The structure of an association of nektobenthic invertebrates from Moreton Bay

Jones, A. R. (1974). The structure of an association of nektobenthic invertebrates from Moreton Bay PhD Thesis, School of Biological Sciences, The University of Queensland. doi:10.14264/uql.2015.490

       
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Author Jones, A. R.
Thesis Title The structure of an association of nektobenthic invertebrates from Moreton Bay
School, Centre or Institute School of Biological Sciences
Institution The University of Queensland
DOI 10.14264/uql.2015.490
Publication date 1974
Thesis type PhD Thesis
Supervisor W. Stephenson
Total pages 187
Language eng
Subjects 06 Biological Sciences
Formatted abstract
An otter trawl study of the nektobenthic invertebrate association was carried out between November 1970 and February 1973 in Moreton Bay. Prior preliminary work indicated that each sample should comprise four replicate short trawls. The first year (Stage I) was confined to a single site to study temporal (circadian and seasonal) changes. Twenty-six species and 35,727 individuals were enumerated from 89 samples. Spatial changes were studied during the second year (Stage II). Five sites in an approximately east-west line were regularly sampled at night. Fifty-nine samples produced 21,381 individuals and 35 species. Further data re size and reproductive condition were subsequently recorded in the laboratory. Abiotic data such as salinity and temperature were recorded.

Analyses were primarily conducted by numerical classifications supplemented by GOWER principal co-ordinate analyses, diversity statistics, analyses of variance and multiple regression. Stage I results showed Chronological cycles on two levels - circadian and annual. The former is associated with the light cycle with most species nocturnal. The latter shows a high positive correlation of numbers of species and individuals with temperature and the between survey classificatory groups generate a successional sequence along the temperature curve. These nektobenthic species appear to have evolved towards an r-selected reproductive strategy with rapid development to exploit the seasonally changing environment.

A classificatory program which partitioned the three-dimensional (sites x species x seasons) Stage II matrix showed variance in space to be greater than variance in time. This closely followed the trend of the nan-partitioning initial classification which made a primary division into shallow inshore sites and deeper offshore sites. Further spatial and temporal changes are evident at lower hierarchical levels. The deepest site shows greater winter abundance for many species; the shallowest rarely does. This appears to be associated with seasonal migrations allied to the fact that the deeper water is more stable and predictable, especially with respect to salinity. More species occur in the deepest site compared with the shallowest.

Few (very rare) species are exclusively site restricted while most show quantitative preference and some appear genuinely ubiquitous. Most species have a protracted breeding season which blurs size class definition. Size bimodality is rarely evident and some species spawn outside Moreton Bay.

Ordination vectors account for little information giving rise to a 'continuum' interpretation of species distributions in space and time. Other lines of evidence support this conclusion. Standardised measures of average habitat width and overlap vary more for the shallower sites. Competition is thus assumed to vary more in these more rigorous habitats. Within each of the portunid genera Portunusand Charybdis, relative size or abundance varied greatly. This led to the hypothesis that competition is lax in Portunus and competitive exclusion occurs for Charybdis.
Keyword Marine ecology
Benthos -- Queensland -- Moreton Bay
Nekton -- Queensland -- Moreton Bay
Additional Notes Other Title: Nektobenthic invertebrates from Moreton Bay.

Document type: Thesis
Collection: UQ Theses (RHD) - UQ staff and students only
 
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