title: Effects of emergent structure on the abundance and size distribution of Trichoptera in Bay of Plenty hill country streams

authors: Cooper, James Aaron

subjects: Trichoptera, Hydrobiosidae, Emergent structure, macroinvertebrates

abstract: Restoration of streams is not limited to recreating structural habitat complexity, but also requires recolonisation of biota that had been excluded prior to restoration. Aquatic insects are a key component of a streams ecosystem, but often do not recolonise restored sites at expected rates. It is hypothesised that this is due to a lack of suitable habitat for the oviposition of certain groups, particularly the Trichopteran family Hydrobiosidae which is known to use emergent stones to access the stream bed for oviposition.
I investigated associations between Trichoptera groups with different oviposition strategies and emergent structure in the form of boulders in six Bay of Plenty stream sites. I compared abundances and size class distribution of Hydrobiosidae, Conoesucidae and Hydropsychidae at sites with and without emergent boulders. Results from that study suggest that the presence of oviposition structure was not linked to either the abundance or size distribution of Hydrobiosidae within the sites we examined where other factors such as degree of shade, water velocity and substrate size were key determinant of larval abundance. This first suggested that Hydrobiosidae may arrive in sites lacking emergent structure via alternative means.
Two potential pathways for the colonisation of Hydrobiosidae in reaches without emergent structure were subsequently identified and investigated: (i) access via the banks or emergent vegetation for oviposition; and/or (ii) Hydrobiosidae drift from upstream areas with suitable oviposition habitat.
A study on longitudinal patterns of Hydrobiosidae drift showed inconclusive results, with no significant changes in drift densities or larval size with distance downstream of emergent structure.
A study on the lateral distribution of Hydrobiosidae in a reach lacking emergent structure provided evidence that adults were utilising stream banks to access submerged oviposition habitat with higher numbers of smaller Hydrobiosidae found near the stream edges compared to within the channel. Findings from my study suggest that there should not be any constraints on the recolonisation of Hydrobiosidae within a restored reach as long as: (i) there is suitable oviposition habitat <2km upstream of a restored site; (ii) there is a source population of adults capable of reaching oviposition habitat within the targeted stream; (iii) the water quality is suitable for colonisation; and (iv) instream conditions such as shade, substrate size and water velocities are within the preferred ranges.

text: Effects of emergent structure on the abundance and size distribution of Trichoptera in Bay of Plenty hill country streams Restoration of streams is not limited to recreating structural habitat complexity, but also requires recolonisation of biota that had been excluded prior to restoration. Aquatic insects are a key component of a streams ecosystem, but often do not recolonise restored sites at expected rates. It is hypothesised that this is due to a lack of suitable habitat for the oviposition of certain groups, particularly the Trichopteran family Hydrobiosidae which is known to use emergent stones to access the stream bed for oviposition.
I investigated associations between Trichoptera groups with different oviposition strategies and emergent structure in the form of boulders in six Bay of Plenty stream sites. I compared abundances and size class distribution of Hydrobiosidae, Conoesucidae and Hydropsychidae at sites with and without emergent boulders. Results from that study suggest that the presence of oviposition structure was not linked to either the abundance or size distribution of Hydrobiosidae within the sites we examined where other factors such as degree of shade, water velocity and substrate size were key determinant of larval abundance. This first suggested that Hydrobiosidae may arrive in sites lacking emergent structure via alternative means.
Two potential pathways for the colonisation of Hydrobiosidae in reaches without emergent structure were subsequently identified and investigated: (i) access via the banks or emergent vegetation for oviposition; and/or (ii) Hydrobiosidae drift from upstream areas with suitable oviposition habitat.
A study on longitudinal patterns of Hydrobiosidae drift showed inconclusive results, with no significant changes in drift densities or larval size with distance downstream of emergent structure.
A study on the lateral distribution of Hydrobiosidae in a reach lacking emergent structure provided evidence that adults were utilising stream banks to access submerged oviposition habitat with higher numbers of smaller Hydrobiosidae found near the stream edges compared to within the channel. Findings from my study suggest that there should not be any constraints on the recolonisation of Hydrobiosidae within a restored reach as long as: (i) there is suitable oviposition habitat <2km upstream of a restored site; (ii) there is a source population of adults capable of reaching oviposition habitat within the targeted stream; (iii) the water quality is suitable for colonisation; and (iv) instream conditions such as shade, substrate size and water velocities are within the preferred ranges.

