Tracking marine species within an urban restoration project in Bergen (Bergen Telemetry Network, BOATS)

12. June 2024

Featured image: Lobster with transmitter. Photo by LFI NORCE.

Written by: Hilde Johannesen

Operated by LFI NORCE (Laboratory of Freshwater Ecology and Inland Fisheries), The Bergen Telemetry Network consists of an infrastructure of acoustic receivers in, or close to, the city of Bergen in Norway. The urban area directly downtown from Bergen is covered as a part of the BOATS project (Bergen`s Ocean Acoustic Tracking System), which started in 2021 with support from Miljødirektoratet (Norwegian Environment Agency).

Over time, the fjord and harbour of Bergen have experienced significant transformations due to urbanization, leading to elevated pollution levels. While efforts have successfully curbed much of the environmental contamination, the current emphasis is on preventing further degradation and removing existing pollutants. Notably, the seabed in Puddefjorden underwent cleaning in 2018; however, restoration efforts for Store Lungegårdsvann are still pending.

In a collaborative initiative, NORCE, The Institute of Marine Research, Bergen Municipality, and the Bergen Aquarium have resolved to document the impact on marine species before, during, and after the seabed restoration in Store Lungegårdsvann. This project encompasses the study of various species, including sea trout, corkwing wrasse, ballan wrasse, cod, pollock, and lobster, alongside an investigation into pollution levels through toxicology studies.

Receiver network and positioning

The network of TBR receivers for the BOATS project was distributed throughout the fjords around Bergen, with the highest concentration placed within Store Lungegårdsvann. The receivers in an area of Store Lungegårdsvann were used to perform exact positioning, using the built-in sync tags to update the clocks continuously for correct time synchronisation throughout the system.

The TBR 800 receivers have a built-in synchronisation tag, ensuring precise time synchronization across the receiver grid network. The sync transmitter used to be a separate transmitter used in addition to the receivers for time synchronisation, but Thelma Biotel has integrated the technology into the TBR 800 receiver. This technology integration simplifies setup processes, enhances data reliability, and reduces operational complexities for researchers. Thelma Boitel’s advanced receivers offer unparalleled accuracy in tracking aquatic species’ movements, underscoring the company’s commitment to providing cutting-edge telemetry solutions.

How to deal with clock synchronisation and sync transmits in different grids depends on the nature of the project. Do not hesitate to contact us for any questions about clock synchronisation and time drift at:

Ballan wrasse moved at a greater range compared to the Corkwing wrasse

Ballan and corkwing wrasse were tagged for the project using Thelma Biotel DT-LP7 transmitters with depth and temperature sensors. The transmitter type was chosen for this project to investigate the depth and temperature variations and preferences in the two wrasse species. When investigating the movement of species, it can often be useful to add sensors for a wider picture of some triggers or influences on the behavioural patterns they exhibit.

The results revealed differences between the two wrasse species regarding their movement patterns and depth preferences. Specifically, Ballan wrasse exhibited a larger movement radius than corkwing wrasse within the fjord systems of Bergen city centre (Figure 1). Ballan wrasse also stayed deeper in the water column during fall and winter, while the two species had similar depth usage in the summer and spring months. These results bring up the question if the more stationary wrasse species, the Corkwing wrasse, can serve as a better biomarker within Store Lungegårdsvann.

Figure 1: The number of detections of Ballan and corkwing wrasse in the Bergen city receiver network. The bigger the size of the circles, the higher number of detections were recorded. Figure from Catharina K. Olsen’s master thesis and edited by LFI NORCE. (Berhe, 2024)

Fine-scale positioning revealed floating docks as important aggregation spots for cod and pollock

Local anglers are particularly interested in cod fishing in and around Puddefjorden and Lungegårdsvann. However, elevated pollution levels, environmental toxins, and heavy metals have led to advisories against consuming cod from the area. To potentially revise these guidelines, cod and pollock in the area are being investigated due to their differing habitat preferences to determine if pollution levels vary between the two species.

The cod and pollock were tagged using AT-LP13 and ADT-LP13 transmitters with integrated activity, depth, and temperature sensors. The additional sensors provide a more comprehensive understanding of fish behaviour, aiding in decision-making for seabed restoration efforts. Thelma Boitel’s telemetry solutions empower researchers with high-quality data, essential for environmental conservation initiatives. Additionally, blood samples were collected from all tagged fish for detailed analysis.

The results revealed that both species were relatively stationary and stayed mainly close to the shallow border between Lungegårdsvann and Puddefjorden. Fine-scale data showed a particularly important “hang out” spot, being around and under the floating docks located in this area (Figure 2). These findings also highlight the value of fine-scale tracking data for a more accurate picture of habitat preferences in different species.

The floating docks will be removed during the project’s restoration phase, which might reveal some interesting findings.

Figure 2: Fine-scale positioning of an individual cod spending time by the floating docks in Store Lungegårdsvann. Figure by LFI NORCE. (Berhe, 2024).

Using activity sensors on lobster to assist in restoration approach

As the lobster resides on the seabed, it is vital to know the behaviour and movement coming into the restoration process. The lobster populations in Norway are vulnerable, and improving their environment could boost their survival, moving in the right direction. In the BOATS project, lobsters were caught and tagged in 2022 and 2023. The transmitter type A-LP13, with an activity sensor, was attached to the lobster’s arm before being released back into Store Lundegårdsvannet. The transmitters could track the movement and activity of the lobsters throughout the seasons due to the larger transmitter size and, thus, a larger battery lifetime.

Fine-scale tracking revealed that the tagged lobsters in Store Lungegårdsvannet stayed in shallow waters and preferred locations with hiding possibilities, such as rocks or vegetation. The activity sensors integrated into the transmitters recorded lower activity levels during the winter season compared to other seasons and decreased activity during the day compared to nighttime.

The combination of sensor information and telemetry movement data offers invaluable insights into the behaviour of various species, paving the way for tailored approaches. In the case of lobsters, understanding their activity patterns is of utmost importance for determining the most effective timing and methods for seabed restoration in Store Lungegårdsvannet.

Lobster being released after tagging. Photo by: LFI NORCE

The BOATS project has provided valuable insights into the species inhabiting Store Lundegårdsvannet thus far. Further investigations utilizing acoustic telemetry hold great promise for uncovering exciting findings regarding the effects of seabed restoration. All investigated species avoided the deep and northeastern regions of Store Lundegårdsvannet, prompting questions about whether these areas are either undesirable or uninhabitable due to the current condition (Figure 3). These inquiries, among others, will hopefully be addressed through post-restoration data collection as the project progresses. The second part of the project, distributing sand throughout Store Lundegårdsvannet, is aimed to be finished by May this year.

Figure 3: Primary species home range for torsk (cod), hummer (lobster) and lyr (pollock) prior to restauration process. Figure by LFI NORCE. (Berhe, 2024).

If you have any questions or inquiries regarding this or any other projects using Thelma Biotel acoustic telemetry equipment, do not hesitate to contact


Berhe, S. et al. (2024). “Fremdriftsrapport “Bergen’s Ocean Acoustic Tracking System (BOATS) – Evaluation of renewal of the Bergen city harbor on municipal development”