TY - BOOK

T1 - The Greenland shark (Somniosus microcephalus)

T2 - Diet, tracking and radiocarbon age estimates reveal the world’s oldest vertebrate

AU - Nielsen, Julius

PY - 2017

Y1 - 2017

N2 - This PhD project has aimed at investigating longevity of the Greenland shark. The largestGreenland sharks measure at least 550 cm, and ever since Poul Marinus Hansen in 1963presented that a recaptured medium-sized Greenland shark had grown 8 cm in 16 year, longevityof the species has been subject for speculation. Conventional age determination techniques forteleost or elasmobranchs are not applicable on the Greenland shark and its longevity has thusremained a mystery for decades.Inspired by alternative age estimation techniques applied on other sharks and whales, I have usedbomb radiocarbon dating and a Bayesian calibration model to estimate longevity of theGreenland shark. The analyzed tissue stems from the eye lens nucleus – unique material whichpresumably reflects age 0 of the shark, as it has not undergone metabolic changes during theanimal’s life. By studying 28 Greenland shark females between 81 cm and 502 cm, I estimate theoldest shark to be between 272 years and 512 years. With an estimated lifespan of at least 272years, 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 theeye lens nucleus in more detail. The center of the nucleus consists of proteins and the analyzedtissue stems from the diet of the shark’s mother. From feeding ecology and satellite tracking, Ihave therefore investigated adult females. Sharks of this life stage mainly occupied continentalshelf 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 northAtlantic, bomb radiocarbon has been widely applied, and I argue that a similar calibrationapproach is valid to use on the Greenland shark.The main aim of this thesis is to clarify the biological assumptions behind the radiocarbon datingleading to the age estimates of the Greenland shark. These age estimates rest on classicalbiological feeding ecology studies, chemical isotope analysis and advanced mathematicalmodelling. This interdisciplinary approach has been crucial for the success of the project. Thethesis also illustrates how a novel cross-combination of techniques can be applied on othermarine species difficult to age determine, and how the Greenland shark is unique to the arcticecosystem. Many aspects of the basic biology of the Greenland shark remain mysterious.

AB - This PhD project has aimed at investigating longevity of the Greenland shark. The largestGreenland sharks measure at least 550 cm, and ever since Poul Marinus Hansen in 1963presented that a recaptured medium-sized Greenland shark had grown 8 cm in 16 year, longevityof the species has been subject for speculation. Conventional age determination techniques forteleost or elasmobranchs are not applicable on the Greenland shark and its longevity has thusremained a mystery for decades.Inspired by alternative age estimation techniques applied on other sharks and whales, I have usedbomb radiocarbon dating and a Bayesian calibration model to estimate longevity of theGreenland shark. The analyzed tissue stems from the eye lens nucleus – unique material whichpresumably reflects age 0 of the shark, as it has not undergone metabolic changes during theanimal’s life. By studying 28 Greenland shark females between 81 cm and 502 cm, I estimate theoldest shark to be between 272 years and 512 years. With an estimated lifespan of at least 272years, 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 theeye lens nucleus in more detail. The center of the nucleus consists of proteins and the analyzedtissue stems from the diet of the shark’s mother. From feeding ecology and satellite tracking, Ihave therefore investigated adult females. Sharks of this life stage mainly occupied continentalshelf 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 northAtlantic, bomb radiocarbon has been widely applied, and I argue that a similar calibrationapproach is valid to use on the Greenland shark.The main aim of this thesis is to clarify the biological assumptions behind the radiocarbon datingleading to the age estimates of the Greenland shark. These age estimates rest on classicalbiological feeding ecology studies, chemical isotope analysis and advanced mathematicalmodelling. This interdisciplinary approach has been crucial for the success of the project. Thethesis also illustrates how a novel cross-combination of techniques can be applied on othermarine species difficult to age determine, and how the Greenland shark is unique to the arcticecosystem. Many aspects of the basic biology of the Greenland shark remain mysterious.

UR - https://soeg.kb.dk/permalink/45KBDK_KGL/1pioq0f/alma99122741098805763

M3 - Ph.D. thesis

BT - The Greenland shark (Somniosus microcephalus)

PB - Department of Biology, Faculty of Science, University of Copenhagen

ER -