title: An investigation of koi carp (Cyprinus carpio) movement in the Waikato region using laser ablation otolith microchemistry

authors: Blair, Jennifer Marie

subjects: Carp

abstract: The koi carp Cyprinus carpio is an invasive fish that has reached high numbers and biomass in the North Island of New Zealand, particularly in the Waikato region. This species has a variety of negative effects on aquatic ecosystems, increasing turbidity, uprooting aquatic macrophytes, and affecting water column
nutrient levels. Recent research in Australia and New Zealand has shown that adult carp, though largely restricted to small scale movements, are capable of moving long distances. Movement in adult carp may be underestimated by these studies, and comparatively little is known about the movement of smaller carp. This study examined the feasibility of using laser ablation otolith microchemistry to track koi carp movement and identify spawning areas.

Water samples from six locations (Lake Waahi, Lake Whangape, Lake Waikare, the Whangamarino River, and the Waikato River at Aka Aka and Rangiriri) were analysed using inductively coupled plasma mass spectrometry (ICP-MS).
Significant differences between sites were found in the water concentrations of many elements. Koi carp were collected from the above locations, as well as from Opuatia Stream, Pungarehu Stream, the Maramarua River and Lake Hakanoa. The elemental concentrations in the asteriscus otoliths were analysed using laser ablation inductively coupled plasma mass spectrometry (LA‐ICP-MS). Elemental concentrations in the edges and nuclei of adult koi carp and the edges
of young-of-the-year (YOY) koi carp were significantly different between capture sites. No significant differences were found in elemental concentrations between sites in the nuclei of YOY koi carp.

A discriminant function analysis (DFA) was carried out using the otolith edge
elemental signatures of koi carp. The model used Ba, Sr, Mg, Rb and Zn concentrations to differentiate between four capture locations: the Waikato River, Pungarehu Stream, Lake Waahi, and Lake Waikare and Pungarehu Stream. The DFA was able to correctly predict the capture location of 82% of koi carp using their otolith edge elemental signatures. 

The classification functions created using koi carp otolith edge signatures were then used as a training set to classify otolith nucleus signatures. The otolith nuclei of 80% of YOY koi carp were classified to their site of capture, suggesting they had not moved between locations. The majority of adult koi carp caught at Lake Waikare, Whangamarino River, Pungarehu Stream and Opuatia Stream had nucleus signatures matching their capture sites, indicating that these fish
originated from their capture location. Koi carp from other sites likely moved there from another location. The majority of adult koi carp (88%) caught at the Waikato River at Rangiriri had otolith nucleus signatures matching Lake Waikare
and Pungarehu Stream. Adult koi carp caught at Lake Waahi and the Waikato River at Aka Aka had otolith signatures corresponding to a range of locations. While some areas (Lake Waikare, Pungarehu Stream) appear to have resident koi
carp populations that likely originated there, others (Lake Waahi, the Waikato River) appear to have koi carp populations of mixed origin. These results indicate that Lake Waikare, Pungarehu Stream and the Whangamarino River may be
important sources of koi carp recruits in the lower Waikato region.

text: An investigation of koi carp (Cyprinus carpio) movement in the Waikato region using laser ablation otolith microchemistry The koi carp Cyprinus carpio is an invasive fish that has reached high numbers and biomass in the North Island of New Zealand, particularly in the Waikato region. This species has a variety of negative effects on aquatic ecosystems, increasing turbidity, uprooting aquatic macrophytes, and affecting water column
nutrient levels. Recent research in Australia and New Zealand has shown that adult carp, though largely restricted to small scale movements, are capable of moving long distances. Movement in adult carp may be underestimated by these studies, and comparatively little is known about the movement of smaller carp. This study examined the feasibility of using laser ablation otolith microchemistry to track koi carp movement and identify spawning areas.

Water samples from six locations (Lake Waahi, Lake Whangape, Lake Waikare, the Whangamarino River, and the Waikato River at Aka Aka and Rangiriri) were analysed using inductively coupled plasma mass spectrometry (ICP-MS).
Significant differences between sites were found in the water concentrations of many elements. Koi carp were collected from the above locations, as well as from Opuatia Stream, Pungarehu Stream, the Maramarua River and Lake Hakanoa. The elemental concentrations in the asteriscus otoliths were analysed using laser ablation inductively coupled plasma mass spectrometry (LA‐ICP-MS). Elemental concentrations in the edges and nuclei of adult koi carp and the edges
of young-of-the-year (YOY) koi carp were significantly different between capture sites. No significant differences were found in elemental concentrations between sites in the nuclei of YOY koi carp.

A discriminant function analysis (DFA) was carried out using the otolith edge
elemental signatures of koi carp. The model used Ba, Sr, Mg, Rb and Zn concentrations to differentiate between four capture locations: the Waikato River, Pungarehu Stream, Lake Waahi, and Lake Waikare and Pungarehu Stream. The DFA was able to correctly predict the capture location of 82% of koi carp using their otolith edge elemental signatures. 

The classification functions created using koi carp otolith edge signatures were then used as a training set to classify otolith nucleus signatures. The otolith nuclei of 80% of YOY koi carp were classified to their site of capture, suggesting they had not moved between locations. The majority of adult koi carp caught at Lake Waikare, Whangamarino River, Pungarehu Stream and Opuatia Stream had nucleus signatures matching their capture sites, indicating that these fish
originated from their capture location. Koi carp from other sites likely moved there from another location. The majority of adult koi carp (88%) caught at the Waikato River at Rangiriri had otolith nucleus signatures matching Lake Waikare
and Pungarehu Stream. Adult koi carp caught at Lake Waahi and the Waikato River at Aka Aka had otolith signatures corresponding to a range of locations. While some areas (Lake Waikare, Pungarehu Stream) appear to have resident koi
carp populations that likely originated there, others (Lake Waahi, the Waikato River) appear to have koi carp populations of mixed origin. These results indicate that Lake Waikare, Pungarehu Stream and the Whangamarino River may be
important sources of koi carp recruits in the lower Waikato region.

year: 2008

title: Rates of photospheric magnetic flux cancellation measured with Hinode

authors: Park, Soyoung

subjects: magnetic fields

abstract: Photospheric magnetic flux cancellation on the Sun is generally believed to be caused by magnetic reconnection occurring in the low solar atmosphere. Individual canceling magnetic features are observationally characterized by the rate of flux cancellation. The specific cancellation rate, defined as the rate of flux cancellation divided by the interface length, gives an accurate estimate of the electric field in the reconnecting current sheet. We have determined the specific cancellation rate using the magnetograms taken by the Solar Optical Telescope (SOT) aboard the Hinode satellite. The specific rates determined with SOT turned out to be systematically higher than those based on the data taken by the Michelson Doppler Imager (MDI) aboard the Solar and Heliospheric Observatory. The median value of the specific cancellation rate was found to be 8 × 106 G cm s-1—a value four times that obtained from the MDI data. This big difference is mainly due to a higher angular resolution and better sensitivity of the SOT, resulting in magnetic fluxes up to five times larger than those obtained from the MDI. The higher rates of flux cancellation correspond to either faster inflows or stronger magnetic fields of the reconnection inflow region, which may have important consequences for the physics of photospheric magnetic reconnection.

text: Rates of photospheric magnetic flux cancellation measured with Hinode Photospheric magnetic flux cancellation on the Sun is generally believed to be caused by magnetic reconnection occurring in the low solar atmosphere. Individual canceling magnetic features are observationally characterized by the rate of flux cancellation. The specific cancellation rate, defined as the rate of flux cancellation divided by the interface length, gives an accurate estimate of the electric field in the reconnecting current sheet. We have determined the specific cancellation rate using the magnetograms taken by the Solar Optical Telescope (SOT) aboard the Hinode satellite. The specific rates determined with SOT turned out to be systematically higher than those based on the data taken by the Michelson Doppler Imager (MDI) aboard the Solar and Heliospheric Observatory. The median value of the specific cancellation rate was found to be 8 × 106 G cm s-1—a value four times that obtained from the MDI data. This big difference is mainly due to a higher angular resolution and better sensitivity of the SOT, resulting in magnetic fluxes up to five times larger than those obtained from the MDI. The higher rates of flux cancellation correspond to either faster inflows or stronger magnetic fields of the reconnection inflow region, which may have important consequences for the physics of photospheric magnetic reconnection.

year: 2009

title: Racism and Employment: A Narrative Review of Aotearoa New Zealand and International Qualitative Studies

authors: Tan, Kyle K. H.

abstract: In Aotearoa New Zealand, employment inequities exist for minoritised ethnic groups (Māori, Pasifika, Asian, racialised migrants and refugees) in the forms of barriers to employment, occupation inequities, differences in promotion to leadership roles, ethnic pay gaps and discriminatory experiences at workplaces. In this review, we compiled Aotearoa qualitative studies to depict the dynamics of racism alongside other intersectional forms of prejudices that disadvantage the employment processes and career progression of minoritised ethnicities. Literature gaps in Aotearoa research were identified through reviewing international literature published between 2016 and 2021. Reviewed Aotearoa studies were categorised into three themes: unemployment and underemployment, workplace discrimination, and strategies for navigating racism. Drawing upon a framework that recognises racialised processes as spanning across micro- (individual), meso- (organisational) and macro- (institutional) levels, we found most Aotearoa studies analysing racism in the workplace focus on micro-level experiences. Compared with international literature, research in Aotearoa has yet to consider the roles of organisations and technologies as racialised structures that engender employment inequities, and the interaction of individuals in response to meso- and macro-structures that build on settler colonialism and racism. Our review echoes the call of Aotearoa scholars to name racism as the overarching oppressive mechanism embedded within organisations and to use anti-racism praxes such as te Tiriti o Waitangi as a way forward to promote employment equity.

text: Racism and Employment: A Narrative Review of Aotearoa New Zealand and International Qualitative Studies In Aotearoa New Zealand, employment inequities exist for minoritised ethnic groups (Māori, Pasifika, Asian, racialised migrants and refugees) in the forms of barriers to employment, occupation inequities, differences in promotion to leadership roles, ethnic pay gaps and discriminatory experiences at workplaces. In this review, we compiled Aotearoa qualitative studies to depict the dynamics of racism alongside other intersectional forms of prejudices that disadvantage the employment processes and career progression of minoritised ethnicities. Literature gaps in Aotearoa research were identified through reviewing international literature published between 2016 and 2021. Reviewed Aotearoa studies were categorised into three themes: unemployment and underemployment, workplace discrimination, and strategies for navigating racism. Drawing upon a framework that recognises racialised processes as spanning across micro- (individual), meso- (organisational) and macro- (institutional) levels, we found most Aotearoa studies analysing racism in the workplace focus on micro-level experiences. Compared with international literature, research in Aotearoa has yet to consider the roles of organisations and technologies as racialised structures that engender employment inequities, and the interaction of individuals in response to meso- and macro-structures that build on settler colonialism and racism. Our review echoes the call of Aotearoa scholars to name racism as the overarching oppressive mechanism embedded within organisations and to use anti-racism praxes such as te Tiriti o Waitangi as a way forward to promote employment equity.

year: 2024-01-01