Abstract
This PhD project has aimed at investigating longevity of the Greenland shark. The largest
Greenland sharks measure at least 550 cm, and ever since Poul Marinus Hansen in 1963
presented that a recaptured medium-sized Greenland shark had grown 8 cm in 16 year, longevity
of the species has been subject for speculation. Conventional age determination techniques for
teleost or elasmobranchs are not applicable on the Greenland shark and its longevity has thus
remained a mystery for decades.
Inspired by alternative age estimation techniques applied on other sharks and whales, I have used
bomb radiocarbon dating and a Bayesian calibration model to estimate longevity of the
Greenland shark. The analyzed tissue stems from the eye lens nucleus – unique material which
presumably reflects age 0 of the shark, as it has not undergone metabolic changes during the
animal’s life. By studying 28 Greenland shark females between 81 cm and 502 cm, I estimate the
oldest shark to be between 272 years and 512 years. With an estimated lifespan of at least 272
years, the Greenland shark is the longest living vertebrate animal in the world.
In order to produce these age estimates, it has been necessary to study the carbon source of the
eye lens nucleus in more detail. The center of the nucleus consists of proteins and the analyzed
tissue stems from the diet of the shark’s mother. From feeding ecology and satellite tracking, I
have therefore investigated adult females. Sharks of this life stage mainly occupied continental
shelf waters in southern Greenland at depths between 200 and 550 m and fed primarily on cod,
redfish and seals. From previous investigations of predatory sharks and whales in the north
Atlantic, bomb radiocarbon has been widely applied, and I argue that a similar calibration
approach is valid to use on the Greenland shark.
The main aim of this thesis is to clarify the biological assumptions behind the radiocarbon dating
leading to the age estimates of the Greenland shark. These age estimates rest on classical
biological feeding ecology studies, chemical isotope analysis and advanced mathematical
modelling. This interdisciplinary approach has been crucial for the success of the project. The
thesis also illustrates how a novel cross-combination of techniques can be applied on other
marine species difficult to age determine, and how the Greenland shark is unique to the arctic
ecosystem. Many aspects of the basic biology of the Greenland shark remain mysterious.
Greenland sharks measure at least 550 cm, and ever since Poul Marinus Hansen in 1963
presented that a recaptured medium-sized Greenland shark had grown 8 cm in 16 year, longevity
of the species has been subject for speculation. Conventional age determination techniques for
teleost or elasmobranchs are not applicable on the Greenland shark and its longevity has thus
remained a mystery for decades.
Inspired by alternative age estimation techniques applied on other sharks and whales, I have used
bomb radiocarbon dating and a Bayesian calibration model to estimate longevity of the
Greenland shark. The analyzed tissue stems from the eye lens nucleus – unique material which
presumably reflects age 0 of the shark, as it has not undergone metabolic changes during the
animal’s life. By studying 28 Greenland shark females between 81 cm and 502 cm, I estimate the
oldest shark to be between 272 years and 512 years. With an estimated lifespan of at least 272
years, the Greenland shark is the longest living vertebrate animal in the world.
In order to produce these age estimates, it has been necessary to study the carbon source of the
eye lens nucleus in more detail. The center of the nucleus consists of proteins and the analyzed
tissue stems from the diet of the shark’s mother. From feeding ecology and satellite tracking, I
have therefore investigated adult females. Sharks of this life stage mainly occupied continental
shelf waters in southern Greenland at depths between 200 and 550 m and fed primarily on cod,
redfish and seals. From previous investigations of predatory sharks and whales in the north
Atlantic, bomb radiocarbon has been widely applied, and I argue that a similar calibration
approach is valid to use on the Greenland shark.
The main aim of this thesis is to clarify the biological assumptions behind the radiocarbon dating
leading to the age estimates of the Greenland shark. These age estimates rest on classical
biological feeding ecology studies, chemical isotope analysis and advanced mathematical
modelling. This interdisciplinary approach has been crucial for the success of the project. The
thesis also illustrates how a novel cross-combination of techniques can be applied on other
marine species difficult to age determine, and how the Greenland shark is unique to the arctic
ecosystem. Many aspects of the basic biology of the Greenland shark remain mysterious.
| Originalsprog | Engelsk |
|---|
| Forlag | Department of Biology, Faculty of Science, University of Copenhagen |
|---|---|
| Status | Udgivet - 2017 |