title: Larval fish of Tauranga Harbour

authors: Brooke, Nathania

subjects: estuary

abstract: Estuaries are important nursery habitats for many fish species, both in New Zealand and worldwide, characterised by high levels of primary production, shallow warmer waters, and affording relative protection from predators. Many estuaries are under constant threat from anthropogenic stressors due to the vicinity of industries that can cause contamination. It is necessary to first understand how larval fish use estuaries in order to understand the potential effects of anthropogenic impacts on their life history stages. Few studies in New Zealand have examined the use of estuaries by pre-settlement larvae. The majority of research undertaken in New Zealand on larval fish has been completed in coastal waters, examining the effects of seasonality, distribution patters, and growth of larvae. The objectives of this research were to increase understanding as to how larval fish use Tauranga Harbour. The study used a stationary channel net at Bridge Marina to intensively sample over one summer, and fortnightly over the ensuing 16 months, in an effort to discover which species of larval fish are found within the harbour; if they were more abundant on the flood or ebb tides; if they were more abundant during the day or night; if any patterns of seasonality were present; and if the abundance was affected by environmental variables such as water temperature or current speed. A choice chamber experiment was conducted to assess if larval kingfish (a species not found in the estuarine sampling programme), were able to differentiate between two different water types - estuarine and oceanic, in an effort to assess if larvae may use olfactory cues when choosing a habitat. 

The larvae of at least 19 species from 18 families were caught during the intensive summer sampling, and at least 13 species from 11 families during the fortnightly sampling, with no new species found during the fortnightly sampling. Three taxa (anchovy Engraulis australis, Tripterygiidae and Gobiidae) were the most abundant over the entire sampling period, making up the majority of all catches. Larvae were found in higher abundances at night compared to the day, and no significant difference was found between abundances on the flood and ebb tides. Seasonality had an effect on larval fish abundance, with higher abundances caught during spring and summer. The kingfish larvae in the choice chamber experiment appeared to display a preference for the oceanic water over the estuarine water.

The findings of this study indicate that larval fish of a range of species use Tauranga Harbour potentially as a nursery. Not surprisingly perhaps, estuarine species were found in the highest abundances. Larval abundance in the estuarine water column is affected primarily by the diel cycle, with larvae displaying behaviours of diel vertical migration and possibly selective tidal stream transport. Abundances of larvae peaked during spring and summer when the water temperature begins to warm after winter, coinciding with the spawning seasons of many fish species. Larval kingfish displayed an attraction towards oceanic water, or perhaps an avoidance of the estuarine water. This suggests that olfactory stimuli are important when choosing potential habitats, signifying that larval fish of estuarine species may actively seek out refuge within an estuary using olfactory cues. This study provides a good benchmark for future studies on larval fish within Tauranga Harbour and other estuarine systems.

text: Larval fish of Tauranga Harbour Estuaries are important nursery habitats for many fish species, both in New Zealand and worldwide, characterised by high levels of primary production, shallow warmer waters, and affording relative protection from predators. Many estuaries are under constant threat from anthropogenic stressors due to the vicinity of industries that can cause contamination. It is necessary to first understand how larval fish use estuaries in order to understand the potential effects of anthropogenic impacts on their life history stages. Few studies in New Zealand have examined the use of estuaries by pre-settlement larvae. The majority of research undertaken in New Zealand on larval fish has been completed in coastal waters, examining the effects of seasonality, distribution patters, and growth of larvae. The objectives of this research were to increase understanding as to how larval fish use Tauranga Harbour. The study used a stationary channel net at Bridge Marina to intensively sample over one summer, and fortnightly over the ensuing 16 months, in an effort to discover which species of larval fish are found within the harbour; if they were more abundant on the flood or ebb tides; if they were more abundant during the day or night; if any patterns of seasonality were present; and if the abundance was affected by environmental variables such as water temperature or current speed. A choice chamber experiment was conducted to assess if larval kingfish (a species not found in the estuarine sampling programme), were able to differentiate between two different water types - estuarine and oceanic, in an effort to assess if larvae may use olfactory cues when choosing a habitat. 

The larvae of at least 19 species from 18 families were caught during the intensive summer sampling, and at least 13 species from 11 families during the fortnightly sampling, with no new species found during the fortnightly sampling. Three taxa (anchovy Engraulis australis, Tripterygiidae and Gobiidae) were the most abundant over the entire sampling period, making up the majority of all catches. Larvae were found in higher abundances at night compared to the day, and no significant difference was found between abundances on the flood and ebb tides. Seasonality had an effect on larval fish abundance, with higher abundances caught during spring and summer. The kingfish larvae in the choice chamber experiment appeared to display a preference for the oceanic water over the estuarine water.

