Relationships between recruits of abalone
            <i>Haliotis midae</i>
            , encrusting corallines and the sea urchin
            <i>Parechinus angulosus</i>

Day, E.; Branch, G. M.

doi:10.2989/025776100784125744

Cited by 25 publications

(15 citation statements)

References 7 publications

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“…Encrusting corallines could have positively affected the colonisation of P. pavonica, or, alternatively, their removal may have enabled A. acetabulum to out-compete this alga. Positive effects of encrusting corallines on the recruitment and survival of invertebrates have been reported (Steneck 1982, Morse & Morse 1984, Sheperd & Turner 1985, Day & Branch 2000, but there is no evidence for such positive effects on algal species. This would support the proposition that patterns of abundance of P. pavonica could be the outcome of interspecific competition, suggesting that the indirect negative effects of the removal of encrusting corallines were stronger than direct positive ones.…”

Section: Discussionmentioning

confidence: 99%

Interplay of encrusting coralline algae and sea urchins in maintaining alternative habitats

Bulleri¹,

Bertocci²,

Micheli³

2002

Mar. Ecol. Prog. Ser.

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In proximity of shelters, grazing by sea urchins plays a fundamental role in establishing and maintaining areas dominated by encrusting corallines. Much attention has been given to the effects of urchins on algal assemblages in shallow subtidal reefs, but few studies attempted to clarify the role played by encrusting coralline algae in this system. It has been shown that encrusting corallines are able to reduce settlement of potential competitors, suggesting that they do not rely on grazing by herbivores to prevent swamping by erect algal species. In shallow subtidal reefs of the Mediterranean Sea, the sea urchins Paracentrotus lividus and Arbacia lixula are the main herbivores, whose grazing commonly leads to a mosaic of areas dominated alternatively by encrusting corallines and turf-forming algae. This study aims to separate the effects of urchins and encrusting corallines on the re-colonisation of encrusting coralline-dominated patches (barren habitat) by surrounding erect algal species (turf-forming algae). Different hypotheses were tested by means of multivariate and univariate analyses. The multivariate hypothesis was that the algal assemblage developing when encrusting corallines and urchins are simultaneously removed would be more similar to that establishing in stands of turf-forming algae, than that developing when none or only 1 of the 2 factors is manipulated. The univariate hypotheses tested were: (1) that there is a negative effect of sea urchins and encrusting corallines on the re-colonisation of barren areas by surrounding turf-forming algal species and (2) that the effects of encrusting corallines are weaker than those of urchins, but that they operate in the same direction. These hypotheses were tested by means of an orthogonal manipulation of urchins and encrusting corallines. At each of 3 study sites, 2 replicate barren patches were assigned to each of these treatments: (1) +corallines+urchins; (2) +corallines-urchins; (3) -corallines+urchins; (4) -corallines-urchins. The results suggest that the occurrence of areas dominated by encrusting corallines on shallow subtidal reefs in the northwest Mediterranean is not simply the result of grazing by sea urchins on turf-forming species. The removal of encrusting corallines also affected the abundance of dominant algal species and determined the development of an algal assemblage resembling those occurring within stands of algal turfs. The effects of the removal of urchins on turf-forming species were generally positive, while those of encrusting corallines varied from negative (Padina pavonica) to positive (Acetabularia acetabulum and filamentous algae). Therefore, the role played by encrusting corallines in maintaining alternative habitats on shallow subtidal reefs should be taken into account, thus avoiding the overestimation of the effects of grazing by sea urchins

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Section: Discussionmentioning

confidence: 99%

Interplay of encrusting coralline algae and sea urchins in maintaining alternative habitats

Bulleri¹,

Bertocci²,

Micheli³

2002

Mar. Ecol. Prog. Ser.

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“…Given the critical relationship between urchins and abalone, the regional recovery of abalone populations, and consequently restoration of the "original" EOCH ecosystem, seems unlikely for several reasons. (1) The lobster-urchin-abalone effect is most obvious in the shallows (0-5 m), where any reduction in lobsters by commercial rock-lobster fishing will be low because fishing operates in waters deeper than 5 m. (2) If rock lobsters remain at a density above 0.25 m −2 (Mayfield and Branch 2000), urchins on which juvenile abalone depend (Tarr et al 1996, Day and Branch 2000a,b, 2002a will be unable to achieve sufficient density to support juvenile abalone (Mayfield and Branch 2000). (3) Since the substantial depletion of herbivores by lobsters EOCH, macroalgae have increased, and siltation rates have risen Branch 2000, Blamey et al 2010, LKB pers obs).…”

Section: Urchin and Abalone Projectionsmentioning

confidence: 99%

“…(3) Since the substantial depletion of herbivores by lobsters EOCH, macroalgae have increased, and siltation rates have risen Branch 2000, Blamey et al 2010, LKB pers obs). (4) Increased siltation and macroalgal growth are likely to smother and outcompete encrusting corallines, upon which abalone recruitment depends (Day and Branch 2000a). (5) Intense illegal fishing of abalone combined with the invasion of lobsters has depleted the abalone stock to levels at which recruitment failure is likely.…”

Section: Urchin and Abalone Projectionsmentioning

confidence: 99%

Modeling a Regime Shift in a Kelp Forest Ecosystem Caused by a Lobster Range Expansion

Blamey¹,

Plagányi²,

Branch³

2013

BMS

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The South African West Coast rock lobster, Jasus lalandii (H. Milne-Edwards, 1837), has expanded its range to the southeast, where its abundance has increased radically. The ecological consequences of this "invasion" are likely to be considerable. We employed a minimally realistic model to simulate the "invasion" and to explore interactions of J. lalandii with the sea urchin, Parechinus angulosus (Leske, 1778), and the abalone, Haliotis midae Linnaeus, 1758, juveniles of which shelter beneath this urchin. Model fits to empirical data were good, although species-interaction terms were difficult to estimate. Base-case trajectories indicated: (1) Lobster biomass peaked at about 1000 t in 1994 and was then reduced by fishing to a stable value approximately 50% lower by 2008. (2) Urchins remained close to carrying capacity in "noninvaded" areas but collapsed to local extinction by 1997 in the invaded area. (3) Abalone declined over 2000-2008 in noninvaded areas because of illegal fishing and collapsed to near zero in the "invaded" area because of illegal fishing combined with increased lobster abundance. Sensitivity analyses favored the hypothesis that the invasion was due to adult immigration rather than larval recruitment. Modeled 50-yr projections indicated that urchins will remain locally extinct in the invaded area, even 50 yrs into the future. The abalone collapse in the invaded area would persist >50 yrs, even if lobsters were absent. We argue that the lobster "invasion" triggered an alternative stable state, making a return to pre-invasion conditions unlikely.

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“…Gabriel's index (Gabriel 1978) was employed as a measure of selectivity and is defined as: W = p 1 q 2 ⁄ p 2 q 1 , where p 1 = proportion of the dietary item in the gut (%); p 2 = proportion of the dietary item available on the substratum (%); q 1 = (100 − p 1 ) and q 2 = (100 − p 2 ). In logarithmic form, the index W yields values from −∞ (negative selection) to +∞ (positive selection), and values of 0 (or close to 0) indicate random selection (Day and Branch 2000a).…”

Section: Available Algae Gut Analyses and Selectivity Indicesmentioning

confidence: 99%

“…Recently settled recruits (1-2 mm shell length) are associated with non-geniculate (encrusting) coralline red algae and consume microflora including bacteria (Day and Branch 2000a). Juvenile abalone (3-35 mm shell length) mainly shelter under the urchin P. angulosus, and feed on both drift macroalgae captured by the urchins and microalgae (Tarr et al 1996, Day and Branch 2000b, 2002a.…”

Section: Introductionmentioning

confidence: 99%

Assessing the ecosystem effects of the abaloneHaliotis midaefrom its diet and foraging behaviour

Zeeman

Branch

Peschak

2012

African Journal of Marine Science

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The South African abalone Haliotis midae is commercially exploited and seriously threatened by overfishing. This not only affects the species itself but potentially the functioning of the ecosystem because of associated changes in community structure. The nature of effects that can follow the loss or reduction of a species depends in part on its position in the foodweb and its feeding behaviour. To assess the ecosystem effects of the adults and subadults of this previously abundant herbivore on the south-west coast of South Africa, we studied their diet and mode of food procurement by (a) in-field observations of adult and subadult abalone, (b) analysis of the gut contents of adults, (c) comparison of diet with the availability of algae, and (d) a mesocosm experiment on subadult feeding behaviour. Both field and dietary studies showed that adults subsist mainly by trapping drift kelp, but also occasionally graze on attached algae such as Plocamium spp., and feed in a manner that is highly selective, with drift kelp constituting 95-98% of the diet, and several species of common algae being avoided. In the mesocosm experiment, subadults preferentially fed on drift kelp, but emerged at night to a greater extent to graze on microflora if no drift material was available. Their propensity to emerge was, however, reduced if the rock lobster Jasus lalandii was present. Collectively, this evidence indicates that any ecosystem effects that subadults and adults of H. midae have as grazers will be weak because they feed mainly by trapping drift material, and the frequency of grazing and the incidence of consumption of attached algae are low.

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Relationships between recruits of abalone Haliotis midae , encrusting corallines and the sea urchin Parechinus angulosus

Cited by 25 publications

References 7 publications

Interplay of encrusting coralline algae and sea urchins in maintaining alternative habitats

Interplay of encrusting coralline algae and sea urchins in maintaining alternative habitats

Modeling a Regime Shift in a Kelp Forest Ecosystem Caused by a Lobster Range Expansion

Assessing the ecosystem effects of the abaloneHaliotis midaefrom its diet and foraging behaviour

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