Lymphocytopenia and the overwinter survival of Atlantic salmon parr, Salmo salar L.

Pickering, A.D.; Pottinger, T.G.. 1988 Lymphocytopenia and the overwinter survival of Atlantic salmon parr, Salmo salar L. Journal of Fish Biology, 32 (5). 689-697. https://doi.org/10.1111/j.1095-8649.1988.tb05409.x

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Abstract/Summary

The overwinter mortality rate of underyearling S2 Atlantic salmon parr (fish that will remain in fresh water for at least two years prior to smoltification) was almost ten times greater than that of S1 parr (fish that will smoltify after 1 year in fresh water) kept under similar conditions. The loss of condition (K factor) of the S2 parr was proportionally greater than that of S1 parr during the early winter months and this coincided with a marked lymphocytopenia and thrombocytopenia in the S2 parr. Limited evidence indicates that S2 parr have chronically elevated blood cortisol levels during the winter months. It is suggested that chronic stress resulting (in part) from nutritional deficiency has a debilitating effect on the defence systems of these fish. The ultimate cause of mortality in most cases was bacterial fin-rot and/or fungal (Saprolegnia) infection. These findings are discussed in relation to the habitat requirements of overwintering salmonid fish.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1111/j.1095-8649.1988.tb05409.x
UKCEH and CEH Sections/Science Areas:	_ Pre-2000 sections
ISSN:	0022-1112
Additional Keywords:	Atlantic salmon, parr, smolt, over-winter, lymphocyte, thrombocyte, condition, cortisol, stress, disease, Saprolegnia, fungus, fin-rot
NORA Subject Terms:	Zoology Biology and Microbiology
Date made live:	24 Aug 2015 14:20 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/511174

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