year: 2018

title: The ecology of ray species in an urbanised estuary: Seasonality, habitat use and pollutant exposure in Tauranga Harbour

authors: Cadwallader, Helen Frances

subjects: Marine ecology

abstract: Information about the movement, seasonality, and use of habitats by marine animals is vital for the mitigation of potential anthropogenic impacts. Ray species may be particularly at risk as they regularly inhabit coastal and estuarine waters. In New Zealand to-date, there has been scant research on the ecology of native ray species in estuarine habitats. In particular, there is a dearth of knowledge pertaining to the spatio-temporal use of the range of habitats within estuaries. The research detailed in this thesis was aimed at addressing the shortfall of information. First, a review of the methodology utilised in ascertaining movement behaviour in non-shark-like batoid elasmobranch species was carried out, as optimisation of tagging research technique underpins the ability to track behaviour of these organisms for long periods. Most studies reviewed adopted tag anchor techniques used on teleost fishes or sharks. As a consequence, the quality of information pertaining to ray habitat use and movements was, in many circumstances, poor. Synthesis of tag longevity using differing anchor methods and field and aquarium longevity experiments led to a recommendation of nylon umbrella darts for soft-skinned non-shark-like rays such as Bathytoshia brevicaudata. Second, seasonality in habitat use within the Tauranga Harbour system was examined using monthly counts of the feeding excavations of Myliobatis tenuicaudatus. This study expanded previous estimations of seasonality and feeding habitat choice in estuaries. It determined that temperature-mediated sinusoidal seasonal patterns in feeding behaviour over a period of 24 months, differed in magnitude and peak month across a range of spatial scales. This could suggest some form of sequential habitat use. Unlike previous studies, evidence of ray feeding was found year-round. This behavioural pattern has implications for calculations of sediment turnover and transport. Peak turnover estimates of ray origin from this study doubled previous estimated calculations. In addition, infaunal prey density, and locational aspects of estuary ‘sub-habitats’ characterised as various ‘zones’ as compared to ‘harbour basin’ habitats, were all found to be influential in the prediction of M. tenuicaudatus feeding activity. There were inverse seasonal differences in the relationship between densities of large infaunal bivalves (putative prey items) and ray feeding activity, suggesting that during some periods, other prey types (soft bodied organisms) may also be important. Suggestions are made that perceived predator risk and human disturbance may have a role in driving habitat preferences in addition to prey density. This study also found that natural mangrove fringe is preferred by M. tenuicaudatus for feeding habitat over areas of ‘fringe’ that had been trimmed to prevent mangrove spread. The implications of this are significant as there is a reduction in ideal feeding habitat with ongoing mangrove trimming regimes. Finally, quantification of metal body burden of M. tenuicaudatus identified low levels of some heavy metals in rays from Tauranga Harbour when compared to Porirua Harbour, and that metals in rays from the outer coast of the Bay of Plenty region were likely to be of volcanic origin. Significantly different metal assemblages of estuarine and offshore animals combined with feeding evidence found year-round in Tauranga Harbour, suggests a separation in populations between these areas. Overall however, it is clear that metal content in Tauranga Harbour rays lies below FZANZ levels of concern and the harbour may be classified as relatively unpolluted. However, the behavioural patterns of rays clearly lead them away from shallower sub estuary areas, that are known to be more contaminated by anthropogenic activity.
In conclusion, this thesis provides previously unknown information about the habits and ecology of the important estuarine mesopredator M. tenuicaudatus in the context of anthropogenic risk associated with an urbanised harbour ecosystem. The information will allow informed management of harbour activities and developmental options with regard to conservation of an ecologically important species.

text: The ecology of ray species in an urbanised estuary: Seasonality, habitat use and pollutant exposure in Tauranga Harbour Information about the movement, seasonality, and use of habitats by marine animals is vital for the mitigation of potential anthropogenic impacts. Ray species may be particularly at risk as they regularly inhabit coastal and estuarine waters. In New Zealand to-date, there has been scant research on the ecology of native ray species in estuarine habitats. In particular, there is a dearth of knowledge pertaining to the spatio-temporal use of the range of habitats within estuaries. The research detailed in this thesis was aimed at addressing the shortfall of information. First, a review of the methodology utilised in ascertaining movement behaviour in non-shark-like batoid elasmobranch species was carried out, as optimisation of tagging research technique underpins the ability to track behaviour of these organisms for long periods. Most studies reviewed adopted tag anchor techniques used on teleost fishes or sharks. As a consequence, the quality of information pertaining to ray habitat use and movements was, in many circumstances, poor. Synthesis of tag longevity using differing anchor methods and field and aquarium longevity experiments led to a recommendation of nylon umbrella darts for soft-skinned non-shark-like rays such as Bathytoshia brevicaudata. Second, seasonality in habitat use within the Tauranga Harbour system was examined using monthly counts of the feeding excavations of Myliobatis tenuicaudatus. This study expanded previous estimations of seasonality and feeding habitat choice in estuaries. It determined that temperature-mediated sinusoidal seasonal patterns in feeding behaviour over a period of 24 months, differed in magnitude and peak month across a range of spatial scales. This could suggest some form of sequential habitat use. Unlike previous studies, evidence of ray feeding was found year-round. This behavioural pattern has implications for calculations of sediment turnover and transport. Peak turnover estimates of ray origin from this study doubled previous estimated calculations. In addition, infaunal prey density, and locational aspects of estuary ‘sub-habitats’ characterised as various ‘zones’ as compared to ‘harbour basin’ habitats, were all found to be influential in the prediction of M. tenuicaudatus feeding activity. There were inverse seasonal differences in the relationship between densities of large infaunal bivalves (putative prey items) and ray feeding activity, suggesting that during some periods, other prey types (soft bodied organisms) may also be important. Suggestions are made that perceived predator risk and human disturbance may have a role in driving habitat preferences in addition to prey density. This study also found that natural mangrove fringe is preferred by M. tenuicaudatus for feeding habitat over areas of ‘fringe’ that had been trimmed to prevent mangrove spread. The implications of this are significant as there is a reduction in ideal feeding habitat with ongoing mangrove trimming regimes. Finally, quantification of metal body burden of M. tenuicaudatus identified low levels of some heavy metals in rays from Tauranga Harbour when compared to Porirua Harbour, and that metals in rays from the outer coast of the Bay of Plenty region were likely to be of volcanic origin. Significantly different metal assemblages of estuarine and offshore animals combined with feeding evidence found year-round in Tauranga Harbour, suggests a separation in populations between these areas. Overall however, it is clear that metal content in Tauranga Harbour rays lies below FZANZ levels of concern and the harbour may be classified as relatively unpolluted. However, the behavioural patterns of rays clearly lead them away from shallower sub estuary areas, that are known to be more contaminated by anthropogenic activity.
In conclusion, this thesis provides previously unknown information about the habits and ecology of the important estuarine mesopredator M. tenuicaudatus in the context of anthropogenic risk associated with an urbanised harbour ecosystem. The information will allow informed management of harbour activities and developmental options with regard to conservation of an ecologically important species.

year: 2020

title: Exploring te ao Māori: The role of museums

authors: Clarkin-Phillips, Jeanette

subjects: museum

abstract: Museums offer many opportunities for developing knowledge of the bicultural heritage of Aotearoa New Zealand. This article reports on research involving a kindergarten located in a national museum. It discusses children’s growing understanding of te ao Māori (the world of Māori) through their regular visits to the collections and exhibits in the museum and suggests teachers in early childhood centres may find connecting with their local museum a valuable resource for enhancing bicultural practice.

text: Exploring te ao Māori: The role of museums Museums offer many opportunities for developing knowledge of the bicultural heritage of Aotearoa New Zealand. This article reports on research involving a kindergarten located in a national museum. It discusses children’s growing understanding of te ao Māori (the world of Māori) through their regular visits to the collections and exhibits in the museum and suggests teachers in early childhood centres may find connecting with their local museum a valuable resource for enhancing bicultural practice.

year: 2012