title: Semi-mechanistic modelling in nonlinear regression: a case study

authors: Domijan, Katarina

subjects: statistics

abstract: This paper discusses the use of highly parameterized semi-mechanistic nonlinear models with particular reference to the PARJIB crop response model of Reid (2002)[Yield response to nutrient supply across a wide range of conditions 1. Model derivation. Field Crops Research77, 161–171]. Compared to empirical linear approaches, such models promise improved generality of application but present considerable challenges for estimation. Some success has been achieved with a fitting approach that uses a Levenberg–Marquardt algorithm starting from initial values determined by a genetic algorithm. Attention must be paid, however, to correlations between parameter estimates and an approach is described to identify these based on large simulated datasets. This work illustrates the value for the scientist in exploring the correlation structure in mechanistic or semi-mechanistic models. Such information might be used to reappraise the structure of the model itself, especially if the experimental evidence is not strong enough to allow estimation of a parameter free of assumptions about the values of others. Thus statistical modelling and analysis can complement mechanistic studies, making more explicit what is known and what is not known about the processes being modelled and guiding further research.

text: Semi-mechanistic modelling in nonlinear regression: a case study This paper discusses the use of highly parameterized semi-mechanistic nonlinear models with particular reference to the PARJIB crop response model of Reid (2002)[Yield response to nutrient supply across a wide range of conditions 1. Model derivation. Field Crops Research77, 161–171]. Compared to empirical linear approaches, such models promise improved generality of application but present considerable challenges for estimation. Some success has been achieved with a fitting approach that uses a Levenberg–Marquardt algorithm starting from initial values determined by a genetic algorithm. Attention must be paid, however, to correlations between parameter estimates and an approach is described to identify these based on large simulated datasets. This work illustrates the value for the scientist in exploring the correlation structure in mechanistic or semi-mechanistic models. Such information might be used to reappraise the structure of the model itself, especially if the experimental evidence is not strong enough to allow estimation of a parameter free of assumptions about the values of others. Thus statistical modelling and analysis can complement mechanistic studies, making more explicit what is known and what is not known about the processes being modelled and guiding further research.

year: 2006

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: Te Whare o Te Kahikatoa: He Kura nui, he Kura roa, he Kura Parawhakawai

authors: Rangihau, Ngatai

subjects: Kahikatoa

abstract: “Te Whare o te Kahikatoa,
Te Iho o te Maire,
Te Pōkaitāniwhaniwha o te Kohu”
(TKPOT, 2010-2016).¹

Ka hoki nei kia Te Maunga rāua ko Hinepukohurangi, ki te taetanga mai hoki o Mataatua waka², ko ngā kura o tawhito, kura wānanga, kura parawhakawai o te iwi o Tūhoe ngā tino whare whakapakari pōkaitāniwhaniwha mō roto i te whare o te kahikatoa. Īnā te rahi o ngā toataumatarau i puta ngā ihu, ka tū rātau hai toa rangatira ārahi i te iwi. Ki te kore ēneki kura o te nehenehe kāre he oranga, kāre e eke te iwi ngā whakairinga tūmanako e wawatatia ana e rātau.
 
Waihoki, ko te kaupapa e rangahau ana i tēnei tuhinga he whakapono, he whakapae, kai konei tonu tēnei hua o te wānanga. He kura hai whakapakari rangatira mō āpōpō. Ahakoa tēnei ao hurihuri koinei tonu tētahi huarahi nā te Māori, nā Tūhoe hai whakaohooho mā ngā uri whakaheke, e mau pū ai a Ngāi Tūhoe ki ōna kura tapu o nehe.

text: Te Whare o Te Kahikatoa: He Kura nui, he Kura roa, he Kura Parawhakawai “Te Whare o te Kahikatoa,
Te Iho o te Maire,
Te Pōkaitāniwhaniwha o te Kohu”
(TKPOT, 2010-2016).¹

Ka hoki nei kia Te Maunga rāua ko Hinepukohurangi, ki te taetanga mai hoki o Mataatua waka², ko ngā kura o tawhito, kura wānanga, kura parawhakawai o te iwi o Tūhoe ngā tino whare whakapakari pōkaitāniwhaniwha mō roto i te whare o te kahikatoa. Īnā te rahi o ngā toataumatarau i puta ngā ihu, ka tū rātau hai toa rangatira ārahi i te iwi. Ki te kore ēneki kura o te nehenehe kāre he oranga, kāre e eke te iwi ngā whakairinga tūmanako e wawatatia ana e rātau.
 
Waihoki, ko te kaupapa e rangahau ana i tēnei tuhinga he whakapono, he whakapae, kai konei tonu tēnei hua o te wānanga. He kura hai whakapakari rangatira mō āpōpō. Ahakoa tēnei ao hurihuri koinei tonu tētahi huarahi nā te Māori, nā Tūhoe hai whakaohooho mā ngā uri whakaheke, e mau pū ai a Ngāi Tūhoe ki ōna kura tapu o nehe.

year: 2017