title: Responses of the fish community and biomass in Lake Ohinewai to fish removal and the koi carp exclusion barrier

authors: Tempero, Grant Wayne

abstract: The objectives of this research were to determine the biomass of koi carp (Cyprinus carpio) and other fish species in Lake Ohinewai in 2016 by two-sample mark-recapture methods and to compare these estimates with similar studies conducted in 2011, 2012, and 2014. In May 2011 the University of Waikato installed a one-way barrier on the outlet of Lake Ohinewai that was designed to prevent adult koi carp moving upstream into the lake, while allowing fish to pass downstream out of the lake, thereby attempting to passively reduce fish biomass in the lake. In addition, an invasive fish removal programme was undertaken in Lake Ohinewai with the aim of reducing the koi carp population from the estimated original biomass of 308 kg/ha (211–466, 95% CL) to below 100 kg/ha. In previous mark-recapture studies it was estimated that the koi carp biomass had been reduced to 39 kg/ha (24–67, 95% CL) in 2012 and 14 kg/ha (7–27, 95% CL) in 2014 by a combination of fish removal and the one-way gate. In 2016, we estimated that the koi carp biomass had increased to 94 kg/ha (49–197, 95% CL).
A mark-recapture study was conducted on the fish community in Lake Ohinewai from 21 November to 7 December 2016. Capture method included fyke net sets for a total of 120 net nights and boat electrofishing for 12 h. Species included in the study were the invasive species koi carp, brown bullhead catfish (Ameiurus nebulosus), rudd (Scardinius erythrophthalmus), goldfish (Carassius auratus) and koi carp-goldfish hybrids, and the native species shortfin eel (Anguilla australis) and longfin eel (Anguilla dieffenbachii). In addition, water samples for nutrient analysis and suspended solids, Secchi depth, CTD (conductivity, temperature, depth) profiles and zooplankton and phytoplankton samples were taken from Lake Ohinewai on three occasions between 21 November 2016 and 20 January 2017.
A total of 1680 fish were caught in the marking phase (21–24 November 2016) and 2058 fish in the recapture phase (5–8 December 2016); 479 of fish caught in the recapture phase were marked. The estimated koi carp population in Lake Ohinewai more than quadrupled in size from 454 (251–889, 95% CL) fish in 2014 to 2063 (1070–4328, 95% CL) fish in 2016. Similar increases in the estimated populations of catfish (925 to 4010), goldfish (512 to 1927) and koi carp hybrids (43 to 252) were also observed. Eels also increased in abundance; between 2014 and 2016 shortfin eels increased from 2305 to 3456 and longfin eels increased from 44 to 100. Total invasive fish biomass also increased from 29 kg/ha (18–50, 95% CL) in 2014 to 154 kg/ha (78–311, 95% CL) in 2016. This change was primarily due to an increase in koi carp biomass, but increases in catfish and goldfish biomasses have also occurred since 2014. Goldfish showed a strong pulse of recruitment in 2016.
The large-scale removal of invasive fish and installation of the one-way barrier resulted in significant changes to the invasive fish community composition. The fish removal programme reduced the proportion of larger (>275 mm fork length) koi carp and goldfish, which can be attributed to size selectivity of the removal methods and emigration of adult koi carp from the lake. Recruitment of smaller koi carp was observed in 2014 when they had bimodal size distribution, comprising juvenile fish (<250 mm FL) and adult fish (>300 mm FL).
