Julius Nielsen

Julius Nielsen
Greenland Institute of Natural Resources

PhD

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31
Publications
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Publications

Publications (31)
Article
Full-text available
The conservation status of the long-lived Greenland shark (Somniosus microcephalus) is unknown, and methods for non-invasively estimating local or regional abundances are wanted. Using a multifrequency split beam echosounder during long line fishery for Greenland sharks, we demonstrate how individual sharks can be identified and separated with high...
Article
Full-text available
Accurate age estimates are key life history parameters for understanding growth, reproduction and susceptibility to exploitation. Using a combination of fin spine growth increments and bomb radiocarbon dating, we provide minimum age estimates for the small Atlantic squaloid shark, black dogfish (Centroscyllium fabricii) sampled in Greenland waters....
Article
Full-text available
The Greenland shark (Somniosus microcephalus, Squaliformes: Somniosidae) is a long-lived Arctic top predator, which in combination with the high historical and modern fishing pressures, has made it subject to increased scientific focus in recent years. Key aspects of reproduction are not well known as exemplified by sparse and contradictory informa...
Article
Full-text available
Using social media, the Greenland Institute of Natural Resources collected data in 2019, on the occurrence of pink salmon (Oncorhynchus gorbuscha). Eighty‐four pink salmon were reported from 22 locations across Greenland. This comprised 76 specimens from 2019 and eight specimens from 2013–2018. Of these, twelve were caught in freshwater and a singl...
Article
Full-text available
To maintain a sustainable harvest of marine mammals, knowledge on key life history parameters such as age is essential. In West Greenland, humpback whale numbers were low during the 1980s due to past commercial whaling. However, the moratorium, which was enforced in 1986, had a positive effect on their abundance and by 2010 it was possible for Gree...
Technical Report
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ICES Scientific Reports/Rapports scientifiques du CIEM
Article
Full-text available
By examining the maturity of 283 black dogfish Centroscyllium fabricii from Greenland waters, a shift in size‐at‐maturity in both sexes over the past 25 years is observed. Size‐at‐first maturity decreased approximately 10 cm in both sexes, and L50 and L95 shifted similarly in males, but not in females. It is argued that bycatch in the Greenland hal...
Article
Full-text available
Current knowledge on the feeding ecology of the Greenland shark (Somniosus microcephalus), a potential top predator in arctic marine ecosystems, is based on small sample sizes as well as narrow size ranges of sharks. Therefore, potential size-related feeding patterns remain poorly documented. Using stomach content data (N=88) and stable isotope val...
Article
Full-text available
Long-lived species share life history traits such as slow growth, late maturity, and low fecundity, which lead to slow recovery rates and increase a population’s vulnerability to disturbance. The Greenland shark (Somniosus microcephalus) has recently been recognized as the world’s longest-lived vertebrate, but many questions regarding its biology,...
Conference Paper
Full-text available
The Atlantic cod Gadus morhua, the Greenland cod Gadus ogac and the Greenland halibut Reinhardtius hippoglossoides are particularly sensitive to persistent organic pollutants (POP) exposure, playing an important role in monitoring the potential effects of these chemicals in Arctic marine ecosystems. DDTs, PCBs, PBDEs and HBCDs were determined in th...
Conference Paper
Full-text available
Polybrominated-diphenyl ethers (PBDEs) include a class of brominated flame retardants (BFRs) that are added to many products (e.g. plastics, household textiles, etc.) to reduce their flammability. The top predator Greenland shark Somniosus microcephalus is an important cold-water species with slow growth and it is also the longest-lived vertebrate...
Thesis
Full-text available
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 t...
Article
Full-text available
I oceanernes pelagiske dybhav – eller “tusmørkezonen” – har organismerne udviklet fascinerende, unikke tilpasninger for at overleve i det ekstreme miljø. Tilpasninger, der ikke ses i andre habitater end dette ukendte mørke, som vi på mange måder kender mindre til end planeterne i vores solsystem. Vi dykker her ned i tusmørkezonen og ser nærmere på...
Conference Paper
Full-text available
Introduction Hexabromocyclododecane (1,2,5,6,9,10-hexabromocyclododecane, HBCD) is a brominated flame retardant (BFR) consisting of 16 possible isomers, three of them (α-, β-and γ-HBCD) are the main components in the commercial mixtures 1. The Greenland shark Somniosus microcephalus is a top predator and the long-lived vertebrate known, with an ave...
Article
Gross morphology and histology of the olfactory rosette of Greenland shark Somniosus microcephalus (Bloch & Schneider, 1801), suggest a well-developed olfactory capability for this top predator and scavenger native to Arctic waters. In the present paper, observations on the olfactory rosette are reported together with the gross morphology and histo...
Article
Full-text available
The Greenland shark (Somniosus microcephalus) has recently been identified as the world’s longest-living vertebrate animal, which raises conservational concern in light of recently high bycatch. We report the complete mitochondrial genome of S. microcephalus to be 16,730 bp and composed by 13 protein-coding genes, two rRNA genes, 22 tRNA genes, and...
Poster
DDTs were analyzed in 1-5 g of white muscle and liver tissue samples from 11 Greenland sharks (6 ♀, 5 ♂, body length (bl) 104-454 cm). Eight specimens were caught by long-lines in the fjords of NW Greenland, the remaining specimens were caught offshore in the SW and SE Greenland. The sharks were collected at different depths (114-745 m). The o,p’-...
Data
Full-text available
Can also be downloaded from: www.sciencemag.org/content/353/6300/702/suppl/DC1 http://science.sciencemag.org/content/sci/suppl/2016/08/10/353.6300.702.DC1/Nielsen.SM.pdf
Article
Full-text available
The Greenland shark (Somniosus microcephalus), an iconic species of the Arctic Seas, grows slowly and reaches >500 centimeters (cm) in total length, suggesting a life span well beyond those of other vertebrates. Radiocarbon dating of eye lens nuclei from 28 female Greenland sharks (81 to 502 cm in total length) revealed a life span of at least 272...
Article
Full-text available
The Greenland shark (Somniosus microcephalus) is the largest predatory fish in Arctic waters. Knowledge of the fundamental biology and ecological role of the Greenland shark is limited, and the sensory biology of the Greenland shark has been poorly studied. Given the potential relevant contribution of chemoreception to the sensory capability of the...
Article
Full-text available
During a recent marine biological expedition to the Northeast Greenland shelf break (latitudes 74–77 °N), we made the first discovery of Atlantic cod (Gadus morhua), beaked redfish (Sebastes mentella) and capelin (Mallotus villosus). Our novel observations shift the distribution range of Atlantic cod >1000 km further north in East Greenland waters....
Article
The Greenland shark Somniosus microcephalus (Bloch and Schneider, 1801) is the largest predatory fish in Arctic waters. The socio-economic significance of Greenland shark is demonstrated by its impact on the fishing cultures in Greenland, Scandinavia and Iceland for centuries. The fundamental biology and ecological role of Greenland shark, on the o...
Article
Full-text available
Here we present a comparison of saddle and eye patch patterns of killer whales from Norwegian, Icelandic, British, Spanish and Greenlandic waters. We found only a small amount of variation in saddle patch shapes, which may reflect a recent phylogenetic divergence from the most recent common ancestor. Eye patch shapes were more variable than saddle...
Article
Full-text available
Greenland sharks are widely distributed and most likely a highly abundant predator in arctic waters. Greenland sharks have previously been considered scavengers , but recent studies suggest that Greenland sharks also predate on live prey. In this study, distribution and feeding ecology in Greenland waters were investigated. Based on data from 25 ye...
Article
Full-text available
Greenland sharks are widely distributed and most likely a highly abundant predator in arctic waters. Greenland sharks have previously been considered scavengers, but recent studies suggest that Greenland sharks also predate on live prey. In this study, distribution and feeding ecology in Greenland waters were investigated. Based on data from 25 yea...

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Projects

Projects (2)
Project
Biology of the Greenland shark. Age, behavior, population genetics, metabolism, etc. more info at www.mbl.ku.dk/JFSteffensen/OldAndCold