ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516474

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Samples of the hiatellid clamPanopea zelandicawere taken from commercial catches near Nelson, New Zealand, where a new fishery developed in 1988. Ages were estimated by counting internal growth rings seen on acetate peels taken from polished and etched sections of the umbo region. Although the estimated ages are not validated, they are based on a validated technique for a similar species in North America, and they provide a preliminary examination of growth and mortality characteristics of this species. Maximum ring count was 34. Growth in shell length appeared rapid to age 10, then slowed. Natural mortality rate appeared to be around 0.20. All individuals examined in a sample taken in March appeared to have spawned recently and were in the redeveloping stages of gametogenesis. Sex ratio was not significantly different from 1:1.

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516475

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Mussel farming places a benthic organism in a pelagic environment; it is therefore important to understand the driving force that transports the food to the mussels. The hydrodynamic regimes in the sidearms and embayments in Pelorus Sound are dominated by the lunar tide, and a net estuarine circulation in the main channel flowing inwards along the bottom and outwards along the top. Salinity gradients extend throughout the sound from the river inflows, with strongest density stratification in the sidearms and embayments: nearest the head of the sound. There, the water column is separated at the pycnocline into upper and lower layers which tend to move in different directions or at different velocities. Local circulation patterns modify tidal flushing patterns, producing extended residence times in some embayments, whereas other embayments off the side of the main channel tend to be flushed more rapidly by through‐flow water and have shorter residence times than would otherwise be expected. The changing inflow of fresh water modifies the local hydraulic regimes in the inner sounds, especially during flood conditions.

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516476

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Tawera bollonsi, originally described from five valves whose colour suggested their derivation from a comparatively late fossiliferous deposit, is a common bivalve living at the Auckland Islands. Discoloration occurs during life and not after death. Its shell is more inflated than in any otherTaweraspecies. It lives in mud, sandy mud, and fine sand in the inlets and harbours, often with the crustaceansCallianassa filholiandHeterosquilla tricarinataand the bivalveChione aucklandica. The size frequency of both living specimens and valves is bimodal. For the living specimens the main peak is at 6–8 mm, with a secondary peak at 38–40 mm. The main peak for valves is at 25–37 mm with a secondary peak at 5 mm. Growth rate is very variable and may be genetically determined. Predation rates for both octopus and gastropod predation varied considerably but, with one exception, were less than 20%. Octopus predation, not previously been reported from waters as cold as the subantarctic Auckland Islands, is a more common cause of death than gastropod predation.

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516477

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The exotic marine‐fouling polychaeteFicopomatus enigmaticus(Fauvel) is recorded and described from New Zealand. Its sudden occurrence in New Zealand around 1967 was marked by its ecological prominence in estuaries of Whangarei and Auckland Harbours, as a nuisance species on submerged artificial structures including pleasure craft and power station intake pipes.

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516478

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Before 1985,Martialia hyadesi(Cephalopoda: Ommastrephidae) in the Pacific Ocean was known only from the Eltanin Fracture Zone and Macquarie Island. A joint Japan‐New Zealand squid survey around New Zealand captured many immature ommastrephid squids. Gel electrophoresis confirmed the presence of immatureM. hyadesi. Aspects of the external morphology are described. The distinctive tentacle club was evident in the smallest specimen examined, 19 mm dorsal mantle length (ML). Arm trabeculae were first evident in specimens of 40–50 mm ML. Immature squid were distributed around and southward of the Subtropical Convergence Zone. The presence of very small squid (< 10 mm ML) indicated spawning on or near the Auckland Island Shelf.

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516479

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Until 1986, the genusCeriodaphniawas thought to be commonly represented in New Zealand by only one species,C. dubiaRichard, 1894. Recent work in the Waikato area has revealed a second very common species, C. cf.pulchellaSars, 1862. The two species differ in the structure of the postabdomen, postabdominal claw, antennules, ocellus, and ephippium. These morphological details, together with guidelines for the rapid identification of the two species from field samples, are discussed.

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516480

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Factors affecting the optical properties and water clarity of Lake Ellesmere were investigated over an 18‐month period. The dominant cause of light attenuation was scattering. Clarity was found to be more dependent on very high levels of inorganic suspensoids than on phytoplankton biomass; however, high levels of chlorophyllawere also present. Fluctuations in inorganic suspensoid levels could be explained by different wind velocities before sampling. Wind velocity is thus one of several parameters that could be used to monitor the degree of light attenuation in this lake. The very compressed euphotic zone explained why macrophyte growth was restricted to shallow and/or sheltered embayments.

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516481

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Stomach contents ofGobiomorphus cotidianus,Retropinna retropinna, Gambusia affinis, andAnguilla australiswere compared between two shallow lakes in the lower Waikato River basin, to examine the relationship between turbidity and diet. Lake Waahi and the south arm of Lake Whangape had been turbid (20–40 g suspended solids (SS) m−3) and devoid of submerged macrophytes since the late 1970s and early 1980s, respectively. The main basin of Lake Whangape had been generally clearer (5 g SS m−3) with dense beds of submerged macrophytes, but at the time of sampling (1987) water clarity had deteriorated (> c. 10 g SS m3) and submerged macrophytes had declined. The mysidTenagomysis chiltoniwas an important prey for all species of fish from turbid water bodies but was less important in stomachs of fish in the main basin of Lake Whangape. Apparently, mysids were not an important prey in Lake Waahi before it became turbid. Chironomid larvae and pupae dominated the diets of small fish in the main basin of Lake Whangape. Fish and mysids were the most important prey of shortfinned eels in both lakes, with mysids most important in Lake Waahi. High mysid densities in the turbid water bodies provide an alternative food resource apparently compensating for those lost by fish when water clarity declined and submerged macrophytes collapsed.

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516482

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Four sampling and four preservation techniques were compared for the quantitative enumeration of microzooplankton (ciliates, rotifers, and nauplii) in a eutrophic lake and in an oligotrophic lake. Counts of most microzooplankton groups were significantly higher in samples preserved with Lugol's iodine and mercuric chloride than with formalin and glutaraldehyde. The collection of samples with nets or pumps, and the concentration of samples with nylon screens gave significantly lower counts than discrete settled samples. All ciliates < 50 jxm in length passed through a 20 μm mesh screen showing that size fractionation by screen or net is not an effective way of partitioning planktonic organisms.

ISSN:0028-8330    

DOI:10.1080/00288330.1991.9516483

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor