title: Canine (Canis familiaris) scent detection of invasive brown bullhead catfish (Ameiurus nebulosus) in water samples, and the effects of sample preservation

authors: Denby, Renee

abstract: Brown bullhead catfish (Ameiurus nebulosus) are an invasive freshwater fish widely recognised as a threat to New Zealand’s aquatic ecosystems. Early detection of new incursions increases the chances of eradication or control, but current survey methods such as netting and electrofishing are expensive and time consuming when fish are at low abundances. Domestic dogs (Canis familiaris) have previously demonstrated the ability to detect the presence of catfish in laboratory water samples, while discriminating against non-target species. The aim of this research was to investigate whether scent detection dogs could plausibly be employed in aquatic biosecurity programmes. The first experiment used a probe design to determine the scent-detection limits for catfish biomass under laboratory conditions. Water samples taken from tanks containing a standard catfish biomass concentration of 15.5 g/L (equivalent to 38,700 kg/ha) were assessed by the dogs and progressively diluted following the successful attainment of identification and discrimination criteria. All three participating dogs were able to detect the presence of catfish at biomass concentrations ≤12.6 kg/ha, with one dog achieving 4.6 kg/ha. Concurrently, the dogs were also able to successfully discriminate against a goldfish (Carassius auratus) distractor scent indicating that they are able to distinguish specific species of fish in the environment. The effects of sample preservation on dogs’ ability to identify and discriminate target scents have rarely been investigated. In practice, field samples from the environment would likely necessitate the preservation of samples prior to assessment by dogs. A second study used a repeated-measures reversal design to investigate dogs’ abilities to detect catfish at a standard biomass concentration of 310 kg/ha which had been refrigerated or frozen for up to 1-week. No statistically significant difference in hit rates between unpreserved (baseline 1: 93%, baseline 2: 98%), refrigerated (97%), and frozen (96%) samples was apparent; (F(3, 6) = 2.061502, p = 0.2069). These results indicate that dogs are capable of detecting and discriminating the scent of catfish at biomass concentrations typical of many freshwater ecosystems in the Waikato region. Further, limited periods of freezing or refrigeration appear to have no significant effect on the scent-detection abilities of dogs. Future research needs to be conducted with field samples from lakes and could explore the effects of preservation on low biomass concentrations. The results from this study are promising for the potential future employment of scent detection dogs in aquatic biosecurity monitoring.

text: Canine (Canis familiaris) scent detection of invasive brown bullhead catfish (Ameiurus nebulosus) in water samples, and the effects of sample preservation Brown bullhead catfish (Ameiurus nebulosus) are an invasive freshwater fish widely recognised as a threat to New Zealand’s aquatic ecosystems. Early detection of new incursions increases the chances of eradication or control, but current survey methods such as netting and electrofishing are expensive and time consuming when fish are at low abundances. Domestic dogs (Canis familiaris) have previously demonstrated the ability to detect the presence of catfish in laboratory water samples, while discriminating against non-target species. The aim of this research was to investigate whether scent detection dogs could plausibly be employed in aquatic biosecurity programmes. The first experiment used a probe design to determine the scent-detection limits for catfish biomass under laboratory conditions. Water samples taken from tanks containing a standard catfish biomass concentration of 15.5 g/L (equivalent to 38,700 kg/ha) were assessed by the dogs and progressively diluted following the successful attainment of identification and discrimination criteria. All three participating dogs were able to detect the presence of catfish at biomass concentrations ≤12.6 kg/ha, with one dog achieving 4.6 kg/ha. Concurrently, the dogs were also able to successfully discriminate against a goldfish (Carassius auratus) distractor scent indicating that they are able to distinguish specific species of fish in the environment. The effects of sample preservation on dogs’ ability to identify and discriminate target scents have rarely been investigated. In practice, field samples from the environment would likely necessitate the preservation of samples prior to assessment by dogs. A second study used a repeated-measures reversal design to investigate dogs’ abilities to detect catfish at a standard biomass concentration of 310 kg/ha which had been refrigerated or frozen for up to 1-week. No statistically significant difference in hit rates between unpreserved (baseline 1: 93%, baseline 2: 98%), refrigerated (97%), and frozen (96%) samples was apparent; (F(3, 6) = 2.061502, p = 0.2069). These results indicate that dogs are capable of detecting and discriminating the scent of catfish at biomass concentrations typical of many freshwater ecosystems in the Waikato region. Further, limited periods of freezing or refrigeration appear to have no significant effect on the scent-detection abilities of dogs. Future research needs to be conducted with field samples from lakes and could explore the effects of preservation on low biomass concentrations. The results from this study are promising for the potential future employment of scent detection dogs in aquatic biosecurity monitoring.

year: 2021

title: Teaching formal methods lite via testing

authors: Utting, Mark

subjects: computer science

abstract: A new style of formal methods course is described, based on a pragmatic approach that emphasizes testing. The course introduces students to formal specification using Z, and shows how formal specification and testing can benefit each other, in both the validation and verification phases. It uses a tools-based approach, with practical work that reinforces formal specification techniques as well as traditional software engineering skills, such as unit and system testing, inspection and defensive programming with assertions. The two main results are to identify several practical uses of formal specifications that are not widely practised or taught and to demonstrate that teaching them results in a more interesting and relevant formal methods course.

text: Teaching formal methods lite via testing A new style of formal methods course is described, based on a pragmatic approach that emphasizes testing. The course introduces students to formal specification using Z, and shows how formal specification and testing can benefit each other, in both the validation and verification phases. It uses a tools-based approach, with practical work that reinforces formal specification techniques as well as traditional software engineering skills, such as unit and system testing, inspection and defensive programming with assertions. The two main results are to identify several practical uses of formal specifications that are not widely practised or taught and to demonstrate that teaching them results in a more interesting and relevant formal methods course.

year: 2001

title: Telomere length in early childhood is associated with sex and ethnicity

authors: Ly, Kien

subjects: Science & Technology

abstract: Telomeres are repetitive DNA sequences at the end of chromosomes that function to protect chromosomes from degradation. Throughout the life course, telomere length decreases with age and is influenced by environmental factors and health conditions. This study aimed to determine the relative telomere lengths in a diverse cohort of about 4000 four-year-old children in New Zealand. Linear regression was used to investigate the relationship between telomere length, child gender, ethnicity, paternal age and deprivation. We observed substantial variation in telomere length according to sex and self-identified ethnicity. Telomere length was longer in females compared to males (coefficient of 0.042, 95% confidence interval (CI) 0.024–0.060). European children had shorter telomere than both the indigenous Māori (coefficient of 0.03, CI 0.007–0.055) and Pacific children (coefficient of 0.15, CI 0.12–0.18). The data suggest that telomere lengths are highly variable and variability between individuals arise from early age, influenced partly by sex and ethnicity. Longer telomeres in indigenous Māori and Pacific children may reflect the heritability of telomere length in genetically less complex populations. This study increases our understanding of telomere dynamics in young children since the majority of telomere studies are conducted in adults.

text: Telomere length in early childhood is associated with sex and ethnicity Telomeres are repetitive DNA sequences at the end of chromosomes that function to protect chromosomes from degradation. Throughout the life course, telomere length decreases with age and is influenced by environmental factors and health conditions. This study aimed to determine the relative telomere lengths in a diverse cohort of about 4000 four-year-old children in New Zealand. Linear regression was used to investigate the relationship between telomere length, child gender, ethnicity, paternal age and deprivation. We observed substantial variation in telomere length according to sex and self-identified ethnicity. Telomere length was longer in females compared to males (coefficient of 0.042, 95% confidence interval (CI) 0.024–0.060). European children had shorter telomere than both the indigenous Māori (coefficient of 0.03, CI 0.007–0.055) and Pacific children (coefficient of 0.15, CI 0.12–0.18). The data suggest that telomere lengths are highly variable and variability between individuals arise from early age, influenced partly by sex and ethnicity. Longer telomeres in indigenous Māori and Pacific children may reflect the heritability of telomere length in genetically less complex populations. This study increases our understanding of telomere dynamics in young children since the majority of telomere studies are conducted in adults.

year: 2019