Royal Netherlands Institute for Sea Research
Royal Netherlands
Institute for Sea Research

Swimming performance and fine-scale behaviours of Wadden Sea fish

Observing animal behaviour in aquatic environments is a difficult task that relies heavily on the use of technologies such as animal-attached tracking (biotelemetry) devices. These devices can provide powerful insight into the migratory pathways, habitat use, and fine-scale movements of aquatic animals such as fish, however, to accurately interpret the acquired movement data, several challenges must be overcome.

Firstly, tag models and attachment methods must be chosen carefully with respect not only to logistical considerations (e.g., cost and preferred data format), but also with concern for animal welfare and species-specific effects of tag-burden and placement. External attachment methods allow tags to be released from the host animal, promoting remote data transmission or tag recapture, however, externally attached devices may influence fish swimming performance and hydrodynamics with potential consequences for the acquired movement data. Despite the increasing popularity of externally attached devices such as satellite and data storage tags for examining fish movement, few studies have examined their potential impact on swimming performance to date. 

Secondly, once obtained, fish tracking data must be interpreted in relation to the movement behaviours they represent. For accelerometer data, this requires a visual comparison of fish movement behaviours and the corresponding data signals.

Based on these two challenges, the aims of this study are therefore to: 

  1. Monitor (using video recordings) and assess the influence of external tag attachment on factors such as tailbeat frequency, stride length, and relative swimming speed for fish held in captivity. 
  2. Identify accelerometer signals associated with activity levels and ecologically relevant behaviours (e.g., high vs. low turning frequency, continuous vs. burst swimming) in captive fish.

This thesis project will include the design and setup of a laboratory experiment, handling, care, and maintenance of fish (sea bass, Dicentrarchus labrax and thicklip grey mullet, Chelon labrosus), and the acquisition and analysis of telemetry data using R statistical software.

This project is part of the Waddentools Swimway Wadden Sea project which aims in part to improve our understanding of the importance of the Dutch Wadden Sea in the lifecycles of large migratory fishes. 


We are seeking a MSc student to assess the impacts of tag burden on the swimming performance of large fish and to identify distinct behavioural signatures in accelerometer data. Starting date is as early as October 2021. Duration: 6 months. Willingness to participate in additional fieldwork activities related to the Swimway Wadden Sea project (e.g., fish capture/tagging, sample collection, acoustic array maintenance) is an asset.


For more information and to apply, please contact Jena Edwards, PhD candidate ( The team consists of Jena Edwards (NIOZ/WUR/WMR), Allert Bijleveld (NIOZ) and Erwin Winter (WMR). 

A tagged thicklip grey mullet recovers before being released (© Mark Rademaker).