise measurement of mcyE transcriptional gene expression and an ELISA that enabled small changes in total microcystin concentrations to be monitored, we demonstrate for the first time that microcystin production is not always constitutive and that significant up- and downregulation in microcystin synthesis can occur on time scales of 2–6 h. Samples were collected over 3 days from a small eutrophic lake during a dense microcystin-producing Microcystis bloom. McyE gene transcripts were detected in only four out of 14 samples. Vicissitudes in both microcystin quotas and extracellular microcystin levels corresponded with changes in mcyE expression. During the period of exalted microcystin synthesis Microcystis sp. cell concentrations increased from 70 000 cells ml−1 to 4 000 000 cells ml−1. These data provide compelling evidence that changes in Microcystis cell concentrations influence microcystin production.

text: Switching toxin production on and off: intermittent microcystin synthesis in a Microcystis bloom Toxic cyanobacterial blooms are increasing in prevalence. Microcystins are the most commonly produced cyanotoxin. Despite extensive research the variables regulating microcystin production remain unclear. Using a RT-QPCR assay that allowed the precise measurement of mcyE transcriptional gene expression and an ELISA that enabled small changes in total microcystin concentrations to be monitored, we demonstrate for the first time that microcystin production is not always constitutive and that significant up- and downregulation in microcystin synthesis can occur on time scales of 2–6 h. Samples were collected over 3 days from a small eutrophic lake during a dense microcystin-producing Microcystis bloom. McyE gene transcripts were detected in only four out of 14 samples. Vicissitudes in both microcystin quotas and extracellular microcystin levels corresponded with changes in mcyE expression. During the period of exalted microcystin synthesis Microcystis sp. cell concentrations increased from 70 000 cells ml−1 to 4 000 000 cells ml−1. These data provide compelling evidence that changes in Microcystis cell concentrations influence microcystin production.

year: 2010

title: Ko Waipā te awa

authors: Kukutai, Josephine

abstract: This thesis examines the experience of the Ngāti Maniapoto (‘Maniapoto’) iwi in the development and implementation of their river settlement legislation, the Ngā Wai o Maniapoto (Waipā River) Act 2012 (the 'Act’) . The overarching purpose of the Act is to restore and maintain the quality and integrity of the waters that flow into and form part of the Waipā River for present and future generations and the care and protection of the mana tuku iho o Waiwaia. The restoration of the Waipā River is essential because of its considerable significance to Maniapoto. The Waipā River is connected to the health and identity of the Maniapoto people and is a taonga (gift) that contains their spiritual and physical wellbeing. The Waipā River is significant because: 
Te Awa o Waipā is a taonga to Maniapoto; the relationship between Maniapoto and the Waipā River is historical, intellectual, physical, and spiritual; to Maniapoto, their relationship with the Waipā River and their respect for it lies at the heart of their spiritual and physical wellbeing, and their tribal identity and culture
The approach to expressing the journey of Maniapoto in the development and implementation of the Waipā River legislation required a Māori lens. I used a Kaupapa Māori approach to examine the development of the Act and again to understand the difficulties in realising the promise of the Act. The focus of this thesis is on the Maniapoto people and their experience of the Act. The Waipā River Settlement and the Waikato River Settlement are closely connected, and the study delves into the history of the Waikato River Settlement and its influence on the Waipā River Settlement. The rangatiratanga (authority) of Maniapoto within their rohe has always been paramount in decision-making. The co-governance and co-management framework however relies on a different form of decision, that of co-decision-making, which is conducted not only in partnership with the Crown but also other Waikato River iwi. Co-governance and co-management change the standard model of traditional autonomous decision-making or rangatiratanga within an iwi and potentially challenges the decisions made. The co-governance and co-management Deed agreed between Maniapoto and the Crown for the Waipā River has changed how people operate in the Maniapoto rohe and how they may have operated previously. This thesis concludes by reflecting on some of the challenges experienced by Maniapoto in the new co-governance and co-management era.

text: Ko Waipā te awa This thesis examines the experience of the Ngāti Maniapoto (‘Maniapoto’) iwi in the development and implementation of their river settlement legislation, the Ngā Wai o Maniapoto (Waipā River) Act 2012 (the 'Act’) . The overarching purpose of the Act is to restore and maintain the quality and integrity of the waters that flow into and form part of the Waipā River for present and future generations and the care and protection of the mana tuku iho o Waiwaia. The restoration of the Waipā River is essential because of its considerable significance to Maniapoto. The Waipā River is connected to the health and identity of the Maniapoto people and is a taonga (gift) that contains their spiritual and physical wellbeing. The Waipā River is significant because: 
Te Awa o Waipā is a taonga to Maniapoto; the relationship between Maniapoto and the Waipā River is historical, intellectual, physical, and spiritual; to Maniapoto, their relationship with the Waipā River and their respect for it lies at the heart of their spiritual and physical wellbeing, and their tribal identity and culture
The approach to expressing the journey of Maniapoto in the development and implementation of the Waipā River legislation required a Māori lens. I used a Kaupapa Māori approach to examine the development of the Act and again to understand the difficulties in realising the promise of the Act. The focus of this thesis is on the Maniapoto people and their experience of the Act. The Waipā River Settlement and the Waikato River Settlement are closely connected, and the study delves into the history of the Waikato River Settlement and its influence on the Waipā River Settlement. The rangatiratanga (authority) of Maniapoto within their rohe has always been paramount in decision-making. The co-governance and co-management framework however relies on a different form of decision, that of co-decision-making, which is conducted not only in partnership with the Crown but also other Waikato River iwi. Co-governance and co-management change the standard model of traditional autonomous decision-making or rangatiratanga within an iwi and potentially challenges the decisions made. The co-governance and co-management Deed agreed between Maniapoto and the Crown for the Waipā River has changed how people operate in the Maniapoto rohe and how they may have operated previously. This thesis concludes by reflecting on some of the challenges experienced by Maniapoto in the new co-governance and co-management era.

year: 2020