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Competition between an invasive urchin and commercially fished abalone: effect on body condition, reproduction and survivorship


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Strain, E M A and Johnson, CR (2009) Competition between an invasive urchin and commercially fished abalone: effect on body condition, reproduction and survivorship. Marine Ecology Progress Series, 377. pp. 169-182. ISSN 0171-8630

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Incursion of the urchin Centrostephanus rodgersii into Tasmania, Australia, and its
establishment at high densities raises questions about its potential interactions with another large
herbivore on subtidal rocky reefs, the commercially fished abalone Haliotis rubra. Surveys on the
southeast coast of Australia show a negative relationship between densities of C. rodgersii and H.
rubra at several spatial scales, suggesting negative interactions. In intact algal beds, we used enclosures
to estimate the effects and relative magnitude of intra- and interspecific competition on the
body condition, gonad development and survival of C. rodgersii and H. rubra. An increased density
of conspecifics led to declines in the dry gonad weight of C. rodgersii and in the dry foot and stomach
content weights of H. rubra. The effects of interspecific competition were asymmetrical. Manipulations
of H. rubra densities had no detectable effect on C. rodgersii. In contrast, in enclosures with
added C. rodgersii, H. rubra showed reduced total and dry weights of stomach contents and
increased mortality relative to controls without urchins. The effects of C. rodgersii on H. rubra could
be linked to differences in feeding habits and morphology. C. rodgersii is a generalist herbivore,
which, even at low densities, reduced the cover and standing biomass of total, brown and red algae
relative to controls without urchins. In contrast, H. rubra is a specialist herbivore, which, even at high
densities, had little effect on the cover and standing biomass of algae relative to the effect of
C. rodgersii. This study suggests that the invader C. rodgersii is the superior competitor in interactions
with H. rubra, and that its presence, even at low densities, affects the abalone fishery.

Item Type: Article
Keywords: Invasion · Fishing · Competition · Centrostephanus rodgersii · Haliotis rubra
Journal or Publication Title: Marine Ecology Progress Series
Page Range: pp. 169-182
ISSN: 0171-8630
Identification Number - DOI: 10.3354/meps07816
Additional Information:

© 2009 Inter Research

Date Deposited: 16 Jul 2009 23:18
Last Modified: 19 Dec 2014 01:35
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