Shortfin eels increased significantly in mean weight following carp removal. Changes in the longfin eel population appeared similar to those of shortfin eels, with an increased proportion of larger eels following removal of koi carp and other invasive fish, but the low sample size hampered comparisons of mean weight.
Water quality indicators such as nutrient concentrations, Secchi depth and total suspended solids showed no improvement in the 5 years following the reduction in invasive fish biomass, except for chlorophyll a concentration, which declined with decreasing biomass of invasive fish from 2011 to 2014, and returned to previous concentrations as invasive fish biomass increased by 2016. It is not entirely clear that this was caused by changes in the fish biomass as total nitrogen also declined from 2009 to 2013. Total phosphorus remained largely unchanged throughout the study period. In addition, phytoplankton species and abundance appear consistent with other hypereutrophic lakes in the Waikato region. The annual mean TLI3, which excludes Secchi depth, ranged from 6.1 to 6.6 between 2006 and 2017, indicating that the lake remained hypertrophic during fish removal. Chemically-driven internal nutrient cycling and catchment nutrient inputs are likely to maintain the hypereutrophic condition and low water clarity will continue to inhibit re-establishment of submerged macrophytes, the absence of which can exacerbate wind resuspension of sediment.
The increase in the koi carp abundance indicates that at least one successful recruitment event occurred following the removal programme and installation of the one-way barrier, either by spawning in the lake or by upstream migration of juvenile young-of-the-year fish from spawning areas lower in the catchment. In addition, reduced interspecific competition has likely contributed to increased recruitment of the catfish and goldfish populations. Therefore, while the Lake Ohinewai one-way barrier appears effective in preventing immigration of adult koi carp into an area, it should not be considered as a mechanism to exclude both adult and juvenile koi carp nor as a sole measure of control.
In Lake Ohinewai, reductions in koi carp biomass were not long lasting, and during the period of low carp abundance there was no convincing evidence for a corresponding improvement in water quality and zooplankton and phytoplankton community composition. Koi carp removal did appear to increase the abundance and size of shortfin eels. Before any restoration programme is initiated it is recommended that a complete assessment of the system is undertaken to determine which factors are driving the decline in water quality. Ecological models can be helpful in determining these driving factors but they are reliant on substantial data for parameterisation and calibration. If reductions in invasive fish biomass are deemed necessary for ecosystem restoration, repeated removal programmes appear to be the only viable way of ensuring low biomasses of target invasive species are maintained

text: Responses of the fish community and biomass in Lake Ohinewai to fish removal and the koi carp exclusion barrier The objectives of this research were to determine the biomass of koi carp (Cyprinus carpio) and other fish species in Lake Ohinewai in 2016 by two-sample mark-recapture methods and to compare these estimates with similar studies conducted in 2011, 2012, and 2014. In May 2011 the University of Waikato installed a one-way barrier on the outlet of Lake Ohinewai that was designed to prevent adult koi carp moving upstream into the lake, while allowing fish to pass downstream out of the lake, thereby attempting to passively reduce fish biomass in the lake. In addition, an invasive fish removal programme was undertaken in Lake Ohinewai with the aim of reducing the koi carp population from the estimated original biomass of 308 kg/ha (211–466, 95% CL) to below 100 kg/ha. In previous mark-recapture studies it was estimated that the koi carp biomass had been reduced to 39 kg/ha (24–67, 95% CL) in 2012 and 14 kg/ha (7–27, 95% CL) in 2014 by a combination of fish removal and the one-way gate. In 2016, we estimated that the koi carp biomass had increased to 94 kg/ha (49–197, 95% CL).
A mark-recapture study was conducted on the fish community in Lake Ohinewai from 21 November to 7 December 2016. Capture method included fyke net sets for a total of 120 net nights and boat electrofishing for 12 h. Species included in the study were the invasive species koi carp, brown bullhead catfish (Ameiurus nebulosus), rudd (Scardinius erythrophthalmus), goldfish (Carassius auratus) and koi carp-goldfish hybrids, and the native species shortfin eel (Anguilla australis) and longfin eel (Anguilla dieffenbachii). In addition, water samples for nutrient analysis and suspended solids, Secchi depth, CTD (conductivity, temperature, depth) profiles and zooplankton and phytoplankton samples were taken from Lake Ohinewai on three occasions between 21 November 2016 and 20 January 2017.
A total of 1680 fish were caught in the marking phase (21–24 November 2016) and 2058 fish in the recapture phase (5–8 December 2016); 479 of fish caught in the recapture phase were marked. The estimated koi carp population in Lake Ohinewai more than quadrupled in size from 454 (251–889, 95% CL) fish in 2014 to 2063 (1070–4328, 95% CL) fish in 2016. Similar increases in the estimated populations of catfish (925 to 4010), goldfish (512 to 1927) and koi carp hybrids (43 to 252) were also observed. Eels also increased in abundance; between 2014 and 2016 shortfin eels increased from 2305 to 3456 and longfin eels increased from 44 to 100. Total invasive fish biomass also increased from 29 kg/ha (18–50, 95% CL) in 2014 to 154 kg/ha (78–311, 95% CL) in 2016. This change was primarily due to an increase in koi carp biomass, but increases in catfish and goldfish biomasses have also occurred since 2014. Goldfish showed a strong pulse of recruitment in 2016.
The large-scale removal of invasive fish and installation of the one-way barrier resulted in significant changes to the invasive fish community composition. The fish removal programme reduced the proportion of larger (>275 mm fork length) koi carp and goldfish, which can be attributed to size selectivity of the removal methods and emigration of adult koi carp from the lake. Recruitment of smaller koi carp was observed in 2014 when they had bimodal size distribution, comprising juvenile fish (<250 mm FL) and adult fish (>300 mm FL).
Shortfin eels increased significantly in mean weight following carp removal. Changes in the longfin eel population appeared similar to those of shortfin eels, with an increased proportion of larger eels following removal of koi carp and other invasive fish, but the low sample size hampered comparisons of mean weight.
Water quality indicators such as nutrient concentrations, Secchi depth and total suspended solids showed no improvement in the 5 years following the reduction in invasive fish biomass, except for chlorophyll a concentration, which declined with decreasing biomass of invasive fish from 2011 to 2014, and returned to previous concentrations as invasive fish biomass increased by 2016. It is not entirely clear that this was caused by changes in the fish biomass as total nitrogen also declined from 2009 to 2013. Total phosphorus remained largely unchanged throughout the study period. In addition, phytoplankton species and abundance appear consistent with other hypereutrophic lakes in the Waikato region. The annual mean TLI3, which excludes Secchi depth, ranged from 6.1 to 6.6 between 2006 and 2017, indicating that the lake remained hypertrophic during fish removal. Chemically-driven internal nutrient cycling and catchment nutrient inputs are likely to maintain the hypereutrophic condition and low water clarity will continue to inhibit re-establishment of submerged macrophytes, the absence of which can exacerbate wind resuspension of sediment.
The increase in the koi carp abundance indicates that at least one successful recruitment event occurred following the removal programme and installation of the one-way barrier, either by spawning in the lake or by upstream migration of juvenile young-of-the-year fish from spawning areas lower in the catchment. In addition, reduced interspecific competition has likely contributed to increased recruitment of the catfish and goldfish populations. Therefore, while the Lake Ohinewai one-way barrier appears effective in preventing immigration of adult koi carp into an area, it should not be considered as a mechanism to exclude both adult and juvenile koi carp nor as a sole measure of control.
In Lake Ohinewai, reductions in koi carp biomass were not long lasting, and during the period of low carp abundance there was no convincing evidence for a corresponding improvement in water quality and zooplankton and phytoplankton community composition. Koi carp removal did appear to increase the abundance and size of shortfin eels. Before any restoration programme is initiated it is recommended that a complete assessment of the system is undertaken to determine which factors are driving the decline in water quality. Ecological models can be helpful in determining these driving factors but they are reliant on substantial data for parameterisation and calibration. If reductions in invasive fish biomass are deemed necessary for ecosystem restoration, repeated removal programmes appear to be the only viable way of ensuring low biomasses of target invasive species are maintained

year: 2017

title: Flow cytometric characterization of freshwater crayfish hemocytes for the examination of physiological status in wild and captive animals

authors: Taylor, Sean

subjects: New Zealand

abstract: Enumeration of invertebrate hemocytes is a potentially powerful tool for the determination of physiological effects of extrinsic stressors, such as hypoxia, disease, and toxicant exposure. A detailed flow cytometric method of broad application was developed for the objective characterization and enumeration of the hemocytes of New Zealand freshwater crayfish Paranephrops planifrons for the purpose of physiological health assessment. Hemocyte populations were isolated by flow cytometric sorting based on differential light scatter properties followed by morphological characterization via light microscopy and software image analysis. Cells were identified as hyaline, semigranular, and granular hemocytes based on established invertebrate hemocyte classification. A characteristic decrease in nuclear size, an increase in granularity between the hyaline and granular cells, and the eccentric location of nuclei in granular cells were also observed. The granulocyte subpopulations were observed to possess varying degrees of granularity. The developed methodology was used to perform total and differential hemocyte counts from three lake populations and between wild and captive crayfish specimens. Differences in total and differential hemocyte counts were not observed among the wild populations. However, specimens held in captivity for 14 d exhibited a significant 63% reduction in total hemocyte count, whereas the relative hemocyte proportions remained the same. These results demonstrate the utility of this method for the investigation of subacute stressor effects in selected decapod crustaceans.

text: Flow cytometric characterization of freshwater crayfish hemocytes for the examination of physiological status in wild and captive animals Enumeration of invertebrate hemocytes is a potentially powerful tool for the determination of physiological effects of extrinsic stressors, such as hypoxia, disease, and toxicant exposure. A detailed flow cytometric method of broad application was developed for the objective characterization and enumeration of the hemocytes of New Zealand freshwater crayfish Paranephrops planifrons for the purpose of physiological health assessment. Hemocyte populations were isolated by flow cytometric sorting based on differential light scatter properties followed by morphological characterization via light microscopy and software image analysis. Cells were identified as hyaline, semigranular, and granular hemocytes based on established invertebrate hemocyte classification. A characteristic decrease in nuclear size, an increase in granularity between the hyaline and granular cells, and the eccentric location of nuclei in granular cells were also observed. The granulocyte subpopulations were observed to possess varying degrees of granularity. The developed methodology was used to perform total and differential hemocyte counts from three lake populations and between wild and captive crayfish specimens. Differences in total and differential hemocyte counts were not observed among the wild populations. However, specimens held in captivity for 14 d exhibited a significant 63% reduction in total hemocyte count, whereas the relative hemocyte proportions remained the same. These results demonstrate the utility of this method for the investigation of subacute stressor effects in selected decapod crustaceans.

year: 2009

title: Caregiver Health Related Quality of Life and Burden When Caring for Children with Traumatic Brain Injury

authors: Rose, Wallis

subjects: Caregiver Burden

abstract: Often family members take on the responsibility of caregiver when another family member sustains a traumatic brain injury (TBI). The caregiving role is a stressful task which may impact negatively upon caregivers’ psychological and physical health. Variables which may contribute to caregiver burden include: caregiver age, educational attainment, income, gender, ethnicity, marital status, supports, time post-injury, and child clinical variables: TBI severity, behavioural functioning and adaptive functioning. The literature varies in its reporting of which areas of health are most affected, and the degree to which sociodemographic and child variables impact upon negative health related quality of life (HRQoL) and burden. To address this the current study explored health outcomes for TBI caregivers using a battery of measures (Medical Study Short Form-36, Hospital Anxiety and Depression Scale, DSM-IV Depression Diagnostic Scale, BAKAS Caregiving Outcomes Scale); questionnaires were also used to collect sociodemographic information and information relating to supports and services used in the rehabilitation of the TBI child. The Behavioural Assessment System for Children was used to collect behavioural and adaptability information from the caregivers about the child. Assessments were carried out at baseline, 1-month, 6-months and 12-months post TBI from a sample of 94 TBI caregivers and at baseline from a sample of 43 Control caregivers.

TBI caregivers experienced poorer overall health and higher levels of depression and were less likely to report positive life changes compared to Control caregivers. Older age and higher income predicted positive life changes. In addition to this higher income predicted better physical and overall health. Ethnicity was found to predict depression with the Māori/‘other ethnicity’ group suffering higher levels of depression. Children’s dysfunctional behaviour was found to predict poorer caregiver health outcomes across several domains; these include physical health, overall health, and depression; while the child’s adaptive functioning was not found to be a predictive factor in any caregiver health domains. New Zealand European and Māori TBI caregivers experienced similar health outcomes and received similar levels of support. However, Māori experienced more positive life changes than New Zealand Europeans. Caregivers’ physical and psychological well-being was found to improve over time, these changes were the greatest between the 1-month and 12-month period.
As a high percentage of children’s TBI’s occur in the home and at school, education aimed at schools and parents to inform of the effects of TBI upon children and families will bring an awareness which may encourage families to seek medical help. In doing so will offer the opportunity to receive or seek support in the initial period post TBI in the hope of reducing the burden for caregivers and producing better health outcomes. Bringing these families into contact with medical services may also help in identifying caregivers at higher risk of poorer health outcomes. Findings of more positive life changes for Māori may suggest cultural ideology is a protective factor in caregiver burden, further investigation may be necessary to understand these cultural differences and how they impact upon the caregiving role.

text: Caregiver Health Related Quality of Life and Burden When Caring for Children with Traumatic Brain Injury Often family members take on the responsibility of caregiver when another family member sustains a traumatic brain injury (TBI). The caregiving role is a stressful task which may impact negatively upon caregivers’ psychological and physical health. Variables which may contribute to caregiver burden include: caregiver age, educational attainment, income, gender, ethnicity, marital status, supports, time post-injury, and child clinical variables: TBI severity, behavioural functioning and adaptive functioning. The literature varies in its reporting of which areas of health are most affected, and the degree to which sociodemographic and child variables impact upon negative health related quality of life (HRQoL) and burden. To address this the current study explored health outcomes for TBI caregivers using a battery of measures (Medical Study Short Form-36, Hospital Anxiety and Depression Scale, DSM-IV Depression Diagnostic Scale, BAKAS Caregiving Outcomes Scale); questionnaires were also used to collect sociodemographic information and information relating to supports and services used in the rehabilitation of the TBI child. The Behavioural Assessment System for Children was used to collect behavioural and adaptability information from the caregivers about the child. Assessments were carried out at baseline, 1-month, 6-months and 12-months post TBI from a sample of 94 TBI caregivers and at baseline from a sample of 43 Control caregivers.

TBI caregivers experienced poorer overall health and higher levels of depression and were less likely to report positive life changes compared to Control caregivers. Older age and higher income predicted positive life changes. In addition to this higher income predicted better physical and overall health. Ethnicity was found to predict depression with the Māori/‘other ethnicity’ group suffering higher levels of depression. Children’s dysfunctional behaviour was found to predict poorer caregiver health outcomes across several domains; these include physical health, overall health, and depression; while the child’s adaptive functioning was not found to be a predictive factor in any caregiver health domains. New Zealand European and Māori TBI caregivers experienced similar health outcomes and received similar levels of support. However, Māori experienced more positive life changes than New Zealand Europeans. Caregivers’ physical and psychological well-being was found to improve over time, these changes were the greatest between the 1-month and 12-month period.
As a high percentage of children’s TBI’s occur in the home and at school, education aimed at schools and parents to inform of the effects of TBI upon children and families will bring an awareness which may encourage families to seek medical help. In doing so will offer the opportunity to receive or seek support in the initial period post TBI in the hope of reducing the burden for caregivers and producing better health outcomes. Bringing these families into contact with medical services may also help in identifying caregivers at higher risk of poorer health outcomes. Findings of more positive life changes for Māori may suggest cultural ideology is a protective factor in caregiver burden, further investigation may be necessary to understand these cultural differences and how they impact upon the caregiving role.

year: 2012