Research Paper

Effect of 12 mm PIT tags on the survival, growth, and ecologically significant behaviours of juvenile critically endangered endemic Zingel asper

¹ Wasser Cluster Lunz − Biologische Station, Inter-University Center for Aquatic Ecosystem Research, Dr. Carl-Kupelwieser Promenade 5, A-3293 Lunz am See, Austria
² UMR INRAE-UPPA, ECOBIOP, Université de Pau et Des Pays De l'Adour, 64310 Saint-Pée-sur-Nivelle, France
³ Office français de la biodiversité − Direction de la recherche et de l'appui scientifique, Pôle R&D Ecohydraulique OFB-IMFT-PPRIME, IMFT, 2 Allée du Professeur Camille Soula, 31400 Toulouse, France
⁴ Office français de la biodiversité − Direction régionale Bourgogne Franche Comté, 57 rue de Mulhouse, 21000 Dijon, France
⁵ Muséum Citadelle de Besançon, Direction Citadelle − Patrimoine Mondial, Ville de Besançon, 2 rue Mégevand, 25034 Besançon, France

^* Corresponding author: sylvie.tomanova@ofb.gouv.fr

Received: 5 September 2024
Accepted: 18 September 2024

Abstract

Understanding the movement ecology and habitat use of freshwater fish is crucial for their conservation, with telemetry being an essential tool. Current tagging methods are restricted by the minimum body size of fish, as tags should not exceed 2% of the fish's body mass. This limitation hinders the study of juvenile small-bodied endangered species, as the reduced fitness of tagged individuals can negatively impact their populations. This study examines the feasibility of using 12-mm PIT tags on juvenile and subadult individuals (63–90 mm fork length) of the critically endangered Rhône streber, Zingel asper. Results indicate that tagging does not significantly affect survival, growth or behavioural traits, despite the tag weight being between 2.2% and 5.4% of the fish's weight. Tag retention was 100%, with 90% of individuals having the PIT tag fully encapsulated in the body cavity wall after 55 days. The only possible negative effect observed was a tendency, albeit statistically non-significant, for slower escape velocity in the smallest tagged individuals. These findings reduce the known minimum body size limit for 12-mm PIT tags for this species. However, the smallest individuals may be more sensitive to tagging, warranting careful consideration to avoid potential negative impacts on wild populations.