摘要:

Attempts were made to induce gynogenesis in bisexual chinook salmon(Oncorhynchus tshawytscha)by insemination of chinook eggs with sperms from either sockeye salmon(O. nerka)or brown trout(Salmo trutta). In both crosses the success rate of induction of embryonic development was low and the hatched fish had poor survival. Physically normal and deformed progeny were found in both crosses. Our study suggests that the timing of pressure shock after insemination, and the method of application of pressure shock, may be critical in the induction of embryonic development. Electrophoretic analysis of soluble proteins and three isozymes revealed that the progeny produced by the two crosses were not truely gynogenetic, as paternal gene expression was detected. However, the persistent expression or non‐expression of the same paternal genes in all the progeny suggests that the activation or inactivation of these paternal genes did not occur at random.

ISSN:0028-8330    

DOI:10.1080/00288330.1990.9516397

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Relative specific growth rates of periphytic diatoms were investigated as a time‐integrated measure of stream enrichment in the South Brook, Canterbury, New Zealand. The control site was expected to show phosphorus (P) limitation of growth rates with dissolved reactive P (DRP) of 6–10 μg I−1; and the impact site, downstream of a discharge, was expected to show no growth limitation by P with DRP > 150 μg I−1. Specific growth rates (μ) were generally high at the upstream site (μ = 0.45–0.59 div d−1) but the relative specific growth rates indicated that the cellular level kinetics were not limited by nutrient availability (i.e., μ: μmax‐P> 0.8). Laboratory and field bioassays were carried out and all corroborated this interpretation, indicating that the discharge should have no effect on the growth rates of the downstream communities. As predicted, no significant differences occurred in growth between sites. It is concluded that relative specific growth rates could be useful to assist with impact monitoring of nutrient‐enriched discharges.

ISSN:0028-8330    

DOI:10.1080/00288330.1990.9516398

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Microhabitat preferences of seven groups of New Zealand benthic invertebrates(Deleatidiumspp., other mayflies, cased caddisflies, uncased caddisflies, beetles, Diptera, and stoneflies) were investigated and habitat suitability functions for use with the instream flow incremental methodology (IFIM) developed for the predominant group,Deleatidiumspp. All invertebrate groups except uncased caddisflies andDeleatidiumspp. exhibited significant preferences for at least two of the three habitat variables (substrate, water velocity, and depth) when each habitat variable was considered independently. Significant relationships were found between invertebrate size and at least one habitat variable for all groups except stoneflies. Models ofDeleatidiumspp. abundance were poor (r= 0.50–0.58) and generally predicted biomass better than numbers. The best models used all three habitat variables together with an index of the amount of periphyton.Deleatidiumspp. abundance in the Waingawa River was most closely related to substrate composition followed by velocity and the amount of periphyton present.

ISSN:0028-8330    

DOI:10.1080/00288330.1990.9516399

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Presence‐absence data for New Zealand's freshwater fish fauna were analysed for evidence of species interactions and of links with land‐use and geological patterns. Co‐occurrence patterns differed between site and regional levels. Native and exotic species had overlapping geographical distributions but tended to be segregated at the site level. Species‐area curves were developed for lotic and lentic sites which explained a small portion of the variation. Regressions involving land‐use and geological variables accounted for more variation. New Zealand catchments appeared to be under‐saturated with species compared to northern temperate catchments. Analysis of co‐occurrence patterns, where distributions overlapped, indicated relatively more negative associations between native andexotic species than among either group of species. The presence‐absence patterns of several native species were related to land use and geological factors. The conclusion from these analyses was that both land‐use changes and introductions of exotic species, particularly salmonids, have caused changes in the distribution of native fish species.

ISSN:0028-8330    

DOI:10.1080/00288330.1990.9516400

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Lake Rotoroa is a small (54 ha), shallow (maximum depth 6 m), urban lake which has been subject to repeated chemical weed control since 1957. The distribution and abundance of aquatic macrophytes in the lake were studied in six SCUBA surveys between 1977 and 1986. During this period three applications of diquat herbicide resulted in periodic decreases in submerged vascular plant growths in the lake. Macrophytes were present over c. 80% of the lake bed to a maximum depth of 5–5.5 m during the period of study. Emergent macrophytes, particularlyBaumea articulata, Iris pseudacorus, Eleocharis sphacelata, andTypha orientalis, and floating‐leavedNymphaea, were recorded around c. 50% of the lakeshore. In 1977 the most abundant submerged vascular plants wereLagarosiphon majorandElodea canadensiswhich were both recorded at all sampling sites.Egeria densa, which was first recorded in the lake in 1977, spread at the expense of these species to become the dominant vascular plant in the lake by 1986. In May 1986 it was present on all sampling profiles (35) and occupied an estimated 35% of the lake's vegetation ‐whercasLagarosiphonandElodeaoccupied an estimated 6% and < 1%, of the vegetation respectively. Extensive beds of charophytes(Chara corallina, Nitella hooked, andN. pseudoflabellata)persisted in the lake during the period of study. In May 1986 charophytes occupied an estimated 52% of the vegetation, their abundance apparently enhanced by selective herbicidal control of vascular species.

ISSN:0028-8330    

DOI:10.1080/00288330.1990.9516401

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Tawera mawsoni(Hedley, 1916), the most southerly occurring of all theTaweraspecies in the Australasian region, lives on sandy substrates from 12 to 450 m depth around Macquarie Island, on Macquarie Ridge, and on Caroline Ridge. Most shells sampled are homogeneous in shape, sculpture, colouring, and shell thickness, except that some from south of Macquarie Island have thinner valves.Tawera mawsoniappears to produce annual growth rings. Shell shape does not appreciably alter with growth. Recruitment rate is low and variable from year to year. Predation appears to be an important cause of mortality, the chief predators being naticids(Falsilunatia pisum)and muricids(Trophon macquariensisandT. mawsoni). No size class ofTawera mawsoniis excluded from predation.

ISSN:0028-8330    

DOI:10.1080/00288330.1990.9516402

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Surveys of phytoplankton populations over a 3‐year period within the Marlborough Sounds revealed numerous dinoflagellate species that are common elsewhere in temperate coastal environments. However, none that have been implicated as the cause of paralytic shellfish poisoning (PSP) were observed. Likewise, a total of 71 samples of cultivated mussles(Perna canaliculus)from farms within Pelorus Sound, Kenepuru Sound, and Port Underwood were tested by mouse bioassay with negative results (< 40 μg/100 g). Although environmental conditions within the Sounds are suitable for the establishment of dinoflagellate dominated blooms, PSP does not occur. This could be because causative species are absent altogether, or because they are very rare, poor competitors with other species, or have so far gone undetected.

ISSN:0028-8330    

DOI:10.1080/00288330.1990.9516403

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Macrobenthic community structure was assessed on intertidal sandflats, a predominant feature of Manukau Harbour. Thirty‐six replicate core samples were collected from each of six 9000 m2sites, during October 1987. The distribution of individuals amongst taxa was similar at the six sites, but the numerical dominance of the most common taxa changed appreciably from site to site. A shift from polychaete‐ to bivalve‐dominated communities was apparent between sites. Examination of a hypothesised relationship between sediment grain size and trophic structure of the macrobenthos highlights the difficulties in using this relationship to monitor environmental change. Identification of core taxa by DECORANA ordination and TWINSPAN classification is considered a useful mechanism in defining taxa likely to play major roles in influencing community structure and function.

ISSN:0028-8330    

DOI:10.1080/00288330.1990.9516404

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The size‐frequency distribution, sex ratio, and visceral index in a population of the aspidochirote holothurianStichopus mollis(Hutton, 1872) were studied on the north‐east coast of New Zealand. AdultStichopus mollisranged in length from 13 to 25 cm, and showed a unimodal size‐frequency distribution. YoungS. molliswere rare, and were found under boulders in the shallow subtidal zone (5–8 m). The population ofS. mollisunder study showed a 1 : 1 sex ratio; three hermaphrodites were found. The viscera index maintained an approximately uniform value throughout the reproductive season. No evidence was found for spontaneous evisceration or seasonal atrophy of the viscera. Two predatory attacks onS. mollisby the asteroidLuidia variawere observed.

ISSN:0028-8330    

DOI:10.1080/00288330.1990.9516405

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A new interpretation of orange roughy(Hoplostethus atlanticus)otoliths indicates that growth rates in this species are exceptionally slow. The otolith interpretations were supported by modal analysis of length‐frequency distributions of small juveniles. Parameters of the von Bertalanffy growth function were estimated to be L8= 42.50 cm standard length (SL), K = 0.059 year−1and t0= ‐0.346 year. This gives an average SL after 1, 2, and 3 years of growth of only 3.1, 5.5, and 7.6 cm, respectively. The estimated average age of maturity is 20 years. It is further suggested that maximum age may exceed 50 years, the instantaneous rate of natural mortality is probably below 0.10, and spawning success may be highly variable. This combination of factors makes orange roughy susceptible to overfishing. The optimal instantaneous rate of fishing mortality is estimated to be less than 0.10.

ISSN:0028-8330    

DOI:10.1080/00288330.1990.9516406

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor