Abstract
Quantifying and understanding movement is critical for a wide range of questions in basic and applied ecology. Movement ecology is also fostered by technological advances that allow automated tracking for a wide range of animal species. However, for aquatic macroinvertebrates, such detailed methods do not yet exist. We developed a video tracking method for two different species of benthic macroinvertebrates, the crawling isopod Asellus aquaticus and the swimming fresh water amphipod Gammarus pulex. We tested the effects of different light sources and marking techniques on their movement behavior to establish the possibilities and limitations of the experimental protocol and to ensure that the basic handling of test specimens would not bias conclusions drawn from movement path analyses. To demonstrate the versatility of our method, we studied the influence of varying population densities on different movement parameters related to resting behavior, directionality, and step lengths. We found that our method allows studying species with different modes of dispersal and under different conditions. For example, we found that gammarids spend more time moving at higher population densities, while asellids rest more under similar conditions. At the same time, in response to higher densities, gammarids mostly decreased average step lengths, whereas asellids did not. Gammarids, however, were also more sensitive to general handling and marking than asellids. Our protocol for marking and video tracking can be easily adopted for other species of aquatic macroinvertebrates or testing conditions, for example, presence or absence of food sources, shelter, or predator cues. Nevertheless, limitations with regard to the marking protocol, material, and a species’ physical build need to be considered and tested before a wider application, particularly for swimming species. Data obtained with this approach can deepen the understanding of population dynamics on larger spatial scales and of the effects of different management strategies on a species’ dispersal potential.
Highlights
Movement ecology has received increasing attention over the years with technological advancements yielding ever more precise location devices to gain a better understanding of what influences the movement and distribution of animals (Nathan et al 2008; Schick et al 2008)
Ecology and Evolution published by John Wiley & Sons Ltd
We developed an experimental method to overcome the technical challenges described above to enable the study of movement behavior of aquatic macroinvertebrates
Summary
Movement ecology has received increasing attention over the years with technological advancements yielding ever more precise location devices to gain a better understanding of what influences the movement and distribution of animals (Nathan et al 2008; Schick et al 2008). The number of studies on smaller species has increased, whereby terrestrial examples such as collembolans and ants are frequently chosen as study objects (Amorim et al 2008; Robinson et al 2008). Aquatic invertebrates and their population distributions, are mostly studied in time and labor intensive field surveys where a defined area is chosen and the occurring a 2015 The Authors.
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