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Jensen, Henrik (2004) Tillväxtmönster och åldersstrukturer hos opåverkade bestånd av strömlevande Arktisk harr i Sibirien. Other thesis, SLU.

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It is hard to find streaming waters where humans haven't affected the fish populations or the running water it self. In many streams the fish populations are over harvested and this results in a lack of older and larger fish. This is also the situation for many populations of Grayling (Thymallus spp.). To be able to develop management plans and to perform actions that improve the situation for the grayling, it is therefore crucial to know what natural, by humans unaffected populations look like. In northern Siberia, it is possible to find unexploited Arctic grayling populations living in undisturbed aquatic environments. The study was conducted in three different streams in the Putorama area in northern Siberia, approximately 300 km south from Norilsk. In two of the streams two locals was investigated in respective stream. Fish were collected by rod and reel and by nets adapted for running waters.The graylings were sampled between 16/6-19/7 2001. The results showed that there were variations in age distribution, growth patterns and age at maturity in the investigated streams. These variations could depend on many factors. One is that the locals were studied at different dates in some locations close to spawning period. Another reason is the difference in distance to nearest lake. In most of the locations, older and larger fish are dominating in the sample. It can't be excluded that juvenile graylings migrate to Lake Schantajskoje or one of the smaller lakes in the area. They may also spend their first years in very narrow streams, but this was not investigated. At what size and age the arctic grayling in northern Siberia mature is difficult to say because of the small sample sizes. Juvenile fish were only caught in two locals. There, the age at maturity seemed to be between four and five years. The fecundity for the graylings in this study correlate rather well with other studies. The fecundity varied between 7200-10900 eggs/kg bodyweight. This study showed that: (i) the majority of the graylings are large (>200g) and old (>7years), (ii) there is quite obvious differences in growth patterns and age at maturity within the same geographical area. Management of exploited grayling populations is difficult because of a general lack of knowledge how natural, unaffected populations are structured. With this study, information have been added to the basic knowledge needed to be able to develop sustainable management schedules for stream living Grayling populations.

Item Type: Thesis (Other)
Keywords: Tillväxtmönster, åldersstruktur, harr, arktisk, Sibirien, fiskbestånd, harrpopulation, beståndsdynamik, tillväxt
Subject (faculty): Faculty of Veterinary Medicine and Animal Science > Dept. of Aquaculture
Divisions: SLU > Faculty of Forest Sciences
Depositing User: Bo-Sören Wiklund
Date Deposited: 20 Dec 2006
Last Modified: 18 Aug 2015 09:46
URI: http://ex-epsilon.slu.se/id/eprint/1371

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