摘要:

A method is described to determine the age of red cod using the bands in sectioned otoliths. The technique was validated by examining the state of otolith margins over a 1‐year period, and by following the progression of length modes in length‐frequency distributions (for age classes 0+ to 3+). Von Bertalanffy growth parameters are estimated for red cod off the south‐east coast of the South Island. Few fish appear to live longer than 4 years. Because of the few age classes in the population at any time, age distributions may be obtained for most of a sample using length modes.

ISSN:0028-8330    

DOI:10.1080/00288330.1996.9516704

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The age of hoki was determined by counting bands in otolith cross‐sections. The technique was validated using the progression of length modes in length‐frequency distributions (for age classes 0+ to 4+) and the progression of strong and weak year classes in age‐frequency distributions from commercial catches sampled off the west coast of the South Island, New Zealand, from 1988 to 1994. Von Bertalanffy growth parameters for the west coast and Cook Strait spawning populations are significantly different, providing further support for a two‐stock hypothesis. In both areas female hoki have a growth rate significantly faster than males, and also a greater life expectancy.

ISSN:0028-8330    

DOI:10.1080/00288330.1996.9516705

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

We analysed satellite radar altimeter data for the New Zealand area during the period November 1992 to June 1994. Sea‐surface height anomalies from the Topex‐Poseidon and ERS—1 radar altimeter data were consistent in locating and identifying variability within most of the recognised major features in the area. Near the New Zealand coast, the tidal models used in the analysis did not perform well. A considerable error in the modelled M2 tidal component was apparent as an aliased signal with a period of about 62 days (sampled at a 10 day orbital repeat period). A correction was made to remove the error. Profiles of cross‐track current anomalies were deduced for the East Auckland Current system and there was good general agreement between Topex‐Poseidon and ERS‐1 products. Using surface measurements along one subsatellite track, the height data were calibrated and a history of absolute cross‐track currents to the north‐east of North Cape was produced. This showed a strong east‐southeastward flow between 33.5°S and 34°S, with a return flow meandering between 32°S and 33°S. The strength of the current at a fixed location varied considerably, with a possible seasonal influence. The histories of cross‐track current‐anomaly profiles, along with current‐anomaly vectors constructed for the track cross‐over points, give a coherent picture of features in the area. In particular, an anticyclonic eddy to the north‐east of New Zealand is identified moving south‐eastward during the spring of 1993.

ISSN:0028-8330    

DOI:10.1080/00288330.1996.9516706

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A karyological investigation was carried out on the testis cells of the tidal pool sacoglossan sea slugStiliger felinusfrom New Zealand. The haploid chromosome set was characterised by 14 elements where median‐, subterminal‐, and terminal‐centromere chromosomes were present. Using flow cytometric analysis, haploid genome size of the species was found to be 2.8 pg: the highest value encountered in the subclass Opisthobranchia.Stiliger felinusdiffers from other Stiligeridae in chromosome number and frequency of cross‐shaped bivalents in spermatocytal metaphase I plates.

ISSN:0028-8330    

DOI:10.1080/00288330.1996.9516707

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

We compared morphometric features of adult‐size (75–95 cm total length) hoki,Macruronus novaezelandiae, from the two main spawning grounds (West Coast South Island, Cook Strait) and from the two main areas of dispersal (Auckland Island‐Campbell Plateau, Chatham Rise) to determine if more than one stock is evident. Significant differences (P >0.001) in head shape were found between the two spawning grounds and between the dispersed areas. When sample sets from the four areas were combined, West Coast and Cook Strait spawning samples were the least similar. Auckland Island‐Campbell Plateau stock morphometrics were closest to West Coast, while those of Chatham Rise were closest to Cook Strait's. The data provide strong evidence that Cook Strait and West Coast spawners are from different stocks. There is also some support for the hypothesis that Auckland Island‐Campbell Plateau hoki are from the same stock as the West Coast spawners, and that Chatham Rise hoki are from the same stock as the Cook Strait spawners.

ISSN:0028-8330    

DOI:10.1080/00288330.1996.9516708

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Specimens of king tarakihi from northern New Zealand were shown to differ from specimens of tarakihi, using two genetic methods: allozymes and random amplified polymorphic DNA (RAPD). Allozyme techniques revealed fixed differences between tarakihi and king tarakihi at one locus and very different electromorph frequencies at a further three loci. There was a genetic distance of 0.35–0.39 between the two morphs. RAPD markers were generated with 10‐base oligonucleotide primers. Three out of 9 primers produced different DNA fragments in tarakihi and king tarakihi collected on the same longline, indicating that the morphs are discrete species. The two morphs could not be distinguished by conventional isoelectric focusing of muscle proteins. We conclude that the king tarakihi is a previously undescribed species found in subtropical waters of northern New Zealand.

ISSN:0028-8330    

DOI:10.1080/00288330.1996.9516709

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This study documents the fauna in the size range 0.1–5.0 mm found on the encrusting brown algaPseudolithodermasp., common on patches of the honeycomb barnacleChamaesipho columnaon mid‐intertidal shores in northern New Zealand. Collections of fauna were made in four different habitats associated with this alga and in the presence or absence of underlying barnacles: (1) maturePseudolithodermacrust on barnacles, (2) maturePseudolithodermacrust occurring on bare rock, (3)Pseudolithodermaflaking off rock, and (4) barnacles withoutPseudolithoderma. The invertebrate species composition differed from assemblages recorded for other, more structurally complex algae, such as coralline turfs. More species were found onPseudolithodermathan on bare barnacles. There were no significant differences in the number of species between different habitats containingPseudolithoderma;however, flakingPseudolithodermahad fewer individuals than otherPseudolithodermahabitats. We hypothesise that less structurally complex habitats, such as encrusting algae, are more suitable to fauna with protective shells or tubes; and speculate that the large numbers of such fauna in this assemblage influence the ecology ofPseudolithoderma.

ISSN:0028-8330    

DOI:10.1080/00288330.1996.9516710

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Small meshed G‐minnow traps were used to assess the habitat associations of juvenile shortfinned eels in Lake Waahi, a shallow mesotrophic lake in the lower Waikato River basin, New Zealand. Five distinctive marginal habitats (raupo, aquatic macrophyte, reed, willow, exposed clay, and mud), and five offshore positions at various depths through the water column and distances from the margin (1–3 m and 50–500 m, respectively) were compared. Eels smaller than 400 mm were closely associated with marginal habitat. The highest catch per unit effort (CPUE) of juveniles occurred in raupo, the most complex cover. CPUE in marginal habitats declined in autumn particularly in the willows which corresponded to defoliation. Offshore sampling revealed that eels smaller than 350 mm were almost exclusively in the margins, and that larger eels were mostly offshore. Beyond 50 m from the margin, the size of eel did not change with increasing distance offshore. Eels were not caught in suspended traps (other fish were), suggesting that eels in this lake were benthic foragers. Reasons for juvenile habitat selectivity are discussed and management implications highlighted.

ISSN:0028-8330    

DOI:10.1080/00288330.1996.9516711

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The distribution and abundance of fish at sites in 38 medium to large New Zealand rivers were examined. Fish density varied from 5 to 200 fish per 100 m2, with an average of 53 fish. Our study sites contained a greater species richness and abundance than records stored on the New Zealand Freshwater Fish Database, where the average density was 28 fish per 100 m2. The average number of species at the study sites was 5, compared to 3 in the national database. Comparison of first‐pass catches with multiple‐pass population estimates showed that there was no difference in capture probability between species and that on average 51% of the population was captured on the first pass. The diadromous habit of many native species, and their ability to penetrate inland, was an overwhelming influence on their distribution. There was little regional variation in species composition, apart from the presence or absence of three non‐diadromous species. Two distinct fish communities were evident: lowland and upland. Lowland communities typically contained the highest density and diversity offish, whereas upland communities were dominated by one or two species. Many river sites were intermediate between lowland and upland, both in species composition and fish density, and showed a gradual reduction in abundance and change in community structure with elevation, as those fish less able to penetrate inland disappeared and non‐diadromous species began to appear. Elevation was the most important discriminating factor, with physical habitat and catchment variables less important. Fish densities were highest in gravel substrate of 50 mm or finer, and the amount of run and pool habitat may have influenced species composition. The relationships between catchment variables and species distribution and abundance were probably a reflection of geographical location.

ISSN:0028-8330    

DOI:10.1080/00288330.1996.9516712

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Shortjawed kokopu from diverse localities feed extensively on several species of cased caddisflies from the stream benthos and on diverse terrestrial invertebrates from the surface. Small caddisflies often dominate the diet numerically and are selected for, whereas other often abundant benthic insects, such as Chironomidae and the mayflyDeleatidium, are avoided. We hypothesise that this selectivity indicates that caddisflies are taken by grazing the benthos rather than from the invertebrate drift. Gravimetrically, large terrestrial invertebrates such as beetles, ants, cicadas, and spiders are more prominent in shortjawed kokopu diet. Stable carbon isotope analysis shows that in Black Creek, a tributary of the Ohinetamatea River, South Westland, a high proportion of the material assimilated from the diet is of terrestrial origin.

ISSN:0028-8330    

DOI:10.1080/00288330.1996.9516713

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor