title: Evaluating the effects of invasive brown bullhead catfish (Ameiurus nebulosus) on kōura (freshwater crayfish, Paranephrops planifrons) in Lake Rotoiti

authors: Francis, Laura Beverley

subjects: catfish

abstract: Brown bullhead catfish (Ameiurus nebulosus) are opportunistic carnivores native to North America and were first detected in Te Weta Bay, Lake Rotoiti, in March 2016. A cordon was placed across the bay to try and contain catfish, but they had already established populations elsewhere. Spread of catfish in the lake raised concern for resident populations of freshwater crayfish or kōura (Paranephrops planifrons), which are of ecological and cultural significance to Māori. Given the limited knowledge of the potential impacts of catfish on native biota, this thesis aims to evaluate the effects of catfish on kōura in Lake Rotoiti. To do this, Bay of Plenty Regional Council (BOPRC) routine fyke netting data was used to explore species trends and relationships. A habitat survey was also conducted using whakaweku (bracken fern bundles) and fyke nets, to generate data on species’ habitat preferences and kōura metrics (e.g., sizes and sex ratios). In addition to fishing, kōura and catfish stomachs were dissected to determine diet. Potential food items of catfish were also collected for stable isotope analysis to estimate dietary overlap between catfish and kōura, and long-term resource acquisition. 

Routine BOPRC fyke netting results indicated that kōura catch per unit effort (CPUE) has declined in Lake Rotoiti, with mean catch rates dropping from 10.6 kōura net-1 night-1 in 2016 to 4.2 kōura net-1 night-1 in 2018. Over the same period, catfish CPUE has increased in the lake, with the highest catch rates in Te Weta Bay, where mean catch rates have increased from 1.1 catfish net-1 night-1 in 2016 to 63.7 catfish net-1 night-1 in 2018. Catfish catch rates were negatively associated with catch rates of kōura (r = −0.180). Mean catfish density also had a significant effect on kōura catch rates, with significantly more kōura being caught at sites without catfish. The negative association between catfish and kōura could be due to catfish eating or competing with kōura, or their differing habitat preferences. Catfish were positively associated with sites that are weedy or muddy and kōura were negatively associated with muddy habitats and were positively associated with rocky habitats. Whakaweku set at shallow depths <1 m in the lake littoral zone were ineffective at catching kōura during the habitat survey. 

Catfish diet consisted largely of chironomid larvae (Chironomidae), detritus, common bullies (Gobiomorphus cotidianus), and to a lesser extent kōura. Kōura were found in 12% of large catfish (>200 mm fork length; FL) stomachs analysed and contributed 5% volumetrically to large catfish diet. Unfortunately, the contribution of kōura to catfish diet could not be established using stable isotopes because isotopic signatures of kōura and bullies were too close to differentiate. Kōura diet consisted primarily of animal remains (common bullies and invertebrates) and detritus. Stable isotopes of carbon and nitrogen revealed that diets of kōura and catfish overlapped, with kōura sharing more of their diet with catfish than vice versa, likely reflecting catfish’s broad diet. This study suggests that catfish are responsible for the recent decline in kōura CPUE in Lake Rotoiti and that catfish are directly and indirectly affecting kōura through predation and competition for shared food resources.

text: Evaluating the effects of invasive brown bullhead catfish (Ameiurus nebulosus) on kōura (freshwater crayfish, Paranephrops planifrons) in Lake Rotoiti Brown bullhead catfish (Ameiurus nebulosus) are opportunistic carnivores native to North America and were first detected in Te Weta Bay, Lake Rotoiti, in March 2016. A cordon was placed across the bay to try and contain catfish, but they had already established populations elsewhere. Spread of catfish in the lake raised concern for resident populations of freshwater crayfish or kōura (Paranephrops planifrons), which are of ecological and cultural significance to Māori. Given the limited knowledge of the potential impacts of catfish on native biota, this thesis aims to evaluate the effects of catfish on kōura in Lake Rotoiti. To do this, Bay of Plenty Regional Council (BOPRC) routine fyke netting data was used to explore species trends and relationships. A habitat survey was also conducted using whakaweku (bracken fern bundles) and fyke nets, to generate data on species’ habitat preferences and kōura metrics (e.g., sizes and sex ratios). In addition to fishing, kōura and catfish stomachs were dissected to determine diet. Potential food items of catfish were also collected for stable isotope analysis to estimate dietary overlap between catfish and kōura, and long-term resource acquisition. 

Routine BOPRC fyke netting results indicated that kōura catch per unit effort (CPUE) has declined in Lake Rotoiti, with mean catch rates dropping from 10.6 kōura net-1 night-1 in 2016 to 4.2 kōura net-1 night-1 in 2018. Over the same period, catfish CPUE has increased in the lake, with the highest catch rates in Te Weta Bay, where mean catch rates have increased from 1.1 catfish net-1 night-1 in 2016 to 63.7 catfish net-1 night-1 in 2018. Catfish catch rates were negatively associated with catch rates of kōura (r = −0.180). Mean catfish density also had a significant effect on kōura catch rates, with significantly more kōura being caught at sites without catfish. The negative association between catfish and kōura could be due to catfish eating or competing with kōura, or their differing habitat preferences. Catfish were positively associated with sites that are weedy or muddy and kōura were negatively associated with muddy habitats and were positively associated with rocky habitats. Whakaweku set at shallow depths <1 m in the lake littoral zone were ineffective at catching kōura during the habitat survey. 

Catfish diet consisted largely of chironomid larvae (Chironomidae), detritus, common bullies (Gobiomorphus cotidianus), and to a lesser extent kōura. Kōura were found in 12% of large catfish (>200 mm fork length; FL) stomachs analysed and contributed 5% volumetrically to large catfish diet. Unfortunately, the contribution of kōura to catfish diet could not be established using stable isotopes because isotopic signatures of kōura and bullies were too close to differentiate. Kōura diet consisted primarily of animal remains (common bullies and invertebrates) and detritus. Stable isotopes of carbon and nitrogen revealed that diets of kōura and catfish overlapped, with kōura sharing more of their diet with catfish than vice versa, likely reflecting catfish’s broad diet. This study suggests that catfish are responsible for the recent decline in kōura CPUE in Lake Rotoiti and that catfish are directly and indirectly affecting kōura through predation and competition for shared food resources.

year: 2019

title: Rolling Our Eyes Towards God: An Intervention Arising from Mormon Missionary YouTube Activity and The Cultural (Mis)Appropriation of Haka

authors: Simon, Hemopereki

abstract: This Kaupapa Māori Research writing inquiry explores the (mis)appropriation of haka and the social media video-sharing platform YouTube in that (mis)appropriation. The article examines the specific case of a group of Latter-day Saint missionaries in Wangarratta, Australia, who wrote and performed an English- language haka that the author finds violent and offensive. The article outlines Aileen Moreton-Robertson’s White Possessive doctrine in relation to the Church and white patriarchal salvation. Haka’s cultural background and appropriation are explained. Theoretical explanations of collective and cultural memory and YouTube as a social media platform and cultural archive follow. The author highlights YouTube grey literature sources on haka cultural (mis)appropriation. The 2006 case study “missionary haka” video is critiqued and analysed. Case study issues are discussed. The Church’s history of racial discrimination and violence and its religious aetiology of skin colour make this video ”misappropriated,” according to research. This performance uses haka to promote white and religious supremacy and the idea that you must be white and/or religious to be fully human. This message helps the LDS Church mission of possessing Indigenous souls and remaining the “true religion”.

text: Rolling Our Eyes Towards God: An Intervention Arising from Mormon Missionary YouTube Activity and The Cultural (Mis)Appropriation of Haka This Kaupapa Māori Research writing inquiry explores the (mis)appropriation of haka and the social media video-sharing platform YouTube in that (mis)appropriation. The article examines the specific case of a group of Latter-day Saint missionaries in Wangarratta, Australia, who wrote and performed an English- language haka that the author finds violent and offensive. The article outlines Aileen Moreton-Robertson’s White Possessive doctrine in relation to the Church and white patriarchal salvation. Haka’s cultural background and appropriation are explained. Theoretical explanations of collective and cultural memory and YouTube as a social media platform and cultural archive follow. The author highlights YouTube grey literature sources on haka cultural (mis)appropriation. The 2006 case study “missionary haka” video is critiqued and analysed. Case study issues are discussed. The Church’s history of racial discrimination and violence and its religious aetiology of skin colour make this video ”misappropriated,” according to research. This performance uses haka to promote white and religious supremacy and the idea that you must be white and/or religious to be fully human. This message helps the LDS Church mission of possessing Indigenous souls and remaining the “true religion”.

year: 2023-02-05

title: Wave induced sediment transport on intertidal flats in a fetch limited environment, Pine Harbour Marina, Auckland

authors: Hull, Joanne Margaret

subjects: Pine Harbour Marina

abstract: This study investigates the nature of sediments and the role of tides, currents, waves and winds in driving sediment transport on the intertidal flats and shallow subtidal areas in the vicinity of Pine Harbour Marina which is situated in a shallow embayment adjoining Tamaki Strait in Hauraki Gulf, northeast North Island, New Zealand. The results from these investigations along with the study of the marina approach channel and dredge spoil dump site are used to examine the causes of sediment infilling the approach channel to the marina. This work was undertaken in support of two resource consents (W9205 and W9258) granted to Pine Harbour Marina by the Auckland Regional Council to undertake maintenance dredging to excavate 4,500 m3 of sediment from the navigation approach channel between June and October 1994.
The sediments of the intertidal and shallow subtidal regions in the vicinity of Pine Harbour Marina were characterised and sediment mixing depths and transport patterns investigated with sedimentation rods, tracer studies, beach surveys and hydrographic surveys. The forcing processes of tide, wave, current and wind in the embayment were also investigated with hydrodynamic monitoring and a wave generation model for fetch limited environments was used to hind cast wave conditions. The data was collected, in conjunction with a monitoring program of the physical impacts of the 1994 dredging, to identify sediment transport pathways and to obtain quantitative sediment volume changes over the intertidal and subtidal channel areas.
Pine Harbour Marina is situated in a fetch limited low wave energy environment, dominated by local wind generated waves. Wave generation model WGEN3DD for limited fetches, was set up to hind cast wave conditions from wind data recorded at the site. The wave climate is characterised by wave heights (Hₛ) between 0.1 m to 0.4 m, and wave periods (Tₛ) between 1.0 and 2.0 s. Large wave events are rare, but wave heights (Hₛ) up to 0.5 m and periods (Tₛ) of 2.5 s are generated by wind speeds greater than 10 m/s from the northwest where fetch is greatest.
Wind driven circulation is important over the shallow intertidal region. On a day-to-day basis suspended sediment is transported north driven by the prevailing south-westerly winds. However large infrequent storms from the north have a greater impact on sediment transport over short time periods where significant volumes of sediment are entrained beneath high energy waves. Greater sediment transport occurs over the intertidal region than the subtidal region because sediment threshold velocities are more frequently exceeded in the shallower water depths. Thus sediment deposited in the approach channel to Pine Harbour Marina is infrequently entrained as wave orbital velocities are attenuated before they reach the bed in the deeper water.
A sediment tracer experiment was undertaken using artificial fluorescent particles to identify the pattern of fine grained sediment dispersion over the intertidal flats. The dominant sediment transport direction detected was towards the southeast during a westerly storm, and a significant concentration of tracer particles accumulated in the approach channel. 
Sediment depth of disturbance rods on the intertidal flats indicate that sediment mixing depths were generally less than 1.5 cm due to shallow disturbance created the movement of small (h = 1.0-1.5 cm) wave ripples. Depth of sediment disturbance increased to between 2.0 and 3.0 cm associated with storm periods. The maximum sediment mixing depth recorded by sedimentation rods was 6.2 cm. Similar mixing depths of 2.5 cm were recorded during
mixing depth experiments involving short cores through buried dyed sediment and vertical mixing of fluorescent tracer particles. Fluorescent tracer was mixed to a maximum depth of 17 cm, which was not attributed to wave action but rather to bioturbation.
Six monthly beach surveys indicated 2.5 cm of accretion occurred over the mid tide region on the northern intertidal flats. This volume of sediment accretion accounts for approximately half of the dredgings material dumped on the intertidal flats. The remaining dumped sediment was resuspended by wave action and either transported back into the approach channel to Pine Harbour Marina, or removed from the area in suspension.
Within 9 months of dredging of the approach channel, an average of 0.5 m of sediment deposition occurred along the northern side of the landward 700 m of approach channel. This was estimated to be approximately 5,250 m³ ± 2,100 m³ of sediment infilling the channel. The increased rate of sediment infilling the approach channel is attributed to natural sediment accumulation combined with the rapid transportation of some dredgings sediment back into the channel.
Initially dredgings sediment appeared to consolidate in situ, but became dispersed as a shallow layer extending up to 100 m over the intertidal flats north of the approach channel. Over the course of the investigation the dredge mounds were observed to be eroded by small drainage channels which became incised into the silty sediment at various locations transporting fine sediment from the dredge mound and intertidal flats into the approach channel. Some 12 months after dredging, the dredge mounds were dissipated and only remnant blocks of gravel to boulder sized fragments of bed rock were left.
This investigation has shown that a significant amount of dredge spoil deposited on the northern intertidal flats during the 1994 dredging operation became transported back into the approach channel within 9 months of the completion of the dredging works. An alternate disposal site for future maintenance dredging works in the approach channel at a further distance from the channel edge would reduce the likelihood of "recycling" of dredged material. Possible alternate disposal options for management of dredge spoil from future maintenance dredging could include: sidecasting disposal further from the channel; offshore disposal site - adjacent or distant; contained disposal; or landfill.

text: Wave induced sediment transport on intertidal flats in a fetch limited environment, Pine Harbour Marina, Auckland This study investigates the nature of sediments and the role of tides, currents, waves and winds in driving sediment transport on the intertidal flats and shallow subtidal areas in the vicinity of Pine Harbour Marina which is situated in a shallow embayment adjoining Tamaki Strait in Hauraki Gulf, northeast North Island, New Zealand. The results from these investigations along with the study of the marina approach channel and dredge spoil dump site are used to examine the causes of sediment infilling the approach channel to the marina. This work was undertaken in support of two resource consents (W9205 and W9258) granted to Pine Harbour Marina by the Auckland Regional Council to undertake maintenance dredging to excavate 4,500 m3 of sediment from the navigation approach channel between June and October 1994.
The sediments of the intertidal and shallow subtidal regions in the vicinity of Pine Harbour Marina were characterised and sediment mixing depths and transport patterns investigated with sedimentation rods, tracer studies, beach surveys and hydrographic surveys. The forcing processes of tide, wave, current and wind in the embayment were also investigated with hydrodynamic monitoring and a wave generation model for fetch limited environments was used to hind cast wave conditions. The data was collected, in conjunction with a monitoring program of the physical impacts of the 1994 dredging, to identify sediment transport pathways and to obtain quantitative sediment volume changes over the intertidal and subtidal channel areas.
Pine Harbour Marina is situated in a fetch limited low wave energy environment, dominated by local wind generated waves. Wave generation model WGEN3DD for limited fetches, was set up to hind cast wave conditions from wind data recorded at the site. The wave climate is characterised by wave heights (Hₛ) between 0.1 m to 0.4 m, and wave periods (Tₛ) between 1.0 and 2.0 s. Large wave events are rare, but wave heights (Hₛ) up to 0.5 m and periods (Tₛ) of 2.5 s are generated by wind speeds greater than 10 m/s from the northwest where fetch is greatest.
Wind driven circulation is important over the shallow intertidal region. On a day-to-day basis suspended sediment is transported north driven by the prevailing south-westerly winds. However large infrequent storms from the north have a greater impact on sediment transport over short time periods where significant volumes of sediment are entrained beneath high energy waves. Greater sediment transport occurs over the intertidal region than the subtidal region because sediment threshold velocities are more frequently exceeded in the shallower water depths. Thus sediment deposited in the approach channel to Pine Harbour Marina is infrequently entrained as wave orbital velocities are attenuated before they reach the bed in the deeper water.
A sediment tracer experiment was undertaken using artificial fluorescent particles to identify the pattern of fine grained sediment dispersion over the intertidal flats. The dominant sediment transport direction detected was towards the southeast during a westerly storm, and a significant concentration of tracer particles accumulated in the approach channel. 
Sediment depth of disturbance rods on the intertidal flats indicate that sediment mixing depths were generally less than 1.5 cm due to shallow disturbance created the movement of small (h = 1.0-1.5 cm) wave ripples. Depth of sediment disturbance increased to between 2.0 and 3.0 cm associated with storm periods. The maximum sediment mixing depth recorded by sedimentation rods was 6.2 cm. Similar mixing depths of 2.5 cm were recorded during
mixing depth experiments involving short cores through buried dyed sediment and vertical mixing of fluorescent tracer particles. Fluorescent tracer was mixed to a maximum depth of 17 cm, which was not attributed to wave action but rather to bioturbation.
Six monthly beach surveys indicated 2.5 cm of accretion occurred over the mid tide region on the northern intertidal flats. This volume of sediment accretion accounts for approximately half of the dredgings material dumped on the intertidal flats. The remaining dumped sediment was resuspended by wave action and either transported back into the approach channel to Pine Harbour Marina, or removed from the area in suspension.
Within 9 months of dredging of the approach channel, an average of 0.5 m of sediment deposition occurred along the northern side of the landward 700 m of approach channel. This was estimated to be approximately 5,250 m³ ± 2,100 m³ of sediment infilling the channel. The increased rate of sediment infilling the approach channel is attributed to natural sediment accumulation combined with the rapid transportation of some dredgings sediment back into the channel.
Initially dredgings sediment appeared to consolidate in situ, but became dispersed as a shallow layer extending up to 100 m over the intertidal flats north of the approach channel. Over the course of the investigation the dredge mounds were observed to be eroded by small drainage channels which became incised into the silty sediment at various locations transporting fine sediment from the dredge mound and intertidal flats into the approach channel. Some 12 months after dredging, the dredge mounds were dissipated and only remnant blocks of gravel to boulder sized fragments of bed rock were left.
This investigation has shown that a significant amount of dredge spoil deposited on the northern intertidal flats during the 1994 dredging operation became transported back into the approach channel within 9 months of the completion of the dredging works. An alternate disposal site for future maintenance dredging works in the approach channel at a further distance from the channel edge would reduce the likelihood of "recycling" of dredged material. Possible alternate disposal options for management of dredge spoil from future maintenance dredging could include: sidecasting disposal further from the channel; offshore disposal site - adjacent or distant; contained disposal; or landfill.

year: 1996