ISSN:0028-8330    

DOI:10.1080/00288330.1999.9516880

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Kaniwhaniwhanusgen. n. is described for the first time from New Zealand. Diagnoses of the male imago, pupa, and larva are presented.Kaniwhaniwhanuscan be distinguished by a combination of hairy eyes, pigmented wings, presence of bare anal point, and absence of inferior volsella in the male imago; the absence of a thoracic horn, presence of anteriorly directed comb‐like hooklets on abdominal tergites TII‐TV, evenly distributed shagreen on posterior abdomen tergites, and the absence of anal macrosetae in the pupa; and by a 4‐segmented antenna, broad single tooth of mentum with four pairs of lateral teeth, and the presence of paired medio‐lateral lobes of the mentum in the larva.Kaniwhaniwhanusappears to be monotypic and is designated by the type species,Kaniwhaniwhanus chapmani. Larvae ofKaniwhaniwhanus chapmaniare known from North Island streams and have been recorded from Lake Grasmere in the South Island.

ISSN:0028-8330    

DOI:10.1080/00288330.1999.9516881

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The life history ofKaniwhaniwhanus chapmaniBoothroyd is described through examination of larval population dynamics, larval drift, and adult emergence. Development of larvae occurred all year but peak larval densities occurred in February, July, and November and indicated several generations with longest generation times in the autumn. Emergence occurred all year and a bimodal diel emergence pattern was apparent at certain times.K. chapmanilarvae were present in the stream drift at all times but not in high densities, and generally only during daylight hours with an early morning/late afternoon drift pattern.K. chapmaniexhibits a generally non‐seasonal life history but rapid growth tends to occur when conditions of temperature and food quality are likely to be optimal resulting in shorter generation times and peaks in larval populations.

ISSN:0028-8330    

DOI:10.1080/00288330.1999.9516882

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Lake Rotorua is a eutrophic polymictic lake in the centre of the North Island, New Zealand. Three studies of its crustacean zooplankton, in 1955–56, 1967–69, and 1994–95 have been made. Despite increased eutrophication since the first study, species composition has not changed: the calanoid copepod,Calamoecia lucasi, dominates for much of the year andBosminacf.meridionalisandCerio‐daphniacf.dubiaare the only limnetic cladocerans. Comparison of their annual cycles in abundance between the studies show little regularity in the seasonal patterns, suggesting that stochastic events, such as storms, may be the most important controlling factors through their effects on food levels.

ISSN:0028-8330    

DOI:10.1080/00288330.1999.9516883

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

This paper describes current initiatives to develop a lake management plan for Lake Taupo, New Zealand. Recently there has been an indication that a shift from dry stock farming to large‐scale dairy farming will occur in the Taupo catchment. The local community has expressed an interest in this shift towards more intensive land use. There is public concern regarding the current state of Lake Taupo's water quality and the ability to maintain environmental quality in the face of increasing development pressures. Concerns about rising levels of nutrients in the lake are supported by trend analysis of lake water quality monitoring data. The Taupo District Council and the Waikato Regional Council have proposed development of a Lake Taupo Management Plan. A number of mechanisms for achieving this process could be explored. These include a plan largely developed by an inter‐agency management group or a more public participatory approach directly involving the community. A general lake planning framework is described and some of the limitations of the process explored. Comparison with experiences at Lake Rotorua, New Zealand, and Lake Tahoe, United States of America, supports a pre‐cautionary approach to the use of predictive ecological models in policy development. The inability of aquatic ecological theory to conform to quantitative approaches in other physical sciences needs to be acknowledged by scientists and conveyed to the public. Until the link between land‐use practice and water quality is better understood, a pre‐cautionary approach to catchment development at Lake Taupo should be encouraged. One cannot assume that common desires for both environmental protectionism, and progressive intensification of land use, will lead to sustainable resource management. The environmental effects of dairy farming indicate that encouraging this land‐use practice will not lead to the desired community expectation of water quality protection at Lake Taupo.

ISSN:0028-8330    

DOI:10.1080/00288330.1999.9516884

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The mandibles, first and second maxillae, and maxillipeds ofBoeckella major, B. pseudo‐chelae, andHemiboeckella searlifrom temporary pools of the upper River Murray catchment were dissected off and examined by light microscopy for features associated with carnivorous feeding. InB. majoradaptations for carnivory are enlarged ventral mandibular teeth, strong falciform medial setae on the second maxillae, falciform endopodal setae on the maxilliped, large body size and large mouthpart size in relation to body size. Its mandibular edge index is 772, in the upper omnivore range.B. majoris predicted to be an omnivore with strong carnivorous tendencies and able to handle large prey items. Carnivorous features inH. searliare enlarged ventral mandibular teeth, a mandibular edge index of 1395, and strong unguiform and falciform setae on the second maxillae. It is predicted to be an omnivore with moderate carnivorous tendencies, but unable to handle prey as large as canB. major. InB. pseudochelaethe only adaptations for carnivory are an edge index of 1080 and falciform setae on the maxilliped. It is predicted to be an omnivore with herbivorous tendencies. Examination of gut contents confirmed these predictions.B. majorguts contained 19 animal taxa, mainly planktonic cladocerans, copepods and rotifers,H. searli12 taxa, mainly copepods and rotifers, andB. pseudochelae8 taxa, mainly rotifers. All had consumed algae. We suggest that predation byB. majormay be an important factor affecting community structure in fishless Australian temporary pools.

ISSN:0028-8330    

DOI:10.1080/00288330.1999.9516885

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The seasonal changes in the dynamics and life histories of the Cladocera in Lake Mangakaware, North Island, New Zealand, were studied over 19 months by sampling at weekly or 2‐weekly intervals. Lake Mangakaware is a 13.3 ha polymictic lake with high nutrient status, low Secchi disc transparencies, and an unstable thermal regime. The four planktonic cladoceran species (Bosmina longirostris, B. meridionalis, Ceriodaphnia pulchella, andC. dubia) exhibited disjunct population maxima. OnlyB. longirostriswas perennially present. All species exhibited low fecundities and low lipid content, indicating that food resources were limited and that competitive interactions and resistance to starvation were probably important in determining species success. Increases in body size in cooler seasons were unrelated to clutch size, giving further support for the view that available food was limited. These results are consistent with previous experimental findings that subtle differences in life history can determine seasonal success and the outcome of competition between similar species.

ISSN:0028-8330    

DOI:10.1080/00288330.1999.9516886

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The ability of black mudfish (Neochanna diversusStokell) to withstand hypoxia and drought was examined by observing an isolated population near Hamilton, New Zealand over the course of a year (September 1988‐November 1989). In addition, a series of experiments were performed to determine what dissolved oxygen levels trigger air‐breathing in the black mudfish, and the length of time this species can survive out of water in a humid environment. Air‐breathing behaviour in black mudfish involves rising to the surface, gulping an air bubble and holding the bubble in the buccal cavity while the fish continues gill ventilation. Water in the study drain started to become hypoxic in mid November and by early December oxygen levels were <3.0 mg litre‐1on the surface and <1.0 mg litre‐1near the bottom (15 cm deep). In the laboratory, at water temperatures ranging from 20 to 22°C, none of the 20 test fish gulped air from the surface until oxygen levels dropped below 2.5 mg litre‐1; c. 45% of the animals began air‐gulping at oxygen levels between 2.0 and 2.5 mg litre‐1and, at oxygen levels below 1.0 mg litre‐1, 100% of the test fish gulped air from the surface. Over a similar temperature range, animals were kept on damp moss for 10 weeks (the drought duration in the drain was 132 days). Under these conditions, test animals lost weight steadily: adults lost 17–24%, and young‐of‐the‐year 30–45%, of their initial weight. On re‐immersion, all adults recovered; however, two young‐of‐the‐year fish died. Within 4 h of re‐immersion, the surviving fish increased their body weight by 6–12%, but within 24 h they returned to their pre‐immersion weight. The mechanisms involved in drought resistance in black mudfish (and their relevance to conservation and habitat preservation) are discussed. A possible option for the restoration, and maintenance, of mudfish in habitats formerly occupied by this species complex is to provide appropriate drought shelters while maintaining a regime of seasonal drought to remove competitors.

ISSN:0028-8330    

DOI:10.1080/00288330.1999.9516887

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The diets of lake resident and both allopatric and sympatric migratory (diadromous) forms of common smelt (Retropinna retropinna(Richardson)) in Lakes Waahi and Whangape (Lower Waikato River system, New Zealand) were examined before and after collapse of macrophyte beds and loss of associated invertebrates. Before this diets were varied, but dominated by chironomid larvae and pupae, supplemented by semiplanktonic crustaceans in small smelt in particular and by corixids in larger smelt. Afterwards diets were less diverse and the main food items were mysid shrimps. The opportunistic, generalist feeding habits of smelt help their survival of habitat changes.

ISSN:0028-8330    

DOI:10.1080/00288330.1999.9516888

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Dietary samples collected at Campbell Island in summer 1997 indicate that southern blue whiting (Micromesistius australis) formed the bulk of the food of black‐browed albatrosses (Diomedea melanophrys impavida) during the chick‐rearing period. Birds preyed upon a single size class of fish with a mode at 80–90 mm standard length; fish were 4–5 months old and belonged to the 0+ age group. Satellite tracking showed that, when performing trips of short duration, adult albatrosses foraged within the 1000 m depth contour in the subantarctic zone north of Campbell Island. The feeding ecology of albatrosses thus suggests that juvenile (0+) southern blue whiting are pelagic and occur in dense schools in the top 5 m of the water column over the Campbell Plateau during the summer months. The high reliance of birds on juvenile southern blue whiting during the chick‐rearing period has implications for the management of the southern blue whiting fishery and the conservation of black‐browed albatrosses and other marine predators occurring in the New Zealand subantarctic area.

ISSN:0028-8330    

DOI:10.1080/00288330.1999.9516889

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor