White shark tagging off New Zealand

Description :

 
Regional Population Connectivity, Oceanic Habitat, and Return Migration Revealed by Satellite Tagging of White Sharks, Carcharodon carcharias, at New Zealand Aggregation Sites.
A joint NIWA/Department of Conservation (DOC) tagging programme was launched in 2005.  Hi-tech electronic tags are being used to gather information on where the sharks are and when, and to record their depth and the temperature of the surrounding water. Three tag types have been used: popup archival tags, acoustic tags, and dorsal fin tags.
Popup tags are implanted in the muscle under the dorsal fin with a tagging pole, and record depth, temperature and location, storing the data for up to a year. They then release themselves from the shark, float to the surface, and transmit summaries of the data to a satellite. If the tags are physically recovered, the high resolution data collected at one minute intervals can be downloaded. Popup tags provide only approximate location data, so they are most useful for tracking long-distance migrations.
Acoustic tags send out coded, individually identifiable sound ‘pings’ that can be detected up to a kilometre away by acoustic data loggers. The tag batteries last long enough to monitor the presence of white sharks in the region in the vicinity of a data logger for two years. Acoustic tags provide accurate fine-scale information on sharks at specific locations.
Dorsal fin tags bridge the gap between popup and acoustic tags. They provide accurate location information by transmitting to orbiting satellites every time the shark is at the surface and the dorsal fin and the tag’s aerial are exposed to air. Their batteries can last for more than one year, so both fine scale and large scale movement patterns can be recorded. However, dorsal fin tags are more difficult to deploy: the shark has to be caught and restrained while the tag is attached to the dorsal fin. So far, only a few of these tags have been deployed in New Zealand.
Since 2005, 44 white sharks have been tagged with popup tags, mainly at the Chatham Islands and Stewart Island. These islands support large colonies of fur seals, which are a major food source for white sharks. Our research has focussed on Stewart Island since 2009. The population there is dominated by males (about 2.2 males for every female). Nearly all of the females are immature, being shorter than the female length at maturity of 4.5 to 5 m. Only about one-third of the males are longer than the male length at maturity of about 3.6 m. This indicates that the white shark aggregations at Stewart Island are not related to mating, and are most likely driven by the abundance of seals for food. Large, mature females are rarely seen anywhere in New Zealand and their distribution, habitat and behaviour are almost completely unknown.

Le jeu de données diffusé est issu d'un traitement automatique appliqué sur les données issues du GBIF. Les règles de l'INPN et plus globalement du SINP (en termes de périmètre et de contrôle sur les données) peuvent impliquer que l'ensemble des données du jeu source ne soit pas restitué dans le SINP.
 The disseminated dataset stems from an automatic treatment applied to data coming from GBIF. INPN rules, and more generally SINP rules (in terms of perimeter and data quality controls) may imply that the whole of the source dataset might not be provided on the SINP platform. 

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Dates publication :

Premiere diffusion : 26/09/2019 

Dernière mise à jour : 14/03/2023