title: The change in the horizontal position of the dune toe and vegetation line on beaches within the Waikato Region

authors: Davies-Calway, Celeste Jade

subjects: dune toe

abstract: Beaches are highly variable landscapes that are constantly changing in response to a range of climatic variables. For example, local wind can cause the movement of sand across the beach and accretion, whilst storms that occur far from the beach create waves and surges which also changes the shape and morphology of the beach. The lower beach face is inundated for longer during a tidal cycle and therefore is subjected more often to wave action conversely, the upper part of the beach is inundated less often and therefore is less affected by wave energy. When storms occur, water levels are higher along the beach, waves are brought into contact with the upper beach face and erosion occurs. This erosion causes escarpment of the dune face and landward movement of the beach face, where sand is transported to offshore bars in the surf zone. Changes also occur during fair weather conditions where accretion occurs across the beach face and dune area and sand is transported back up onto the beach and sand dunes.

Beach morphology has traditionally been monitored using beach profiles, however new methods are emerging that provide more information with the potential for greater spatial and temporal data collection. In New Zealand the vegetation line and the position of the dune toe is often used as a proxy for the shoreline and setback distances are measured relative to this feature. Beach morphodynamics have been studied extensively but typical monitoring and predictive methods are not optimised to track and predict changes in the dune toe position. Beach profile surveys are the most common and reliable monitoring method used for monitoring beaches and they are used extensively throughout the world. Although beach profiles give valuable information on several different aspects of beach processes, they may not be the optimal method for tracking dune toe movement and there are other methods that might be more effective.

The aim of the research was to provide information to help optimise the monitoring and prediction of changes in the dune toe by determining: (i) the horizontal and vertical variation of the dune toe to establish how often the horizontal and vertical position of the sand dune toe changes, (ii) the alongshore variation of the dune toe along the beach length, (iii) what causes the changes in the dune toe, (iv) compare using the dune toe for beach monitoring with traditional beach monitoring methods, (v) testing different methods to measure the dune toe and vegetation line, (vi) predicting the dune toe in the future using a model. The main study sites for the research were Whangapoua Beach, Matarangi Beach, Buffalo Beach, Hot Water Beach and Tairua beach of eastern Coromandel Peninsula, and Ngarunui Beach, Raglan, where field surveys were conducted. An historical dataset of beach profiles from 20 Eastern Coromandel beaches were analysed for long term patterns. A new method for measuring dune toe using video analysis and a model for predicting the future dune toe changes was tested at Tairua Beach, Coromandel Peninsula.

The results show that, from the field survey of beach profiles, there was low variability at the dune toe compared with further down the beach. The range of distribution of the vegetation line was larger than the range of distribution for the dune toe and the dune toe was generally more seaward than the vegetation line. The vegetation line was generally not at the same location as the dune toe which has strong implications for using vegetation as a measure of dune movement. The alongshore dune toe underwent small changes throughout the survey period and there was alongshore variation of the dune toe, along with changes in the dune toe horizontal position and height of the dune toe throughout the year survey period, which was expected. Video analysis was shown to be a potential new technique for measuring the vegetation line which could be used for beach monitoring. A model was used to predict the change in the dune toe, and it predicted that there was no change in the dune toe between 1998 and 2011; however, the analysis of the imagery showed there were numerous occasions where water reached the dune toe and therefore erosion of the dune toe occurred.

text: The change in the horizontal position of the dune toe and vegetation line on beaches within the Waikato Region Beaches are highly variable landscapes that are constantly changing in response to a range of climatic variables. For example, local wind can cause the movement of sand across the beach and accretion, whilst storms that occur far from the beach create waves and surges which also changes the shape and morphology of the beach. The lower beach face is inundated for longer during a tidal cycle and therefore is subjected more often to wave action conversely, the upper part of the beach is inundated less often and therefore is less affected by wave energy. When storms occur, water levels are higher along the beach, waves are brought into contact with the upper beach face and erosion occurs. This erosion causes escarpment of the dune face and landward movement of the beach face, where sand is transported to offshore bars in the surf zone. Changes also occur during fair weather conditions where accretion occurs across the beach face and dune area and sand is transported back up onto the beach and sand dunes.

Beach morphology has traditionally been monitored using beach profiles, however new methods are emerging that provide more information with the potential for greater spatial and temporal data collection. In New Zealand the vegetation line and the position of the dune toe is often used as a proxy for the shoreline and setback distances are measured relative to this feature. Beach morphodynamics have been studied extensively but typical monitoring and predictive methods are not optimised to track and predict changes in the dune toe position. Beach profile surveys are the most common and reliable monitoring method used for monitoring beaches and they are used extensively throughout the world. Although beach profiles give valuable information on several different aspects of beach processes, they may not be the optimal method for tracking dune toe movement and there are other methods that might be more effective.

The aim of the research was to provide information to help optimise the monitoring and prediction of changes in the dune toe by determining: (i) the horizontal and vertical variation of the dune toe to establish how often the horizontal and vertical position of the sand dune toe changes, (ii) the alongshore variation of the dune toe along the beach length, (iii) what causes the changes in the dune toe, (iv) compare using the dune toe for beach monitoring with traditional beach monitoring methods, (v) testing different methods to measure the dune toe and vegetation line, (vi) predicting the dune toe in the future using a model. The main study sites for the research were Whangapoua Beach, Matarangi Beach, Buffalo Beach, Hot Water Beach and Tairua beach of eastern Coromandel Peninsula, and Ngarunui Beach, Raglan, where field surveys were conducted. An historical dataset of beach profiles from 20 Eastern Coromandel beaches were analysed for long term patterns. A new method for measuring dune toe using video analysis and a model for predicting the future dune toe changes was tested at Tairua Beach, Coromandel Peninsula.

The results show that, from the field survey of beach profiles, there was low variability at the dune toe compared with further down the beach. The range of distribution of the vegetation line was larger than the range of distribution for the dune toe and the dune toe was generally more seaward than the vegetation line. The vegetation line was generally not at the same location as the dune toe which has strong implications for using vegetation as a measure of dune movement. The alongshore dune toe underwent small changes throughout the survey period and there was alongshore variation of the dune toe, along with changes in the dune toe horizontal position and height of the dune toe throughout the year survey period, which was expected. Video analysis was shown to be a potential new technique for measuring the vegetation line which could be used for beach monitoring. A model was used to predict the change in the dune toe, and it predicted that there was no change in the dune toe between 1998 and 2011; however, the analysis of the imagery showed there were numerous occasions where water reached the dune toe and therefore erosion of the dune toe occurred.

year: 2020

title: Responses of the fish community and biomass in Lake Ohinewai to fish removal and the koi carp exclusion barrier

authors: Tempero, Grant Wayne

abstract: The objectives of this research were to determine the biomass of koi carp (Cyprinus carpio) and other fish species in Lake Ohinewai in 2016 by two-sample mark-recapture methods and to compare these estimates with similar studies conducted in 2011, 2012, and 2014. In May 2011 the University of Waikato installed a one-way barrier on the outlet of Lake Ohinewai that was designed to prevent adult koi carp moving upstream into the lake, while allowing fish to pass downstream out of the lake, thereby attempting to passively reduce fish biomass in the lake. In addition, an invasive fish removal programme was undertaken in Lake Ohinewai with the aim of reducing the koi carp population from the estimated original biomass of 308 kg/ha (211–466, 95% CL) to below 100 kg/ha. In previous mark-recapture studies it was estimated that the koi carp biomass had been reduced to 39 kg/ha (24–67, 95% CL) in 2012 and 14 kg/ha (7–27, 95% CL) in 2014 by a combination of fish removal and the one-way gate. In 2016, we estimated that the koi carp biomass had increased to 94 kg/ha (49–197, 95% CL).
A mark-recapture study was conducted on the fish community in Lake Ohinewai from 21 November to 7 December 2016. Capture method included fyke net sets for a total of 120 net nights and boat electrofishing for 12 h. Species included in the study were the invasive species koi carp, brown bullhead catfish (Ameiurus nebulosus), rudd (Scardinius erythrophthalmus), goldfish (Carassius auratus) and koi carp-goldfish hybrids, and the native species shortfin eel (Anguilla australis) and longfin eel (Anguilla dieffenbachii). In addition, water samples for nutrient analysis and suspended solids, Secchi depth, CTD (conductivity, temperature, depth) profiles and zooplankton and phytoplankton samples were taken from Lake Ohinewai on three occasions between 21 November 2016 and 20 January 2017.
A total of 1680 fish were caught in the marking phase (21–24 November 2016) and 2058 fish in the recapture phase (5–8 December 2016); 479 of fish caught in the recapture phase were marked. The estimated koi carp population in Lake Ohinewai more than quadrupled in size from 454 (251–889, 95% CL) fish in 2014 to 2063 (1070–4328, 95% CL) fish in 2016. Similar increases in the estimated populations of catfish (925 to 4010), goldfish (512 to 1927) and koi carp hybrids (43 to 252) were also observed. Eels also increased in abundance; between 2014 and 2016 shortfin eels increased from 2305 to 3456 and longfin eels increased from 44 to 100. Total invasive fish biomass also increased from 29 kg/ha (18–50, 95% CL) in 2014 to 154 kg/ha (78–311, 95% CL) in 2016. This change was primarily due to an increase in koi carp biomass, but increases in catfish and goldfish biomasses have also occurred since 2014. Goldfish showed a strong pulse of recruitment in 2016.
The large-scale removal of invasive fish and installation of the one-way barrier resulted in significant changes to the invasive fish community composition. The fish removal programme reduced the proportion of larger (>275 mm fork length) koi carp and goldfish, which can be attributed to size selectivity of the removal methods and emigration of adult koi carp from the lake. Recruitment of smaller koi carp was observed in 2014 when they had bimodal size distribution, comprising juvenile fish (<250 mm FL) and adult fish (>300 mm FL).
Shortfin eels increased significantly in mean weight following carp removal. Changes in the longfin eel population appeared similar to those of shortfin eels, with an increased proportion of larger eels following removal of koi carp and other invasive fish, but the low sample size hampered comparisons of mean weight.
Water quality indicators such as nutrient concentrations, Secchi depth and total suspended solids showed no improvement in the 5 years following the reduction in invasive fish biomass, except for chlorophyll a concentration, which declined with decreasing biomass of invasive fish from 2011 to 2014, and returned to previous concentrations as invasive fish biomass increased by 2016. It is not entirely clear that this was caused by changes in the fish biomass as total nitrogen also declined from 2009 to 2013. Total phosphorus remained largely unchanged throughout the study period. In addition, phytoplankton species and abundance appear consistent with other hypereutrophic lakes in the Waikato region. The annual mean TLI3, which excludes Secchi depth, ranged from 6.1 to 6.6 between 2006 and 2017, indicating that the lake remained hypertrophic during fish removal. Chemically-driven internal nutrient cycling and catchment nutrient inputs are likely to maintain the hypereutrophic condition and low water clarity will continue to inhibit re-establishment of submerged macrophytes, the absence of which can exacerbate wind resuspension of sediment.
The increase in the koi carp abundance indicates that at least one successful recruitment event occurred following the removal programme and installation of the one-way barrier, either by spawning in the lake or by upstream migration of juvenile young-of-the-year fish from spawning areas lower in the catchment. In addition, reduced interspecific competition has likely contributed to increased recruitment of the catfish and goldfish populations. Therefore, while the Lake Ohinewai one-way barrier appears effective in preventing immigration of adult koi carp into an area, it should not be considered as a mechanism to exclude both adult and juvenile koi carp nor as a sole measure of control.
In Lake Ohinewai, reductions in koi carp biomass were not long lasting, and during the period of low carp abundance there was no convincing evidence for a corresponding improvement in water quality and zooplankton and phytoplankton community composition. Koi carp removal did appear to increase the abundance and size of shortfin eels. Before any restoration programme is initiated it is recommended that a complete assessment of the system is undertaken to determine which factors are driving the decline in water quality. Ecological models can be helpful in determining these driving factors but they are reliant on substantial data for parameterisation and calibration. If reductions in invasive fish biomass are deemed necessary for ecosystem restoration, repeated removal programmes appear to be the only viable way of ensuring low biomasses of target invasive species are maintained

text: Responses of the fish community and biomass in Lake Ohinewai to fish removal and the koi carp exclusion barrier The objectives of this research were to determine the biomass of koi carp (Cyprinus carpio) and other fish species in Lake Ohinewai in 2016 by two-sample mark-recapture methods and to compare these estimates with similar studies conducted in 2011, 2012, and 2014. In May 2011 the University of Waikato installed a one-way barrier on the outlet of Lake Ohinewai that was designed to prevent adult koi carp moving upstream into the lake, while allowing fish to pass downstream out of the lake, thereby attempting to passively reduce fish biomass in the lake. In addition, an invasive fish removal programme was undertaken in Lake Ohinewai with the aim of reducing the koi carp population from the estimated original biomass of 308 kg/ha (211–466, 95% CL) to below 100 kg/ha. In previous mark-recapture studies it was estimated that the koi carp biomass had been reduced to 39 kg/ha (24–67, 95% CL) in 2012 and 14 kg/ha (7–27, 95% CL) in 2014 by a combination of fish removal and the one-way gate. In 2016, we estimated that the koi carp biomass had increased to 94 kg/ha (49–197, 95% CL).
A mark-recapture study was conducted on the fish community in Lake Ohinewai from 21 November to 7 December 2016. Capture method included fyke net sets for a total of 120 net nights and boat electrofishing for 12 h. Species included in the study were the invasive species koi carp, brown bullhead catfish (Ameiurus nebulosus), rudd (Scardinius erythrophthalmus), goldfish (Carassius auratus) and koi carp-goldfish hybrids, and the native species shortfin eel (Anguilla australis) and longfin eel (Anguilla dieffenbachii). In addition, water samples for nutrient analysis and suspended solids, Secchi depth, CTD (conductivity, temperature, depth) profiles and zooplankton and phytoplankton samples were taken from Lake Ohinewai on three occasions between 21 November 2016 and 20 January 2017.
A total of 1680 fish were caught in the marking phase (21–24 November 2016) and 2058 fish in the recapture phase (5–8 December 2016); 479 of fish caught in the recapture phase were marked. The estimated koi carp population in Lake Ohinewai more than quadrupled in size from 454 (251–889, 95% CL) fish in 2014 to 2063 (1070–4328, 95% CL) fish in 2016. Similar increases in the estimated populations of catfish (925 to 4010), goldfish (512 to 1927) and koi carp hybrids (43 to 252) were also observed. Eels also increased in abundance; between 2014 and 2016 shortfin eels increased from 2305 to 3456 and longfin eels increased from 44 to 100. Total invasive fish biomass also increased from 29 kg/ha (18–50, 95% CL) in 2014 to 154 kg/ha (78–311, 95% CL) in 2016. This change was primarily due to an increase in koi carp biomass, but increases in catfish and goldfish biomasses have also occurred since 2014. Goldfish showed a strong pulse of recruitment in 2016.
The large-scale removal of invasive fish and installation of the one-way barrier resulted in significant changes to the invasive fish community composition. The fish removal programme reduced the proportion of larger (>275 mm fork length) koi carp and goldfish, which can be attributed to size selectivity of the removal methods and emigration of adult koi carp from the lake. Recruitment of smaller koi carp was observed in 2014 when they had bimodal size distribution, comprising juvenile fish (<250 mm FL) and adult fish (>300 mm FL).
Shortfin eels increased significantly in mean weight following carp removal. Changes in the longfin eel population appeared similar to those of shortfin eels, with an increased proportion of larger eels following removal of koi carp and other invasive fish, but the low sample size hampered comparisons of mean weight.
Water quality indicators such as nutrient concentrations, Secchi depth and total suspended solids showed no improvement in the 5 years following the reduction in invasive fish biomass, except for chlorophyll a concentration, which declined with decreasing biomass of invasive fish from 2011 to 2014, and returned to previous concentrations as invasive fish biomass increased by 2016. It is not entirely clear that this was caused by changes in the fish biomass as total nitrogen also declined from 2009 to 2013. Total phosphorus remained largely unchanged throughout the study period. In addition, phytoplankton species and abundance appear consistent with other hypereutrophic lakes in the Waikato region. The annual mean TLI3, which excludes Secchi depth, ranged from 6.1 to 6.6 between 2006 and 2017, indicating that the lake remained hypertrophic during fish removal. Chemically-driven internal nutrient cycling and catchment nutrient inputs are likely to maintain the hypereutrophic condition and low water clarity will continue to inhibit re-establishment of submerged macrophytes, the absence of which can exacerbate wind resuspension of sediment.
The increase in the koi carp abundance indicates that at least one successful recruitment event occurred following the removal programme and installation of the one-way barrier, either by spawning in the lake or by upstream migration of juvenile young-of-the-year fish from spawning areas lower in the catchment. In addition, reduced interspecific competition has likely contributed to increased recruitment of the catfish and goldfish populations. Therefore, while the Lake Ohinewai one-way barrier appears effective in preventing immigration of adult koi carp into an area, it should not be considered as a mechanism to exclude both adult and juvenile koi carp nor as a sole measure of control.
In Lake Ohinewai, reductions in koi carp biomass were not long lasting, and during the period of low carp abundance there was no convincing evidence for a corresponding improvement in water quality and zooplankton and phytoplankton community composition. Koi carp removal did appear to increase the abundance and size of shortfin eels. Before any restoration programme is initiated it is recommended that a complete assessment of the system is undertaken to determine which factors are driving the decline in water quality. Ecological models can be helpful in determining these driving factors but they are reliant on substantial data for parameterisation and calibration. If reductions in invasive fish biomass are deemed necessary for ecosystem restoration, repeated removal programmes appear to be the only viable way of ensuring low biomasses of target invasive species are maintained

year: 2017

title: Mātauranga Māori to inform understanding of population dynamics and health of pipi in Waihī Estuary, Bay of Plenty.

authors: Kettle, Tyla

abstract: Estuaries are among the most productive ecosystems on earth. They hold significant value to Māori as they connect the whenua (land), awa (river) and moana (ocean), and are an important source of kaimoana (seafood) including shellfish. However, due to increased anthropogenic pressures, many estuaries are degraded, affecting taonga (Māori treasure) species such as pipi (Paphies australis). My thesis uses kaupapa Māori methodology and is co-developed with Ngāti Whakahemo, tangata whenua (people of the land) of Waihī Estuary. This project fundamentally draws upon mātauranga Māori (traditional Māori knowledge), combined with western science to map the historic and current distribution, abundance and health of pipi in Waihī Estuary; as well as explore the perceptions of threats to pipi and estuary ecology from tangata whenua and the regional authority. 
Participatory mapping was used via kōrero/interviews with kaumātua to identify sites of significance for pipi, which were then sampled in November 2020. Mātauranga ā iwi from Ngāti Whakahemo informed the sampling locations. Previous pipi sampling methodology and protocols undertaken by the Ministry for Primary Industries (MPI) were used to facilitate temporal comparisons of pipi distribution and abundance. Environmental factors including sediment grain size, organic content, total nitrogen (TN) and total phosphorus (TP) were also measured to help understand what drives the population dynamics of pipi. Perceptions of tangata whenua and staff members of the Bay of Plenty Regional Council (BOPRC) were also explored following methods similar to Klain et al. (2018) and implementing a dread risk tool via participatory mapping.
Results show that culturally significant sites identified by kaumātua support high pipi abundances of large size (40mm+), with low abundances of pipi in the upper reaches of the estuary. The inclusion of sites identified by MPI allowed for more comprehensive survey on pipi population dynamics by utilising a stratified survey design. Pipi size and abundance was significantly correlated with environmental factors with high pipi densities associated with medium grain size fractions and low levels of TN, TP and organic content. Over harvesting was perceived by kaumātua and BOPRC staff members as the dominant threat to pipi abundance and Waihī Estuary. Nutrients related to sewage inputs and runoff were rated as the second highest perceived threat and diseased shellfish ranked third by kaumātua and BOPRC staff members. 
This study demonstrates that the sharing of mātauranga ā iwi can fundamentally inform western science methods and can be used as an approach to research in the marine science realm. The research space was shared by researchers and kaumātua, was honourable of the mātauranga, iwi voices were heard and a co-developed field survey plan/research plan was produced. Iwi concerns were made a priority throughout, and incorporated into the monitoring, mapping and management frameworks. Thus, I had a Māori-centred agenda which is important as Ngāti Whakahemo are looking to utilise the results from my research to inform their iwi environmental management plan. This approach will help to strengthen current marine management practices and in turn Aotearoa New Zealand’s ecosystems due to iwi environmental management plans being informed by such results.

text: Mātauranga Māori to inform understanding of population dynamics and health of pipi in Waihī Estuary, Bay of Plenty. Estuaries are among the most productive ecosystems on earth. They hold significant value to Māori as they connect the whenua (land), awa (river) and moana (ocean), and are an important source of kaimoana (seafood) including shellfish. However, due to increased anthropogenic pressures, many estuaries are degraded, affecting taonga (Māori treasure) species such as pipi (Paphies australis). My thesis uses kaupapa Māori methodology and is co-developed with Ngāti Whakahemo, tangata whenua (people of the land) of Waihī Estuary. This project fundamentally draws upon mātauranga Māori (traditional Māori knowledge), combined with western science to map the historic and current distribution, abundance and health of pipi in Waihī Estuary; as well as explore the perceptions of threats to pipi and estuary ecology from tangata whenua and the regional authority. 
Participatory mapping was used via kōrero/interviews with kaumātua to identify sites of significance for pipi, which were then sampled in November 2020. Mātauranga ā iwi from Ngāti Whakahemo informed the sampling locations. Previous pipi sampling methodology and protocols undertaken by the Ministry for Primary Industries (MPI) were used to facilitate temporal comparisons of pipi distribution and abundance. Environmental factors including sediment grain size, organic content, total nitrogen (TN) and total phosphorus (TP) were also measured to help understand what drives the population dynamics of pipi. Perceptions of tangata whenua and staff members of the Bay of Plenty Regional Council (BOPRC) were also explored following methods similar to Klain et al. (2018) and implementing a dread risk tool via participatory mapping.
Results show that culturally significant sites identified by kaumātua support high pipi abundances of large size (40mm+), with low abundances of pipi in the upper reaches of the estuary. The inclusion of sites identified by MPI allowed for more comprehensive survey on pipi population dynamics by utilising a stratified survey design. Pipi size and abundance was significantly correlated with environmental factors with high pipi densities associated with medium grain size fractions and low levels of TN, TP and organic content. Over harvesting was perceived by kaumātua and BOPRC staff members as the dominant threat to pipi abundance and Waihī Estuary. Nutrients related to sewage inputs and runoff were rated as the second highest perceived threat and diseased shellfish ranked third by kaumātua and BOPRC staff members. 
This study demonstrates that the sharing of mātauranga ā iwi can fundamentally inform western science methods and can be used as an approach to research in the marine science realm. The research space was shared by researchers and kaumātua, was honourable of the mātauranga, iwi voices were heard and a co-developed field survey plan/research plan was produced. Iwi concerns were made a priority throughout, and incorporated into the monitoring, mapping and management frameworks. Thus, I had a Māori-centred agenda which is important as Ngāti Whakahemo are looking to utilise the results from my research to inform their iwi environmental management plan. This approach will help to strengthen current marine management practices and in turn Aotearoa New Zealand’s ecosystems due to iwi environmental management plans being informed by such results.

year: 2021