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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 285 (1980), S. 324-326 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Our investigations were prompted by observations that algal plants of both stunted and lush forms, characters usually ascribed to different degrees of wave exposure12-14, occur metres apart on the same shore in similar conditions of exposure. We hypothesized plant density to be an important factor. ...
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 292 (1981), S. 177-177 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Schiel And Choat Reply—Our recent paper1 reported two of our findings for large marine algae: (1) individual plants in dense, monospecific stands tend to be larger compared with plants of the same age in sparser stands, and (2) the number of Crustacea in algal fronds may be quite high with no ...
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 37 (1990), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Populations of the estuarine glass fish, Ambassis vachelli Richardson, were used to study the relationship between somatic growth and widths of daily increments in the sagittal otoliths. Variations in the somatic growth of A. vachelli were induced by a series of experimental feeding regimes which included feeding to satiation with two food sources and a starvation treatment. After 33 days of exposure to the experimental feeding regimes significant differences in the mean wet weight of individuals amongst the feeding treatments were recorded. Fishes subject to a starvation treatment showed a significant reduction in wet weight compared to the pretreatment population and the two experimental feeding regimes. No changes in lengths of fishes were recorded.Validation techniques revealed that daily increments were laid down in the sagittal and asteriscal otoliths. Estimates of ring widths from samples of sagittal otoliths revealed significant treatment effects. The increments of fishes from the starvation treatment showed a significant decline in mean increment width relative to the feeding treatments. This difference was detected only after a 15 day period of experimental feeding. It is suggested that the gradual decline in increment width reflects the exhaustion of readily mobilized energy reserves.
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  • 4
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Molecular tools were used to investigate relationships between species of Plectropomus, an Indo-Pacific group with a potentially recent evolutionary history on the Great Barrier Reef. Plectropomus laevis appeared to be basal, with evidence of hybridization between P. leopardus/maculatus and P. maculatusllaevis.
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  • 5
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Reefs dominated by red algae, associated with high echinoid densities, are consistent features of the shallow subtidal around northeastern New Zealand. Factors determining the abundance of juvenile Evechinus chloroticus were investigated in such a habitat. Using a factorial design, a field experiment was used to assess the influence of predators and adult E. chloroticus on juvenile abundance. The use of 2 m2 exclusion cages enhanced juvenile E. chloroticus abundance over a 16 month period, an effect independent of conspecific adults. We attributed this effect to the exclusion of benthic-feeding, predatory fish. Several species forage over the study area at high densities and are known from gut content analysis to prey on juvenile E. chloroticus in the field. Invertebrate predators are at very low densities in the area. The possibility of caging and site artefacts confounding this interpretation is discussed. Adult E. chloroticus did not directly affect conspecific juvenile densities during the experimental period. However their removal produced a significant change in community structure toward one dominated by macroscopic brown algae. Echinoid removal led to rapid recruitment of laminarian and fucoid algae, predominantly Ecklonia radiata and Sargassum sinclairii. In addition, densities of herbivorous gastropods, particularly the limpet Cellana stellifera decreased in the echinoid exclusion area, as did the feeding rates of predatory fish. The consequences of E. chloroticus removal may be dependent upon the size of the area from which they are excluded. Despite the high densities of predatory fish, a low though consistent number of juvenile E. chloroticus escape predation. We suggest that these represent sufficient input into the adult grazing population to maintain the habitat. This interpretation argues against a key role for predators in structuring shallow water reef communities in northeastern New Zealand.
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  • 6
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A fauna of small invertebrates in a perennial algal turf habitat showed marked seasonal fluctuations in abundance. These were characterised by a summer (December) peak in the abundance of gammarid amphipods and an autumn (April) peak in polychaete densities. Invertebrate abundance was lowest during the period February–March which coincided with an influx of very high densities of juveniles (0+ year class) of the sparid fish Chrysophrys auratus. Both juvenile C. auratus and also the mullid Upeneichthys porosus achieved their highest densities over coralline turf areas and fed on the associated invertebrates. Gammarid amphipods constituted the main food items of each species. All these observations suggested a key role of fish predators in determining the observed seasonal patterns of invertebrate abundance. This hypothesis was investigated by the use of replicated fish exclusion shields and cages which excluded both species from the algal turf and also permitted an assessment of Upeneichthys porosus feeding in the absence of Chrysophrys auratus. The experiment ran from November until June and covered the period of invertebrate and fish abundance changes. Little evidence of a fish predation effect on either the densities of or the timing of abundance peaks of the invertebrate fauna was detected. Sediment analysis of the cage and control experimental sites revealed no evidence of a cage effect on the microhabitat. It is suggested that seasonal changes in the abundance of invertebrates occurs independently of the high densities of predatory fish recorded in this habitat.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 68 (1986), S. 387-394 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The subtidal coralline flats of northeastern New Zealand support a characteristic guild of grazing herbivores. The most important members of this guild are an echinometrid echinoid, patellid, turbinid and trochid gastropods. Densities of these herbivores fluctuate through time. Interactions within and among the different species of echinoids and gastropods were investigated experimentally. Different combinations of species were caged at densities up to 5 times that of ambient for a 24 week period in an experiment designed to differentiate between intra- and interspecific competition. The echinoidEvechinus chloroticus and the turbinid gastropodCookia sulcata exhibited reduced mean dry weight with increasing intraspecific densities. There was little evidence of density-related mortality in these species. The limpetCellana stellifera showed comparatively large losses of weight and enhanced mortalities in intraspecific experimental treatments but this was not related to density. Investigation of interspecific interactions amongstEvechinus andCookia revealed no evidence of a negative influence of one species on the other. In terms of dry weight,Cookia was indifferent to the presence ofEvechinus, andEvechinus benefited in the reciprocal interaction.Cookia also enjoyed an enhanced mean dry weight when in the presence ofCellana compared to the equivalent intraspecific treatments. There were no coherent trends in proportional mortality in any treatments with enhanced interspecific densities. Cellana, in the presence ofCookia, exhibited a dramatic decrease in mortality rate and increase in mean dry weight. The presence of the turbinid gastropod was clearly beneficial to the limpet when compared to the intraspecific treatments with enhanced intraspecific densities and the control cages containingCellana at ambient density. We suggest that subtidal areas constitute poor habitats for limpets in the absence of agents such asCookia which may provide or maintain suitable sites for attachment and grazing. For the combinations of densities and species investigated there was a consistent trend towards positive interspecific interactions. It seems unlikely that at the sites investigated interspecific competition could act to restrict distributions, or limit abundances of species.
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  • 8
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The distribution patterns of presettlement reef fish and how they were influenced by the proximity of reefs were investigated off the coast of Northland, New Zealand, from 1981–1986. We used ichthyoplankton tows and visual counts of fish. Distributions of presettlement fish of some species were influenced by the proximity of reefs, regardless of whether reefs were on the coast of the mainland or islands across the shelf. Presettlement fish of families that lay demersal eggs were most abundant near reefs: Gobiescocidae, Acanthoclinidae, Tripterygiidae, Eleotridae, and Gobiidae. The distribution of presettlement sparids, mullids (pelagic eggs), and blenniids and monacanthids (demersal eggs) was not determined in a predictable way by the proximity of reefs. High-frequency sampling over three days suggested that patches of presettlement sparids of 1 to 2 km in dimension may move quickly through a study area. High abundance of presettlement gobiescocids and tripterygiids were found in 0 to 2 m of water over rocky reefs at high and low tides. Presettlement eleotrids were associated with reefs in deeper water (3 to 20 m) and in some habitats with aggregations of mysids. The lack of general patterns of distribution for presettlement reef fish suggests that modelling patterns of drift of these fish as a single group is inappropriate; this concurs with evidence from tropical waters.
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  • 9
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The occurrence of unusual symbiotic microorganisms was examined in the intestines of a range of fish from the Great Barrier Reef, Australia. The fish taxa examined included 26 species of the family Acanthuridae, as well as representatives of phylogenetically related and herbivorous taxa. The microorganisms, referred to as protists, were only found in herbivorous and detritivorous members of the Acanthuridae. Protists were not found in planktivorous acanthurids, nor in any members of the families Kyphosidae, Pomacentridae, Scaridae, Zanclidae, Siganidae and Bleniidae we examined. In addition, protists were absent from the herbivorous acanthurids A. xanthopterus and A. nigricans. A range of protist forms, characterized by differences in size (8 to 417 μm), shape and mode of cell division (daughter-cell production and binary fission), was observed. The occurrence of these forms appeared to be correlated with host feedingecology. Large forms (〉100 μm) of the protists were only found in acanthurids which fed over hard-reef substrata. Smaller forms were found in sand-grazing and detritivorous species. One of the protist forms appears identical to protists previously reported from Red Sea acanthurids.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 117 (1993), S. 205-211 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Estimates of daily feeding rates were obtained for two groups of herbivorous labroid fishes, one confined to cold water and the other to tropical reef environments. These were the family Odacidae, represented by Odax pullus from New Zealand waters, (Goat Island Bay: Latitude 36° South; on the northeastern coast of New Zealand) and the family Scaridae, represented by Scarus rivulatus, S. schlegeli and S. sordidus from the northern Great Barrier Reef (Lizard Island; a mid-shelf reef at 14° South latitude). Observations on the odacid were made in 1984 and in 1992, and on the scarids in 1984 and 1988. O. pullus displayed a diurnal feeding pattern in which the rates (expressed as bites min-1) are greatest early in the day. The mean combined feeding rate for three size groups (juveniles, subadults and adults) peaked (average of 2.9 bites) from 06.00 to 08.00 hrs and declined fourfold to a combined average of 0.7 bites min-1 by midday. The greatest mean feeding rate recorded was 3.7 bites min-1, with an overall mean of 1.8 bites min-1. For subadults and adults there were consistent trends in feeding, with subadults feeding at a greater rate than adults and both groups displaying a decline in feeding rate during the day. The change in feeding rate with time of day was statistically significant in both groups. The pattern for juvenile O. pullus was different from that in the two larger size groups in that juveniles did not show a uniform decline in feeding with time of day. For scarids, the daily feeding rate varied by site, but the pattern was similar for all species, characterised by initial low rates increasing to higher but variable levels by midday. The influence of both site of feeding and time of day on feeding rate was confirmed by analysis. The overall mean values for each species were 20.1 bites min-1 for S. rivulatus, 19.7 bites min-1 for S. schlegeli and 14.9 bites min-1 for S. sordidus. For scarids, the peak feeding rates varied from 19.3 to 32.8 bites min-1, with overall rates from 14.9 to 21.1 bites min-1. Estimates of activity and movement patterns during feeding were obtained for O. pullus. Distance moved per unit time was highly variable, 0.1 to 47.5 m min-1, with a mean of 8.5 m min-1 (SD=9.9). Trends in movement among sexes and size classes were obscured by the variable movement patterns of individual fishes.
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