摘要:

The presence of suitable gravel size alone can stimulate female rainbow trout(Salmo gairdneri)to excavate nests for spawning on the shores of Lake Rotoma. Emergent fry result from lake‐shore spawning, and could contribute significantly to the trout fishery in Lake Rotoma. Lake‐shore spawning could be enhanced by the use of stable artificial spawning beds that have adequate depth and appropriate sizes of gravel.

ISSN:0028-8330    

DOI:10.1080/00288330.1983.9516010

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

A total of 4393 female and small male rock lobsters,Jasus edwardsii,were tagged and released near Stewart Island and in eastern Foveaux Strait between 1974 and 1978. Most recaptures had not moved more than 5 km but 16% of immature females and small males underwent highly directional movements along the southeast coast of Stewart Island, and 16 were recaptured in Fiordland. Rock lobsters which undertook long distance movements included those which were classified by fishermen as migratory animals, plus some small, local inshore animals. These observations add support to the hypothesis that a regular migration of immature rock lobsters takes place around southern New Zealand, probably with no single area of origin or destination.

ISSN:0028-8330    

DOI:10.1080/00288330.1983.9516011

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Protein and enzyme variation in 2 populations of the mud crabMacrophthalmus hirtipes(Jacquinot, 1853) (Ocypodidae) from 1 marine and 1 estuarine habitat were investigated by poly‐acrylamide gel electrophoresis. A survey of 24 loci revealed that 22 were common to both populations; 20 were monomorphic and 2 were highly polymorphic. Two alleles were detected for each of the polymorphic loci, esterase‐2 (EST‐2) and ester‐ase‐3 (EST‐3). The frequencies of the EST‐3 alleles were similar in the 2 populations. However, the frequencies of the 2 EST‐2 alleles in the estuarine population were significantly different from those for the marine population. Expression of 1 locus, esterase‐4 (EST‐4) was confined to the estuarine population. Two alkaline phosphatase loci (AKPH‐1 and AKPH‐2) were detected in the estuarine population, but only AKPH‐1 was found in the marine population. EST‐4 and AKPH‐2 were neither sex nor age specific. These interpopulational genetic differences may reflect differences in environmental conditions measured between the 2 habitats.

ISSN:0028-8330    

DOI:10.1080/00288330.1983.9516012

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Two new hosts are recorded forDeretrema minutumManter, 1954 from freshwater habitats at Lake Ellesmere, Canterbury. These are the mysidTenagotnysis chiltoniTattersall, 1923 which acts as a second intermediate host and harbours the encysted metacercariae, and the smelt,Retropinna retropinna(Richardson, 1848), which contains adult worms. AdultD. minutumwere also found in the inangaGalaxias maculatusJenyns, 1842. A large proportion of metacercariae within the crustacean host exhibited progenesis which results in the production of numerous eggs. Ovigerous metacercariae were identical with adultD. minutumrecovered from the intestine of freshwater fishes from Lake Ellesmere. A description of the metacercaria is given.

ISSN:0028-8330    

DOI:10.1080/00288330.1983.9516013

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Recolonisation of previously dry channels by stream invertebrates was studied in the Rakaia River during winter 1981 and summer 1982. The winter experiment continued for 42 days, with stable low flows, whereas the summer experiment was characterised by fluctuating large flows which caused it to be abandoned after 27 days. The fauna was dominated numerically by Chironomidae, a leptophlebiid mayfly(Deleatidium),and oligochaetes during the winter, and byDeleatidiumalone during the summer. Recolonisation was considered complete after 33 days in winter and 15 days in summer. Flow fluctuations were the main factor affecting colonisation rates, and it was assumed that drift was the main source of colonising animals. Small freshes during low‐flow periods in winter resulted in a rapid increase in total density of invertebrates and number of taxa present and also affected the population structure ofDeleatidiumlarvae in colonisation baskets. Before these freshes numbers had increased steadily over a 27 day period. In summer large floods during high flow periods initially decreased benthic invertebrate numbers in samples but numbers increased rapidly once the flood had passed. This appears to be the first study of its kind on a large unstable river system.

ISSN:0028-8330    

DOI:10.1080/00288330.1983.9516014

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Tintinnids from the surface plankton of New Zealand coastal waters are illustrated with scanning electron micrographs. Brief notes are given on their taxonomy, and their use of silica grains, diatom valves, and coccoliths in construction of the lorica is discussed. Distributional data are given for each species and these are related to the hydrological regime.

