58 results for Hicks, Brendan J., Journal article

  • Acetylene reduction associated with Zostera novazelandica Setch. and Spartina alterniflora Loisel., in Whangateau Harbour, North Island, New Zealand

    Hicks, Brendan J.; Silvester, Warwick B.

    Journal article
    University of Waikato

    Nitrogen fixation (acetylene reduction) was investigated in Zostera novazelandica Setch. and Spartina alterniflora Loisel., in the North Island of New Zealand. Moderate rates of acetylene reduction were found in sediments in which plants were growing (means ± 95% confidence limit: 15.2 ± 2.8 |jmol C2H4 nrr2 h~l for Zostera and 24.7 ± 4.6 |amol C2H4 m~2 h"1 for Spartina). Activity was closely correlated with the dry weight of root; (r2 = 0.65, N = 15 for Zostera, and r2 = 0.85, A' =10 for Spartina). Sediment close to the plant beds, but without plants, exhibited only low rates of acetylene reduction (2.9 ± 2.2 and 4.5 ± l.OjLtmol C2H4 m~2 h"1, respectively). Sediments associated with Z. novazelandica and S. alterniflora in New Zealand exhibit moderate rates of nitrogenase activity compared to rates found in other countries. N fixation may contribute significantly to the nutrition of these plants in New Zealand estuaries.

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  • Nitrogen fixation in the New Zealand mangrove (Avicennia marina (Forsk.) Vierh. var. resinifera (Forst f.) Bakh.)

    Hicks, Brendan J.; Silvester, Warwick B. (1985)

    Journal article
    University of Waikato

    Nitrogenase activity in mangrove forests at two locations in the North Island, New Zealand, was measured by acetylene reduction and 15N2 uptake. Nitrogenase activity (C2H2 reduction) in surface sediments 0 to 10 mm deep was highly correlated (r = 0.91, n = 17) with the dry weight of decomposing particulate organic matter in the sediment and was independent of light. The activity was not correlated with the dry weight of roots in the top 10 mm of sediment (r = –0.01, n = 13). Seasonal and sample variation in acetylene reduction rates ranged from 0.4 to 50.0 µmol of C2H4 m–2 h–1 under air, and acetylene reduction was depressed in anaerobic atmospheres. Nitrogen fixation rates of decomposing leaves from the surface measured by 15N2 uptake ranged from 5.1 to 7.8 nmol of N2 g (dry weight)–1 h–1, and the mean molar ratio of acetylene reduced to nitrogen fixed was 4.5:1. Anaerobic conditions depressed the nitrogenase activity in decomposing leaves, which was independent of light. Nitrogenase activity was also found to be associated with pneumatophores. This activity was light dependent and was probably attributable to one or more species of Calothrix present as an epiphyte. Rates of activity were generally between 100 and 500 nmol of C2H4 pneumatophore–1 h–1 in summer, but values up to 1,500 nmol of C2H4 pneumatophore–1 h–1 were obtained.

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  • Ecological values of Hamilton urban streams (North Island, New Zealand): constraints and opportunities for restoration

    Collier, Kevin J.; Aldridge, Brenda Michelle Te Aroha; Hicks, Brendan J.; Kelly, Johlene; Macdonald, Amy; Smith, Brian J.; Tonkin, Jonathan D. (2009)

