HTTP - Helgoland Tope Tagging Project

Background and Objective

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

1. identify seasonal migration behaviour of this endangered shark species in the North Sea
2. identify aggregation patterns, diurnal (vertical) migration and activity patterns
3. collect data for the evaluation of the protection and conservation status of this red-listed species
4. collect data to evaluate the use of existing and planned marine protected areas for the protection of this highly migratory species

Approach

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.

Our Research Questions

• Can we characterize seasonal migration behaviour of tope in the North Sea/Northeast Atlantic?
• Can we identify aggregation patterns as well as diurnal migration and activity patterns?
• Can we, based on data on migration routes and habitat use of tope, evaluate the feasability of established or planned marine protected areas for the protection of this endangered species, and are we able to identify further potential conservation measures?