ISSN:0028-8330    

DOI:10.1080/00288330.1983.9516015

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The seasonal succession of the major phytoplankton species is described for Lake Rotongaio, a small crater lake which flows into Lake Taupo via a short channel. The dynamics of only the 4 most abundant species are described. Expressed as cell numbers,Anabaena oscillarioidesdominated in the warmer and stratified periods from November 1979 to April 1980 and again from September 1980 to the end of the observation period in January 1981. During destratification the diatomsSynedra ulnaandCyclotella menenghinianaattained maximum numbers. The green algaChlorella vulgarispeaked immediately before the September 1980 stratification. When expressed as cell volumes, however, the diatoms were always greater thanAnabaena.It is proposed that these seasonal changes can largely be explained as being long‐term versions of short‐term population fluctuations seen during thermal stratification. These are interpreted to have been responses to vertical mixing with resulting changes in the availability of light for photosynthesis in the epilimnion. During thermal stratification,Anabaenais buoyed upwards, whereas the diatoms sink to the hypolimnion. To compensate for such losses the growth rates of the diatoms must have been of an approximately similar magnitude to the growth rates leading to their winter maxima. TheSynedrapopulation decline may have been influenced by low temperature in mid‐winter. Nutrient recirculation did not appear to be an important factor for phytoplankton bio‐mass. There is little evidence for any important direct competition between the species for resources; the phytoplankton dynamics and bio‐mass appear to be mediated directly by external events and not, in any important way, by internally generated conditions.

ISSN:0028-8330    

DOI:10.1080/00288330.1983.9516016

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Lake Rotongaio, a warm monomictic lake, was sampled at monthly intervals for 1 year to investigate water temperature, transparency, chemistry, zooplankton, and benthic macroinver‐tebrates. Phytoplankton composition and standing crop represented by concentration of chlorophylla,were measured for 6 months. Secchi disc values were always less than 2 m because of the large standing crops of algae dominated throughout the year byAnabaena oscillarioides.The major ion composition of the lake water indicated a source typical of a pumice aquifer. The average concentration of dissolved reactive phosphorus during the circulation period was 275 mg m‐3and the average reactive N:P ratio was 0.55. The decline in concentration of inorganic N during the breakdown of thermal stratification could not be accounted for by mixing, and 606 kg or 6.71 mg m‐3d‐lof inorganic N was lost from the lake. The zooplankton comprised rotifers (57%), crustaceans (34%), and ciliates (9%). There was 1 species of calanoid copepod, 2 species of cladocera, and 6 species of rotifer. Ninetyone percent of the benthic macroinverte‐brates were chironomids; the rest were other insects, oligochaete worms, and molluscs.

ISSN:0028-8330    

DOI:10.1080/00288330.1983.9516017

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The findings of the Organisation for Economic Co‐operation and Development Cooperative Programme on Eutrophication are largely inapplicable to lakes in New Zealand. This is because the relative distributions of nutrient nitrogen and phosphorus in New Zealand lakes and those of the OECD study are very different. The limnological feature central to the OECD findings is that phosphorus is the nutrient limiting algal growth, nutrient nitrogen usually being massively in excess of algal requirements. This is not true in New Zealand, where nitrogenous material in fresh waters is very much less abundant. In many lakes here the relative availability of nitrogen to phosphorus approximates that required for balanced algal growth, and in some, shortage of nitrogen limits growth. Water managers aiming to control eutrophication in New Zealand lakes are advised to use the OECD predictive equations with the utmost caution.

ISSN:0028-8330    

DOI:10.1080/00288330.1983.9516018

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

A spectrophotometric method based on the use of an integrating sphere for measurement of absorbances of turbid (light scattering) suspensions has been applied to the estimation of the intrinsic optical properties of waters from Lakes Ngaroto, Rotoroa, and Hakanoa in the Waikato Basin. Measurements of absorbances both in the normal spectrophotometric configuration and with the integrating sphere allowed determination of the wavelength dependence of scattering and estimation of the scattering coefficientb(λ) as well as the absorption coefficient,a(λ). Filtered samples from the 3 lake waters exhibited absorption spectra which were featureless except for an exponential rise ina(λ) towards shorter wavelengths, evidently caused by the presence of dissolved/colloidal organic matter (yellow substance). The absorption spectra of particulate materials, concentrated from the lake water samples by a modification of the method of Kirk (1980), exhibited structure caused by superposition of the in vivo absorption spectra of algal photosynthetic pigments and the exponential absorption spectra of yellow substance chemically adsorbed by mineral particles. In all 3 lakes, light absorption in the visible by particulates was greater than by dissolved matter. Light scattering was apparently a more important contributor to total attenuation of a light beam than was light absorption. However, the spectral nature of light absorption was primarily responsible for giving structure to the visible reflectance spectra, which was manifested as lake‐water colour. The calculated chromaticity coordinates for synthesized reflectance spectra showed the 3 lakes to be dominantly yellow‐coloured, having a rather low degree of spectral purity which results in a brownish appearance. The chromaticity analyses were in reasonable agreement with the field descriptions of lake appearance.

ISSN:0028-8330    

DOI:10.1080/00288330.1983.9516019

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor