摘要:

Volumetic hypolimnetic oxygen depletion, caused primarily by the decomposition of organic material in the hypolimnion (VHDRorg), is considered to be an important indicator of the trophic state of lakes and is used to detect change of trophic state. The observed volumetric hypolimnetic depletion rate (VHDRobs) is usually different from VHDRorgbecause of phenomena which can alter the concentrations of oxygen in the hypolimnion. The nine different phenomena which can affect the rate at which the observed hypolimnetic dissolved oxygen depletes are reviewed. In many instances, if the limnology of the system is understood, the perturbations to the hypolimnetic respiration rate, VHDRorgcaused by these phenomena can be ignored and VHDRobsused for lake management. Guidance is provided as to when the effects of these phenomena can be ignored and when they cannot be. Should corrections be necessary, methods for calculating the effects of physical perturbations are outlined. However, most of the effects caused by biological perturbations from changes in algal species cannot be eliminated, except for those caused by hypolimnetic production.

ISSN:0028-8330    

DOI:10.1080/00288330.1995.9516634

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Habitat use of eight native fish species was determined by electroshocking depth‐stratified lanes < 0.125 m, 0.125–0.25 m, 0.25–0.5 m, and 0.5–0.75 m. Two runs and two riffles were sampled in 34 rivers. Water depth, velocity, and substrate size were measured. Bluegilled bullies (Gobiomorphus hubbsi), upland bullies (G. breviceps), common bullies (G. cotidianus), longfinned eels (Anguilla dieffenbachii), and shortfinned eels (A.australis) made up over 80% of the total number and biomass of fish sampled. Overall, fish densities were highest along river margins in depths of less than 0.25 m, and higher in riffles than in runs. The fish species could be classified into four habitat guilds: a fast‐water guild that occupied central portions of riffles, an edge‐dwelling guild, an intermediate guild, and finally a guild that was ubiquitous. Minimum flow requirements based on habitat for the edge‐dwelling and fast‐water guilds would be conflicting, with one benefiting from low flows and the other from high flows. A minimum flow assessment based on the intermediate guild provides a compromise between these two extremes.

ISSN:0028-8330    

DOI:10.1080/00288330.1995.9516635

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A possum (Trichosurus vulpecula) control operation using aerially sown baits containing sodium monofluoroacetate (1080) was conducted in June 1993 in and adjoining Tararua Forest Park, New Zealand. In total, 66 water samples from eight sites collected over a period of 4 months were analysed for residual 1080 potentially resulting from the control operation. No 1080 was detected in any of the samples (quantifiable level 0.0003 mg l−1).

ISSN:0028-8330    

DOI:10.1080/00288330.1995.9516636

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Human perception of two important visual aspects of the appearance of river and lake water, clarity and colour, was investigated from the perspective of bathing and aesthetics in New Zealand. Bankside interviews were conducted at the same time as measurements were made for clarity and colour. We found that water appearance, perceived suitability of the water for bathing, and bathing activity are closely linked, as is perception of water clarity and colour. Water is perceived as just suitable for bathing at a horizontal black disc visibility of 1.2 m (equivalent Secchi depth c. 1.5 m) with a 90 percentile of 2.2 m (equivalent Secchi depth c. 2.75 m), confirming earlier work. As might be expected, blue waters are preferred to yellow waters, and water is perceived as just suitable for bathing if the Munsell colour is greater than around 30 units (i.e., at the low end of the green‐yellow range). For bathing waters, consideration of personal safety is very important; for aesthetics, surroundings are important. People's perception of visual aspects (i.e., clarity and colour) appears to have a strong influence on their rating of overall site suitability.

ISSN:0028-8330    

DOI:10.1080/00288330.1995.9516637

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

In a study of human perception of the appearance (clarity and colour) of rivers and lakes for bathing and aesthetic water use, we have shown that: bankside observers can reasonably accurately assess colour (hue) in some circumstances; and that the phenomenon of perceptual set (seeing what is expected to be seen) may influence the visual perception of some waters. Further, perceived naturalness of a water seems to provide for a more positive response towards a water body than might otherwise be expected.

ISSN:0028-8330    

DOI:10.1080/00288330.1995.9516638

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A new bothid flounder,Engyprosopon raoulensissp. nov., collected from Raoul Island (Kermadec Island group) and Norfolk Island, is described on the basis of 17 specimens in the fish collection of the Museum of New Zealand. This species clearly differs from the known species in having a shorter pectoral fin on the ocular side of both sexes, a caudal fin without distinct markings, a larger number of scales in the lateral line, gill rakers without serrations, and biserial teeth on the upper jaw. The present species is a new southern record for species of the genusEngyprosopon, and is probably at the southern boundary of distribution of this genus.

ISSN:0028-8330    

DOI:10.1080/00288330.1995.9516639

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

To determine whether post‐settlement juveniles of New Zealand soft‐sediment macro‐fauna drift in the water column, samples were collected, day and night, above an intertidal sandflat in Manukau Harbour, New Zealand. Forty benthic taxa were collected in the net samples. Most taxa were Polychaeta (18 taxa), Bivalvia (9 taxa), or Amphipoda (4 taxa). All bivalves and gastropods collected were post‐settlement juveniles, 3 mm or less in size. Most of the polychaetes captured were either metamorphosing planktonic larvae or young benthic stages. In contrast, most of the captured arthropods were adults. Generally, benthic species found in the water column were also common in the benthos. Definite patterns in migratory activity were exhibited by some taxa over each 24 h sampling period. Taxa collected in the water column varied with sampling date, time of day, state of the tide, and depth of sampling. Only one of the benthic species collected in the net samples showed some ability to partition itself vertically within the water column. The large number and variety of soft‐bottom macrofauna collected emphasises the potential importance of post‐settlement dispersal in the survival of post‐larval organisms.

ISSN:0028-8330    

DOI:10.1080/00288330.1995.9516640

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Sea level data from 15 tide gauges around New Zealand were analysed to assess the effect of meteorological forcing. Many of the data were of poor quality and special care was needed with the data processing to make the data usable. Analyses were carried out in both the time domain and the frequency domain in the frequency band from 1 to 9° h−1, resulting in the same general outcomes: that sites exposed to the prevailing westerly winds respond to changes in barometric pressure at greater than the conventional inverted barometer response, whereas eastern sites sheltered from the west respond at less than the inverted barometer. At northern sites, sea level generally changes in advance of changes in barometric pressure by 3 to 4 hours; however, for individual events, the reverse may be true. For other sites (from the mid‐North Island southwards), sea level generally responds to barometric pressure changes after a few hours. For north‐eastern sites, the percentage of the variation in sea level which can be explained by changes in barometric pressure is low and there appears to be no correlation between sea level and regional wind stress, leading to the conclusion that, to a large extent, variation in sea level is caused by waves propagating into the area.

ISSN:0028-8330    

DOI:10.1080/00288330.1995.9516641

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Knowledge of the New Zealand trachyrincine grenadiers is reviewed.Idiolo‐phorhynchus andriasheviSazonov, 1981 andTrachyrincus longirostris(Gunther, 1878) are redescribed andTrachyrincus aphyodesn. sp. is described.T. aphyodesdiffers fromT. longirostris, with which it has been confused, by having more pyloric caeca (119–211 cf. 35–62) and a larger mouth (upper jaw length 29.4–34.0 cf. 24.7–28.2% head length). A key to the three known New Zealand trachyrincine grenadiers is given.

ISSN:0028-8330    

DOI:10.1080/00288330.1995.9516642

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The population of toheroa (Paphies ventricosaGray) at Oreti Beach, South Island, New Zealand, was until recently considered relatively minor in comparison to those of the North Island west coast beaches. It is now the sole remaining toheroa population in New Zealand to support recreational toheroa gathering. This paper analyses count data from 22 systematic surveys of large toheroa (> 8 cm) at Oreti Beach between 1971 and 1990. A variance estimator appropriate to two‐dimensional systematic surveys is developed to enable computation of confidence intervals for these abundance estimates. It is concluded that the recreational harvest taken during open days can not be reliably estimated by pre‐ and post‐harvest surveys and should instead be determined from inspection and enumeration of open day participants. At current population and harvest levels the impact of occasional open days at Oreti Beach is slight; however, the high annual variability of toheroa populations and the uniqueness of this one remaining harvestable stock suggest a need for continued population surveys.

ISSN:0028-8330    

DOI:10.1080/00288330.1995.9516643

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor