2 results for Ayling, Tony, 1947-

  • The role of biological disturbance in determining the organisation of sub-tidal encrusting communities in temperate waters

    Ayling, Tony, 1947- (1976)

    Doctoral thesis
    The University of Auckland Library

    Biological disturbance was found to be one of the most important mechanisms control1ing community organisation in the temperate sub-tidal region. The different types of biological disturbance structuring three encrusting communities were investigated on the east coast of Northland, New Zealand. The operation of each type was determined and the rate of disturbance measured. Experimental exclusion treatments were set up to demonstrate the effects of the major disturbance agents on community structure. The urchin Evechinus chloroticus was the most abundant agent of biological disturbance and affected the widest spectrum of encrusting organisms. The abundant balistid fish Navodon scaber was another major agent of biological disturbance in this region. Disturbance of algal populations also resulted from a guild of abundant herbivorous gastropods. Two episodes of fungal/bacterial infection degraded numbers of the large sponges Ancorina alata and Polymastia fusca. The operation of the different disturbance agents was found to be generally unpredictable in both time and space. There was no escape from biological disturbance for encrusting organisms in either small or large size. Re-occupation processes on patches of free primary space were investigated both experimentally and by using settlement plates (artificial free space patches). Recruitment was found to be irregular in space and time, especially for long-lived sessile organisms. Settlement processes as well as growth and mortality of newly settled organisms were investigated with a view to understanding community development. Only one verifiable example of substrate preparation or biological succession was found to operate in the communities studied. It is postulated that community organisation is flexible and not rigidly directed along a single successional pathway. Multiple developmental pathways and multiple stable configurations are possible in the same locality, resulting from the operation of different disturbance regimes.

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  • Okakari Point to Cape Rodney marine reserve: a biological survey

    Ayling, Tony, 1947- (1978)

    Report
    The University of Auckland Library

    The Marine Reserve at Leigh was gazetted in November I975 but it is worth-while to trace the course of exploitation in the reserve area both before and after its official establishment. While it is difficult to determine with any accuracy the extent of exploitation in the past, some general points can be made. Commercial and amateur fishing for snapper and crayfish have been carried out for many years in this area and the original populations of both these species have probably been considerably depleted. Experienced spearfishermen operated in the reserve area from the early 1950's until the early 1970's, with a peak in this activity in the mid 1950's. These people swam long distances and speared relatively few fish and probably affected the entire reserve to a limited extent, but had a slightly greater effect in the central third of the reserve around Goat Island. The species speared by this group were primarily snapper, Kingfish, blue moki, red moki and porae. Inexperienced spearfishermen fished only in the immediate Goat Island Bay and Channel area and had a peak effect in the late 1960's and early 1970's. This group speared most species more than 20-30 cm long, especially red moki and leatherjackets. Scuba diving for crayfish, both 'commercial' and amateur, was widespread in the reserve area during the 1960's and early 1970's, adding effect of commercial pottinq.

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