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 years. Only the smallest sharks (220 cm or less) showed signs of the radiocarbon bomb pulse, a time marker of the early 1960s. The age ranges of prebomb sharks (reported as midpoint and extent of the 95.4% probability range) revealed the age at sexual maturity to be at least 156 ± 22 years, and the largest animal (502 cm) to be 392 ± 120 years old. Our results show that the Greenland shark is the longest-lived vertebrate known, and they raise concerns about species conservation.

The effects of long-term moderate exercise on the behaviour and the food intake – growth relationship of individually marked Arctic charr, Salvelinus alpinus L., were examined. Direct monitoring of food intake of individual fish was carried out using an X-radiographic method. Growth (weight gain) was significantly improved with increasing swimming speed, and a maximum specific growth rate was obtained at a swimming speed of approximately 1.75 body lengths/s. Growth appeared to be suppressed by high levels of aggressive interactions, and an increase in swimming speed caused a marked increase in schooling behaviour, with a concomitant reduction in agonistic activity. The exercising fish did not consume more food than controls, and moderately exercised Arctic charr showed improved growth – food intake ratios at all levels of food intake compared with fish held in standing water. Furthermore, the proportions of nonfeeding fish were significantly reduced at increasing water velocities. Thus, the relationship between food intake and growth may be strongly influenced by agonistic activity, which appears to be most prevalent in fish subjected to low water velocities.

No abstract

No abstract

In light of ocean warming and loss of Arctic sea ice, harvested marine fishes of boreal origin (and their fisheries) move poleward into yet unexploited parts of the Arctic seas. Industrial fisheries, already in place on many Arctic shelves, will radically affect the local fish species as they turn up as unprecedented bycatch. Arctic marine fishes are indispensable to ecosystem structuring and functioning, but they are still beyond credible assessment due to lack of basic biological data. The time for conservation actions is now, and precautionary management practices by the Arctic coastal states are needed to mitigate the impact of industrial fisheries in Arctic waters. We outline four possible conservation actions: scientific credibility, ‘green technology’, legitimate management and overarching coordination.