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Migration of Atlantic salmon, Salmo salar L., parr through a Norwegian fjord: potential infection path of Gyrodactylus salaris
- LUND, R.A., HEGGBERGET, T.G.
- Aquaculture research 1992 v.23 no.3 pp. 367-372
- Gyrodactylus salaris, Salmo salar, drainage, hatcheries, parasites, parr, rivers, salinity, salmon, streams, temperature
- Hatchery-reared Atlantic salmon, Salmo salar L., parr (0+) ranging in length from 74 to 95 mm were sampled in a stream with no hatchery in its drainage area. No fish had previously been released in this stream. The parr, therefore, had migrated during a period when the salinity of the fjord was between 20 and 30·5%₀, a minimum distance of 2.7km through the fjord, which was the distance to the nearest hatchery. This is the first observation of pre-smolt migration between streams via a fjord. Earlier, the salmon in the river had been infected by the monogean Gyrodactylus salaris. Probably, this infection had been spread by parr migrating from a neighbouring stream through the fjord. Parasite dispersion coincided with a period of low fjordwater salinity (12--14.5%₀) and sea temperatures ranging from 8.2 to 16.5°C, which is within the suggested tolerance level of G. salaris survival on salmon parr.