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17 results on '"Thorsteinsson, Vilhjálmur"'

2. THE EVOLUTIONARY GENETIC STATUS OF ICELANDIC EELS

Author

Avise, John C, Nelson, William S, Arnold, Jonathan, Koehn, Richard K, Williams, George C, and Thorsteinsson, Vilhjálmur

Subjects
Biological Sciences, Ecology, Evolutionary Biology, Genetics, Evolutionary biology
Abstract

The Iceland population of Anguilla eels contains an elevated frequency of fish with vertebral numbers lower than those typical of European localities. Several distinct hypotheses have been advanced to account for these morphologically atypical fish: for example, they could represent (1) genetically "pure" American expatriates, (2) genetically "pure" European types with ontogenetic abnormalities, or (3) hybrids between American and European forms. Here we critically test these and other possibilities by examining the joint distributions of allozyme markers, mitochondrial DNA markers, and vertebral numbers in Icelandic eels. The particular patterns of association among the genetic and morphological traits demonstrate that the Iceland population includes, in low frequency, the products of hybridization between American and European eels. Approximately 2-4% of the gene pool in the Iceland eel population is derived from American eel ancestry. This hybrid zone is highly unusual in the biological world, because the mating events in catadromous eels presumably take place thousands of kilometers from where the hybrids are observed as maturing juveniles. The molecular data, in conjunction with the geographic distributions, strongly suggest that the differences in migrational behavior and morphology between American and European eels include an important additive genetic component. Evolutionary hypotheses are advanced to account for the original separation of North Atlantic eels into American and European populations, and for the presence of hybrids in Iceland.

Published
1990

7. Thermal niche of Atlantic cod Gadus morhua : limits, tolerance and optima

Author

Righton, David A., Andersen, Ken Haste, Neat, Francis, Thorsteinsson, Vilhjalmur, Steingrund, Petur, Svedäng, Henrik, Michalsen, Kathrine, Hinrichsen, Hans-Harald, Bendall, Victoria, Neuenfeldt, Stefan, Wright, Peter, Jonsson, Patrik, Huse, Geir, van der Kooij, Jeroen, Mosegaard, Henrik, Hüssy, Karin, and Metcalfe, Julian

Published
2010

12. Method name: Internal tagging of cod with DSTs and double tagging with a DST and a conventional tag

Author

Thorsteinsson, Vilhjálmur

Subjects
Double tagging, Fish, Gadus morhua, Data storage tags, T-bar tags, Surgical implantation, DST, Cod
Abstract

Some objectives of experiments where this tagging method has been used: Research of the behaviour of sexually mature cod in Icelandic waters; Study of Behaviour that influences catchability such as Availability and Accessibility (Harden Jones 1974) . Migration, Vertical movements, Geographic distribution, Habitat preference, Exploitation, Mortality, Growth (Pálsson & Thorsteinsson 2003) , Spawning behaviour (Thorsteinsson & Marteinsdóttir 1998) Double tagging with a DST and conventional tag CT to observe tag retention and differential returns of tags. Published Current 14.4 N/A National Guidelines & Policies Method

Published
2005

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