An Allometric Tridimensional Model of Self-Thinning for a Gregarious Tunicate

Guinez, Ricardo; Castilla, Juan Carlos

doi:10.2307/2680235

Cited by 13 publications

(24 citation statements)

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“…In previous studies, where volume was not measured (Guiñez and Castilla 1999, Guiñez and Castilla 2001, Guiñez et al 2005, the allometry of individual massindividual area occupied was used, with mass assumed to be proportional to volume. In our study, individual volume was measured providing a more accurate estimation of the SST exponent.…”

Section: Estimation Of the Theoretical Sst Exponentsmentioning

confidence: 99%

“…For this reason, in our study we assumed that multilayered packing on ropes, i.e., cylinders, and flat substrates are equivalent and do not consider the increase of available surface with layers. Therefore, the number of layers (L) was obtained as the quotient of sample density and effective density (i.e., N/N e ) (Guiñez and Castilla 2001), and is denoted by L p ¼ N/N p and L im ¼ N/N im ; depending on the method used to measure the surface area occupied. The number of layers (L) enables us to incorporate explicitly the effect of packing on the self-thinning model (Guiñez and Castilla 1999).…”

Section: Effective Density and Number Of Layersmentioning

confidence: 99%

“…Two alternative procedures have been used to fit the self-thinning line (1) to purposefully select data points undergoing mortality and fit the selfthinning line, or (2) to fit the biomass-density line by using all the data points and shift it upwards to the point where the majority of observations lie below it. On the other hand, several central tendency regression techniques have been commonly used to fit the self-thinning model, including ordinary least squares (OLS; Castilla 1999, Alunno-Bruscia et al 2000), robust linear models (RLM, LachanceBernard et al 2010), reduced major axis (RMA, Guiñez and Castilla 1999, Guiñez and Castilla 2001, Guiñez et al 2005, Filgueira et al 2008 or equivalently geometric mean regression (GMR, Hughes and Griffiths 1988) and non linear regression (NLM, Guiñez and Castilla 1999). Bi et al (2000) pointed out that the subjective selection of data points is inappropriate and proposed to apply the stochastic frontier function (SFF) to fit the self-thinning line, as frontier functions envelope data, rather than central tendency techniques that intersect data.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of self‐thinning models and estimation methods in multilayered sessile animal populations

et al. 2012

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Abstract. Self-thinning (ST) models have been widely used in the last decades to describe population dynamics under intraspecific competition in plant and animal communities. Nevertheless, their applicability in animal populations is subjected to the appropriate inclusion of space occupancy and energy requirements. Specifically, the disposition of gregarious sessile animals in complex matrices hampers the application of classical ST models. This paper reviews the self-thinning models, regression methods (central tendency and frontier techniques) and discrimination criteria currently applied for gregarious sessile species through application to the analysis of mussel populations (Mytilus galloprovincialis) grown in suspended culture. In addition, we propose to model the temporal evolution of site occupancy in the stochastic frontier function (SFF). Our results confirm that the number of layers should be included in the classical bidimensional ST model for the analysis of multilayered populations. The estimated parameters obtained by the different fitting techniques depended on the measurement method of the variables in the model. This, together with the proximity between the space and food selfthinning theoretical exponents (SST and FST, respectively) highlights the difficulty in discriminating the competition limiting factor (space/food) from the self-thinning exponent. On the other hand, the SFF provided congruent results for biomass and individual mass analysis, in contrast to the lack of robustness observed for the central tendency regression methods. Furthermore, the SFF approach allowed a dynamic interpretation of the ST process providing insight into the temporal evolution of site occupancy. These results highlight the suitability of the stochastic frontier approach in the analysis of self-thinning dynamics in sessile animal populations.

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Section: Estimation Of the Theoretical Sst Exponentsmentioning

confidence: 99%

Section: Effective Density and Number Of Layersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Evaluation of self‐thinning models and estimation methods in multilayered sessile animal populations

et al. 2012

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“…Self-thinning (ST) has been reported in sessile animals such as barnacles (Hughes and Griffiths 1988), tunicates (Guiñez and Castilla 2001) and mussels (reviewed by Guiñez 2005) and probably occurs also in scallop spat collector bags . Although ST appears an undesirable 248 M. Fréchette et al: Aquat.…”

Section: Introductionmentioning

confidence: 99%

“…Two methods have been developed to take multi-layering into account in ST models, the effective-density method (Guiñez and Castilla 2001) and the multi-layer method (Guiñez and Castilla 1999). The effective-density method is based on a projection of the population as a single-layered matrix of individuals.…”

Section: Introductionmentioning

confidence: 99%

Body size, population density and factors regulating suspension-cultured blue mussel (Mytilusspp.) populations

Fréchette¹,

Lachance-Bernard²,

Daigle

2010

Aquat. Living Resour.