The findings of this study indicate that larval fish of a range of species use Tauranga Harbour potentially as a nursery. Not surprisingly perhaps, estuarine species were found in the highest abundances. Larval abundance in the estuarine water column is affected primarily by the diel cycle, with larvae displaying behaviours of diel vertical migration and possibly selective tidal stream transport. Abundances of larvae peaked during spring and summer when the water temperature begins to warm after winter, coinciding with the spawning seasons of many fish species. Larval kingfish displayed an attraction towards oceanic water, or perhaps an avoidance of the estuarine water. This suggests that olfactory stimuli are important when choosing potential habitats, signifying that larval fish of estuarine species may actively seek out refuge within an estuary using olfactory cues. This study provides a good benchmark for future studies on larval fish within Tauranga Harbour and other estuarine systems.

year: 2015

title: Functional responses of an invasive top predator Mustela erminea to invasive meso-predators Rattus rattus and Mus musculus, in New Zealand forests

authors: Jones, Christopher David

subjects: New Zealand

abstract: Context: Management of suites of invasive mammal species can lead to perverse outcomes, such as meso-predator release, or can achieve desirable reductions in the abundance of top-order predators by controlling their prey. Predictive models for predator–prey systems require estimates of predator functional responses, i.e. predation rates as functions of prey density.
Aims: In New Zealand, estimates of the functional responses of stoats (Mustela erminea) to mice (Mus musculus) and ship (black) rats (Rattus rattus) are required to improve management models for these invasive species.
Methods: We derived fitted relationships between the presence or absence of mouse or ship-rat remains in stoat guts and corresponding indices of prey abundance in beech and podocarp forests, respectively. To convert field data on stoat-gut contents to minimum kill rates, we used data on feeding activity and estimates of gut-passage time, observed in captive stoats.
Key results: The most parsimonious fitted curves were Type II functional responses, with a steeper stoat–mouse curve for autumn–winter, indicating a more specialist feeding habit than that in spring–summer. Estimated kill rates of mice per stoat per day reached an asymptote of 1.13 during autumn–winter. Our maximum observed kill rate for spring–summer was 11% less than the extrapolated upper limit of 1.04 mice per stoat per day for New Zealand ecosystems. No asymptote was reached within the limits of the data for the stoat–rat relationship.
Conclusions: Recent models for trophic interactions between stoats and the primary rodent prey have overestimated kill rates by stoats in forested ecosystems, particularly at very low and very high densities of mice. We show how data on stoat-gut contents can be rescaled to estimate minimum kill rates of rodent prey.
Implications: The functional-response relationships we have derived can be used to improve modelled predictions of the effects of natural or management-driven perturbations of invasive stoats and their primary rodent-prey populations.

text: Functional responses of an invasive top predator Mustela erminea to invasive meso-predators Rattus rattus and Mus musculus, in New Zealand forests Context: Management of suites of invasive mammal species can lead to perverse outcomes, such as meso-predator release, or can achieve desirable reductions in the abundance of top-order predators by controlling their prey. Predictive models for predator–prey systems require estimates of predator functional responses, i.e. predation rates as functions of prey density.
Aims: In New Zealand, estimates of the functional responses of stoats (Mustela erminea) to mice (Mus musculus) and ship (black) rats (Rattus rattus) are required to improve management models for these invasive species.
Methods: We derived fitted relationships between the presence or absence of mouse or ship-rat remains in stoat guts and corresponding indices of prey abundance in beech and podocarp forests, respectively. To convert field data on stoat-gut contents to minimum kill rates, we used data on feeding activity and estimates of gut-passage time, observed in captive stoats.
Key results: The most parsimonious fitted curves were Type II functional responses, with a steeper stoat–mouse curve for autumn–winter, indicating a more specialist feeding habit than that in spring–summer. Estimated kill rates of mice per stoat per day reached an asymptote of 1.13 during autumn–winter. Our maximum observed kill rate for spring–summer was 11% less than the extrapolated upper limit of 1.04 mice per stoat per day for New Zealand ecosystems. No asymptote was reached within the limits of the data for the stoat–rat relationship.
Conclusions: Recent models for trophic interactions between stoats and the primary rodent prey have overestimated kill rates by stoats in forested ecosystems, particularly at very low and very high densities of mice. We show how data on stoat-gut contents can be rescaled to estimate minimum kill rates of rodent prey.
Implications: The functional-response relationships we have derived can be used to improve modelled predictions of the effects of natural or management-driven perturbations of invasive stoats and their primary rodent-prey populations.

year: 2011

title: Heritage-making in Aotearoa planning: Unsettling norms in contested urban space

authors: Hill, Carolyn Joy

subjects: Authorised heritage discourse

abstract: Heritage is currently a high-profile and often contentious topic in urban environments. As cities face growing challenges of climate change, intensification needs and cultural contestation, state-mandated heritage continues to have a significant influence on how cities are perceived, whose pasts are remembered, and what future change can be. However, this is being increasingly tested as urban pressures bring questions of who has a right to the city to the fore. 
Situated within the field of critical heritage studies, this thesis critically examines how heritage is officially “made” in the cities of Aotearoa New Zealand, and how emerging views and values may reshape these established norms for more spatially and culturally just futures. Focused on urban locations within the so-called “CANZUS” states (Canada, Australia, New Zealand and the United States of America (USA)), the thesis centres on statutory heritage – the objects and places that are identified and managed within state-mandated planning systems that create dominant assumptions about what is worthy of protection. As such, its contribution is at the intersection of heritage and planning as it critically queries heritage’s future legacy claims and considers what other legacies may be imagined. 
The thesis includes four key enquiries. First, it explores the history of state-led heritage-making in Aotearoa, focusing on the city of Tāmaki Makaurau / Auckland. It examines the tension between contemporary urban intensification priorities and heritage / special character regulation, critiquing the narrative of heritage as a “public good” given its entanglement with spatial and cultural inequity. Second, it studies three cases of urban heritage protest across Australia, Aotearoa and the USA. These cases expose the continued inadequacy of statutory heritage-making for Indigenous and emerging aspirations, as normative approaches are embedded not only by the heritage sector itself but by the planning and legislation systems that structure its mandate. 
Third, the thesis explores the current thinking of those shaping and working within heritage’s statutory framing across Aotearoa. It finds that heritage policy leaders are cognisant of, and concerned to change, heritage’s entrenched Eurocentricity, expert dominance and material orientation, but that shifting established practice remains a multi-dimensional challenge. Finally, it investigates the perspectives of young emerging planners in the city of Kirikiriroa / Hamilton, which again foregrounds the obstacles to displacing systemic norms but also highlights planning policy’s significant potential to shape different heritage futures. 
This thesis has important implications both for Aotearoa’s urban environments and for CANZUS cities more broadly. Grounded in contemporary real-world examples, it not only exposes heritage’s imbrication with issues of urban inequity but its deeper role in maintaining settler state security, making “home” on Indigenous land. It finds that unpicking this legacy will involve more than adding the heritages of “others” into the existing canon. Rather, deeper reconsideration of heritage’s societal purpose as part of Indigenous, multi-storied and dynamic cities is required. Finally, it highlights the central role for planning in transforming the heritage field, both through statutory policy reform and through integration with broader urban objectives. However, planners will need to be better equipped for critical engagement with heritage if they are to creatively support more inclusive, democratic and malleable alternatives.

text: Heritage-making in Aotearoa planning: Unsettling norms in contested urban space Heritage is currently a high-profile and often contentious topic in urban environments. As cities face growing challenges of climate change, intensification needs and cultural contestation, state-mandated heritage continues to have a significant influence on how cities are perceived, whose pasts are remembered, and what future change can be. However, this is being increasingly tested as urban pressures bring questions of who has a right to the city to the fore. 
Situated within the field of critical heritage studies, this thesis critically examines how heritage is officially “made” in the cities of Aotearoa New Zealand, and how emerging views and values may reshape these established norms for more spatially and culturally just futures. Focused on urban locations within the so-called “CANZUS” states (Canada, Australia, New Zealand and the United States of America (USA)), the thesis centres on statutory heritage – the objects and places that are identified and managed within state-mandated planning systems that create dominant assumptions about what is worthy of protection. As such, its contribution is at the intersection of heritage and planning as it critically queries heritage’s future legacy claims and considers what other legacies may be imagined. 
The thesis includes four key enquiries. First, it explores the history of state-led heritage-making in Aotearoa, focusing on the city of Tāmaki Makaurau / Auckland. It examines the tension between contemporary urban intensification priorities and heritage / special character regulation, critiquing the narrative of heritage as a “public good” given its entanglement with spatial and cultural inequity. Second, it studies three cases of urban heritage protest across Australia, Aotearoa and the USA. These cases expose the continued inadequacy of statutory heritage-making for Indigenous and emerging aspirations, as normative approaches are embedded not only by the heritage sector itself but by the planning and legislation systems that structure its mandate. 
Third, the thesis explores the current thinking of those shaping and working within heritage’s statutory framing across Aotearoa. It finds that heritage policy leaders are cognisant of, and concerned to change, heritage’s entrenched Eurocentricity, expert dominance and material orientation, but that shifting established practice remains a multi-dimensional challenge. Finally, it investigates the perspectives of young emerging planners in the city of Kirikiriroa / Hamilton, which again foregrounds the obstacles to displacing systemic norms but also highlights planning policy’s significant potential to shape different heritage futures. 
This thesis has important implications both for Aotearoa’s urban environments and for CANZUS cities more broadly. Grounded in contemporary real-world examples, it not only exposes heritage’s imbrication with issues of urban inequity but its deeper role in maintaining settler state security, making “home” on Indigenous land. It finds that unpicking this legacy will involve more than adding the heritages of “others” into the existing canon. Rather, deeper reconsideration of heritage’s societal purpose as part of Indigenous, multi-storied and dynamic cities is required. Finally, it highlights the central role for planning in transforming the heritage field, both through statutory policy reform and through integration with broader urban objectives. However, planners will need to be better equipped for critical engagement with heritage if they are to creatively support more inclusive, democratic and malleable alternatives.

year: 2024-12-16