Goals and approaches in the analysis of locomotion in fish, with a focus on laboratory studies

Abstract

There are many reasons to investigate fish locomotion. Topics include activity rhythms, energetics, orientation in time and space, responses to a variety of stimuli, including those originating from food, conspecifics or predators, and ontogenetic changes. Habitat selection and orientation along physical gradients are of considerable interest in ecology. Besides movements of individual fish, group behavior (schooling/shoaling) is relevant in a variety of biological and fishery contexts.

According to this diversity of goals, the approaches and the complexity of analysis vary. In the simplest case, activity provides a unidimensional measurement of how much an individual moves. More complex, swim path analysis aims at describing the shapes of the trails by considering parameters such as speed, steadiness of swimming, length of the straight trajectories vs. turns (directions and angles), use of area, distance to conspecifics, etc. By including the vertical axis, a two‐dimensional (2D) path may be extended to a three‐dimensional path GD). A variety of methodological approaches have been used to record fish movements, including visual monitoring, arrays of photocells, time‐lapse photography, movie‐filming, video‐taping, and ultrasonic systems. Due to its superior analytical potentials and ease of application, computer‐aided video‐systems presently prevail in laboratory applications, whereas ultrasonic telemetry and sonar systems dominate field research.

An example is presented of a computerized, video‐based, 2D‐path analysis of minnows (Phoxinus phoxinus) that were chemically stimulated. Nine parameters were considered and the benefits of multivariate as compared to univariate statistics are shown. With a sufficient number of parameters, the former is superior in distinction and allows judgments on behavior of individuals.

Key words:

• Locomotory behavior
• swim path analysis
• video image analysis
• orientation
• chemosenses
• shoaling
• schooling

Notes

Dedicated to HM, Ernst August, Prinz von Hannover.