Three-dimensional kernel utilization distributions improve estimates of space use in aquatic animals

Abstract

Tracking data have previously been used to define animal movement patterns through two-dimensional (2D) kernel utilization distributions and separate analysis of vertical locations. Here we describe the use of three-dimensional (3D) kernel utilization distributions to estimate the volumetric space use of individuals based on tracking data and to estimate the overlap in activity space between individuals. Data from European eels (Anguilla anguilla) from Norwegian coastal waters were used to compare the information conveyed by 2D and 3D activity space estimates and the utility of this approach for aquatic species. The use of 3D kernels produced detailed representations of space use in A. anguilla that permitted examination of depth use in a geographic context. Comparison of 2D and 3D home ranges showed that 2D analyses overestimated the amount of overlap between individuals by 13%-20%, because individuals sometimes occurred in the same location but used different depths. Hence, the 3D approach provided more comprehensive representations of animal movement in three dimensions while producing a metric that can be used for testing hypotheses relating to scientific descriptions of activity space, habitat use, and movement parameters.Résumé : Les données de repérage ont servi dans le passé à définir les patrons de déplacement des animaux à l'aide de distributions bidimensionnelles (2D) des noyaux d'utilisation et par analyse séparée des positions verticales. Nous décrivons ici l'utilisation de distributions tridimensionnelles (3D) des noyaux d'utilisation afin d'estimer l'utilisation volumétrique de l'espace par les individus d'après des données de repérage et pour évaluer le chevauchement dans l'espace des activités entre les individus. Nous utilisons des données sur des anguilles européennes (Anguilla anguilla) des eaux côtières de la Norvège pour comparer l'information fournie par les estimations 2D et 3D de l'espace des activités et évaluer l'utilité de cette métho-dologie pour les espèces aquatiques. L'emploi de noyaux 3D génère des représentations détaillées de l'utilisation de l'espace par A. anguilla qui permettent l'examen de l'utilisation de la profondeur dans un contexte géographique. Une comparaison des domaines vitaux 2D et 3D montre que les analyses 2D surestiment le chevauchement entre les individus de 13%-20%, parce que les individus peuvent quelquefois se retrouver au même point, mais utiliser des profondeurs différentes. Ainsi, la méthodologie 3D produit des représentations plus complètes des déplacements des animaux en trois dimensions, tout en fournissant une métrique que peut servir à tester des hypothèses concernant les descriptions scientifiques des paramètres de l'espace des activités, de l'utilisation des habitats et du déplacement.[Traduit par la Rédaction]

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