CBER Reports

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Electrofishing survey of the fish community in the Whangamarino Wetland
(The University of Waikato, 2008-07-14) Hicks, Brendan J.; Brijs, Jeroen; Bell, Dudley G.; Powrie, Warrick
A previous fish community survey carried out in the Whangamarino Wetland system recorded 18 different fish species by netting, electrofishing, and interviews with local eel fishermen and reports from Acclimatisation Society staff (Strickland, 1980). Strickland reported that the most widespread and common species in the wetland were shortfinned eels, mosquitofish, goldfish and catfish. In August 2007 and March 2008, the Centre for Biodiversity and Ecology Research (CBER) were contracted to carry out an electric fishing survey of the fish community in the Whangamarino Wetland and its tributaries. Boat and backpack electrofishing caught a diverse range of native and introduced fish. A total of 1,491 fish comprising 8 native fish species and 5 introduced fish species were caught in a total fished area of 26,600 m2 or 2.66 ha from a total of 34 sites. Koi carp, shortfinned eels, goldfish and common smelt were the most widespread fish species throughout the wetland system. Fish distribution, density and biomass varied between sites throughout the Whangamarino Wetland as well as between the two different time periods (August 2007 and March 2008). Mean densities and biomasses of fish species at most sites increased substantially in March 2008 compared to August 2007.
Comparative boat electrofishing surveys of Lake Waahi in 2007 and 2011
(Centre for Biodiversity and Ecology Research, The University of Waikato, 2011-05-05) Tempero, Grant Wayne; Hicks, Brendan J.
We conducted boat electrofishing surveys of Lake Waahi, which is located to the west of Huntly and flows into the Waikato River. The purpose of this was to repeat surveys that took place on 7 March 2007 and 26 March 2011 concerning the density and distribution pattern fish species within the lake. Due to wind and possibly low water clarity, catch rates were lower in 2011 than those found in 2007 as we only caught 108 fish in 2011 compared to 493 in 2007. Species composition included three native species and five introduced species. Native species caught were common smelt, common bully and shortfin eel and introduced species were perch, rudd, goldfish, catfish and koi carp, gambusia were also sighted but not captured.
Passage of inanga (Galaxias maculatus) over artificial ramps as a means of restoring upstream access to stream habitat
(Centre for Biodiversity and Ecology Research, School of Science & Engineering, University of Waikato, 2008) Hicks, Brendan J.; Roper, M.R.; Ito, T; Boubée, J. A. T.; Campbell, David I.
The effects of substrate type, flow rate, and slope on fish passage over artificial ramps was evaluated for inanga (Galaxias maculatus); a small diadromous fish native to New Zealand, Australia, Tasmania, Lord Howe Island, Chatham Island, Chile, Argentina, and the Falkland Islands. Five substrate types (smooth, corrugated, herring-bone baffle, and two plastic moulded cores of ground drainage products Polyfo® and Stripdrain®) were tested on slopes of 3 - 5 % and flows of 4 - 6 ls-1. Slope, fish size, and substrate type each had a significant influence on the mean distances swum. Stripdrain® was the most effective substrate type, enabling the greatest distances to be achieved and a maximum vertical elevation of 0.39 m to be attained. The results of this study have further highlighted the potential for ramps to provide fish passage past small in-stream barriers, as well as the need to refine ramp slopes and lengths in order to meet the specific barrier remediation needs.
Water flow between Ohau Channel and Lake Rotoiti following implementation of the diversion wall part B
(Centre for Biodiversity and Ecology Research, The University of Waikato, 2010) Hamilton, David P.; Paul, Wendy J.; McBride, Chris; Immenga, Dirk
To help improve water quality in Lake Rotoiti, a diversion wall was completed in July 2008, to divert the water emanating from the Ohau Channel towards Okere Arm in Lake Rotoiti. The objective was that this water would be directly transported into the Kaituna River instead of entering the main basin of Lake Rotoiti. A report was produced in response to a request from the Rotorua Lakes Technical Advisory Group to determine water velocities in the region of the wall, to consider the effectiveness of the diversion. This subsequent report has been written to follow-up on the recommendation that vertically resolved measurements of water current and direction in Lake Rotoiti should be investigated. The timing of the data collection was April to May when an underflow is more likely to be present.
Effect of different operational regimes of Okere gates on the effectiveness of the Ohau Channel diversion wall in Lake Rotoiti
(Centre for Biodiversity and Ecology Research, The University of Waikato, 2010-11-22) Muraoka, Kohji; Paul, Wendy J.; Hamilton, David P.; von Westernhagen, Nina
The Centre for Biodiversity and Ecology Research was requested by Environment Bay of Plenty (EBoP) to present model results that demonstrate the water flow implications of four different water level operational regimes in Lake Rotoiti. The aim was to quantify the proportion of nutrient-enriched Lake Rotorua water being transported from Ohau Channel around the diversion wall and into Lake Rotoiti. Environment Bay of Plenty did not wish to compromise the effectiveness with which the wall diverted this nutrient-enriched water from Rotorua directly to the Kaituna River.
Lake Ohinewai pest fish removal
(Centre for Biodiversity and Ecology Research, The University of Waikato, 2011-05-25) Daniel, Adam Joshua; Morgan, Dai K.J.
Most riverine lakes in the Waikato region have deteriorated from a macrophyte-dominated state to an algal-dominated state. Pest fish have further compounded water quality issues by resuspending nutrient-rich sediment and are believed to be a major barrier to water quality improvements. The University of Waikato has an ongoing programme funded by the Ministry of Business, Innovation and Environment, to produce pest fish management tools for end users that include removing pest fish from five lakes as an objective. The goal of the fish removals is to test the assumption that removing pest fish will improve water quality. Lake Ohinewai was selected as one of the five lakes to attempt a pest fish removal in 2009 and the removal operation was scheduled for January 2011. The Department of Conservation agreed to assist with funding for consumables and the construction of an experimental barrier to assist with the Lake Ohinewai removal project. University of Waikato staff began removing pest fish from Lake Ohinewai in January 2011 with the assistance of the Department of Conservation and volunteers. A one-way fish barrier was designed and installed during May 2011 to prevent adult pest fish from recolonising the lake.
Boat electrofishing survey of fish populations in the Ohau Channel in December 2010
(Centre for Biodiversity and Ecology Research, The University of Waikato, 2011-11-15) Hicks, Brendan J.; Tana, Raymond; Bell, Dudley G.
The original purpose of this series of surveys was to apply an independent method to estimate the densities of common smelt and bullies in the Ohau Channel at fixed points along the bank which coincided with trap netting sites used by the National Institute of Water and Atmospheric Research (NIWA). Since the low number of smelt captured by a single day’s boat electrofishing became apparent compared to the numbers captured by seasonal trapping, the aim of the survey has been modified to provide on-going monitoring of the fish communities and abundance in the Ohau Channel, especially fish species that are taonga to Maori (eels, goldfish, and koura).
Lake Rotokawau: Water quality and sediment study
(Centre for Biodiversity and Ecology Research, The University of Waikato, 2011-07) Pearson, Lisa Kyle; Hamilton, David P.; Hendy, Chris H.
Lake Rotokawau is a small (0.52 km2), deep (74 m), oligotrophic lake in the Rotorua Lakes District, located approximately 4.1 km east of Lake Rotorua. The lake is privately owned and managed by the local iwi, Ngati Rangiteaorere. During a site visit carried out on the 25 July 2010, surface and bottom water samples and a sediment core were collected, together with a water column profile (CTD) of temperature, dissolved oxygen, fluorescence, conductivity and depth. The CTD cast showed an anoxic hypolimnion and that the lake likely had not mixed during at the time of sampling, in mid-winter. This observation is highly unusual amongst the Te Arawa lakes and suggests that the lake may remain stratified for multiple years. The lack of mixing could be due to several factors including: presence of higher-salinity bottom waters, high water depth to area ratio, and sheltered aspect. The sediment core collected in the central basin revealed the presence of Ruapehu ash (1995-6 eruption) preserved in the upper 5 cm of the sediment record and the Tarawera Tephra (1886 eruption) located at 13 cm below the sediment water interface. The Ruapehu Ash layer is not preserved in sediment from any other Rotorua lakes and has likely been preserved due to the lack of seasonal mixing. The sediment and pore water chemistry are similar to that of the other lakes in the Rotorua region but however multiple sediment cores are necessary to fully assess variability across the whole lake area. It is recommended that a routine monitoring programme be established so that any improvement or degradation in water quality can be detected and the mixing frequency of the lake determined. The water quality monitoring should include water column profiles of temperature, dissolved oxygen, fluorescence, conductivity and depth, nutrient analysis (ammonium, nitrate, nitrite, phosphate, silicon, total nitrogen and total phosphorus) of surface and bottom waters and water clarity readings (e.g. Secchi disk and light attenuation). Our observations point to the highly unusual nature of Lake Rotokawau in terms of mixing status and indicate a strong need to preserve significant biological and landscape features of this lake which has not been subject to problems with invasive species that characterise several other lakes in this region.
Groundwater in the Okataina caldera: Model of future nitrogen loads to Lake Tarawera
(Centre for Biodiversity and Ecology Research, The University of Waikato, 2009-09) Gillon, Nicholas; White, Paul; Hamilton, David P.; Silvester, Warwick B.
Protection and restoration of water quality are a major priority of the New Zealand government. To support this objective, a monitoring and an action programme named “The Regional Water and Land Plan” was set up by the Environment Bay of Plenty Regional Council in February 2005 for the Rotorua lakes district. Lake Tarawera is part of this programme. The plan includes a Tarawera River management plan developed originally by Bay of Plenty Catchment Commission (1985). Currently water quality of Lake Tarawera is slightly worse than during the 1990s (Environment Bay of Plenty 1997). The Trophic Level Index (TLI), a measure of water quality, is 2.9 in Lake Tarawera. Environment Bay of Plenty wishes to reduce the TLI to 2.6, to improve the water quality of the lake. Actions have already been programmed to support this initiative, including sewage treatment. Most of the water inflow to the lake is from groundwater. Nitrogen loads to the lake from groundwater are largely unknown as there is limited monitoring data. Development of highly productive pasture in the last 50 years, coupled with a residence time for the groundwater estimated on average to be c. 200 years, look likely to result in increasing nutrient loads to the lake with potential for deterioration of water quality. The objective of this study was to assess current and future groundwater nutrient loads to Lake Tarawera, particularly nitrogen loads. Following a consideration of the Lake Tarawera catchment water balance, a hydrogeological model was created. Nitrogen discharge with groundwater to Lake Tarawera is assessed based on pre-development land use, current land use and scenarios of future land use, allowing conclusions to be made for priorities for the maintenance of lake water quality.
Lake Rotoiti fieldwork and modelling to support considerations of Ohau Channel diversion from Lake Rotoiti
(Centre for Biodiversity and Ecology Research, The University of Waikato, 2005-03) Hamilton, David P.; McBride, Chris G.; Uraoka, Toradji
A detailed assessment of the water quality effects of the Ohau Channel inflow to Lake Rotoiti was carried out using field and computer modelling analyses. The modelling assessment evaluates the effects on Lake Rotoiti of partial (50%) or complete (100%) diversion of the Ohau Channel. A comprehensive bathymetric survey of Lake Rotoiti and the eastern end of Lake Rotorua was also carried out to provide information for the application of a three-dimensional model run by NIWA, so that different diversion wall positions and designs might be tested prior to possible implementation. Field measurements based on temperature, conductivity and chlorophyll fluorescence carried out from February to May 2004 captured instances when the Ohau Channel entered Lake Rotoiti as a buoyant overflow. These data and historical records suggest that approximately 20% of the buoyant surface inflow enters the main basin of Lake Rotoiti, while the remainder is short-circuited through the Kaituna arm to the outflow.
Sediment removal as a restoration measure for the campus lakes
(Centre for Biodiversity and Ecology Research, The University of Waikato, 2008-05) Paul, Wendy J.; Hamilton, David P.
The Campus Lakes, Oranga and Knighton, were formed about 1969 as a means of draining the wet, swampy land that the University of Waikato was sited on. Since Prof. Wilf Malcolm, (Vice-chancellor, 1985-1994) first expressed concern about the water quality of the Campus Lakes (Kingsbury, 1989), they have been the subject of at least four reports and one thesis. A number of approaches for improving the lake water quality have been tried or recommended, largely without success. The lakes continue to be unsightly with exotic weed growing to nuisance proportions and phytoplankton scums and blooms occurring annually, as well as discoloration from high concentrations of suspended sediments. The indigenous biodiversity values are low due to domination by pest fish and exotic macrophytes. This report is part of a larger scale recommendation to take an integrated approach towards the management of Oranga and Knighton lakes. The focus of this study was to investigate the possibility of removal of 0.2 m of the nutrient and organic-rich surficial sediments from the two lakes, and disposal of that sediment by spreading it onto the university playing fields. The specific aims of this study were to determine contaminant concentrations (heavy metals and persistent organochlorines) in the sediments and relate these concentrations to soil environmental guideline values for human health with parkland/recreational land use.
Modelling of restoration scenarios for Lake Ngaroto
(Centre for Biodiversity and Ecology Research, The University of Waikato, 2008-08) Paul, Wendy J.; Özkundakci, Deniz; Hamilton, David P.
Waipa District Council is investigating restoration options for Lake Ngaroto, a shallow lake that has become hypertrophic through high external (catchment) nutrient loading from its catchment, which is associated with land use that is predominantly dairy farming. Shallow lakes like Lake Ngaroto, which have high external loading, typically have high internal nutrient loading, which may also need to be addressed to gain immediate improvements in water quality. By contrast, reduction of external nutrients is more likely to be associated with gradual and long-lasting effects on water quality. This report is a culmination of data collection and analysis, and model development and simulation of restoration scenarios for Lake Ngaroto. Data were gathered on flow, nutrient concentrations, temperature, dissolved oxygen, suspended sediments, meteorological variables and the lake morphology for the lake and its catchment. These data were used to produce a water balance and input files for DYRESM-CAEDYM, a one dimensional, coupled hydrodynamic-water quality model. Once calibrated, using the measured lake data (ammonium (NH4-N), nitrate (NO3-N), phosphate (PO4-P), total phosphorus (TP), total nitrogen (TN), chlorophyll a (Chl a), suspended solids (SS), temperature, dissolved oxygen (DO)) as a means of comparison for modelled data, a number of scenarios were carried out to simulate outcomes of lake restoration measures.
Variability of physical and biological parameters in Lake Taupo: Bio-fish survey 2004-5
(Centre for Biodiversity and Ecology Research, The University of Waikato, 2005-12) Hamilton, David P.; McBride, Chris P.; Chong, Lisa; Gibbs, Max M.
This project was initiated by the Lakes and Waterways Action Group (LWAG) in response to declining water quality of Lake Taupo (Gibbs, 2004). Information was sought on variability of physical and biological parameters across different parts of the lake particularly in relation to use of only one profiling site (Station A) or three profiling sites (Stations A, B, and C) used in previous studies (e.g. Gibbs, 2004). Furthermore, the Taupo District Council (TDC) has a concern that some taste and odour problems (e.g. geosmin) experienced in its water supply may be due to cyanobacteria that accumulate in the near-shore region where water supply intakes are located. The TDC also sought information about variability of phytoplankton biomass across Lake Taupo. The objective of this study was to carry out a series of BIO-FISH transects of Lake Taupo, to observe the variability of temperature, chlorophyll a, dissolved oxygen and conductivity.
Analysis of catchment hydrology and nutrient loads for lakes Rotorua and Rotoiti
(2005-01) Beya, Jose; Hamilton, David P.; Burger, David F.
A water and nutrient budget has been derived from lakes Rotorua and Rotoiti to complement an earlier report to the Lakes Water Quality Society that considered only internal (bottom sediment-derived) sources of nutrients for these two lakes. Twenty-six inflows to Lake Rotorua that have been monitored for varying periods are considered in this report. The combined annual mean discharge of these inflows varies between 12 and 17m3s-1 depending on the time period selected, which likely reflects long-term variations in rainfall and groundwater levels. Correlations of discharge in the Utuhina Stream with discharges of other major inflows were generally significant and reinforce the concept that discharges from individual streams respond in a synchronous fashion across the catchment of Lake Rotorua.
How many koi? Preliminary estimates of koi carp abundance from boat electrofishing
(Centre for Biodiversity and Ecology Research, The University of Waikato, 2007-04-25) Hicks, Brendan J.
Single-pass boat-based electrofishing estimates of the abundance of koi carp (Cyprinus carpio) were made in the Waikato River, associated lakes and tributaries, and in two ponds. Catches were converted to density and biomass estimates using distances estimated from global positioning coordinates and a regression equation that related removal population estimates to the number of fish caught in the first pass. Biomass estimates ranged from 26 to 4,053 kg ha-1, with a median of 548 kg ha-1. Ninety-six of the 105 biomass estimates for sites with koi exceeded 150 kg ha-1, a threshold biomass considered to represent the point at which removal of invasive fish will improve water quality. High as these biomass estimates are, the size frequency distribution suggests that koi are still increasing in abundance in the Waikato basin despite the period of at least 25 years since their initial introduction. Removal of koi will be challenging. Extrapolations of koi densities to whole lakes suggest that Lake Whangape (1,079 ha) might have 165,000 spawners (604 tonnes), and Lake Waikare (3,438 ha) might have 466,000 spawners (851 tonnes). Lake Waahi (444 ha) might have 32,000 spawners (75 tonnes). Added to this, koi are distributed widely in the Waikato River below the Karapiro Dam, probably downstream as far as the estuary. Preliminary estimates of koi densities in four zones suggest that there are 65,000 koi in the river (70 tonnes) and its side channels. These biomass estimates must be regarded as preliminary because 1) an unknown proportion of the fish sensed the electrical field before falling within the capture voltage gradient threshold and were observed to swim away and 2) densities assumed for extrapolations might not apply to all of the extrapolated area. Despite these reservations, these estimates of koi in the Waikato River are conservative because extensive willow fringes and shallow margins were not fishable with the electrofishing boat. Most tributaries hold koi, and these add to the total. The extensive wetlands of the Waikato Basin (e.g., the Whangamarino and Opuatia wetlands) also hold unknown numbers of koi. Any eradication efforts should initially be focussed on water bodies where natural recolonisation cannot occur, or where it can be prevented by suitable artificial barriers to the upstream migration of koi.
The potential for inferring trophic state of Lake Wairarapa using zooplankton community composition
(Centre for Biodiversity and Ecology Research, The University of Waikato, 2006-08) Duggan, Ian C.
The use of biotic responses to infer lake trophic state (i.e., the bioindicator approach) is commonly neglected in favour of chemical and physical methods. Duggan et al. (2001a, 2001b, 2002) found that trophic state was the main determinant of rotifer distribution among North Island, New Zealand, lakes. Based on these responses developed a quantitative bioindicator index, using rotifer community composition, to infer Trophic Lake Index (TLI) values (sensu Burns et al. 1999). This approach was recently used successfully to infer trophic state changs in lakes of the Auckland region (Duggan & Barnes 2006). In this report I evaluate whether Lake Wairarapa would be a suitable candidate for monitoring trophic state using zooplankton during Wellington Regional Council's regular quarterly sampling, and what the number of net samples would be required during monitoring (i.e.., to collect greater than 300 individual zooplankton).
The distribution of fish in the urban gully system streams of Hamilton City
(Centre for Biodiversity and Ecology Research, The University of Waikato, 2006-11-27) Aldridge, Brenda Michelle Te Aroha; Hicks, Brendan J.
The distribution of fish in the urban gully system streams of Hamilton City was investigated using various methods of fishing. Fishing methods used in the city wide survey included trap netting using Gee minnow and fyke nets, electric fishing, and spotlighting at selected sites. Water quality and habitat parameters were assessed at each of the sites to add information to instream freshwater fish assemblages (i.e., preferred habitat). Culverts were assessed downstream of all sites because, native freshwater fish of New Zealand are largely migratory, having both freshwater and marine life histories. Freshwater fish migrate between habitats, therefore barriers to swimming fish passage may determine the presence of fish species at inland sites. Pest fish were less common than native fish in this survey, although they represent a greater proportion of the fish caught, because the small pest fish mosquitofish are prolific breeders and were present in very high numbers at a few sites. This study has shown that some urban streams can support diverse fish assemblages where water quality and habitat conditions permit. Threatened species were found to be present in streams previously thought of as supporting little stream life with low fish habitat or biodiversity value. The need for restoration and management of these streams is vital if the diversity and distribution of native fish is to be maintained.
Nutrient water budget for Lake Tarawera
(Centre for Biodiversity and Ecology Research, The University of Waikato, 2006-09-14) Hamilton, David P.; Hamilton, Matthew; McBride, Chris G.
A nutrient budget has been constructed for Lake Tarawera using two techniques. One technique involved analysis of incoming stream discharges and concentrations of nutrient species (total nitrogen (TN), ammonium, nitrate, total phosphorus (TP) and phosphate) based on measurements taken at weekly to fortnightly intervals in the summer of 2005/06. The second technique involved an analysis based on the predominant land use together assigned coefficients for areal rates of nutrient export. Both techniques produced very similar nutrient load estimates of approximately 12-13 tonnes TP per year and 95-100 tonnes TN per year. On the basis of comparisons of incoming nutrient loads, discharge and nutrient concentrations in the Tarawera River outflow, and total lake volume, it is estimated that incoming water will reside in the lake for an average duration of 10 years, and that 86 % of TP and 72 % of TN will be trapped within the lake; either buried in the lake sediments or lost as nitrogen gas in the process of denitrification. A water budget constructed from stream discharges, rainfall and evaporation revealed that nearly 80 % of the water entering the lake (not including rainfall) was from sources that were not gauged as part of the summer (2005/06) stream survey; groundwater appears to be the dominant source of water for Lake Tarawera.
Habitat characteristics of geothermally influenced waters in the Waikato
(Centre for Biodiversity and Ecology Research, The University of Waikato, 2003-06) Stevens, Mark I.; Cody, Ashley D.; Hogg, Ian D.
The Waikato province contains almost 80% of New Zealand's geothermal systems (Environment Waikato 1998). Thus, this region represents an important resource in terms of the habitat associated with increased soil and water temperatures for both geothermal vegetation (Beadel & Bill 2000) and aquatic organisms (Parkyn & Boothroyd 200; Duggan & Boothroyd 2001). Associated issues and values range from exploitative resource use, such as thermal energy extraction and the utilisation of mineralised fluids, to historical, amenity, cultural, spiritual, conservation and scientific values (Environment Waikato 1998; Merrett & Clarkson 1999). The environmental management objectives of Environment Eaikato are derived from these. The objectives are to maintain the variety of characteristics and to achieve protection and efficient of the regional geothermal resource (Environment Waikato 1998). The present report provides an inventory of the ecological and physical/chemical characteristics of geothermally influenced water in the Waikato province. The area was surveyed between April 10th and May 9th and assessments of habitat and in situ measurement of environmental parameters (eg DO, pH, conductivity, temperature) were used to determine habitat characteristics.
Zooplankton composition and a water quality assessment of seventeen Waikato lakes using rotifer community composition
(Centre for Biodiversity and Ecology Research, Department of Biological Sciences, 2008) Duggan, Ian C.
Zooplankton species composition was documented from 17 Waikato lakes from net haul samples collected in late 2007 (summer) and early 2008 (autumn). The lakes examined were Harihari, Mangahia, Maratoto, Ngahewa, Ohinewai, Okowhao, Parangi, Rotokawau, Rotomanuka, Serpentine East, Serpentine North, Serpentine South, Taharoa, Tutaeinanga, Waahi, Waikare and Whangape.

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