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-We sampled 27 month-old mussel populations grown on collector ropes in Cascapédia Bay, Quebec, to test whether density-dependent growth was present concomitantly to self-thinning, a process which was previously shown to occur in this system and thought to be driven by spatial constraints. Biomass-density curves of raw samples were curvilinear, suggesting density-dependent growth. However, at least two cohorts were present. Fractionating the samples on the basis of age yielded a linear relationship for the main, 2 year-old cohort. This implies density-independent growth and rules out food regulation in these populations. Therefore, our results are consistent with inferences drawn previously from the values of the self-thinning exponent, that is, space-regulated self-thinning. Our results suggest that curvilinearity of the raw biomass-density curves resulted from a bias caused by including the 1 year-old cohort and spat of the year in the analysis. This conclusion is supported by a model showing that samples with mixed cohorts can yield linear, concave or convex biomass-density curves without density-dependent growth. The shape of the curves depends on the scaling relationships between cohort abundances. It appears that the shape of biomass-density curves may be a useful complementary criterion -in addition to the value of self-thinning exponents -for the identification of food or space as factors regulating cultured populations. Key words:Mussel culture / Population regulation / Mussel density / Self-thinning Résumé -Le processus d'autoréduction (mortalité par compétition, "self-thinning") observé chez les populations de moules élevées sur collecteurs de naissain dans la baie de Cascapédia (Québec) a été attribué à la compétition pour l'espace. Dans le but de déterminer si la compétition affecte également la croissance individuelle, nous avons étudié la courbe biomasse-densité d'échantillons en culture depuis 27 mois. Nous observons des courbes concaves, ce qui à première vue correspond à un processus dépendant de la densité. Toutefois, les échantillons comptaient au moins deux cohortes. L'analyse des moules de la cohorte principale, âgée de 2 ans, indique une relation linéaire. La croissance est donc indépendante de la densité, ce qui exclut toute forme de compétition pour la nourriture et confirme les conclusions des travaux antérieurs, fondées sur la valeur de l'exposant de la fonction d'autoréduction. L'analyse suggère que la concavité des courbes biomasse-densité brutes s'explique par un biais causé par l'inclusion des moules âgées d'un an et du naissain dans l'analyse. Cette conclusion est appuyée par un modèle de l'effet du mélange des cohortes. Ce modèle indique qu'en absence de compétition, les courbes biomasse-densité peuvent être linéaires, convexes ou concaves, la forme de la relation dépendant de la relation entre les effectifs des cohortes. Il semble que la courbe biomasse-densité soit un outil diagnostique utile -s'ajoutant à l'exposant de la fonction d'autoréduction -pour la mise en évid...

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Down under the southeastern Pacific: marine non-indigenous species in Chile

et al. 2005

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This article presents the first compilation of marine non-indigenous species (NIS) of algae and macroinvertebrates invading Chilean waters. A total of 32 cosmopolitan and non-cosmopolitan species are reported. Among them there are six species considered as extending their southern range of distribution in connection with El Nin˜o events. The article highlights negative and positive impacts caused by marine NIS invasions. Among the first are Codium fragile var. tomentosoide, considered as a pest in Gracilaria chilensis aquaculture facilities in northern Chile, and Ciona intestinalis, a pest in scallop aquaculture installations. Among the second are bio-engineers species, such as the ascidian Pyura praeputialis and the sea grass Heterozostera tasmanica, which have caused an increase in local biodiversity and enhancement of nursery grounds via the creation of new habitats. Further more, invaders such as the algae Mastocarpus papillosus, Porphyra linearis and P. pseudolinearis represent new exploitable resources, extracted by coastal food gatherers along the coast (M. papillosus) or potential species to develop aquaculture. Additional information is presented on the anemone Anemonia alicemartinae, which appears to be a native species (?), having shown in the past 40-50 years, a geographical southward range extension of approximately 1900 km. The number of NIS reported for Chile is compared with those published for the southwestern Atlantic, South Africa, North America (Atlantic and Pacific coasts) and New Zealand. It is suggested that probably the low number of Chilean NIS is due to the fact that the Chilean coasts are environmentally less stressed than other coasts in the world, due to the scarcity of estuaries, gulfs, enclosed bays, lagoons and low human populations. These kinds of sheltered areas have been suggested as centers for bio-invasions, due to the high rate of human-mediated transfer and increase of pollutants. Furthermore, none of NIS reported from Chile show a fast geographical expansion rate (exception of A. alicemartinae), nor invading strategies such as those described for marine NIS in other latitudes, where notorious ecological unbalances following invasions have been observed. An alternative hypothesis is that the low number of marine NIS invading Chile is underestimated, since the modern list of species generated through specific taxonomically intensive port and harbor surveys is still lacking. Fifteen Biological Invasions (2005) 7: 213-232 Ó Springer 2005 species (five invertebrate and 10 fish) have been deliberately imported to Chile for aquaculture. The invertebrates appear to be controlled within aquaculture facilities and have not established naturalized populations or caused direct ecological impacts on local communities. On the contrary, several millions of salmoniforms (and rainbow trout) have escaped from farming facilities in southern Chile and established naturalized populations. Studies on ecological impacts are lacking. These escapees are also playing a role in the enhancement of ar...

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An Allometric Tridimensional Model of Self-Thinning for a Gregarious Tunicate

Cited by 13 publications

References 0 publications

Evaluation of self‐thinning models and estimation methods in multilayered sessile animal populations

Evaluation of self‐thinning models and estimation methods in multilayered sessile animal populations

Body size, population density and factors regulating suspension-cultured blue mussel (Mytilusspp.) populations

Down under the southeastern Pacific: marine non-indigenous species in Chile

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