摘要:

Nutrient limitation of growth of the algal community in Lake Horowhenua was assessed by: reference to nutrient concentrations; short‐term physiological assays, which indicate nutrient deficiencies in algae; and a laboratory growth assay where the algal community responds with chlorophyllaproduction over a period of 4 days on relief of shortage of the limiting nutrient. Shortage of phosphorus limited algal growth during winter months whereas nutrient nitrogen shortage restricted growth in summer.

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516484

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

This study examined the diet of sympatric populations of migratory juvenile rainbow trout and landlocked koaro in the Waipehi and Omori Streams, Lake Taupo, New Zealand. In both species, diet was dominated, both numerically and by weight, by aquatic prey: Ephemeroptera, Trichoptera, and Diptera larvae were the most numerous prey items. Adult koaro and juvenile rainbow trout both fed on small koaro. Terrestrial prey items were present in low numbers in the diets of both koaro and juvenile rainbow trout, but were more important in terms of weight. Resource partitioning was weak although koaro consumed more small benthic invertebrates such as chironomid larvae, whereas the diet of rainbow trout contained more Ephemeroptera larvae and terrestrial insects. In the Waipehi Stream, koaro consumed both rainbow trout ova and koaro ova; in Omori Stream, trout ova were important in the diet of juvenile rainbow trout. Since the diets of koaro and juvenile rainbow trout in some Taupo tributaries are similar, populations may co‐exist by temporal and/or spatial partitioning of food resources, whereas trout predation on small koaro may be a limiting factor for koaro populations.

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516485

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The toxic concentration of unionised ammonia (NH3) was assessed for juvenileGalaxias maculatusby running a 96 h LC50 test. The 96 h LC50 concentration at 15°C and pH ≥ 8 was 1.60 mg NH31−1, with a 95% confidence limit of 1.47–1.73 mg NH31−1. This is intermediate compared to toxic concentrations reported for other freshwater fish species.

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516486

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Gut contents of 23 invertebrate taxa that dwell among bryophytes in two small New Zealand alpine streams with different riparian vegetation were examined. Bryophyte fragments were found in guts of 14 taxa, but only the tipulidLimonia hudsoniand the oeconesid caddisfliesZelandopsyche ingensandOeconesus similiscommonly consumed bryophytes. Bryophyte‐dwelling animals consumed more periphyton at the unshaded site or riparian vegetation at the shaded site than did animals dwelling amongst gravels. Stable carbon isotope ratios were compared between selected animals and plants, and indicated that animals in the unshaded site relied primarily on autochthonous detritus, whereas animals from the shaded site relied on allochthonous detritus. An indication of the food value of five bryophytes(Fissidens rigidulus, Cratoneuropsis relaxa, Bryum blandum, Plagiochila retrospectans, andHepa‐tostolonophora paucistipula)and of seven common riparian plants(Chionochloa pallens, C. flavescens, Hebe subalpina, H. odora, Nothofagus solandrivar.cliffortioides, Blechnum capense, andMarsippo‐spermum gracile)was obtained by comparing their proximate biochemical composition. This revealed that bryophytes contained more refractory and indigestible compounds than riparian plants and represented a less nutritious food source for animals. Avoidance of bryophyte tissues thus reflects a combination of the presence of alternative foods and their low nutritional value; bryophytes may also contain antifcedant compounds.

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516487

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Isolates ofVibrio ordaliiwere recovered from salmon(Oncorhynchus tshawytschaandOncorhynchus nerka)cultured in New Zealand. The fish suffered from clinical vibriosis, from seven outbreaks in five geographically distinct areas. Affected fish showed gross signs and histopathology similar to those reported from North America. The presence of a plasmid, designated pVO1, approximately 30 kilobases (kb) in size, was seen in allV. ordaliistrains examined This plasmid was identical in size and restriction endonuclease cleavage analysis to a plasmid (pMJ101) previously found inV. ordaliistrains elsewhere. After togging pVO1 with the transposon Tn1 from the R plasmid RP4, attempts to isolate plasmid‐less derivatives using a variety of curing agents were unsuccessful. All of the New Zealand isolates possessed identical chromosomal DNA cleavage patterns. These patterns were only slightly different from that of the type strain but substantially different from that of theVibrio anguillarumtype strain.

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516488

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516489

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516490

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor