Analysis Of Individual Growth Research Articles

Parameters of the Spondylus limbatus GB Sowerby II, 1847, population in the Central-West Gulf of California, Mexico

ABSTRACT The main Spondylus limbatus population parameters were estimated based on the analysis of individual growth and reproductive aspects of specimens collected monthly (n = 30) from January to December 2009 in the fishing area of Agua Verde, Gulf of California. The size structure determined from shell measurements was 82–167 mm and the direct reading of shell sections indicated ages of 1–14 years. The data were adjusted to the von Bertalanffy, Gompertz, logistic, Richards and Schnute (Type 1) growth models. The von Bertalanffy model provided the best fit to describe individual growth in this species (SH∞ = 142.7 mm, k = 0.47, t0 = −0.20 years). The spawning season was determined through gonadal histology, and the size and age at sexual maturity through a logistic model. Reproductive activity occurred from March to September, with spawning peaks in July and August. The size and age at sexual maturity were 10.8 mm and 2.7 years, respectively. This information provides the necessary knowledge to implement management measures in the area. We recommend independent studies to establish management measures for each fishing area.

Methodological Advances in the Analysis of Individual Growth With Relevance to Education Policy

The purpose of this article is to demonstrate how recent methodological developments in the analysis of individual growth can inform important problems in education policy. Specifically, this article focuses on a method referred to as growth mixture modeling. Growth mixture modeling is a relatively new procedure for the analysis of longitudinal data that relaxes many of the assumptions associated with conventional growth curve modeling. In particular, growth mixture modeling tests for the existence of unique growth trajectory classes through a combination of latent class analysis and standard growth curve modeling. Antecedent predictors of the latent classes can be incorporated as well as relations from the latent classes to specific outcomes. This article applies growth mixture modeling to data from the Early Childhood Longitudinal Study-Kindergarten class of 1998-1999. The specific policy question posed in this article focuses on the estimation of latent growth trajectory classes in reading proficiency and the effects of full-day or part-day kindergarten programs on growth within reading trajectory classes. Results identify a 3-class solution corresponding to slow-developing, normal-developing, and fast-developing reading growth in children. The results further show that full-day kindergarten attendance benefits children in the slow-reading development class relative to the normal and fast-reading development class, but the effect is lessened when holding constant socioeconomic status and age of entry into kindergarten. The implications of the method for quantitative education policy analysis are also discussed.

A Growth Curve for the Newt Triturus cristatus

-I constructed Von Bertalanffy growth curves for a population of crested newts (Triturus cristatus) in northern France. Data were collected through capture-recapture of individually recognized newts over a six year period. The assumption that year to year growth diminishes with size following a linear negative relationship was tested and could not be rejected. Observations on seasonal growth were used to estimate average size of one year old juveniles. Inclusion of these data increased the precision with which the parameters in the Von Bertalanffy model were estimated. The parameter defining growth curve shape was not convincingly different for males and females. Asymptotic body size was significantly larger for females than for males. Comparison with growth curves estimated from published data indicated significant differences between populations, with slower growth and smaller size at maturation in Norwegian T cristatus than in French T: cristatus. l , l. 34, o. 2, pp. 227-232, 2000 i t e Study of A phibians and Reptiles A wide range in body size is usually observed in mature individuals of long-lived organisms characterized by indeterminate growth. One reason for this phenomenon is that natural selection favors reproduction commencing at an early age. However, as larger individuals may produce more offspring than smaller ones, investment in early reproductive activity may reduce growth and diminish lifetime reproductive success (Stearns, 1992). Parameters in the tradeoff between growth and reproduction are under strong selection as well as under the influence of environmental and phylogenetic constraints. As data accumulate for amphibians, we will be in a better position to evaluate patterns of geographical variation in life history parameters, and develop testable hypotheses about how life history attributes evolve in natural populations (e.g., Reznick et al., 1990; Manly, 1998). I here contribute to the growing data set with the analysis of individual growth and sexual size dimorphism in a population of the crested newt from France (Triturus cristatus). Capture-recapture data allow retrospective sexing of juveniles and the reconstruction of largely gender-specific post-metamorphic growth trajectories. Variation in growth parameters is documented through comparison with populations of crested newts experiencing different climatic conditions, and with a phylogenetically closely related species, the marbled newt, T marmoratus (Arntzen and Sp rreboom, 1989; Zajc and Arntzen, 1999). MATERIAL AND METHODS I estimated population parameters of T cristatus at an aquatic breeding site near Ambleteuse in northwestern France. Metamorphosis is in the year newts are born and larvae and efts had age 0. The observed size distributions indicated that juveniles had age 1 (see Arntzen and Teuis, 1993 for details). Because the population was newly established, adult newts had age <2 at pond age 2. Because adults were at least two years old (two years being the minimum age of maturation observed in the wild-Dolmen, 1983; Francillon-Vieillot et al., 1990; Arntzen and Teunis, 1993), I concluded that they were two years old. Extending this approach, adult newts first encountered at pond age 3 were 2.5 ? 0.5 yr old, etc. The accuracy of the age estimate declined with more annual cohorts contributing to the breeding population. By combining individual recognition (by pattern mapping, Hagstr6m, 1977) with capture-recapture for age determination and juvenile sex identification I avoided bodily harm of newts. 227 This content downloaded from 157.55.39.231 on Thu, 06 Oct 2016 04:43:12 UTC All use subject to http://about.jstor.org/terms