摘要:

This study aimed to determine whether the relatively slow growth of wildPagrus auratusin south‐eastern Australia can be increased in captivity to a rate acceptable for aquaculture. Juvenile snapper from Port Hacking, New South Wales (34°47'S) were reared at ambient water temperatures. The fish were fed on a dry, sinking pellet with 42% protein. At the start of the trial in April 1989, the snapper had a mean fork length (FL) of 121 + 11 mm SD, an average weight of 50 g, and an estimated age of 8 months. After 12.5 months their mean FL was 249 ± 15 mm and their mean weight was 403 ± 70 g. Our data indicate that, like the reproductively isolated population in Japan, growth ofPagrus auratusfrom Australasia can be rapid enough for aquaculture, and that there is potential to increase growth rate further.

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516461

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Settlement of the puerulus stage ofJasus edwardsii(Decapoda: Palinuridae) near the shore takes place over a wide depth range. It occurs intertidally, and, as determined by crevice collectors, also takes place down to depths of at least 50 m. At sites along the east coast of the North Island of New Zealand, depth of greatest settlement found on collectors varied with locality and time, but was within the upper 11.5 m. Surface‐buoyed collectors caught fewer animals than did collectors at greater depths. Settlement levels generally increased with depth to about 10–12 m, then decreased with increasing depth and distance from shore. The ability of/,edwardsiito settle over a wide depth range may improve its chances of recruitment. A device (closing crevice collector) for measuring puerulus settlement ofJ. edwardsiiat depth is described.

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516462

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The surface distribution of salinity, temperature, nitrate‐nitrogen (N03‐N), and chlorophyll a in the southern New Zealand, Foveaux Strait region in February 1977, 1978, 1979, and 1980 was highly variable. The source of new nitrogen appears to be incursions of high‐salinity water west and east of Stewart Island. Although it seems likely that the source of this high‐nutrient, high‐salinity water is vertical, a horizontal advective source cannot be ruled out The chlorophyllacontent of surface waters was not related directly to the NO3‐N concentrations. This lower food chain variability may be linked to variability in economically important species. Oysters grew twice as fast in the summer of 1978/79 as they did in 1979/80. But the mean chlorophyllavalues were very similar for February of both years (2.5 and 2.2 μg 1−1, respectively). The elevated NO3‐N levels in 1979 may have resulted in much higher phytoplankton levels later that summer and resulted in the higher oyster growth rate that year. The mechanisms driving this variability have yet to be determined.

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516463

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The submerged vegetation of Lakes Sumner, Marion, Katrine, Taylor, and Sheppard was surveyed in May 1987. These high‐altitude lakes lie at c. 600 m a.s.l., within the largely unmodified upper Hurunui catchment. Submerged vegetation was diverse and included numerous short shallow‐water species, dense swards ofIsoetes alpinus, low covers of taller native vascular plants, and charophyte meadows beyond the depth limit of vascular plants to a maximum of 15 m. A sparse deepwater bryophyte community was observed from 11 to 32 m depth in Lake Sumner. Displacement of native vegetation by dense growths of the adventive oxygen weedElodea canadensisover mid‐depths of 3–6 m was noted in all lakes, except Lake Marion.

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516464

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Reticulation of the sewage from Taupo township, New Zealand, proceeded in sages between 1974 and 1986, with initial stages servicing the central retail area and the streets closest to and parallel with the lake shore. Subsequent stages serviced streets further from the lake resulting in a progressive reduction in the volume of septic tank effluent entering the ground‐water table, but not necessarily a corresponding reduction in the nutrient concentrations entering Lake Taupo. The rate of reduction of the nutrient load in the ground water entering the lake was a function of the original load, and the proportion of the ground‐water recharge volume associated with the septic tank effluent water in each subcatchmenL An estimated reduction of 60% in the DIN load on Lake Taupo from this source has occurred between 1978 and 1989. Consequently, reticulation of the sewage from Taupo township has had a beneficial effect on the quality of the inshore waters of Lake Taupo along most of the foreshore.

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516465

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Results from a numerical model for the relative distribution of amplitudes at the shore for several of the main seiche oscillation modes in Lake Taupo are given. Data of this kind are useful for improved water level measurements on the lake shore. Accurate level measurements are needed for water use monitoring and also for earth deformation recording in a volcanic area.

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516466

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Macroinvertebrate colonisation of perspex multiplate artificial substrates suspended in the Ohinemuri River, New Zealand, was investigated over a 70‐day period. Community development was examined in terms of the colonisation and extinction rates of the MacArthur‐Wilson equilibrium model for island faunas. Although colonisation and extinction rates were equal at 35 days, permanent stability was not attained: the extinction rate and colonisation rate continued to fluctuate as new taxa continued to colonise. This lack of permanency was attributed to changes to the surface of the plates through increases in the accumulation of fine paniculate matter, and to changes in the drifting fauna that affect the pool of potential colonisers. Stream drift was an important source of colonisers, especially in the initial stages of colonisation. Although many members of the New Zealand aquatic fauna have non‐seasonal life cycles, and are present as larvae at all times of year, they may occur seasonally in the drift. Therefore colonisation patterns may differ seasonally. Drift was not the only source of artificial substrate colonisers.

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516467

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Temperature avoidance behaviour of inanga,Galaxias maculatus, was studied in the laboratory using a two‐choice tank. The final preferred temperature of inanga is about 20°C but fish acclimatised to cooler temperatures (15 and 17°Q prefer warmer waters (up to 23 and 26°C, respectively). Fish acclimatised to temperatures of 15,17, and 20°C showed total avoidance at 29.5,31, and 31.5°C, respectively. Water temperature therefore is an important factor influencing upstream migration and distribution of inanga and thermal discharges can be disruptive.

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516468

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Samples of algae, epilithon, tree leaves, aquatic invertebrates, and feathers of blue duck{Hymenolaimus malacorhynchos)were collected for stable carbon isotope analysis from Manganuiateao River, central North Island, New Zealand, to elucidate the diet of blue duck and the carbon pathways involved. 513C values for leaves were typical of terrestrial vegetation elsewhere (‐27 to ‐31%o), but, in contrast to other values found in New Zealand, algae were much richer in13C (> ‐17.0%c) than terrestrial vegetation. Larvae of the caddisfliesOlinga feredayiandAoteapsyche colonica, and the dipteranAphrophila neozelandicawere usually enriched with13C (mostly > ‐20.0%c) relative to other taxa, indicating mat they had been assimilating higher proportions of algal‐derived carbon. In contrast, 813C values < ‐20.0%e were recorded for the mayfliesDeleatidiumspp. andColoburiscus humeraUs, and the caddisflyBeraeoptera roria, indicating that their diets were composed of a higher proportion of organic matter of terrestrial origin. Feathers from blue ducks living in the lower part of the study section were enriched with13C (‐21.9 to ‐15.6‰) compared with those from the upper part of the study section (‐25.0

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516469

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Microhabitat preferences of 12 benthic invertebrate taxa were investigated in four New Zealand rivers. Most taxa showed significant habitat preferences. Generally, taxa were more abundant in water less than 0.75 m deep and in gravel or coarser substrates, and no taxa showed a clear preference for fine substrate (sand and fine gravel) or deep water.Coloburiscus humeralis, Zelandoperlaspp., andAoteapsychespp. preferred coarse substrate and water velocities of more than 0.75 m s−1, whereasNesa‐meletusspp. andPycnocentrodesspp. were associated with similar substrate but lower water velocities (0.2–0.8 m s−1). Naididae preferred low (< 0.3 m s−1) water

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516470

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor