A remarkable creature lives beneath the ice floes of the Arctic. Greenland sharks swim excruciatingly slowly, have been known to eat polar bears and live for an implausibly long time. Peter is bringing their mysteries to the surface.
The general aim of this project is to deploy satellite tags on Greenland sharks and collect tissue samples for the purpose of age determination in order to better understand the species’ movements and the age structure of its population(s).
Fishing pressure and a lack of basic knowledge of the species’ natural history are threats to the future of the Greenland shark Somniosus microcephalus – thought by some to be the longest-lived vertebrate on earth. Effective conservation and management of any fish species requires a thorough understanding of growth rates, age at first reproduction, fecundity, distribution, population structure, etc.
Depth and location alter the amount of radioactive carbon incorporated into bodily tissues, which in turn impacts the accuracy of age estimates based on radiocarbon dating. Our two proposed projects are therefore directly related to one and other in that the water masses occupied by an animal and determinations of its age are linked. This research will address both these issues by deploying pop-up satellite archival tags (PSATs) on sharks in eastern and western Greenland, and by collecting tissue samples for radiocarbon analysis. In other research, we have already successfully deployed PSATs on Greenland sharks in north-western Greenland and had them remain attached for the full programmed period of 3.5 months. PSATs deployed in both areas will be programmed to release after one to three and nine to 12 months to provide insights into the water masses the sharks move through. These data will be important for our ageing studies, which comprise the second portion of the study. Eye lenses will be collected from sharks of various sizes for age determination using radiocarbon dating. Several fishermen and fisheries biologists are willing to assist us and supplement our efforts.
The general aim of this project is the deployment of satellite tags and collection of tissues from Greenland sharks for age determination in order to better understand their movements and the age structure of their population(s). Detailed objectives are to:
Sawsharks are some of the most threatened species in our seas; protecting them requires good information on where they move and what their populations look like. Jane and Paddy are using a variety of methods to improve our understanding of the conservation status and management of sawsharks threatened by fishing in south-eastern Australia.