Helgoland Tope Tagging Project
Tope is the biggest shark species resident in German waters and is classified as "critically endangered". Tagging experiments with satellite pop-up tags in the North Sea are expected to provide information on migration behaviour of this species and thus allow a more precise estimate of distribution and population size.
Tope (Galeorhinus galeus) are listed as "vulnerable" in the IUCN Red List of endangered species. Their status in German national waters is "critically endangered". In general, the northeast Atlantic population of this species is considered "data limited", which means that information on biology, distribution and abundance of this highly migratory species are considered insufficient.
To close existing gaps in the knowledge on distribution, migration, behaviour and biology of tope, individual sharks are tagged with satellite pop-up archival and conventional tags during their seasonal aggregation around Helgoland island in the summer months.
Aim of the project is to
Tope aggregate around Helgoland Island in the summer months, where we target them with rod and line fishery from a small boat. After taking length and weight measures and after determining the sex of the specimen, a quick, minimally invasive operation is conducted attaching a satellite pop-up tag (MiniPAT) and a regular spaghetti-tag (Floy-Tag) to the dorsal fin and below the dorsal fin basis, respectively. Afterwards, the shark is carefully released as fast as possible.
The satellite tag continuously records depth, temperature and ambient light levels over a period of 270 days. Then, the tag detaches from the shark, drifts to the surface and transmits archived data via satellite.
The expected data then allow us to reconstruct migration pathways of this widely migrating shark species. Additionally, small-scale distribution patterns like diurnal vertical migration and habitat preferences of tope can be identified. Aggregation patterns of sharks in a certain area may provide an indication for installing or evaluating the effectiveness of protected areas.
7.2017 - 7.2019
Project status: ongoing