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Responses of temperate mobile macroinvertebrates to reef habitat structure and protection from fishing

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Alexander, TJ (2011) Responses of temperate mobile macroinvertebrates to reef habitat structure and protection from fishing. PhD thesis, University of Tasmania.

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Abstract

This study assesses the importance of crevices and other physical aspects of reef
structure to macroinvertebrates associated with rocky reefs. No-take marine reserves
have the potential to interact with reef structure to influence the organisation of the
benthic community. Despite wide recognition that such relationships influence
ecosystem structure, very few quantitative field studies have reported previously on
relationships between reef structure and macroinvertebrates at the assemblage level,
and none on interactions additionally involving protection from fishing.
The relative importance of protection from fishing and reef habitat structure were
determined by surveying reef structure and invertebrates at three spatial scales at
protected and fished sites around the ‘no-take’ Maria Island marine reserve. Small
reef features and protection from fishing both affected abundances of the majority of
taxa, while rugosity – the most commonly employed metric of reef structure –
proved to be a poor predictor of invertebrate abundance and richness. Models
developed on the basis of Tasmanian data that use habitat surrogates to describe the
spatial distribution of invertebrate assemblages and populations were found to have
limited predictive ability when applied in New South Wales and Western Australian
bioregions. Single habitat predictors tended to dominate species models for each
bioregion suggesting that surrogates identified in one region should not be
extrapolated outside that region without local validation. Analysis of a long-term (16
years) ecological dataset from eastern Tasmania indicated that the strength of
relationships between reef structure and exploited rock lobsters (Jasus edwardsii)
decreased within newly-declared MPAs. Cascading trophic effects also apparently
affected habitat links for prey sea urchins (Heliocidaris erythrogramma) and abalone (Haliotis rubra). Given the changing nature of relationships through time and space,
caution is clearly required when generalising from results of studies undertaken in a
single time period or single region.
Cryptic invertebrates sampled below flat sandstone blocks were significantly
influenced by the surface structure of the underlying reef. These cryptofaunal
assemblages were similar between sites inside and outside the Maria Island marine
reserve; however juvenile abalone, one of the most abundant species in this habitat,
were recorded in much lower numbers at protected sites. Combined with evidence of
declining adult populations, this finding suggests the possibility that recruitment
failure may occur for abalone populations in Tasmanian marine reserves with
abundant rock lobsters.
Through analysis of relationships between mobile invertebrates and reef structure at
protected and fished sites, and at multiple spatial- and temporal-scales, this project
has provided valuable insight into temporal stability and instability, and spatial
specificity of linkages between temperate reef-associated invertebrates and their
environment.

Item Type: Thesis (PhD)
Keywords: invertebrates, marine reserve, reef habitat, structure, sea urchin, rock lobster, temperate Australia
Additional Information:

Copyright 2011 the Author

Date Deposited: 05 Sep 2011 04:47
Last Modified: 11 Mar 2016 05:53
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