摘要:

Iso‐electric focusing was used to identify fish tissue in Westland petrel (Procellaria westlandica) diet samples. Forty‐five percent of the samples from Westland petrel stomachs produced clear protein banding patterns and more than half of these were identified as species common in fisheries’ waste. Proteins in the other samples were presumably too digested for this technique. Iso‐electric focusing is a comparatively quick and inexpensive technique and is particularly useful for diet studies where flesh eaten is likely to be relatively undigested at the time of sampling.

ISSN:0028-8330    

DOI:10.1080/00288330.1998.9516817

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A sediment accumulation record based on the levels of “unsupported”210Pb was obtained from a core taken from the centre of Wellington Harbour, New Zealand. Sediment accumulation rates (SARs) varied from 3 to 5 mm yr‐1. Before 1920, SARs were sufficiently high to dilute unsupported levels of210Pb to background, but had fallen below the mean by 1925 maintaining constant SARs until 1953. These data provide a higher resolution chronology of early 20th century SARs than was previously available. Comparison with137Cs data confirms that there was a significant increase in SARs between 1953 and 1967, but that these have remained fairly constant since 1974. Data from the two radionuclides are consistent after 1974, and210Pb data are consistent with other chronological measurements before 1953. Therefore, it is suggested that the two radionuclides are immobile in the marine sediments of Wellington Harbour and that differences between the two SARs are real.

ISSN:0028-8330    

DOI:10.1080/00288330.1998.9516818

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Dynamic heights of the ocean surface to the north‐east of North Cape, New Zealand are determined from 18 months of Topex‐Poseidon altimeter measurements along a repeat track crossing the East Auckland current system. The anomalies in the heights and in the cross‐track geostrophic currents derived from these heights both portray strong cyclic signals with period of c. 140 days travelling towards New Zealand, and a signal with period of at least 18 months in the opposite sense. Sea‐surface temperature (SST) anomalies and anomalies in the along‐track SST gradients exhibit similar periodicity. The coherence between anomalies in velocity and temperature gradient and that between anomalies in height and temperature both reach c. 0.74 at the period of 140 days and 0.88 for the long‐period signal. A correspondence is also shown between the positions of maximum flow in the East Auckland current and positions of high sea‐surface temperature gradient. Winds are shown to affect the strength of the 140‐day signal in the temperature gradient data, and to impair its coherence with the matching signal in the velocity anomaly data. In particular, if temperature gradient data are smoothed through times and places where the recent history of the curl of the wind‐stress is significantly positive (Ekman pumping occurring) the coherence in the 140‐day signal between the velocity and temperature gradient is increased from 0.74 to 0.92. Similar impacts on the longer period signal are not found, nor are they evident for either of the two prominent signals in the coherence between SST and height anomalies.

ISSN:0028-8330    

DOI:10.1080/00288330.1998.9516819

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The occurrence, abundance, and distribution of seabirds was studied in a physically dynamic region off the coast of Otago, New Zealand. Eleven line‐transect surveys were conducted in late summer and autumn of 1994–96, when surface swarms of “krill”,Nyctiphanes australis, were present in the study area. Twenty species of seabird were recorded. The abundance and occurrence of species varied between sitting and flying counts. The most numerous species were sooty shearwaters (Puffinus griseus), red‐billed gulls (Larus novaehollandiae), black‐billed gulls (L. bulleri), and black‐backed gulls (L. dominicanus). Most species were recorded throughout the study area, and different species were commonly observed together. Spatial similarity matrices revealed strongest association between red‐ and black‐billed gulls and black‐backed gulls. The small (kilometre) scale distribution of seabirds varied between surveys, between transects, and between repeated runs of the same transect 1–3 h apart. Correlations between seabird abundance, salinity gradient, and krill density were weak. Counts of seabirds were highly positively skewed. This skewness, together with spatial and temporal variability in the distribution of flocks, would make abundance estimation at sea difficult.

ISSN:0028-8330    

DOI:10.1080/00288330.1998.9516820

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Continuous time‐series of near‐bed and near‐surface currents and temperature were recorded, at the shelf edge and on the shelf of northeast New Zealand, between June 1994 and January 1996. Tidal analysis of the current records show that typical tidal currents in the region are dominated by the Mj constituent, with amplitudes between 5 and 10 cm s‐1. The amplitude of the M2tide varies in response to the existence of an internal tide, and the tide was also found to include higher harmonics of the M2tide during periods of strong internal tide activity. These higher harmonics are likely to be the result of a non‐linear internal tide. Mean flows at the surface throughout the records were generally parallel to the bathymetry and towards the southeast, with typical speeds of between 20 and 30 cm s‐1, sometimes reaching 60 cm s‐1near Cape Brett. It is suggested that flow curvature around Cape Brett could be a significant localised upwelling mechanism. Near‐bed currents showed a strong cross‐shelf component in response to along‐shelf wind stress, indicating episodic wind‐driven upwelling events driving slope water onto the shelf between the autumnal and vernal equinoxes. It is estimated that such upwelling introduces a net supply of 10 ± 3 mmol m‐3of nitrate to the shelf waters between Cape Brett and Hauraki Gulf.

ISSN:0028-8330    

DOI:10.1080/00288330.1998.9516821

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Collections of three species of oreos (smooth oreo,Pseudocyttus maculatus;black oreo,Allocyttus niger;and warty oreo,A. verrucosus) from Australasian waters were examined for genetic variation. Allozyme heterozygosity was high in each species (25–29 loci: mean heterozygosity per locus per sample ranging from 0.100 to 0.148), but mitochondrial DNA variation was less extensive (10 six‐base restriction enzymes: nucleotide diversity ranging from 0.0012 to 0.0021). Collections of smooth oreos from Western Australia, Tasmania, and New Zealand did not permit the null hypothesis of a single stock to be confidently rejected. Black oreos from Tasmania and New Zealand were provisionally identified as separate stocks. Warty oreos from Tasmania were provisionally identified as separate from a Western Australia/New South Wales stock.

ISSN:0028-8330    

DOI:10.1080/00288330.1998.9516822

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This paper assesses the potential effectiveness of the visible implant fluorescent elastomer (VIFE) tagging system for identifying groups of snapper (Pagrus auratus:Sparidae) in the field. Retention rate after surface tagging longline‐caught fish was 93% over a 2‐week period, with no mortality attributable to tagging. Incidence of fin or scale infection did not differ between tagged and control fish. A protocol for tagging snapper underwater was also developed. This technique caused less stress to the fish than remote fishing methods, but was labour intensive when large sample sizes were required. Orange VIFE tags were visible to divers at ranges of up to 6 m in water visibility of 8–10 m, when exposed to light frequencies capable of inducing fluorescent emissions. Red, green, and yellow tags were only identifiable at shorter ranges, depending on ambient light levels and direction. The range of tag detection increased with increasing water clarity. We suggest that VIFE tagging has better retention rates and is less intrusive compared with previously employed externally readable tags. Because tags are identifiablein situwithout the necessity of recapture, this method has potentially wide‐ranging applications in fish ecology and behavioural studies for adult as well as juvenile fishes.

ISSN:0028-8330    

DOI:10.1080/00288330.1998.9516823

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The distributions of shortfinned eels (Anguilla australis) and longfinned eels (A. dieffenbachii) of all sizes in three New Zealand coastal streams were investigated during summer by sampling stratified, randomly chosen pool, run, and riffle sites from tidal to upper reaches. In all streams, both species were widespread, although a greater proportion of the total population of shortfinned eels was present in the lower reaches and small eels (<300 mm total length (TL)) had advanced further up stream than longfins in two of the streams. The biomass (g m‐2) of longfinned eels <300 mm TL was greatest in riffles, whereas that of comparable‐sized shortfinned eels was evenly distributed across habitat types in all streams; in contrast, eels ≥300 mm TL of both species showed no consistent pattern of habitat use between streams. Multiple regression analysis of species biomass (g m‐2) for four size groups (<100; 100–199; 200–299; ≥300 mm TL) against 16 habitat variables, indicated that the distribution of shortfinned eels <300 mm TL was most closely associated with distance from the ocean, whereas that of longfinned eels of the same size group was most closely associated with water velocity and substrate. Medium‐large eels (≥300 mm TL) of both species were strongly associated with cover, with longfinned eels using a greater variety (macrophytes, banks, in‐stream debris, shade) than shortfinned eels (primarily riparian cover). Overall, our findings suggest that the longfinned eel is a more generalist species, living in a broad range of habitats, whereas the shortfinned eel is more specialised, as is reflected in differences in their distributions and habitat associations.

ISSN:0028-8330    

DOI:10.1080/00288330.1998.9516824

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The food‐web communities of two stony tributaries of the Taieri River in New Zealand were documented. We placed heavy emphasis on algal and macroinvertebrate taxonomy, identifying most taxa to species or morpho‐species level. Food‐web attributes were derived from symmetrical matrices using an Excel macro. The values of the food‐web attributes are generally consistent with generalities that have previously been reported in food‐web studies, although some hypothesisied relationships between connectance and food‐web size did not hold. The patterns detected were robust to the inclusion or exclusion of species that were identified in gut contents but not in field samples. The attributes strongly reflected the trophic status of the streams. Dempsters Creek was classified as autotrophic (based on high primary production and a high ratio of production to respiration) and displayed a larger food‐web size and longer food‐chains than those seen in Healy Creek, which was classified as hetero‐trophic (lower primary production and production to respiration ratio). The importance of dynamic environmental attributes such as production and disturbance in structuring food‐webs is emphasised in this study.

ISSN:0028-8330    

DOI:10.1080/00288330.1998.9516825

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The macroinvertebrate community was surveyed at eight littoral zone sites in Lake Coleridge, New Zealand. Sites covered a range of conditions including exposure to prevailing winds, shore‐line topography, and proximity to river inputs—which are a major source of suspended sediment to the lake. The littoral zone contained an abundant and diverse macroinvertebrate fauna (47 taxa). Three communities were identified: a shallow‐water community inhabiting the wave‐break zone, dominated by Trichoptera and chironomid larvae; a middle‐zone community associated with macrophyte beds, with high macroinvertebrate abundance and dominated by gastropods and oligochaetes; and a community in fine sediments below the macrophytes dominated by oligochaetes. The depth distribution of these communities was related to substrate, macrophyte abundance, and shore‐line profile. Superimposed on this pattern were the effects of hillside slope and exposure to prevailing north‐west winds. Greatest abundance was associated with macrophytes on stable shores at 4–7.5 m depth, i.e., below the effective wavebase depth. Sediment deposition had only a localised direct effect close to where river water enters the lake. Indirect effects were mediated through the effects of suspended solids on water clarity, bottom limits, and production of macrophytes and periphyton. Estimates of the proportion of littoral macroinvertebrate biomass to whole‐lake zooplankton biomass was 10:1 and for production was 1.3:1, indicating the potential importance of the littoral zone to whole‐lake production.

ISSN:0028-8330    

DOI:10.1080/00288330.1998.9516826

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor