Development of a novel histopathological gill scoring protocol for assessment of gill health during a longitudinal study in marine-farmed Atlantic salmon (Salmo salar)

• Published in: Aquaculture international Vol. 20; no. 5; pp. 813 - 825
• Main Authors: Mitchell, Susan O., Baxter, Emily J., Holland, Celia, Rodger, Hamish D.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.10.2012; Springer Nature B.V
• Subjects: Biomedical and Life Sciences; Disease; Environmental monitoring; Freshwater & Marine Ecology; Histopathology; Life Sciences; Longitudinal studies; Marine; Microscopy; Muggiaea atlantica; Pancreas; Parasites; Pathology; Pelagia noctiluca; Phytoplankton; Plankton; Salmo salar; Salmon; Solmaris corona; Water quality; Zoology; Zooplankton; Ireland; ANE, Eire; Gill pathology; Jellyfish; Scoring system; Epitheliocystis; Aquaculture
• ISSN: 0967-6120; 1573-143X
• DOI: 10.1007/s10499-012-9504-x

Gill health and disease in farmed Atlantic salmon ( Salmo salar ) were studied at a marine site on the west coast of Ireland. Fish were sampled on a regular basis during the summer and autumn of 2009. A novel histopathological scoring system was devised to give a semi-quantitative measure of gill pathology. The index criteria for gill histopathology were lamellar hyperplasia, lamellar fusion, circular anomalies (necrosis or sloughing) and lamellar oedema, a score from 0 to 3 being assigned for each parameter. Ancillary criteria, such as hypertrophy, haemorrhage and the presence of specific pathogens, were assigned a score of 0 or 1. Environmental monitoring undertaken included zooplankton and phytoplankton sampling, as well as temperature and oxygen recordings for the site. Epitheliocystis was frequently observed at low levels but was not associated with any significant gill pathology. Clinically significant gill pathology was observed on one occasion during the sampling period, coinciding with the occurrence of Pelagia noctiluca , Muggiaea atlantica and Solmaris corona . Throughout the longitudinal study, the scoring system provided an accurate and effective means of assessing gill health, demonstrating the ability of this practical tool to be used in future studies of gill health and disease.