    Journal article
    University of Waikato

    Urban streams globally are characterised by degraded habitat conditions and low aquatic biodiversity, but are increasingly becoming the focus of restoration activities. We investigated habitat quality, ecological function, and fish and macroinvertebrate community composition of gully streams in Hamilton City, New Zealand, and compared these with a selection of periurban sites surrounded by rural land. A similar complement of fish species was found at urban and periurban sites, including two threatened species, with only one introduced fish widespread (Gambusia affinis). Stream macroinvertebrate community metrics indicated low ecological condition at most urban and periurban sites, but highlighted the presence of one high value urban site with a fauna dominated by sensitive taxa. Light-trapping around seepages in city gullies revealed the presence of several caddisfly species normally associated with native forest, suggesting that seepage habitats can provide important refugia for some aquatic insects in urban environments. Qualitative measures of stream habitat were not significantly different between urban and periurban sites, but urban streams had significantly lower hydraulic function and higher biogeochemical function than periurban streams. These functional differences are thought to reflect, respectively, (1) the combined effects of channel modification and stormwater hydrology, and (2) the influence of riparian vegetation providing shade and enhancing habitat in streams. Significant relationships between some macroinvertebrate community metrics and riparian vegetation buffering and bank protection suggest that riparian enhancement may have beneficial ecological outcomes in some urban streams. Other actions that may contribute to urban stream restoration goals include an integrated catchment approach to resolving fish passage issues, active reintroduction of wood to streams to enhance cover and habitat heterogeneity, and seeding of depauperate streams with native migratory fish to help initiate natural recolonisation.

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  • Acetylene reduction associated with zostera novazelandica Setch. and Spartina alterniflora Loisel., in Whangateau harbour, North Island, New Zealand

    Hicks, Brendan J.; Silvester, Warwick B. (1990)

    Journal article
    University of Waikato

    Nitrogen fixation (acetylene reduction) was investigated in Zostera novazelandica Setch. and Spartina alterniflora Loisel., in the North Island of New Zealand. Moderate rates of acetylene reduction were found in sediments in which plants were growing (means ± 95% confidence limit: 15.2 ± 2.8 |jmol C2H4 nrr2 h~l for Zostera and 24.7 ± 4.6 |amol C2H4 m~2 h"1 for Spartina). Activity was closely correlated with the dry weight of root; (r2 = 0.65, N = 15 for Zostera, and r2 = 0.85, A' =10 for Spartina). Sediment close to the plant beds, but without plants, exhibited only low rates of acetylene reduction (2.9 ± 2.2 and 4.5 ± l.OjLtmol C2H4 m~2 h"1, respectively). Sediments associated with Z. novazelandica and S. alterniflora in New Zealand exhibit moderate rates of nitrogenase activity compared to rates found in other countries. N fixation may contribute significantly to the nutrition of these plants in New Zealand estuaries.

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  • Estimating the abundance of banded kokopu (galaxias fasciatus gray) in small streams by nocturnal counts under spotlight illumination

    Hicks, Brendan J. (2002)

    Journal article
    University of Waikato

    The abundance of banded kokopu (Galaxias fasciatus Gray) in small streams has usually been determined by the labour intensive and invasive method of electric fishing. Recently, nocturnal counts under spotlight illumination have been used to determine presence or absence and relative abundance of banded kokopu, but the proportion of the population seen was unknown. We compared 20 spotlight counts of banded kokopu in approximately 20 m reaches in streams in the North Island, New Zealand, to population estimates determined by removal electric fishing in the same reaches. Spotlight counts were related to population estimates over a range of densities, and on average, spotlight counts were 64% of the population estimates. Though we tried to separate age-0 fish from older fish visually in the spotlight counts, the size frequency distribution of the fish caught by electric fishing showed that the visual separation was not reliable. In addition, visual counts were generally inefficient for age-0 fish (40-70 mm total length), as only about 40% were observed. Banded kokopu were also recorded in streams using time-lapse video recordings with a camera sensitive to low light levels. Diel activity showed two major peaks, one in the early morning from 0400 h to 0900 h, and the other in the afternoon and evening from 1300 h to 1900 h. Fish were less disturbed by the observer.s approach after dark than during the day, so we suggest that from dusk to about 2200 h is the best time for visual counts of banded kokopu by spotlight in summer months.

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  • Book review: Ikawai: freshwater fishes in Māori culture and economy

    Hicks, Brendan J.; Watene-Rawiri, E.M. (2012)

    Journal article
    University of Waikato

    This article reviews the book : “Ikawai: freshwater fishes in Māori culture and economy”, by RM McDowall.

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  • Influence of open and closed river systems on the migrations of two northern New Zealand populations of banded kokopu (Galaxias fasciatus)

    Hicks, Brendan J.; Tana, Raymond (2012)

    Journal article
    University of Waikato

    Otolith microchemical analysis by laser ablation inductively coupled mass spectrometry (ICP-MS) was used to investigate the migratory life histories of banded kokopu (Galaxias fasciatus) in two streams on the North Island of New Zealand. Known differences in marine and freshwater chemistry were used as a premise to document the migratory life strategies of banded kokopu between these environments. More specifically, temporal trends in high and low strontium/calcium ratios (Sr/Ca) identified in fish otoliths were used to determine evidence of migration between fresh and saltwater environments. Trace element analysis of fish captured above the Whau Valley Reservoir reflected non-migratory life histories and exhibited consistently low Sr/Ca ratios across the entire otolith. However, one fish from above the reservoir indicated unusually high Sr/Ca ratios in early adulthood. These high Sr levels were attributed to localised inputs from mineral-rich seepages associated with past mining practices in the region and low calcium availability within the Pukenui Stream. Otoliths from banded kokopu collected from Komiti Stream were shown to be migratory with a marine larval stage (high Sr/Ca ratio levels at the otolith nucleus), followed by a freshwater adult phase (low Sr/Ca ratio levels towards the edge) indicating their amphidromous origins. The study provides further evidence of non-diadromous recruitment for banded kokopu as a consequence of a large in-stream barrier and will add to the known distribution of landlocked species in New Zealand.

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  • Growth and population dynamics of crayfish Paranephrops planifrons in streams within native forest and pastoral land uses

    Parkyn, Stephanie M.; Collier, Kevin J.; Hicks, Brendan J. (2002-11)

    Journal article
    University of Waikato

    Population dynamics of crayfish (Paranephrops planifrons White) in streams draining native forest and pastoral catchments, Waikato, New Zealand, were investigated from September 1996 to July 1998. Crayfish densities were generally greater in native forest streams because of high recruitment over summer, but varied greatly between streams in both land uses. Peak densities in summer were 9 crayfish m-2 in native forest and 6 crayfish m-2 in pasture streams, but peak biomass in summer was much greater in pasture streams. Mark-recapture data showed that crayfish, particularly juveniles, in pasture streams grew faster than in native forest streams, through both greater moult frequency and larger moult increments. Females reached reproductive size at c. 20 mm orbit-carapace length (OCL) after their first year in pasture streams, but after 2 years in native forest streams. Annual degree days >10°C appeared to explain the differences in the timing of life cycles. Estimates of annual crayfish production (range = 0.8-3.4 g dry weight m-2 year-1) were similar in both land uses, and P/B ratios were between 0.95 and 1.2. Despite deforestation and conversion to pasture, crayfish in these Waikato hill-country streams have maintained similar levels of annual production to those in native forest streams, although juvenile growth rates have increased and longevity has decreased.

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  • Fish and macroinvertebrates in lowland drainage canals with and without grass carp

    Hicks, Brendan J.; Bannon, Henry James; Wells, R.D.S. (2006-07)

    Journal article
    University of Waikato

    Diploid grass carp (Ctenopharyngodon idella L.) were introduced to a lowland Waikato drainage canal at an initial density of 40-80 kg ha -1(83-167 fish ha -1) to control aquatic macrophytes and improve water flow. A near-by canal was left without grass carp to act as an untreated control. After 7 months, macrophytes occupied 17% of the water column in the treated canal compared to 78% in the untreated canal. Fish and macroinvertebrates in both canals were examined before and after the release of grass carp by sampling with replacement by fyke netting on seven occasions. Brown bullhead catfish (Ameiurus nebulosus (Lesueur)) and shortfinned eels (Anguilla australis Richardson) comprised most of the resident fish biomass in both canals; however, before grass carp stocking, eels were more abundant than catfish in the treated canal. There was no change in the abundance of resident fish after stocking, but young-of-the-year catfish had greater mortality and grew faster in the treated canal than in the untreated canal. Macroinvertebrates were primarily associated with aquatic macrophytes. Grass carp reduced aquatic macrophyte abundance in the treated canal by about 80%, which by inference reduced the abundance of associated macroinvertebrates, but there was no observed impact of grass carp stocking on the resident fish assemblage. We examined the relationship between head width and fish length, and from this determined that 70% of the grass carp could have escaped through the downstream retention screen. Despite this possibility, grass carp remained in the canal and effectively controlled aquatic macrophytes for 18 months.

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  • Chronosequences of strontium in the otoliths of two New Zealand migratory freshwater fish, inanga (Galaxias maculatus) and koaro (G. brevipinnis)

    Hicks, Brendan J.; West, David William; Barry, B. J.; Markwitz, A.; Baker, Cindy F.; Mitchell, C.P. (2005)

    Journal article
    University of Waikato

    Half of the freshwater fish fauna in New Zealand is diadromous (i.e., migrates between the sea and freshwater); unimpeded access to and from the sea is important for the conservation of diadromous fish. The genus Galaxias (Galaxiidae: Osmeriformes) contains five diadromous species that spawn in freshwater, migrate to sea as larvae, and then migrate back into freshwater as 50-55-mm juveniles. Microchemistry of the otolith, a calcified structure in the fish's head, allows an independent test of assumptions about these migrations. Concentric layers of CaCO3 with some Sr as SrCO3 comprise the otolith, creating a chronosequence that reflects a fish's migratory history. More Sr accumulates in the otolith when a fish is in seawater than when it is in freshwater. High-resolution nuclear microscopy was used to measure the molar ratios of Sr/Ca in two galaxiid species. Otoliths of inanga (G. maculatus) caught in freshwater all showed a central zone of 100-200 μm in radius with Sr/Ca of 0.008-0.012, indicating early rearing in the sea. Sr/Ca values decreased to 0.001-0.002 as the fish moved into freshwater. Of six adult koaro (G. brevipinnis) caught in a river with sea access and no lakes, five had migrated to sea but one had not, raising questions about the generalized assumptions of migration.

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  • Habitat requirements of black mudfish (Neochanna diversus) in the Waikato region, North Island, New Zealand.

    Hicks, Brendan J.; Barrier, R.F.G. (1996-03-01)

    Journal article
    University of Waikato

    Black mudfish (Neochanna diversus) were found at 39 of 80 sites in the Waikato region, New Zealand, ranging from large wetlands to small swampy streams. Of the sites with mudfish, 87% were dry at some time during summer. Sites with mudfish also generally had emergent and overhanging vegetation and tree roots, and showed low to moderate human impact. Black mudfish coexisted at some sites with juvenile eels or mosquitofish, but were absent from all sites with common bullies (Gobiomorphus cotidianus) or inanga (Galaxias maculatus). Sites with mudfish had almost exclusively semi-mineralised substrates or peat; only one site had mineralised substrate. Geometric mean catch rate for the 39 sites with mudfish was 0.70 fish per trap per night. Mean summer water depth was only 2.1 cm at sites with mudfish, compared to 22.6 cm at 41 sites without. Winter and maximum water depths were also less at sites with mudfish than at sites without mudfish. Mean turbidity was 11.5 nephelometric turbidity units (NTU) at sites with mudfish, but 21.3 NTU at sites without mudfish. Mudfish catch rates were negatively correlated with summer water depth, winter water depth, disturbance scale rating, and turbidity. A discriminant function model based on these variables successfully predicted 95% of the sites with mudfish. Habitat preference curves are also presented.

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  • Otolith microchemistry of koi carp in the Waikato region, New Zealand: a tool for identifying recruitment locations

    Blair, Jennifer Marie; Hicks, Brendan J. (2012)

    Journal article
    University of Waikato

    We assessed differences in the otolith microchemistry of koi carp, a colour variant of the invasive common carp Cyprinus carpio, at various locations in the Waikato region of New Zealand. Although koi carp are abundant here, little is known about where and in what habitats they breed. We investigated the feasibility of determining the natal habitats of adult koi carp (in the Waikato River, selected tributaries, and riverine lakes in the catchment) using otolith elemental signatures and employing laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Differences in elemental concentrations in water among the sites indicated that variation in otolith microchemistry was likely. Ratios of manganese (Mn), rubidium (Rb), strontium (Sr), and barium (Ba) to calcium (Ca) in otolith edges differed significantly among the sites, and Sr:Ca in the water and otoliths was positively correlated. A discriminant function analysis using Rb, Sr, and Ba accurately classified the otolith edge signatures of koi carp from some locations, but the otolith signatures of koi carp caught from adjacent locations were often indistinguishable. This suggests that our results could have been confounded by either (1) recent movement of koi carp or (2) a lack of differences in water chemistry among sites. Taken together, these results demonstrate that otolith microchemistry can be used to test retrospectively for koi carp migration between sites on a broad scale in the Waikato region, but fine-scale movements may not be detectable.

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  • Growth of rainbow trout (Oncorhynchus mykiss) in warm-temperate lakes: implications for environmental change

    Blair, Jennifer Marie; Ostrovsky, Ilia; Hicks, Brendan J.; Pitkethley, Robert J.; Scholes, Paul; Tonn, William (2013)

    Journal article
    University of Waikato

    To predict potential effects of climate and anthropogenic impacts on fish growth, we compared growth rates of rainbow trout (Oncorhynchus mykiss) in nine closely located warm-temperate lakes of contrasting morphometry, stratification and mixing regime, and trophic state. Analyses of long-term mark–recapture data showed that in deep oligotrophic and mesotrophic lakes, trout growth rates increased with increasing indices of lake productivity. In contrast, in shallow eutrophic lakes, where fish habitat volume is constrained by temperature and dissolved oxygen, trout growth rates declined with increasing productivity. Growth rates were higher in lakes with greater volumes of favourable habitat (i.e., dissolved oxygen > 6.0 mg•Lˉ¹ and temperature < 21 °C) and lower in lakes with increased turbidity, chlorophyll a, and nitrogen concentrations. Our findings suggest that increases in lake productivity and temperatures as a result of global climatic change are likely to be more detrimental to salmonid habitat quality in shallower, productive lakes, while salmonids will better endure such changes in deeper, oligotrophic lakes. Fishery managers can use this information to aid future stocking decisions for salmonid fisheries in warm-temperate climates.

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  • Movement, social cohesion and site fidelity in adult koi carp, Cyprinus carpio

    Osborne, Matthew W.; Ling, Nicholas; Hicks, Brendan J.; Tempero, Grant Wayne (2009)

    Journal article
    University of Waikato

    Koi carp is an ornamental variant of the common carp, Cyprinus carpio L., that was introduced to New Zealand in the 1960s and has since become a major aquatic pest. A total of 1265 wild adult koi carp were caught by boat electric fishing, dart tagged and released at multiple sites in the lower Waikato River and associated lakes and wetlands between September 2002 and February 2005. Subsequent recaptures by boat electric fishing and recreational fishing returned 76 koi carp (6% of all tagged fish). Of these, 85% were recaptured less than 5 km from their release site; only one fish moved more than 50 km. On seven occasions, pairs or small groups of koi carp (20% of all tag returns) that had previously been tagged and released at the same locations and times were subsequently recaptured together after considerable periods of time at liberty (mean 551 days ± 419 SD). Adult koi carp in the Waikato River showed a high degree of site fidelity, exhibited prolonged social groupings and females moved downstream more often than males.

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  • Seasonal changes in abundance of brown trout (Salmo trutta) and rainbow trout (s. gairdnerii) assessed by drift diving in the Rangitikei river, New Zealand

    Hicks, Brendan J.; Watson, N. R. N. (1985)

    Journal article
    University of Waikato

    Numbers and approximate sizes of brown trout (Salmo trutta L.) and rainbow trout (5. gairdnerii Richardson) were estimated by snorkel divers at 6 sites in the middle reaches of the Rangitikei River, North Island, New Zealand, over 14 months. The results showed that different species and sizes of trout varied in abundance with time. The species of fingerling trout (6-12 cm FL) could not be identified because of their small size and shoaling behaviour. Rainbow trout abundance varied seasonally and was greatest in January and April (between 18 and 60 fish per kilometre) when fish between 23 and 38 cm FL were the most abundant size class. Brown trout abundance showed much less variation with time (between 5 and 36 fish per kilometre at most sites). Also in contrast to rainbow trout, the majority of brown trout were > 38 cm FL, and in June, when the greatest density was observed (56 fish per kilometre), 70 redds were seen at the same site. Two sites were dived within a 48 h period to test the variability of the method. Comparisons between the 3 dives at each site revealed no significant differences between the numbers offish in different species and size classes.

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  • Effects of turbidity and light intensity on foraging success of juvenile mandarin fish Siniperca chuatsi (Basilewsky)

    Li, Wei; Zhang, Tanglin; Zhang, Chaowen; Li, Zhongjie; Liu, Jiashou; Hicks, Brendan J. (2013)

    Journal article
    University of Waikato

    This study aimed to evaluate the effects of turbidity and light intensity on foraging success of juvenile mandarin fish Siniperca chuatsi. Predation on crucian carp Carassius auratus by juvenile mandarin fish was tested at five levels of turbidity combined with two light intensities, imitating daylight and night in two turbidity types. Foraging success was significantly lower in clay-induced turbidity than in algal-induced turbidity. In clay-induced turbidity trials, there was a slight but insignificant increase in foraging success of mandarin fish with increasing turbidity under lighted conditions. In algal-induced turbidity trials, there were no significant differences in foraging success of mandarin fish among turbidity levels at both light and dark levels, but at 80 NTU turbidity level, foraging success was lower than in all the other turbidity levels. There was no significant difference in foraging success at different turbidities under darkness. These results suggest that piscivory of mandarin fish is influenced by different turbidity types but is not significantly influenced by increased turbidity combined with decreased light intensity.

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  • Preliminary estimates of mass-loss rates, changes in stable isotope composition, and invertebrate colonisation of evergreen and deciduous leaves in a Waikato, New Zealand, stream.

    Hicks, Brendan J.; Laboyrie, J. Lee (1999-06-01)

    Journal article
    University of Waikato

    Rates of mass loss are important in the choice of tree species used in riparian rehabilitation because leaves that break down fast should contribute to stream food-webs more rapidly than leaves that break down more slowly. To examine comparative mass-loss rates of some native evergreen and introduced deciduous trees in a New Zealand stream, fallen leaves were incubated in bags with 2 x 3 mm mesh openings. The native trees were mahoe (Melicytus ramiflorus), kahikatea (Dacrycarpus dacrydioides), silver beech (Nothofagus menziesii), rewarewa (Knightia excelsa), tawa (Beilschmiedia tawa), and the introduced trees were silver birch (Betula pendula) and alder (Alnus glutinosa). The leaf bags were left in the Mangaotama Stream for 28 days from mid April to mid May 1995 when mean water temperature was 14.5deg.C, giving a total of 406 degree days. Rates of mass loss followed the sequence: mahoe > silver birch > alder > kahikatea > silver beech > rewarewa > tawa. Mean mass-loss rate for mahoe, assuming a negative exponential model, was 0.0507 k day-1 (0.00350 k (degree day)-1), and for tawa was 0.0036 k day-1 (0.00025 k (degree day)-1). C:N ratio decreased on average from 45:1 to 35:1, and d15N increased between 0.7 and 3.0[[perthousand]] (1.8 +/- 0.41[[perthousand]], mean +/-1 standard error), excluding kahikatea. Changes in d13C were smaller and not consistent in direction. Biomass of invertebrates was greatest in bags that had lost 25-45% of their initial leaf biomass.

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  • Diet of rainbow trout in Lake Rotoiti: an energetic perspective

    Blair, Jennifer Marie; Hicks, Brendan J.; Pitkethley, Robert J.; Ling, Nicholas (2012)

    Journal article
    University of Waikato

    We characterised seasonal and ontogenetic changes in diet and prey energy density of rainbow trout (Oncorhynchus mykiss) in Lake Rotoiti, New Zealand, to better understand the prey requirements of trout in central North Island lakes. Common smelt (Retropinna retropinna) was the dominant prey item of rainbow trout larger than 200 mm (77.8% of diet by weight), followed by kōura (freshwater crayfish Paranephrops planifrons; 6.3%), common bully (Gobiomorphus cotidianus; 5.5%), and kōaro (Galaxias brevipinnis; 3.4%). Juvenile rainbow trout (<200 mm) consumed amphipods, aquatic and terrestrial insects, oligochaetes, tanaid shrimps, and smelt. Trout consumed kōaro only in autumn and winter; consumption of other species did not vary seasonally. The maximum size of smelt consumed increased with increasing trout size, but trout continued to consume small smelt even as large adults. Consumption of larger prey items (kōaro and kōura) also increased with increasing trout size. This study indicates the importance of smelt for sustaining rainbow trout populations, as predation on other species was relatively low. These findings provide a basis for bioenergetic modelling of rainbow trout populations in lakes of the central North Island of New Zealand.

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  • The palatability of flavoured novel floating pellets made with brewer's spent grain to captive carp

    Morgan, Dai K.J.; Verbeek, Casparus Johan R.; Rosentrater, Kurt A.; Hicks, Brendan J. (2012)

    Journal article
    University of Waikato

    The palatability to common carp, Cyprinus carpio L. of three newly developed differently flavoured floating pellets made from a high proportion (40%) of brewer's spent grain (BSG) was tested using a multiple-offer feeding experiment. The addition of ‘bold’ flavours, such as vanilla or strawberry essence, may help mask the unpleasant taste of some piscicides; however, their inclusion must not compromise uptake by carp. There were no significant differences between the consumption rates of the three varieties, and all flavours were readily consumed. Therefore, it is suggested that highly flavoured pellets made with BSG have a strong potential to mask the flavour of an unpalatable toxin, and further research is now needed to test this hypothesis.

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  • Distribution and abundance of fish and crayfish in a Waikato stream in relation to basin area

    Hicks, Brendan J. (2003-06-01)

    Journal article
    University of Waikato

    The aim of this study was to relate the longitudinal distribution of fish and crayfish to increasing basin area and physical site characteristics in the Mangaotama Stream, Waikato region, North Island, New Zealand. Fish and crayfish were captured with two-pass removal electroshocking at 11 sites located in hill-country with pasture, native forest, and mixed land uses within the 21.6 km2 basin. Number of fish species and lineal biomass of fish increased with increasing basin area, but barriers to upstream fish migration also influenced fish distribution; only climbing and non-migratory species were present above a series of small waterfalls. Fish biomass increased in direct proportion to stream width, suggesting that fish used much of the available channel, and stream width was closely related to basin area. Conversely, the abundance of crayfish was related to the amount of edge habitat, and therefore crayfish did not increase in abundance as basin area increased. Densities of all fish species combined ranged from 17 to 459 fish 100 m-2, and biomass ranged from 14 to 206 g m-2. Eels dominated the fish assemblages, comprising 85-100% of the total biomass; longfinned eels the majority of the biomass at most sites. Despite the open access of the lower sites to introduced brown trout, native species dominated all the fish communities sampled.

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