1992. A comparison of von Bertalanffy and polynomial functions in modelling fish growth data. Can. 1. Fish. Aquat. Sci. 49: 1228-1 235.We compared the von Bertalanffy growth function (VBGF) and five polynomial functions JPF) in modelling fish growth for 16 populations comprising six species of freshwater fishes. Ranked results of the variance explained by each grswth function indicated that VBGF described growth data better than three-and four-parameter polynomial functions. Log-transforming length and age greatly improved the goodness-of-fit of the three-parameter polynomial function. Statistical comparison of growth between populations or sexes was done using a general linear model for polynomial functions. An analysis of residual sum of squares was proposed to compare the resultant VBGFs because the nonlinear formulation of the VBGF prevented traditional analysis of covariance procedures. Fitting of different growth functions to the same growth data set yielded the same result in the intraspecies growth comparisons for three species (eight populations) but different results for two species (seven pspulations). Where ages of the fish were less than the maximum age in the samples, dLldt were similar for all growth functions except the parabola based on the log-transformation of length alone. %he VBGF proved to be the best growth model for all 16 populations.Nous avons comparit la fonction de croissance fond& sur I'equation de von Bertalanffy et cinq fonctions polynomiales appliquees a la rnodklisation de B a croissance des poissons dans le cas de 16 populations (six espPces) de poissons dulcicoles. D1aprPs le classement des r6sultats de la variance par rapport a chaque fonction de crsissanee, la fonction de croissance reposant sur I'equation de von Bertalanffy fournit un meilleur tableau des donnites sur la croissance que les fonctions polynomiales a trsis et quatre parametres. La transformation lagarithmique des donnees sur la longueur et l'dge a grandernewt arndiore la qualit6 d'applieation de la fonction polynomiale a trois param6tres. Naus avons procede 2 une comparaison statistique de la csoissance entre les populations ou les sexes au moyen d'une modelisation lineaire gherale pour les fonctions polynomiales. Nous avons propose d'analyser la sornrne des carres obtenue, dans le but de comparer les ritsultats reposawt sur 116qua-tion de von Bertalanffy, car la formulation non liweaire de ce type de fonction nous ernpechait de faire I'analyse de covariance classique. En cornparant les donwees sur la croissance a l'interieur d'une meme espece, l'application de diverges fonctions de croissance au meme ensemble de donnees a abouti aux rnihes conclusions chez trois especes (huit populations), mais les resuitats differaient chem deux autres espgces (sept populations). Lorsque 112ge des poissons etait inferieus a I'age maximal des echantillons, les rapports dLldt ittaient semblables pour tautes les fonctions de croissance, exception faite de la parabsle representant la transformation logarithmique de la longueur seu...

Six geographic regions along the Laurentian Great Lakes in Ontario, represented by 286 lakes, were examined to identify the existence of regional similarities of fish species composition and their association to geographic location and regional patterns of lake morphology and pH. Lakes differed significantly among regions with respect to surface area, maximum depth, and pH. Species presence/absence data were summarized using correspondence analysis, and the resultant scores were used in multivariate analysis of variance and canonical variates analysis. These results indicated that the fish faunas of the six geographical areas were distinct. Interregional distances based on fish community scores, lake morphology–chemistry data, and geographical distances were contrasted using Mantel's test. Regional faunal similarities were correlated significantly with geographical proximity, but not with lake morphology. We propose that post—glacial dispersal and lake thermal regimes are important determinants in structuring regional patterns of fish assemblages, whereas environmental conditions such as lake depth and pH assume greater importance in determining species compositions of individual lakes.

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Fish and benthic invertebrates from 40 lakes in south-central Ontario showed significantly concordant patterns based on community structure. Fish communities were associated significantly with lake morphological characteristics, but were uncorrelated with water chemistry. Large, deep lakes differed from shallow lakes in their fish species, having richer faunas due to the additional cold-water species. Centrarchid species occurred more frequently in small, shallow lakes than in larger lakes. The invertebrate community was not correlated with lake morphology, but showed a significant association with water chemistry, principally lake pH. A strong contrast in the abundance of Chaoborus and Holopedium existed, but it was unclear whether this was due to a predator–prey relationship or to differences in acid tolerance. Although the lakes showed similar patterns in the composition of both communities, each community was associated with a different set of environmental factors. Biotic processes within and between communities explain this paradox in community–environment relationships. Such biotic interactions may involve direct processes such as fish predation on a particular invertebrate taxon or indirect factors, e.g., where fish limit the abundance of invertebrate predators, thereby limiting the impact of these invertebrate predators.

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